Prepared by

Pacific Northwest National Laboratory & Oak Ridge National Laboratory

June 4, 2007

June 2007 • NREL/TP-550-41085

PNNL-16362

High-Performance Home Technologies: 

Solar Thermal 

& Photovoltaic Systems

Volume 6 Building America Best Practices Series
High-Performance Home Technologies:

Solar Thermal & Photovoltaic Systems

Building America Best Practices Series

Prepared by

Pacific Northwest National Laboratory, a DOE national laboratory

Michael C. Baechler

Theresa Gilbride, Kathi Ruiz, Heidi Steward

and

Oak Ridge National Laboratory, a DOE national laboratory

Pat M. Love

June 4, 2007

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United 

States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, 

express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, 

apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to 

any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily 

constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or 

Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the 

United States Government or any agency thereof.

June 2007 • NREL/TP-550-41085

PNNL-16362
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

High-Performance Home Technologies: Solar Thermal & Photovoltaic Systems

Acknowledgments

Building America Best Practices Series

The U.S. Department of Energy’s (DOE) Building 

America Program is comprised of public/private 

partnerships that conduct systems research to 

improve overall housing performance, increase 

housing durability and comfort, reduce energy 

use, and increase energy security for America’s 

homeowners. Program activities focus on finding 

solutions for both new and existing homes, as well 

as integrating clean onsite energy systems that will 

allow homebuilders to provide homes that produce 

as much energy than they use. In addition to the 

DOE management and staff, Building America 

includes seven consortia, four national laboratories, 

and hundreds of builders, manufacturers, and 

service providers. Building America works closely 

with the U.S. Department of Housing and Urban 

Development’s (HUD) Partnership for Advancing 

Technology in Housing (PATH) and works with 

other federal agencies to coordinate research findings and disseminate information. In addition, DOE 

co-manages the ENERGY STAR Program along with 

the U.S. Environmental Protection Agency. These 

partners make the Program a successful source of 

knowledge and innovation for industry practitioners 

and government policy makers.

The U.S. DOE Building America Program funded the 

development of this series of handbooks. DOE also 

funded the Building America consortia and national 

laboratories to form the basis for these best practices. 

The seven consortia are listed on the back cover of 

this document. The consortia have taken on the 

hard work of applied research, field testing, training 

builders, and transforming the results into building 

practices. Numerous drawings, descriptions, photos, 

and case studies originated with the consortia.

Many builders have chosen to use the Building 

America process in collaboration with the consortia. 

Builders are quoted throughout the Best Practices 

Series, and more than a dozen builder case studies 

are featured in this document. These builders 

deserve thankful recognition for contributing to 

Building America’s success, the Best Practices 

Series, and for furthering the application of solar 

technology.

Building America partners worked diligently on this 

project to further the cause of energy efficiency, solar 

energy, and zero energy homes. These groups have 

voluntarily supplied technical materials, review 

comments, and photographs. Contributors include 

the Solar Rating and Certification Corporation, the 

Florida Solar Energy Center, SunPower Corporation, 

Heliodyne, Inc., Aztec Solar, Aurora Energy LLC., 

Decker Homes, Alternative Power Enterprises, Inc., 

Solargenix Energy LLC, the Sacramento Municipal 

Utility District, Lakeland Electric, the Southwest 

Technology Development Institute at New Mexico 

State University, Rheem Water Heaters, and 

Solmetric Corporation.

This project required coordination among the 

national laboratories. Pacific Northwest National 

Laboratory and Oak Ridge National Laboratory 

have taken the lead at producing this document. 

The National Renewable Energy Laboratory made 

its library of Building America, solar, and zero 

energy home documents available to the authors, 

reviewed the drafts, and has responsibility for 

posting the document to the Building America 

website. Researchers at Sandia National Laboratory 

reviewed the document as well.

The authors and DOE offer their gratitude to 

the many contributors that made this project 

a success. 

Unless otherwise noted, photographs were 

taken by Michael Baechler of Pacific Northwest 

National Laboratory.

Building America welcomes 

reader feedback on the Best 

Practices Series. Please submit 

your comments to Michael Baechler 

(michael.baechler@pnl.gov) or 

Pat Love (lovepm@ornl.gov).
High-Performance Home Technologies: Solar Thermal & Photovoltaic Systems

Table of Contents

Building America Best Practices Series

Chapter 1.

Managers’ Overview

Chapter 2.

Solar Sells: Closing the Deal

Chapter 3.

Solar-Thermal Water Heating

Chapter 4.

Photovoltaic Power Generation

Chapter 5.

Planning and Orientation

Chapter 6.

Rack-Mounted Systems

Chapter 7.

Worker Safety

Chapter 8.

Solar Ready

Chapter 9.

Looking Back, Looking Ahead

Appendix I (following the Case Studies)

PV System Installation Checklist

Courtesy of ConSol

Case Studies

• Bob Ward Companies – 

Maximum Efficiency Greenland

BelAir, MD

• Centex Avignon

Pleasanton, CA

• Clarum Homes’s Vista Montana

Watsonville, CA

• CARB Cold Climate Homes

Hadley, MA and Madison, WI

• Georgia Department of Natural Resources 

SIPS Cottage

Okefenokee, GA

• Grupe – Carsten Crossings

Rocklin, CA

• Habitat for Humanity – Metro Denver

Wheat Ridge, CO

• Habitat for Humanity – Loudon County 

Lenoir City, TN

• John Wesley Miller Companies – 

Armory Park del Sol

Tuscon, AZ

• Premier Homes – Premier Gardens

Sacramento, CA

• Pulte Homes – Civano

Tucson, AZ

• The Garst House

Olympia, WA

• Tindall Homes – Legends at Mansfield

Columbus, NJ
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Introduction – 

Reach for the Sky

Building America Best Practices Series

Showing support at the Solar Decathlon. Photo 

courtesy of Wendy Butler-Burt, DOE.

Chapter 1.

Managers’ Overview

Chapter 2.

Solar Sells: Closing the Deal

Chapter 3.

Solar-Thermal Water Heating

Chapter 4.

Photovoltaic Power Generation

Chapter 5.

Planning and Orientation

Chapter 6.

Rack-Mounted Systems

Chapter 7.

Worker Safety

Chapter 8.

Solar Ready

Chapter 9.

Looking Back, Looking Ahead

Case Studies

Energy efficiency and solar technology are important elements to any building or community design. 

Also, they are important to the nation and to the 

Earth. Both Presidents Bush and Clinton have 

expressed a commitment to solar technology as 

an important goal for national and environmental 

security. Homes that are attempting to reach this 

goal are called Zero Energy Homes (ZEH). 

This document is the sixth volume of the Building 

America Best Practices Series. It presents information useful throughout the United States for 

enhancing the energy-efficiency practices in each 

of the specific climate zones that are presented in 

the first five Best Practices volumes (described on 

page 2 of Chapter 1).

Research by the U.S. Department of Energy (DOE) 

Building America Program is identifying system 

engineering issues that must be resolved before the 

long-term goal of large numbers of cost effective, 

affordable, and marketable zero net energy homes 

(ZEH) is achieved. Part of this continuing research 

is the monitoring and analysis of data from a 

number of homes that have been constructed 

utilizing solar technologies.

Based upon these evaluations, this Best Practices 

document provides an introduction to current photovoltaic and solar thermal building practices. Passive 

solar heating is not described in great detail. Information on window selection and shading is included 

in Chapter 5, “Planning and Orientation.” 

Here’s what you’ll find inside:

The first chapter is for managers. It provides an 

overview of the technologies and explains how 

reliability is up and consumer acceptance is through 

the roof for today’s ZEH. Look here for an explanation of how builders are making a profit with solar 

technologies.

The second chapter provides additional details 

about marketing solar systems. This chapter 

explains how the leading builders in the country 

are selling zero energy homes. You will see some 

of the model homes that display photovoltaic and 

energy efficiency technology, visit open houses at 

demonstration homes, and learn other techniques 

used to turn savings into profits.

The next two chapters introduce solar thermal

and photovoltaic (PV) technologies. These 

chapters describe components and how systems fit 

together. Examples of system installations are used 

to show best practices for builders and installers.

The site planning and orientation chapter 

describes how to analyze the solar potential for 

a building site. It provides references to free 

models that can help with design and economic 

considerations. This chapter also describes research 

that shows the wide flexibility available for 

positioning solar systems.

The next chapter discusses roof and rackmounting systems.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

INTRODUCTION Reach for the Sky 

Chapter 7 describes safety measures and regulations for installers.

Chapter 8 briefly describes how to build homes 

ready for solar technologies. These solar-ready

homes are pre-plumbed, pre-wired, and structurally 

supported to easily add solar technologies after the 

initial sale. 

The next chapter looks at the history of solar 

development and some of the great designs from 

the Solar Decathlon, and summarizes the thirteen 

case studies described in the next paragraph.

Thirteen case studies are provided at the end of 

this document. These case studies review building 

projects of all scales from around the country. 

The lessons learned apply to building design, 

materials selection, mounting techniques, and 

marketing opportunities.

“We can imagine a day when 

technologies like solar panels and highefficiency appliances...will allow us to 

build Zero Energy Homes that produce as 

much energy as they consume. That’s the 

promise that technology holds for us all.” 

President George W. Bush, April 27, 2005

“We will work with businesses and 

communities to use the sun’s energy 

to reduce our reliance on fossil fuels by 

installing solar panels on 1 million more 

roofs around our nation by 2010.” 

President Bill Clinton, June 26, 1997.

Reach for the sky to bring solar energy to your 

homes. (left) Photo courtesy of John Harrison of 

the SRCC and FSEC. (right) Photo courtesy of 

Newt Loken of Solar Assist.

Building America welcomes reader feedback on the Best Practices Series. Please submit your 

comments to Michael Baechler (michael.baechler@pnl.gov) or Pat Love (lovepm@ornl.gov).
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems -JUNE 2007 CHAPTER 1 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 1.

Managers’ Overview

Building America Best Practices Series

The long-term goal of DOE’s involvement, according to Lew Pratsch, DOE 

Zero Energy Homes project manager, 

is to make zero energy homes truly 

affordable for the average consumer. 

Pratsch predicts that within the next 

decade, zero energy homes will 

be commonplace.

“We set out to provide exceptional value for our customers by adding solar power, 

and in the process we did something exceptional for our business.” 

John Suppes, President of Clarum Homes of Palo Alto, California

Many business owners come to a point in their careers when it is time to bring new energy to their 

enterprises by inviting in a new generation of partners. This document is literally about bringing new 

energy into home construction businesses by inviting in a new generation of energy efficiency and 

solar power.

Building America, DOE’s program for energy efficiency in new home construction, has worked with 

builders all over the United States for more than ten years to develop comfortable, durable, and efficient 

houses. Teams of builders and building scientists have proven that energy efficiency is a vital part of 

quality and value-based construction when incorporated into an integrated systems design. This approach 

to efficient construction is an essential step in creating consumer value.

(above) It is difficult to pick out houses with 

integrated photovoltaic systems. All of these 

homes are so equipped.

Builders’ Brief

• Systems engineered building design and energy efficiency are the best bet for value, comfort, and reliability.

• Highly efficient houses, combined with solar technologies, add up to today’s Zero Energy Homes (ZEH) 

– homes with utility bills reduced by at least 50%. Tomorrow’s ZEH will produce as much annual energy as 

they consume.

• Innovation has made solar technologies more stylish, reliable, and consumer-friendly.

• Government and utilities at all levels support solar with tax credits, rebates, accelerated building permits, 

and other incentives.

• Production builders have strong advantages in cost savings and design benefits over retrofit installations.

• Consumers buy ZEH houses at up to twice the rate of neighboring non-ZEH communities.

• Satisfied homeowners tend to recommend their builder to others twice as much as neutral owners.

• Zero Energy Homes differentiate your company in the market and position your business for the future.

Installers’ Brief

• Production builders offer tremendous advantages for the installation 

of solar technologies in comparison 

to the retrofit market.

• Work with builders as a supplier, 

marketer, and installer to drive 

down costs.

• Work with builders to develop 

quality assurance plans.

• For success, installers need to work 

within the builders’ business model 

as do contractors in other trades.
p.2 / CHAPTER 1 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 1 Managers’ Overview 

But the next step makes homes more than efficient, 

it makes them power producers. The nation has 

an ambitious goal of developing zero energy 

homes—ZEH—that produce as much power as 

they consume over the course of a year. Energy 

efficient design and quality construction can drive 

the cost of powering a home down by more than 

50%. But to reach ZEH, homes must incorporate 

some type of on-site energy generation. Solar 

power systems for heating water and producing 

electricity are technologies that are working today 

to help reach ZEH. 

The nation’s leaders and energy planners identify 

solar power as a critical technology for new home 

construction. These leaders are concerned with 

national security, environmental protection, and 

consumer affordability. But builders must consider 

business ramifications. This chapter tries to answer 

two questions applicable to your business:

• What’s changed to make solar technology 

a viable part of your business?

• What’s the business case for bringing the 

sun in?

Other chapters in this document will tell you about 

best practices to consider in using and selling solar 

technologies, how the technologies work, code 

and safety issues, and some of the history of solar 

technology development. Many of the points briefly 

raised in this chapter are described in greater detail 

in these later chapters.

Is it Time for Solar?

You’ve seen solar technologies on roofs for the 

last 30 years. But why should you as a builder 

bring these technologies into your business at 

this point in time? 

The solar industry has matured over the last 30 

years. Solar thermal has moved from a freewheeling 

industry of untested products and companies to 

an industry made up of resilient businesses that 

have weathered many economic cycles installing 

certified products. PVs have matured from technical 

novelties with a narrow niche in satellites and 

specialty products to power systems scaled for 

utilities, commercial buildings, and homes. 

Working with today’s technologies will give your 

company the confidence to take advantage of the 

ongoing advances that are emerging from the 

solar industry. 

THE CHECKLIST:

What’s happened in the last 30 years:

 ̨ Solar technologies are supported by codes 

and certifications.

 ̨ Solar thermal systems are objectively rated 

for performance.

 ̨ Training and certification is available for 

solar installers. 

 ̨ Building integrated systems have led to clean 

architecture and design.

 ̨ Better understanding of solar orientation means 

more flexibility in panel placement.

 ̨ Long lasting and dependable technologies are 

readily available.

 ̨ Solar companies know how to work with 

builders and consumers.

 ̨ Consumers love “green” buildings.

 ̨ Government at all levels and utilities 

support installations.

Technology and Installer 

Certifications and Ratings

Testing, certification, and codes programs apply 

to solar systems as well as installers. Sticking to 

systems that meet these standards takes much 

of the guesswork out of making solar part of 

your homes.

Builders (and consumers) can easily look up a 

comparison of solar thermal system performance. 

Under a voluntary program, solar thermal collectors 

individually, and water heating systems as a whole, 

are independently tested, certified, and evaluated by 

Integrated System Design 

– Want to Learn More?

By any economic or engineering 

yardstick, the best way to bring value to 

your customer and profit to your company 

is to make homes as energy efficient as 

possible. Energy efficiency resulting from 

a systems engineered design brings with 

it tremendous potential for increased 

consumer comfort, higher quality 

construction with reduced call backs, and 

reduced materials and installation costs 

that may offset the cost of increased 

efficiency, and, of course, a more affordable house with reduced energy bills. 

Energy efficiency also allows builders to 

differentiate their product in the market 

place. When economic cycles result in 

increased housing inventory, consumers 

will likely choose the highest quality 

houses available to them. Surveys show 

that consumers put a high value on 

energy efficiency. More information on 

systems engineered building design 

is available on the Building America 

website at www.buildingamerica.gov. 

Best practices manuals are available 

on the web site offering overviews 

of building practices for each of five 

climate zones (Baechler et al. 2004, 

2005a, 2005b, 2005c, and 2006). 

Building America’s Best Practices Guide, Vol. 2: 

Builders and Buyers Handbook for Improving 

New Home Efficiency, Comfort, and Durability 

in the Hot-Dry and Mixed-Dry Climates
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 1 / p.3

Managers’ Overview Chapter 1

the Solar Rating and Certification Corporation (SRCC). The 

SRCC provides system comparisons 

on a selected state basis. Ratings, 

product information, and educational materials are 

available at the SRCC website: www.solar-rating.

org. See Chapter 3 for more information.

The California Energy Commissions (CEC)

lists photovoltaic modules and inverters eligible 

for its incentives at www.consumerenergycenter.

org/erprebate/equipment.html. PV system installation is governed by the National Energy Code 

and components are ULTM listed.

The North American Board of Certified Energy 

Practitioners (NABCEP) offers solar thermal and 

PV installer certifications. For more information, 

including requirements, costs, and prerequisites, 

visit: www.nabcep.org/pv_installer.cfm.

The Interstate Renewable Energy Council 

(IREC) works to assure the competency and 

expertise of instructors, training programs, and 

continuing education classes emphasizing renewable energy, including solar applications. For a 

complete listing of renewable energy courses by 

state or technology, go to the IREC web site at: 

www.irecusa.org. 

“We are making homes that will last 

easily 100 years, because we are 

concerned about durability too. Many of 

things that make a home more energy 

efficient also make it last longer—making 

it more weather resistant, keeping out 

humidity and dampness problems.” 

Mark Bergman, owner of Tindall Homes 

in Columbus, New Jersey

Building Integrated PVs are products that produce 

electricity from solar power while serving as a 

construction material, such as roofing. (right) 

Photo courtesy of Decker Homes.

What are the Technologies?

Technologies are described in more detail in the remainder of this document. Here are working 

definitions of the two key technologies.

Solar Thermal: These systems collect and store solar energy as heat. The most common uses include 

heating water for domestic consumption, swimming pools and hot tubs, and space heating. Solar 

thermal systems for water heating consist of collectors, storage tanks, and plumbing systems. Solar 

thermal systems may also be used to directly heat air for space heating, but these systems are not yet 

mature for production building. 

Photovoltaic (PV) or Solar Electric: These systems use solar panels made of silicon and other elements 

to convert sunlight directly to electricity. There are no moving parts. The systems produce direct current 

(DC) electricity, the same type of power produced by batteries. Inverters convert the power to alternating 

current (AC) for powering typical household appliances. Inverters allow the systems to be connected 

to the electric utility distribution grid, so power can be sold to the utility when not used onsite. These 

grid-connected photovoltaics are the simplest and most common PV systems installed on houses. PV 

systems may also be connected to batteries allowing for electric storage.

“I love the construction, I love that 

they’re very well put-together. When 

you compare the energy savings across 

time, there was no question where to buy.” 

Owner of a Premier Homes solar home 

as quoted in Hanson and Bernstein 2006
p.4 / CHAPTER 1 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 1 Managers’ Overview 

Architecture, Design, and Orientation

Perhaps the biggest breakthrough in residential 

solar systems is in the area of buildings integration. 

Emerging in the last five years are PVs that can be 

installed in some roofing systems to make them 

nearly invisible. Some PVs actually become part of 

the roof rain-shedding system. Some PV and solar 

thermal systems are mounted very near—and parallel to—the roof at nearly all standard roof pitches. 

Visually, these systems appear like skylights. 

Thin film photovoltaics can be adhered directly to 

the flat part of raised seam metal roofs and do not 

change the roof profile. Efficiencies of thin film 

products are about half those of silicon-crystal 

arrays; however, the costs per watt are about the 

same. Researchers believe the potential for increasing thin film efficiency is tremendous.

Solar thermal systems have become better packaged. Many manufacturers package the majority 

of valves, sensors, and controllers that need to go 

inside the house on compact boards or within 

housings to provide clean, uncluttered appearances 

in utility areas.

Research shows that more architectural freedom 

exists for lot placement and solar exposure. Facing 

due south is best, but little efficiency is lost when 

either type of solar system is rotated towards the 

east or west, within reasonable bounds. Western 

exposure can be helpful for PVs to assist with utility 

peak load reduction.

Business Services

As solar systems have become better integrated with 

house design and visual appeal, solar businesses 

are becoming better integrated in the building 

industry. Solar companies have become adept 

at working with home builders and consumers. 

Some PV companies provide ongoing web-based 

monitoring of PV electric output, notifying consumers if problems arise. The best solar companies 

understand how:

• community development is staged, 

• to coordinate with other trades,

• to reduce costs through bulk materials 

purchase, delivery, and installation.

Government and Utility Action

Government at all levels supports solar initiatives. 

In some areas local governments are providing 

preferential treatment of permit applications for 

builders who include solar technologies in their 

homes. Utilities provide incentive payments for 

both solar system types and will often buy back 

photovoltaic electricity not consumed on site. 

“We don’t limit ourselves to putting 

these tiles on the backs of our houses. 

We put tiles on the front, back, or sides 

of the houses, wherever they will get the 

most solar gain. They blend in so well 

with the cement tiles that buyers have 

no objection to seeing them. You almost 

can’t tell they’re there.” 

“We had no difficulty at all working solar 

into the production schedule. The solar 

installation does not interfere with any 

other critical path in the construction 

process. It really doesn’t add any time 

for installation.”

Mark Fischer, Senior Vice President at Grupe, 

a California-based production builder

Although visible, solar thermal systems that 

sit above the roof have low silhouettes and 

resemble skylights.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 1 / p.5

Managers’ Overview Chapter 1

State governments and public benefit programs 

often provide incentives and tax credits. The 

federal government is currently providing tax 

credits. In combination, government and utility 

programs may pay a sizable portion of a solar 

system purchase price.

Along with incentives, jurisdictions are also considering code changes and programs to encourage 

solar development. Austin, Texas, is discussing 

possible code requirements to make all homes 

solar capable by 2015. California’s New Solar Home 

Partnership will require in 2011 that production 

builders offer PV systems to their customers or install 

equivalent PV systems elsewhere. The Solar Ready 

chapter describes measures that help make homes 

ready to accept solar technology after construction 

is complete.

Examples of Local Government Permit Incentives

Scottsdale, AZ 

All qualified green building projects receive fast track plan review service. 

www.scottsdaleaz.gov/greenbuilding/Incentives.asp

San Diego County, CA

The County does not charge for the building permit and plan check of residential photovoltaic systems.

www.sdcounty.ca.gov/dplu/greenbuildings.html

Marin County, CA

The incentives include waiver of the Title 24 energy fee and fast-track permit processing.

www.co.marin.ca.us/depts/CD/main/comdev/advance/best/incentive.cfm

Why Utilities Care About Solar Energy

Electric utilities care about ZEHs and solar energy for two reasons:

First, if it can be acquired cost effectively, solar energy 

is a non-polluting source of power equivalent to 

other sources such as energy efficiency or coal-fired 

generators. This is the key motivation for solar thermal 

programs at Lakeland Electric in Florida and the 

Sacramento Municipal Utility District in California. 

Second, PV systems can be designed to be 

especially good at reducing peak demand. 

Peak demand is the time of day when 

the most energy is required and it is most 

expensive for the utility to purchase. 

0 -1.0

12 1 2 3 4 5

AM PM

6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11

500

1,000

1,500

2,000

2,500

3,000

-0.5

-0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5 kW

Avg. High Temp = 98°F

Average 15 Minute Interval Peak Demand ZEH vs. Non-ZEH July, 2005

Avg. Min Temp = 65°F

System Peak MW

Average of ZEH Net Grid Load (kW)

Average of Power Produced by PV (kW)

Average of Non-ZEH Net Grid Load (kW)

California’s New 

Solar Homes Partnership

California’s New Solar Home Partnership... “is intended to transform the 

new home industry and have consumers 

ask for solar in their new home to lower 

their energy bills,” said Energy Commission Chairman Jackalyne Pfannenstiel. 

A new home that qualifies for the New 

Solar Homes Partnership will be at least 

15 percent more efficient than Title 24, 

California’s current energy efficiency 

standards. Qualified homes will include 

Energy Star-rated appliances, and a 

roof top PV system with a 10-year 

warranty to protect against defective 

workmanship or system and component 

breakdown. The program also includes 

incentive payments.

The partnership encourages builders to 

install PV systems on new homes as a 

standard feature, just like granite countertops. Beginning in 2011, builders will 

be required to offer solar as a standard 

feature in new home developments of 

50 or more. Currently, California has 

over 23,000 photovoltaic system installations, of which, 1,500 are installed on 

new homes. 

The New Solar Homes Partnership is 

a component of the California Solar 

Initiative, which was signed into law in 

2006. The California Energy Commission 

and the Public Utilities Commission each 

administer coordinated elements of the 

Initiative. For updates about the New 

Solar Homes Partnership and a copy 

of the program guidebook, visit 

the Go Solar California website at: 

www.gosolarcalifornia.ca.gov.

Solar thermal meter used by Lakeland Electric. 

Photo courtesy of Jeff Curry of Lakeland Electric. 

In addition to saving about 60% of a typical home’s 

energy bill, ZEHs at Premier Gardens substantially 

reduce peak demand. In July 2005 when Sacramento 

experienced its hottest July on record, Premier Gardens 

had peak demands that were 75% less than typical 

new houses at 4.5 kW peak load.
p.6 / CHAPTER 1 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 1 Managers’ Overview 

Reliability and Efficiency

Solar thermal technologies are well proven generators of hot water. In Hawaii, the most expansive 

solar water heating market in the U.S., the Hawaiian Electric Company has found that with nearly 

120,000 installations, less than 0.2% of systems 

have resulted in warranty claims (2 in 1,000). 

Turning that number around, over 99.8% of solar 

water heater systems perform without a consumer 

claim (Richmond 2005).

As photovoltaic modules have proven their reliability, warranty periods have increased, with 25-year 

warranties common since 1999 (Wohlgemuth 

2003). Based on a world-wide assessment, the PV 

module failure rate is down to 0.01% (1 in 10,000) 

per year (IEA 2002). 

Inverters form the gateway between the photovoltaic 

system and the electric utility grid. Modern inverters 

have reached efficiency levels near 95% at converting DC power to AC power. Research suggests that 

newer inverters in Europe last 10 to 15 years (IEA 

2002; Wilk 2002; Nordmann, Jahn, and Nasse 2004). 

New inverters in the U.S. will be released in 2008 

that carry a ten-year warranty.

Another recent development expected to further 

improve PV performance is plug-and-play connectors yielding more reliable in-field wire connections 

(IEA 2005).

European experience has shown that overall system 

performance as a percentage of power production in 

comparison to rated capacity (including modules, 

inverters, mounting, and wiring) rose from about 

60% in systems installed before 1995 to 80% in 

systems installed after 1995 (Nordmann, Jahn, 

and Nasse 2004). Performance at 80% of rated 

capacity continues to be a reasonable expectation 

for PV systems. 

The Business Case

Solar thermal technology is mature and reliable 

and is now being packaged in ways that make it 

more easily incorporated into production building. 

Anticipated solar thermal technologies are expected 

to push costs down. PV has gained consumer, 

government, and utility attention and is emerging as 

a reliable product that easily fits into home designs. 

So, technically, these products are available and 

can be strong additions to home offerings.

This section now looks at the business case for solar 

technologies and opportunities for a comparative 

advantage for builders’ business performance. 

As noted earlier, energy efficiency and systems 

integrated design are important parts of the ZEH 

package. By themselves, those elements make 

good business sense and they should be used by 

all builders to increase building performance and 

consumer value. The business case for adding solar 

to your product mix requires looking at how well 

homes equipped with solar sell, how consumers 

respond to solar communities, other benefits that 

may result from consumer responses or incentives, and competitive advantages that accrue to 

production builders.

From a national security, consumer value, company 

profit, or any other perspective, energy efficiency 

makes sense. But today’s ZEH homes takes energy 

efficiency three steps further: 

• First, by producing renewable energy, solar 

technologies give consumers a positive 

contribution back to their community. A 

common benefit identified by consumers is 

environmental protection.

• Second, even though it is no longer an 

obvious add-on to a house, solar technologies 

are visible badges demonstrating lifestyle 

choices and quality construction; and

• Third, while PV is costly alone, in combination with 30% to 40% improvements in 

energy efficiency, it provides a positive cash 

flow in combination with utility bills and 

mortgage payments.

Lesson Learned from ZEH Communities

Consumers at every price point embrace ZEH 

when they have the opportunity. California has the 

most developed housing market for ZEHs with the 

most consumers responding to product offerings. 

“We all want to make money but at some 

point as a society we have to evaluate 

what we are doing. Our homes save more 

than 60% of power over houses built to 

the state code. Over the lifetime of the 

house, our (Tindall) homes will save more 

in energy costs than the purchase price 

of the house. If we all did this, we could 

make a big difference.”

Mark Bergman, owner of Tindall Homes 

in Columbus New Jersey.

With an internet connection, PV system 

performance can be verified at any time from 

most anywhere.

“The PV system was inspected 

while the city inspectors were already

on site doing other inspections. That may 

vary by jurisdiction, but that was the case 

in Rocklin.”

Mark Fischer, a senior vice president at Grupe, a 

Stockton, California-based production builder.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 1 / p.7

Managers’ Overview Chapter 1

Homebuyer quotes from SheaHomes: 

“It’s best to integrate the solar electric 

system into the entire home purchase 

rather than having it offered as an 

option in a piecemeal way. It should 

all be rolled into one.” 

“We wanted to get the house because 

the system was already there. We didn’t 

have to decide about it. We’re glad it is 

here. We’re lucky to have the PV.”

“We thought about offering solar as an 

option, but I like the way it makes us 

unique, and I didn’t think it would be 

successful as an option based on how 

other builders have done with it. When 

you make it standard, buyers accept it 

without hesitation. Once you decide to 

do a whole development with solar, its 

easy to work it into your schedule, and 

to train your subcontractors. And we 

decided it was the right thing to do.”

Mark Fischer, a senior vice president 

at Grupe, a Stockton, California-based 

production builder

Building America has worked with builders in many 

ZEH projects in California. Four ZEH communities with 100 to 300 houses each offer many 

lessons. All four builders outsold their competition. 

Consumer attitudes and energy performance have 

been documented at two of the projects (Farhar 

and Coburn 2006; Coburn, Farhar, and Pratsch 

2006; Baccei 2006). And, the builder of a third 

community presented business implications at the 

2007 PCBC Builders conference in San Fracisco. A 

more detailed description of market studies and 

sales strategies is found in Chapter 2: Solar Sells. 

Some of the findings are summarized here.

• ZEH sells faster – All four ZEH communities 

report selling homes at a faster clip than nearby 

projects. One builder started selling in early 

2006 and is outselling its competitors by over 

2.5 times.

• Selling homes faster saves the builder 

money – Grupe Homes has reported the financial 

impacts from an increased sales rate. Grupe 

achieved a sales rate of 4.6 home sales per month 

versus 1.9 for their competitors, a rate 2.5 times 

faster than competing projects in the Whitney 

Ranch Master Plan. Grupe has calculated that 

its increased costs of $2.6 million due to energy 

efficiency, solar PV, and green features, would be 

paid off in less than 9 months due to the greater 

sales rate.

• Consumers are interested – Surveys show 

consumer interest in PV and solar thermal technologies. In a survey of Colorado homeowners 

conducted in 2000, 57% were favorable to installing PV on existing houses and 16% were highly 

motivated, even when informed about costs 

(Farhar and Coburn 2000). National studies, 

and detailed analyses of specific communities, 

show that consumers are willing to purchase 

energy efficient and solar technologies as long 

as costs are offset by utility savings.

• Educate consumers – Builders are in a 

strong position to sell solar technologies, but 

must inform consumers. In one survey, over 

three-fourths of all respondents indicated that 

if their builder had recommended solar thermal 

they would have either seriously considered it 

or wanted to learn more.

• Strive for 50% savings – One observation 

of ZEH projects is that consumers respond to 

achieving at least 50% reductions in energy 

consumption through a combination of energy 

efficiency and solar technologies.

Premier Gardens solar-powered homes. Photo 

courtesy of the Sacramento Municipal Utility District.

STANDARD HOME ZERO ENERGY HOME

$3,160 $3,240

$173

TOTAL MONTHLY = $3,333

TOTAL MONTHLY = $3,320

< MORTGAGE BILLS >

< E

< $5 ENERGY EFFICIENCY

< $25 SOLAR HOT WATER

< $50 SOLAR PV 2.4 kW

NERGY BILLS > $80

Consumer monthly costs for Zero Energy Homes need be no more than typical homes. 

Energy savings and incentives can offset added upfront costs, as shown in this example.

Consumers in ZEH developments and in national surveys show a strong willingness to purchase energy efficiency and solar 

systems if their overall cash flow is positive (Farhar and Coburn 2006; Coburn, Farhar, and Pratsch 2006; NAHB RC 2006).
p.8 / CHAPTER 1 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 1 Managers’ Overview 

• ZEH consumers are satisfied – Market 

studies of Premier Gardens community has 

found that ZEH consumers tend to be higher 

educated and more satisfied than a neighboring 

community. Other market research has shown 

that highly satisfied consumers tend to recommend their builder much more frequently than 

other customers.

• Incorporate solar into standard package

– A detailed study was done of homeowner 

attitudes in a ZEH community in San Diego 

built by SheaHomes (Farhar and Coburn 2006; 

Coburn, Farhar, and Pratsch 2006) that includes 

both solar thermal and PV. The builder in this 

project concluded that it is more profitable to 

offer solar systems as standard features, not as 

an optional package.

• Consumers prefer standard package 

– Consumers also have shown a preference 

for making both PV and solar thermal standard 

features. Some SheaHomes customers noted 

that it took much of the guesswork out of their 

purchase. Other survey findings support this 

conclusion. One study found that: “Consumers 

are much more likely to purchase a solar system 

from the builder as the home is being built 

because they view the installation as being 

much more simple and safe in terms of the roof 

warranty during the construction stage (Ghent 

and Keller 1999).”

• ZEH homes appreciate more – An important piece of economic data for homeowners 

is value appreciation. For many consumers, their home is their largest investment. 

SheaHomes went up in value by over 55%, 

compared to an increase of about 45% for 

a nearby community. The original cost of a 

SheaHomes house was about $40,000 less than a 

comparison home but ended up at slightly higher 

resale value (Farhar & Coburn 2006).

Production Builder Advantages

Successful production builders excel in designing 

homes, developing construction processes, and 

selecting materials to drive down costs and increase 

consumer value. These traits apply to installing solar 

and energy efficiency features in new homes. And 

production builders have tremendous advantages 

in planning and structural access. These features 

are described in Chapters 3 and 4. 

Production builder advantages show up in lower 

solar equipment costs. Studies of California’s PV 

incentive programs show that systems installed in 

large new home developments are, on average, far 

more economical than retrofitted systems (Wiser, 

Bolinger, Cappers and Margolis 2006). Systems 

installed (or planned for installation) under the 

California Energy Commission’s program in large 

new residential developments (totaling 1,946 

systems) have costs about 13% less ($1.2/Watt) on 

average, compared to the general retrofit market (in 

2004 dollars in costs per watt of AC power produced). 

Similarly, 340 installations used in affordable 

housing applications, which often involve new 

construction and presumably enable bulk system 

installation, show costs that are 21% ($1.9/Watt) 

lower than the general retrofit market. 

Researchers working with solar thermal have 

suggested that new home production builders could 

reduce water heating system costs by up to 40% 

in comparison to retrofit markets (Burch 2005). 

These researchers are working on new polymer 

technologies that could bring costs down by up 

to another 50%.

Another builder advantage is the availability of 

consumer financing in the form of a mortgage. In 

the Colorado survey described earlier, responders 

identified utility bills and mortgage payments 

as preferred methods of paying for PV systems. 

Consumers in ZEH developments and in national 

surveys show a strong willingness to purchase 

energy efficiency and solar systems if their overall 

cash flow is positive (Farhar and Coburn 2006; 

Coburn, Farhar, and Pratsch 2006; NAHB RC 2006). 

In other words, they are interested in ZEH features, 

as long as their increased mortgage payment is 

offset by reduced utility costs. 

Advantages production builders bring to ZEH 

include:

Desire More Information 

on Solar Incentives? Visit 

the Database of State 

Incentives for Renewable 

Energy (DSIRE)

Established in 1995, DSIRE is 

maintained by the North Carolina 

Solar Center (NCSC) and the Interstate 

Renewable Energy Council (IREC). This 

online database contains information on 

renewable energy policies administered 

by federal, state, and local organizations 

as well as a comprehensive list of 

energy-efficiency incentives. The homepage features a U.S. map that allows 

the user to click on a state and pull 

up a summary of programs, financial 

incentives, regulations and policies, 

eligible sectors, contact information, and 

more. DSIRE also contains information 

on Federal financial incentives (not 

including research and development or 

outreach programs) and summary maps 

showing national trends in renewable 

energy incentives. The DSIRE database 

is updated frequently, often on a daily basis. 

You can find DSIRE at www.dsireusa.org.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 1 / p.9

Managers’ Overview Chapter 1

“In a few years, you will see 

this everywhere.” 

Mark Fischer, senior vice president at Grupe, 

a Stockton, California-based production builder.

• Precise building design and timing allow 

for clear solar system specification and bulk 

ordering of systems without long-term storage 

requirements.

• Ready access to framing and roofs at the right 

time in the construction sequence allow for easy 

installation of piping runs, control wiring, and 

roof mounts. 

• Ability to identify trades, staff, or subcontractors to coordinate timing and avoid problems 

with protecting southern exposures from roof 

and plumbing vents, maintain roof space for 

collectors, and design pipe runs. 

• Bulk delivery of supplies and equipment to the 

construction site for installation of collectors.

Declining Costs

Solar thermal products are the result of a mature 

industry. The costs for domestically produced 

products has stabilized. However, new products 

from Asia and Europe are entering the U.S. market. 

In addition, researchers have developed new 

polymer-based collectors that may reduce costs 

by up to 50% (Burch and Hillman 2006). These 

new products are likely to bring innovations and 

increased competition.

PV system costs have declined substantially over 

time. In California, in systems receiving funds from 

the Energy Commission, costs have declined from 

more than $12 per watt (in 2004 dollars in costs per 

watt of AC power produced) in 1998 to less than $9 

per watt for 2004-2005, representing a 7.3 percent 

annual decline. In Japan, costs for standard 3-kW 

residential systems averaged roughly $7.4 per watt in 

2004, which is $1.4 per watt lower than similar costs 

in California (Wiser, Bolinger, Cappers and Margolis 

2006). Japan’s costs suggest there is still room in 

today’s technologies for further cost reductions.

Markets Are Available for 

Renewable Energy Credits

Financial markets have developed that allow for the 

sale and purchase of the environmental benefits that 

accrue from ZEHs. The financial instruments used 

to transfer the benefits are called Renewable Energy 

Credits (RECs) or green credits. Utilities and corporations purchase these credits either to offset their own 

emissions or to help them meet the requirements of 

regulators. As with all markets, the value of RECs 

varies over time. In some cases, incentives that 

come from utilities or state or regional programs 

sometimes include provisions for REC ownership. 

In exchange for the incentive, these entities take 

ownership of the RECs. But, if utilities or agencies 

have not laid claim, RECs may be calculated and 

sold as part of builders’ business plans. RECs may 

be claimed for both solar thermal and PV systems. 

So, incentives offered for one type of system may 

not have claimed all available RECs.

For more information about state REC markets 

and programs, visit the DSIRE website, described 

on page 8 of this chapter.

DOE’s Green Power Network offers information 

on markets, brokers, and state programs, and can 

be found at: www.eere.energy.gov/greenpower/

markets/certificates.shtml?page=0.

The Bottom Line – 

Positioning in the Market 

and for the Future

Experience in California, the most developed ZEH 

market in the nation, suggests that zero energy homes 

can outsell their counterparts. Houses that cut energy 

bills by at least 50% with a combination of energy 

efficiency and solar technologies may be the most 

attractive to consumers. Government incentives and 

utility power purchases go far to reduce costs, and 

markets exist to sell RECs for even more income.

Incorporating solar technologies and energy efficiency 

into your houses can help sales. The case studies 

near the end of this document offer examples of ZEH 

communities and individual dynamic prototypes. See 

how these builders have used ZEH for a competative 

advantage in their markets. Check out the resources 

listed at the end of this chapter or visit the Building America website at www.buildingamerica.gov

for more information on getting started.

“We are saving the customer about 

$2,500 a year in utility bills on 

these big homes.” 

Mark Bergman, owner of 

Tindall Homes in Columbus, New Jersey.

“Before you consider solar, you need to 

spend the money on conservation. We 

have taken Herculean steps to reduce 

the demand, everything from installing 

a ground source heat pump for heating 

and hot water, to air-to-air heat 

exchangers on the ventilation system, 

to buying compact florescent bulbs and 

the most energy efficient ENERGY STAR 

appliances on the market.”

Sam Garst, Olympia, Washington
p.10 / CHAPTER 1 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 1 Managers’ Overview 

Builders that pursue zero energy homes are focusing on the future. Their experience with PV and solar 

thermal technologies, and the systems integrated building design approach, allows them to confidently 

evaluate and incorporate new technologies as they emerge in the marketplace. Solar technologies and 

high performance homes position builders in the market as innovative and value-focused. 

Resources and References

Baccei, Bruce. 2006. “Impacts of Zero Energy Homes on Buyers and Owners.” Solar 2006 

Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, 

Boulder, CO.

Baechler, Michael and Pat Love. 2004. Building America Best Practice Series: Volume 1 – 

Builders and Buyers Handbook for Improving New Home Efficiency, Comfort, and Durability 

in the Hot and Humid Climate, Version 1. U.S. Department of Energy, Washington, D.C. 

www.buildingamerica.gov.

Baechler, Michael, Z. Todd Taylor, Rosemarie Bartlett, Theresa Gilbride, Marye Hefty, 

Heidi Steward, and Pat Love. 2005a. Building America Best Practice Series: Volume 4 

– Builders and Buyers Handbook for Improving New Home Efficiency, Comfort, and 

Durability in the Mixed Humid Climate, Version 1. U.S. Department of Energy, Washington, D.C. 

www.buildingamerica.gov.

Baechler, Michael, Z. Todd Taylor, Rosemarie Bartlett, Theresa Gilbride, Marye Hefty, 

Heidi Steward, and Pat Love. 2005b. Building America Best Practice Series: Volume 

3 – Builders and Buyers Handbook for Improving New Home Efficiency, Comfort, and 

Durability in the Cold and Very Cold Climates, Version 1. U.S. Department of Energy, 

Washington, D.C. www.buildingamerica.gov.

Baechler, Michael, Z. Todd Taylor, Rosemarie Bartlett, Theresa Gilbride, Marye Hefty, 

Pat Love. 2005c. Building America Best Practice Series: Volume 2 – Builders and Buyers 

Handbook for Improving New Home Efficiency, Comfort, and Durability in the Hot-Dry and 

Mixed Dry Climates, Version 1. U.S. Department of Energy, Washington, D.C.

www.buildingamerica.gov.

Baechler, Michael, Z. Todd Taylor, Rosemarie Bartlett, Theresa Gilbride, Marye Hefty, 

Heidi Steward, and Pat Love. 2006. Building America Best Practice Series: Volume 5 

– Builders and Buyers Handbook for Improving New Home Efficiency, Comfort, and 

Durability in the Marine Climate, Version 1. U.S. Department of Energy, Washington, D.C. 

www.buildingamerica.gov.

Burch, Jay and Tim Hillman. 2005. “Cold-Climate Solar Domestic Water Heating Systems: 

Life-Cycle Analyses and Opportunities for Cost Reduction.” Solar 2005 Conference Proceedings, 

edited by R. Campbell-Howe. American Solar Energy Society, Boulder, CO.

California New Solar Home Partnership information can be found at www.gosolarcalifornia.ca.gov.

Coburn, Timothy, Barbara Farhar, and Lew Pratsch. 2006. “Comparative Analysis of Utility 

Consumption and Costs of Near-ZEHs and Comparison Homes in California.” In Proceeding of 

the 2006 ACEEE Summer Study on Energy Efficiency in Buildings, Washington, D.C. 

“We are selling at a pace that is 

double that of our competition at 

Whitney Ranch. If just 20% of this 

increased sales rate is due to the solar 

and green features, then the Grupe 

Green program has paid for itself.”

Mark Fischer, senior vice president at Grupe, 

a Stockton, California-based production builder.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 1 / p.11

Managers’ Overview Chapter 1

DSIRE is a website with information about incentives for renewable energy and energy efficiency. 

Available at www.dsireusa.org.

Farhar, B.C. and T.C. Coburn. 2006. A New Market Paradigm for Zero-Energy Homes: The 

Comparative San Diego Case Study. NREL/TP-550-38304-01. Prepared by the National Renewable 

Energy Laboratory for the U.S. Department of Energy. www.nrel.gov/docs/fy07osti/38304-01.pdf

Hanson, M. and M. Bernstein. 2006, The Role of Energy Efficiency in Homebuying Decisions: 

Results of Initial Focus Group Discussions. WR-352-CON, Rand Corp.

Farhar, Barbara, and Timothy Coburn. 2000. A Market Assessment of Residential Grid-Tied PV 

Systems in Colorado. NREL/TP-550-25283. National Renewable Energy Laboratory, Golden, CO.

Ghent, P. and C. Keller. 1999. A Comprehensive Review of Market Research on Solar Water 

Heaters.NREL/SR-550-27123. Prepared for the National Renewable Energy Laboratory by Focus 

Marketing Services, Westlake Village, CA.

International Energy Agency (IEA). 2005. Trends in Photovoltiac Applications: Survey Report 

of Selected IEA Countries Between 1992 and 2004. IEA-PVPS T1-14:2005.

International Energy Agency (IEA). 2002. Reliability Study of Grid Connected PV Systems 

Field Experience and Recommended Design Practice. Report IEA-PVPS T7-08: 2002, Edited by 

Hermann Laukamp, www.iea-pvps.org/products/download/rep7_08.pdf.

National Association of Home Builders Research Center (NAHBRC). 2006. The Potential 

Impacts of Zero Energy Homes. Prepared for the National Renewable Energy Laboratory, 

Golden, CO.

Nordmann, Thomas, Ulrike Jahn and Wolfgang Nasse. 2004. “Performance of PV Systems Under 

Real Conditions.” European Workshop on Life Cycle Analysis and Recycling of Solar Modules.

Richmond, Ron. 2005. Presentation at the 2005 Solar Power Conference, October 5-7, 2005, 

Washington, D.C.

Szaro, Jennifer, Carol Emrich, William Wilson, and James Dunlop. 2002. Photovoltaic 

Systems Performance and Reliability Database. Southeast Regional Experiment Station 

– Florida Solar Energy Center, Cocoa, FL.

Wilk, Heinrich. 2002. “Reliability of PV Systems in Austria, Lessons Learned.” In Operational 

Performance, Reliability and Promotion of Photovoltaic Systems: Proceedings of October 2001 

Workshop. IEA-PVPS T2-03:2002. Prepared by Jahn Ulride and Wolfgang Nasse. International 

Energy Agency (IEA).

Wiser, Ryan, Mark Bolinger, Peter Cappers, and Robert Margolis. 2006. Letting the Sun 

Shine on Solar Costs: An Empirical Investigation of Photovoltaic Cost Trends in California. 

LBNL-59282, NREL/TP-620-39300. Prepared for the U.S. DOE by Lawrence Berkeley National 

Laboratory, Berkeley, CA, and the National Renewable Energy Laboratory, Golden, CO. Available at 

http://eetd.lbl.gov/EA/EMP.

Wohlgemuth, John H. 2003. “Long Term Photovoltaic Module Reliability.” NCPV and Solar 

Program Review Meeting 2003. NREL/CD-520-33586, pp. 179-182. National Renewable Energy 

Laboratory, Golden, CO.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 2 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 2.

Solar Sells: Closing the Deal

Building America Best Practices Series

Solar can be a great selling tool if sales staff know how to use it: “If you are going 

to put it in, be prepared to train your whole organization on why it’s a good deal, 

especially sales staff. You have to train them so that they can tell potential buyers 

why solar is so great.”

Mark Fischer, a senior vice president at Grupe, a Stockton, California builder

Most real estate marketing professionals try to link homebuyers with properties that meet consumer 

expectations. With ZEH homes, sales staff must help buyers expand their expectations and raise the bar 

in expected home performance. Consumers select products and new innovations that offer benefits they 

desire. When selling ZEH, marketers must help consumers understand these benefits.

This chapter presents information that explains why consumers care about energy costs and efficiency. 

It examines the advantages that production builders have for installing solar thermal and photovoltaic 

systems. And this chapter examines how some builders are selling ZEH homes.

Sales display in the education center at the 

“Zero Energy” Fallen Leaf community in 

Sacramento, California. 

“Solar is definitely making us more 

competitive; there is no doubt about 

that. People just need to be better 

educated about it (solar). For the most 

part, most people don’t understand the 

true benefits.” 

Sheri Gage, sales manager at Premier 

Meadows, a community in California

“We sold 23 of our first 30 homes in 

the first three months, even though the 

market in Sacramento is very slow right 

now; it is the slowest housing market in 

the country. Our project is doing better 

than most of our competitors.” 

Mark Fischer, a senior vice president at 

Grupe, a California-based production builder 

producing 200 to 300 homes per year

“It is an opportunity to set ourselves 

apart as a small builder. The market will 

be wanting more energy efficiency as 

time goes on and we want to stay 

ahead of it.” 

John Ralston, Vice President of Sales 

and Marketing for Roseville, California-based 

Premier Homes

Builders’ Brief

• Consumers select products and new 

innovations that offer benefits they desire.

• Consumers care about value and are willing 

to pay for it.

• Real-world experience shows efficiency and 

ZEH contribute to customer satisfaction.

• Highly satisfied customers refer their builders 

to twice as many people.

• Energy reductions greater than 50% seem 

to “close the deal” for many consumers.

• Homeowners brag about their ZEH and 

low utility bills.

• Solar is a tangible badge of efficiency, 

innovation, and green building.

• Educate buyers with green showrooms.

Installers’ Brief

• PV and solar thermal companies may have more 

experience than the builder with ZEH technologies 

and can help educate sales staff and consumers. 

• Sales staff must tell the ZEH story. Provide 

them with materials to help educate 

consumers about the benefits of energy 

efficiency and solar technologies.

• Provide sample products to put in showrooms.

• Produce brochures, videos, and signs that 

show consumers how they will save money, be 

more comfortable, and help the environment.

• Collect testimonials that marketers can use to 

educate consumers.

• Provide materials for the homeowners 

manuals that help consumers understand and 

maintain their system.
p.2 / CHAPTER 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 2 Solar Sells: Closing the Deal 

Efficiency, Comfort, and 

Consumer Satisfaction

Wouldn’t it be great if, for every home you sold, 

you added a new sales associate to bring in more 

leads? That is what energy efficiency can do. Happy 

customers will sell your products for you. And energyefficient homes make happy customers. Compared 

to standard homes, energy-efficient homes cost less 

to own, are more comfortable to live in, and require 

less maintenance. Customers like these benefits and 

it contributes to their satisfaction.

Market research shows:

• 10% to 30%, and sometimes more, of builders’ 

sales come from referrals (Farnsworth 2003). 

• J.D. Power found that truly delighted home 

buyers (those rating their builders a 10 on a 

10-point scale) recommend their builder to 

nearly twice as many people as the average 

new-home buyer (J.D. Power 2005).

• Energy efficiency is the number one upgrade 

sought by homebuyers of new homes 

(Professional Builder Magazine 2001).

• Nearly 90% of new homebuyers are willing 

to spend more for energy efficiency 

(Johnston 2000 and NAHB 2002).

• Buyers rate energy efficiency as a home 

builder’s most important product-related 

reason for referring new customers 

(Professional Builder Magazine 2003).

Solar Technologies: The Rest of the Story

Energy efficiency is important to consumers, but it 

is only half the story of a ZEH. Consumers respond 

well to solar technologies that make up the other 

part of the story. Chapter 1: Managers’ Overview 

summarizes a variety of market studies and lessons 

learned from ZEH communities. The bottom line is that 

ZEH communities outsell their neighboring non-ZEH 

communities. And, even when neighboring houses 

are energy efficient, consumers in ZEH communities are more satisfied with their home purchase 

(Baccei 2006).

Market research suggests that consumers are 

interested if asked about PV technology. A survey 

of Colorado residents conducted in 2000 found that 

57% were favorable to installing PV on existing 

houses (Farhar and Coburn 2000). 16% of the 

surveyed homeowners were found to be highly 

motivated to purchase PV systems. 

But, sales staff need to inform consumers about 

energy efficiency and solar technologies. After 

learning about current technology and product 

options, for example, consumers are more likely to 

consider purchasing a solar water heating system 

(Ghent and Keller 1999). In a study of Phoenix 

and Las Vegas recent home buyers, the number 

who said they were extremely or somewhat likely 

to buy a solar water heater rose from 60% to 74% 

after an interview session that included showing 

the consumers photos and a description of solar 

panels (SMC 1999).

In a national sample survey of recent homebuyers, 

78% of the respondents agreed that, if their builders 

had recommended solar water heating for their 

new homes, they would have seriously considered 

it or would have wanted to learn more about it 

(NAHBRC 2004).

Four ZEH Builders 

Out Sold Their Competition

California has the most developed housing market 

for ZEHs. Building America has worked with builders in many ZEH projects in California. Four of the 

largest ZEH communities offer lessons learned in 

consumer response. Consumer attitudes and energy 

performance have been documented for two of 

the projects (Farhar 2006; Baccei 2006). Informal 

discussions with builders and observations offer 

insights into the other two communities. Three of 

these home builders are featured in case studies at 

the end of this handbook.

“I couldn’t imagine moving [except to 

another] solar energy home.”

“Yeah, for us it was the energy package, 

first and foremost. And we were pretty 

much set on that. That was what made 

our decision easier.” 

Owners of a Premier Homes ZEH home as 

quoted in focus group study by Hanson, M 

and M. Bernstein (2006)

The builder with the top customer 

satisfaction rating in the nation in 2003, 

Pulte Homes of Phoenix, is a Building 

America partner offering ENERGY STAR 

qualified homes. Pulte’s Phoenix division 

has had one or more positive referrals 

from 93% of its homebuyers. In short, 

what Pulte has done is bundle energy 

efficiency with other attributes valued 

by their consumers, such as economic 

value, comfort, and quality construction.

“The sales office is actively marketing 

the energy efficiency of our homes; 

they state it in the first five sentences 

to the potential buyer.”

John Moynihan New Jersey solar contractor 

who works closely with solar home builder 

Mark Bergman.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 2 / p.3

Solar Sells: Closing the Deal Chapter 2

“Solar electric power adds value to the 

homes we build. By giving homeowners 

the tools they need to generate their 

own electricity, we’re enabling them to 

save money on their utility bills. We’re 

also differentiating our homes in the 

marketplace.”

John Suppes, President of Clarum Homes, 

which is building ZEH developments in 

California and Arizona. 

Sales staff receive training at Bob Ward Homes 

Maximum Efficiency Greenland Model. (Photos 

courtesy of Joseph Wiehagen of the National 

Association of Home Builders Research Center.) 

The Other Side of the Coin – What Consumers See

The message for selling ZEH is overwhelmingly positive. Energy efficiency technology contributes to 

better comfort, more durable construction, and lower energy costs. Solar technologies save money, are a 

badge of innovation, and produce power. ZEH are good for the environment and good for national security.

But there is another side to the coin. Consumers see messages all the time that influence their thinking. 

These messages relate to climate change, blackouts, rising utility prices, and energy shortages. Here is 

a sampling of recent findings and headlines.

This graphic, based on a figure published in 2001 by the United Nations-backed Intergovernmental 

Panel on Climate Change, has been dubbed the “hockey stick” chart due to its shape. In June 2006 the 

National Research Council found global mean surface temperatures were the highest of the last four 

centuries and it is plausible that the northern hemisphere was warmer during this time than during any 

comparable period over the preceding millennium (NRC 2006).

Recent Headlines from around the United States.

“Sweltering California declares power emergency: Rolling blackouts possible, 

100,000 still without electricity” MSNBC, July 24, 2006

“Record oil prices fueling interest in alternative energy investments”

San Antonio Business Journal, June 18, 2006

“Electric rate jolt coming”

by Paul Adams, The Baltimore Sun, February 20, 2006

“Cold comfort: As price of gas rises, consumers rethink typical heating methods” 

Atlanta Journal-Constitution, October 25, 2005

“Electric Agency Acknowledges Flaws in System” 

The New York Times, February 20, 2004

”Few Indications Efforts to Cut Blackout Risks Are Under Way”

The New York Times, December 13, 2003

“Under Deregulation, Montana Power Price Soars” 

The New York Times, August 21, 2003

“PG&E Files for Bankruptcy - $9 billion in debt, firm abandons bailout talks with state”

by David Lazarus, San Francisco Chronicle, April 7, 2001

“Electrical Bills Rise Joltingly”

San Diego Union-Tribune, June 29, 2000

“The market was beating us up, solar 

will set us apart.”

Don Rives, Sales Manager at Premier Homes 

Premier Gardens and Premier Bay Estates
p.4 / CHAPTER 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 2 Solar Sells: Closing the Deal 

SheaHomes, Clarum Homes, Premier Homes, and 

Grupe Homes all report selling homes at a faster clip 

than nearby projects. Early in project development, 

Grupe Homes was outselling their competitors by nearly 

2-to-1 based on internal company reports. In autumn 

of 2006, they were still selling about 50% faster.

Clarum Home’s absorption rate (the pace at which 

they sell homes) is about twice the state average. 

Last year they were outselling the state average 

by about 66%. In one ZEH community, Clarum 

planned on a three-year development schedule, but 

sold out in the first year. This project in Watsonville, 

California, is the largest ZEH community in the U.S. 

These findings are based on builder interviews and 

observations of the California market. 

Mark Fischer of Grupe Homes notes that consumers 

are attracted to achieving at least 50% reductions in 

energy consumption, achieved through a combination of energy efficiency and solar technologies.

Market studies of Premier Gardens found that 

solar consumers tended to be higher educated 

and more satisfied than a neighboring community 

(Baccei 2006).

Make Solar a Standard Feature

All 306 homes in the SheaHomes development 

included solar thermal hot water and 120 homes 

included PV systems. The builder in this project 

concluded that it is more profitable to offer solar 

systems as standard features, not as an optional 

package. Consumers agreed, noting that making 

solar a standard feature took much of the guesswork 

out of their purchase. Based on and analysis of 

utility bills, energy costs in the SheaHomes community were 14% to 54% less than the comparison 

community (Farhar and Coburn 2006).

The SheaHomes result is backed up by a review of 

marketing studies on solar thermal by Ghent and Keller 

(1999), who reported that consumers preferred that 

new home builders offer solar thermal options. One 

study found that: “Consumers are much more likely 

to purchase a solar system from the builder as the 

home is being built because they view the installation 

as being much more simple and safe in terms of the 

roof warranty during the construction stage.”

Value Appreciation

For many consumers, their home is their largest 

investment. SheaHomes went up in value by over 55%, 

compared to about 45% for a comparison community. 

The original cost of the SheaHomes houses was about 

$40,000 less than the comparison homes but ended 

up at slightly higher resale costs. 

Clarum Homes of Palo Alto, CA, is 

the builder of the nation’s largest 

zero energy homes community, Vista 

Montana, with 177 PV powered singlefamily homes and 80 PV townhouses in 

Watsonville, California, sold out in 2004.

“All 257 homes sold out in the first year 

they were on the market (rather than 

the three years planned). Prices were 

initially advertised as ranging from 

$379,000 to $499,000 but some units 

sold for as much as $600,000.”

John Suppes, President of Clarum Homes

Green Building Programs offer builders 

marketing clout. Energy efficiency and solar 

help homes qualify for green certification.

“Its best to integrate the solar electric 

system into the entire home purchase 

rather than having it offered as an option 

in a piecemeal way. It should all be 

rolled into one.”

“We wanted to get the house because 

the system was already there. We didn’t 

have to decide about it. We’re glad it is 

here. We’re lucky to have the PV.” 

SheaHomes homebuyers as quoted 

by Coburn, Farhar, and Pratsch 2006.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 2 / p.5

Solar Sells: Closing the Deal Chapter 2

Production Builder Cost Advantage

Production builder advantages show up in solar 

equipment costs. Studies of California’s PV incentive 

programs show that systems installed in large 

new home developments are, on average, far 

more economical than retrofitted systems, saving 

13% to 21% over retrofit systems (Wiser, Bolinger, 

Cappers and Margolis 2006). Researchers suggest 

that production builders may drive down solar 

thermal costs by up to 40%. For consumers who 

know they want solar technologies, these savings 

are important. Costs to consumers are even lower 

thanks to their ability to roll ZEH costs into their 

primary mortgage.

Selling Value

Builders are interested in providing value to clients. 

But consumers may have a different view of how 

solar fits into the equation.

For consumers, part of the value equation relates 

to the cost of energy. With ZEH, part of the homes 

costs amount to a locked in price for power over 

the life of the solar equipment. In an era of large 

jumps in power and fuel costs, ZEH help to manage 

risks and reduce future price shocks. Not a bad 

benefit when some utilities seek out 89% increases 

in electric rates (See the Baltimore Sun headline 

listed on page 3).

Consumers are Willing to Pay

Most market research into solar technologies show 

that financial benefits are important to consumers. 

Research also shows that consumers are interested 

in a positive cash flow. By combining solar with 

energy efficiency improvements, the total package 

results in a positive cash flow in combination with 

utility bills and mortgage payments. PV does not 

achieve positive cash flow by itself, but it does help 

sell homes with high levels of energy efficiency. 

Both detailed studies of the SheaHomes community 

(Coburn, Farhar, and Pratsch 2006) and a national 

survey (NAHBRC 2006) found similar results. 

Getting Green

Builders who choose to advertise their “green” 

designs have found that buyers are willing to 

pay for environmental features. Local, regional, 

and national programs offer methodologies and 

certification processes for green construction. The 

certification programs award points based on green 

features incorporated into home and site designs. 

Depending on the exact measures implemented, 

there are a range of certification levels that can 

be reached. Using suggested Building America 

energy-efficiency practices, a new home can earn 

a green certification within a number of different 

programs. Adding solar technologies to make a ZEH 

pushes the point totals even higher. For example, 

a ZEH following Building America recommendations could qualify for the LEED silver rating, or, 

in parts of California, the Alameda County Green 

Building Guidelines. By adding other measures, 

the highest levels of certification are within reach. 

Green building programs may have requirements 

in addition to meeting point totals.

How Industry Leaders 

Sell ZEH Homes

Two ZEH communities in California offer examples of 

how to sell ZEH and green technologies. The photos 

show green rooms used at each community. The green 

rooms offer samples and exhibits related to energy 

efficiency, solar technologies, and green building 

materials and techniques. In addition, the communities’ model homes display their PV systems.

The National Association of Home Builders Research 

Center sponsors an annual award competition 

called the Energy Value Housing Award. The Center 

has compiled the winning builder’s marketing 

techniques into a document that can be purchased 

on the Web at www.nahbrc.org/tertiaryR.asp?Cate

goryID=1705&DocumentID=3404 (Sikora 2002). 

Here are some of the best practices recommended 

by the NAHB Research Center and other sources:

“Reaching 50% energy savings 

closes the deal.”

Mark Fischer, a senior vice president 

at Grupe, a Stockton, California, based 

production builder

“Our advertising includes billboards, 

newspaper ads, and me. I am their 

walking, living, breathing advertisement 

for solar out here.” 

Sheri Gage, sales manager and owner of 

one of the first solar homes completed at 

Premier Meadows, Live Oak, California

“People who are naturally inclined 

to educate themselves are typical 

customers. About 80% of our buyers 

looked us up on the web first. We 

probably have more Ph.D.s living in our 

little development than any other part 

of town. This doesn’t mean you have 

to be a genius to appreciate the homes 

we built. But it shows that education 

and a willingness to learn about energy 

efficiency can drive sales.”

John Wesley Miller, owner of John Wesley 

Miller Companies, Tucson, Arizona
p.6 / CHAPTER 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 2 Solar Sells: Closing the Deal 

• Educate customers and sales professionals. Show 

buyers how living in an energy-efficient home 

will benefit them with lower household costs. 

Vital to customer education is an informed sales 

staff and team of local sales professionals.

• Walk-throughs and model homes can be invaluable educational tools for both buyers and sales 

staff. Model homes with display cutaways of 

energy features such as insulated attics and 

wall sections help explain the energy-efficient 

construction process. Labels, flags, and banners 

create a fun, self-explanatory message to give 

buyers a focus while they drive or walk the 

development. Recent research suggests just 

how important model homes, models of house 

features, and other educational tools are to 

shoppers (Farnsworth 2003).

• Training sessions are effective for educating 

sales staff and professionals. Slides, sample 

products, and energy bills work as aids. One 

builder in Maryland built a prototype ZEH. The 

builder offered onsite workshops for other area 

builders and held open houses for consumers. 

All of these activities were covered by local 

and national press. The Bob Ward Maximum 

Efficiency Greenland Model is described in a 

case study in this document. 

• One way to educate consumers is to emphasize 

an energy-efficiency or ZEH upgrade when 

signing the final papers. One builder has a wall 

of testimonials, photos, and utility billing history 

in his waiting room. All prospects are given an 

opportunity to view this “wall of fame” before 

the final sale is made. Another builder has the 

buyer meet with the building site supervisor 

after the sale is made. This person gives them 

one more chance to sign up noting, from a 

builders’ perspective, what a better house they 

will get (Rashkin 2002). 

• Publications are an educational tool that 

customers and sales professionals can take 

home. Develop your own brochures or books 

or give away reprints of magazine articles, 

ENERGY STAR brochures, or Building America 

brochures. Vendors and trade associations can 

provide excellent materials, often at no charge. 

For example, excellent information on window 

performance is available at the Efficient Windows 

Collaborative Web site at www.efficientwindows.

org/index.cfm. Give potential buyers a checklist 

so they can compare the energy saving measures 

in your homes with those of other builders.

• Advertising can be used to explain the energyefficiency advantages and distinguish builders 

from their competition. The ENERGY STAR Web 

“We thought about offering solar as an 

option, but I like the way it makes us 

unique. When you make it standard, 

buyers accept it without hesitation. 

Once you decide to do a whole 

development with solar, it’s easy to 

work it into your schedule and to train 

your subcontractors. And we decided it 

was the right thing to do.”

Mark Fischer, a senior vice president at Grupe, 

a Stockton, California, production builder

Information centers make energy features 

tangible. The more builders tell consumers 

about ZEH features, the more consumers 

want them.

STANDARD HOME ZERO ENERGY HOME

$3,160 $3,240

$173

TOTAL MONTHLY = $3,333 TOTAL MONTHLY = $3,320

< MORTGAGE BILLS >

< E

< $5 ENERGY EFFICIENCY

< $25 SOLAR HOT WATER

< $50 SOLAR PV 2.4 kW

NERGY BILLS > $80

Consumer monthly costs for Zero Energy 

Homes need be no more than typical homes. 

Energy savings and incentives can offset added 

upfront costs, as shown in this example. 

A full-size version of this figure is located on 

page 7 of Chapter 1.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 2 / p.7

Solar Sells: Closing the Deal Chapter 2

site (www.energystar.gov) has useful information 

for designing advertising.

• The Internet and compact disk formats are another 

forum for presenting all of your education and 

advertising messages. Some marketers suggest 

that all builders should have a Web site, even if 

it is simple and offers only limited information. 

CDs with brochures or slide shows can be given 

to potential buyers to take home and replay 

your message. Katharine Kent, a solar retailer 

in Tucson, Arizona, sees the internet as possibly 

her most effective tool. Potential customers can 

educate themselves before approaching a retailer 

directly. “It is surprising how many people look 

on the web first,” notes Kent. “If we are at a home 

show, some [people] will want to sign up for an 

estimate right there, but many times they go home 

and look at our web site before they call.”

• Seek out free publicity. Nothing is more cost 

effective than sending a news release to local 

media to announce business news and other 

company activities. News releases can cover your 

company’s involvement in educational activities, 

for example, teaching school children about 

energy efficiency or other charitable actions.

• Offer energy-efficiency guarantees. Energy 

performance guarantees can help convince 

buyers that energy savings are real. Partnerships 

with outside companies can help to establish 

guarantees. For example, Environments for 

Living (www.eflhome.com) offers energy cost 

and comfort gauruntees for builders who will 

meet their specifications.

• Make buyers aware of energy-efficient mortgages.

• Take advantage of the testing data available on 

your homes. Information may include blower 

door and duct tightness test data and HERS 

Index rating to share with buyers. Use these data 

to inform your customers and differentiate your 

houses. If you cannot provide testing, make it 

available as an option for homebuyers.

Treasure Homes and Grupe Homes in California 

devote entire rooms to interactive displays showing 

solar and energy efficiency technologies.

To further the learning experience, 

Grupe turned the garage of one of its 

model homes into an energy efficiency 

and solar showroom for training sales 

staff and educating potential buyers. It’s 

worked well. “Grupe’s sales staff is sold 

on solar; they are passionate about it.” 

Bill Daking, Davis Energy Group

HERS Index 

HERS ratings adopted in 2006 are reported on an index from 

0 to 100. Zero represents a house that produces as much 

energy as it consumes annually. 100 represents a reference 

home that meets the minimum requirements of the 2006 

International Energy Conservation Code. For more information 

visit www.natresnet.org.

Difference equals percentage reduction in 

energy use. For example, a score of 70 is 

30% more efficient than a score of 100.

A reference home that meets the 

minimum requirements of the 2006 

International Energy Conservation Code.

A home that produces as much

energy as it consumes annually.
p.8 / CHAPTER 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 2 Solar Sells: Closing the Deal 

Resources and References

Baccei, Bruce. 2006. “Impacts of Zero Energy Homes on Buyers and Owners.” In Solar 2006 

Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, 

Boulder, CO.

Coburn, Timothy, Barbara Farhar, and Lew Pratsch. 2006. “Comparative Analysis of Utility 

Consumption and Costs of Near-ZEHs and Comparison Homes in California.” In Proceeding of 

the 2006 ACEEE Summer Study on Energy Efficiency in Buildings, Washington, D.C. 

Efficient Windows Collaborative

www.efficientwindows.org/index.cfm

ENERGY STAR 

www.energystar.gov

Environments for Living

www.eflhome.com

Farhar, Barbara, and Timothy Coburn. 2000. A Market Assessment of Residential Grid-Tied PV 

Systems in Colorado. NREL/TP-550-25283. National Renewable Energy Laboratory, Golden, CO.

Farhar, B.C. and T.C. Coburn. 2006. A New Market Paradigm for Zero-Energy Homes: The 

Comparative San Diego Case Study. NREL/TP-550-38304-01. Prepared by the National Renewable 

Energy Laboratory for the U.S. Department of Energy. www.nrel.gov/docs/fy07osti/38304-01.pdf

Farnsworth, Christina. 2003. “The Weakest Link.” Builder Magazine, December 2003. 

www.builderonline.com/article-builder.asp?channelid=55&articleid=375&qu=consumer+survey

Ghent P., and C. Keller. 1999. A Comprehensive Review of Market Research on Solar Water 

Heaters. NREL/SR-550-27123. Prepared for the National Renewable Energy Laboratory by Focus 

Marketing Services, Westlake Village, CA.

Hanson, M. and M. Bernstein. 2006. The Role of Energy Efficiency in Homebuying Decisions: 

Results of Initial Focus Group Discussions, WR-352-CON, Rand Corp.

HERS Rating Information

www.natresnet.com

J.D. Power and Associates. 2005. 2005 New-Home Builder Customer Satisfaction Study. 

West Lake Village, California. www.jdpa.com

Johnston, David. 2000. “Buyer Green.” Professional Builder, September 2000. 

www.housingzone.com

National Research Council (NRC). 2006. Surface Temperature Reconstructions for the Last 

2000 Years. The National Academies, Washington, D.C.

National Association of Home Builders. 2002. What 21st Century Home Buyers Want. 

NAHB, Washington, D.C.

“Energy efficiency has been a selling 

point with my customers, somthing that 

sets me apart. People appreciate that 

I’m thinking out of the box in a way that 

makes sense to them and saves them 

money in the long run.” 

Barrett Burr, homebuilder
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 2 / p.9

Solar Sells: Closing the Deal Chapter 2

National Association of Home Builders Research Center (NAHBRC). 2006. The Potential 

Impacts of Zero Energy Homes. Prepared for the National Renewable Energy Laboratory, 

Golden, CO.

NAHBRC – Energy Value Housing Award

www.nahbrc.org/tertiaryR.asp?CategoryID=1705&DocumentID=3404

Professional Builder. 2003. “Customer Service Standard Setters.” September 2003. 

www.housingzone.com

Rashkin, Sam. 2002. “Surprise! Energy Efficiency Sells without Rebates: Results of Mainstream 

Builders Selling ENERGY STAR Labeled Homes.” In Proceedings of the 2002 ACEEE Summer 

Study on Energy Efficiency in Buildings, Washington D.C.

Sikora, Jeannie. 2002. Energy Value Housing Award Guide: How to Build and Profit with 

Energy Efficiency in New Home Construction. National Association of Home Builders 

Research Center, Upper Marlboro, MD.

Symmetrics Marketing Corporation (SMC). 1999. New Home Buyer Solar Water Heater 

Trade-Off Study. Prepared for the National Renewable Energy laboratory by Symmetrics 

Marketing Corporation, Mesa, AZ.

Wiser, Ryan, Mark Bolinger, Peter Cappers, and Robert Margolis. 2006. Letting the Sun 

Shine on Solar Costs: An Empirical Investigation of Photovoltaic Cost Trends in California. 

LBNL-59282, NREL/TP-620-39300. Prepared for the U.S. DOE by Lawrence Berkeley National 

Laboratory, Berkeley, CA, and the National Renewable Energy Laboratory, Golden, CO. 

http://eetd.lbl.gov/EA/EMP.

Solarvoltaics alone will never get a 

home to zero energy bills. A superefficient building envelope and 

high-performance appliance are key to 

cutting energy costs.

“I’ve been in since December 2005, and 

my electric bills have ranged from a 

high of $70 to a low of $1.60 per month 

(for a 1,990 sq ft home). People have 

been walking into my sales office who 

are paying between $250 and $800 a 

month on their electric bills.” 

Sheri Gage, Sales Manager and owner of one 

the first solar homes completed at Premier 

Meadows, a near-ZEH Premier Homes 

development north of Sacramento, CA
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 3.

Solar-Thermal Water Heating

Building America Best Practices Series

Anyone who has touched their steering wheel on a sunny day and burned their fingers, has experienced 

first hand the physics that work within solar collectors. Solar thermal systems collect heat from the sun for 

use in space or water heating. For production builders, systems for water heating are mature technologies 

that can easily be incorporated into new home construction. Solar heated water may be used for space 

conditioning, pool heating, or domestic consumption. These best practices focus on domestic hot water 

use. Space conditioning with solar heated water or air is emerging as an efficient technology, but is not 

yet mature for production building. Pool heating is simple and cost effective, but applies only where 

pools are built with new houses.

This chapter is divided into three parts. The first summarizes the pieces that go into solar thermal systems. 

The second describes how the pieces are fitted into systems. And the third summarizes best practices for 

solar installers and builders.

Photo courtesy of Bill Guiney of Solargenix

Builders’ Brief

• Solar thermal installers can be certified by NABCEP; find out if they are or what their plans are 

for becoming certified. 

• Only install systems that have been SRCC certified – some states, such as Florida, require their own certification.

• Incorporate solar information into the homeowners manuals and materials that you provide.

• Select packaged systems where possible for the benefits of pre-engineering.

• Choose the simplest systems that will work in your climate. 

• In warm climates, with virtually no freezing, Integrated Collector Storage (ICS) systems provide an 

inexpensive and straightforward option.

• Some builders have incorporated solar water heating systems into tile roofs.

• With freeze protection, reliable solar water heating is available anywhere in the country.

• Provide space in home designs for pipe runs from solar collectors to storage tanks.

• Insist that solar installers meet with other trades to work out equipment compatibility, supply, 

and installation issues.

• Experience has shown that when inspections are done, failure rates on solar thermal systems are very low.

Installers’ Brief

• Use specialized knowledge to educate 

builders and other trades. New 

construction provides an opportunity 

to optimize the equipment and 

installation process.

• Take advantage of the bulk purchase 

opportunities afforded by production 

building.

• Work with site supervisors, roofers, 

plumbers, and others to determine 

the best installation sequence and 

schedule what materials to provide and 

to avoid shading from vents and other 

roof penetrations.

• Confirm solar exposure before 

mounting hardware on the roof.

• Provide quality assurance inspections. 

• Many problems are related to 

craftsmanship – use quality assurance 

techniques to avoid problems.

• Work with the builder to develop 

inspection protocols.

• Correct installation and craftsmanship 

problems immediately.
p.2 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

Background information on solar thermal 

installations is readily available. Much of it is 

free and accessible on the Web. The References 

and Additional Information section has several 

documents listed that generally contributed to 

this text and that can provide greater detail than 

found here.

Solar Thermal Building Blocks 

– The Basics

Water heating systems are made up of components 

that (1) collect solar heat, (2) store the heat, 

(3) control operation, (4) deliver hot water

where it is needed, and (5) protect the system 

against freezing. Components can be combined 

in a variety of ways but these five basic functions must be met, although some systems are 

simple enough that passive physics provides the 

control and push heat transfer fluids where they 

need to go.

Solar Heat Collection

All systems require a solar collector. Typically sitting 

on the roof, this is the one part of the solar thermal 

system that is readily visible outside the house. The 

solar collector is the boiler of the solar thermal 

system. Resembling skylights, solar collectors 

are a common sight in some markets. They have 

been commercially available for over a century 

and installed across the nation since the 1980s. 

Typically, one or two collectors are installed for 

residential solar water heating systems. 

Four key differences set modern collectors apart 

from their predecessors:

• Improved materials make modern collectors 

more durable, efficient, and environmentally 

friendly. Component upgrades include more 

reliable and efficient pumps and controls.

• Collectors may be mounted to blend in with the 

house. Research and modeling has shown that 

collectors mounted flush or parallel to the roof, 

minimizing their profile, work nearly as well as 

collectors set at an optimized angle, and create 

a more aesthetic installation. Builders also 

have flexibility in the direction the collectors 

face. Collectors facing within 45° of south 

work well.

• Similar to windows and appliances, solar thermal 

systems are rated for their energy efficiency, 

durability, and safety. These ratings allow for 

side-by-side comparisons. The box on page 3 

describes the SRCC rating system.

• Modern testing, commissioning, and certification greatly improve system reliability.

Prior to World War II, half of Miami 

homes had solar thermosiphon water 

heaters and over 80% of new homes 

had them installed. It was the advent of 

the war and the need to ration copper 

and other metals, and then extremely 

cheap electric power and promotion of 

electricity use by utilities that shut the 

industry down by 1954. Ironically, it may 

be modern national security priorities 

that again bring solar technologies into 

prominence. For more information on the 

history of solar technology see Chapter 9, 

“Looking Back, Looking Ahead.”

Solar thermal collectors in Florida and California. 

Photo left courtesy of Jeff Curry of Lakeland Electric. 

Photo right courtesy of Rheem Water Heating.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.3

Solar-Thermal Water Heating Chapter 3

Objective Testing and Rating

The Solar Rating and Certification Corporation (SRCC) rates and certifies solar collectors 

and overall systems. In 1980, SRCC established its certification and rating program for solar 

collectors (referred to as OG-100). The program evaluates the maintainability of solar collectors 

and a thermal performance rating of all-day energy output under prescribed conditions. SRCC 

programs are in place for solar water heating and swimming pool collectors and water heating 

systems. Systems are generally for residential solar water heating. Program participation is voluntary 

and currently 45 manufacturers participate. SRCC ratings are especially important now as solar 

components from China and Europe are entering the U.S. market.

Testing is directed to durability and performance with test procedures specified by the International 

Standards Organization (ISO) for water heating collectors and the American Society of Heating, 

Refrigerating, and Air Conditioning Engineers (ASHRAE – see the References and Resources 

section at the end of this chapter) for space heating collectors. Manufacturers have the option of 

using ISO or SRCC durability (quality) standards.

The purpose of the rating is to show how two or more collectors perform under test conditions. 

The SRCC label states the number of Btus that a collector will produce over a day under the test 

conditions. This approach makes for easy comparisons across collectors. The collectors are rated 

for a variety of weather conditions and dimensions and capacities are listed.

The SRCC also certifies solar water heating systems (OG-300). This certification integrates 

results of collector tests and passive system tests with evaluations against minimum standards of 

system durability, reliability, safety and operation; as well as factors affecting total system design, 

installation, maintenance, and service. The complete system of collectors, tanks, pumps, motors, 

valves, piping, and even the operating and installation manuals are evaluated. 

The SRCC uses the Solar Energy Factor (SEF) as its performance rating for solar domestic 

water heating systems. The SEF is defined as the energy delivered by the system divided by 

the electrical or gas energy put into the system. The SEF is similar to the Energy Factor given 

to conventional water heaters by the U.S. Department of Energy and published by the Gas 

Appliance Manufacturers Association. 

In addition, and quite useful to those wishing to determine the savings of a solar water heating 

system, SRCC also publishes annual performance ratings for certified solar systems. These ratings 

include kWh and therm savings for the certified systems. Comparisons of certified system performance 

(based on modeling) are available for representative cities within many states.

Note that Florida has its own certification requirement and the Florida Solar Energy Center has 

ratings, manuals, and other useful information. 

Other resources available on the SRCC website include the following:

• Training videos for solar thermal system installation and inspection

• SRCC installation guides

• Listings of SRCC-rated solar collectors and systems

All resources are available at www.solar-rating.org.

The SRCC provides rating and 

performance information.
p.4 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

Four types of collectors are typically available. 

Glazed Flat Plate Collector: The workhorse of 

the industry, flat plate collectors can be used in any 

climate. These collectors are typically two to three 

inches thick and resemble a skylight if mounted 

directly on, or just above, the roof. A flat plate 

collector consists of an absorber, a transparent cover, 

a frame, insulation, and copper pipes carrying heat 

transfer fluid (usually water or propylene glycol). 

Typically, a special solar safety glass is used as 

the transparent cover. The cover slows down heat 

loss and traps solar energy inside the collector. 

Insulation on the bottom of the collector, behind 

the absorber, and on the sides reduces conductive 

heat loss. Foam and batt type insulations are used. 

Aluminum is a typical frame material. 

Absorbers sit within the collector and are usually 

black to absorb the most solar energy possible. 

The most efficient absorbers use a selective surface 

coating. This coating enables the conversion of 

a high proportion of solar radiation into heat 

and holds onto that heat. Solar paints have 

high absorption but lose much of the heat. 

Galvanically applied selective coatings include 

black chrome, black nickel, and aluminum 

oxide with nickel. Relatively new is a titaniumnitride-oxide coating.

Evacuated Tube Collector: In this type of collector, small diameter metal pipes act as absorbers 

inside larger evacuated glass tubes. These pipes are 

called heat pipes. The evacuated glass tubes act like 

a thermos to hold in absorbed heat. The tubes are 

interconnected with a manifold, along the top of 

the collector. A heat pipe collector incorporates a 

special fluid that vaporizes at low temperatures 

and is resistant to freezing. The vapor rises in the 

individual heat pipes and warms up the carrier 

fluid in the manifold. After giving up its heat, the 

condensed liquid then flows back into the base of 

the heat pipe.

These evacuated tube collectors must be properly 

angled to allow for the ongoing process of vaporizing and condensing. Evacuated tubes perform 

more efficiently than other collectors in cloudy 

weather and tend to reach higher temperatures 

than flat plate collectors. There are two types of 

connections used where the heat pipe ties into the 

heat transfer manifold at the top of the collector. 

Either the heat exchanger extends directly into the 

manifold (“wet connection”) or it is connected 

by a heat-conducting material (“dry connection”). With the “dry connection,” installers can 

exchange individual tubes without emptying the 

entire system of its fluid. Glass tubes can be fragile 

(left) Glazed flat plate collector.

(right) Evacuated tube collector. Photo courtesy 

of Leif Juell, Alternative Power Enterprises, Inc.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.5

Solar-Thermal Water Heating Chapter 3

and should be handled carefully. Evacuated tube 

collectors are also suited to situations requiring 

high temperature fluids, such as in commercial 

or industrial processes.

Integrated Collector Storage (ICS): ICS or 

batch heaters combine a solar collector with a 

storage tank. When there’s demand for hot water, 

water pressure from domestic plumbing moves 

hot water from the top of the solar batch heater as 

water pressure pushes cold water into the bottom. 

Water moves directly into the home’s water tank or 

distribution system. These systems are the lowest 

cost solar systems but should only be used where 

there is no chance of freezing. The combined collector, tank, and 40 gallons of water can place more 

than 500 pounds on the roof. These systems were 

the earliest to be marketed in the late 1800s.

Unglazed Flat Plate Collector: These simple 

collectors consist of an absorber that incorporates 

channels for water flow. The absorber consists of 

rubber-like Ethylene Propylene Diene Monomer 

(EPDM) mat, metal, or extruded polypropylene 

plastic. They capture enough solar energy to reach 

the warm temperatures ideal for pool heating. These 

systems are light weight, come in a multitude of 

sizes, have some color options, and may be installed 

on roofs, trellises, or out buildings. More energy 

is produced in the U.S. with these systems than 

with PV or domestic hot water systems combined. 

This document does not describe these systems 

beyond this brief paragraph, but every house or 

community built with a heated pool should come 

equipped with solar pool heaters. 

Collector mounting: Typically, collectors are 

mounted to roofs using low profile stand off mounts. 

Most collectors are installed just above, and parallel to the roof. Usually, one or two collectors are 

installed. Stand off mounts hold collectors above 

the roof surface, allowing air and runoff to flow 

beneath the collector. Additional information about 

mounting is described in Chapter 6: Solar System 

Mounts.

Heat Storage

In some solar thermal systems, the heat storage 

tank or tanks may be the largest component. One 

or more storage tanks may hold heated water.

Single Tank: Most systems that heat potable water 

directly have only one tank that typically has one 

auxiliary heating element. The tank has hot water 

delivered directly from the solar collector, with 

(left) Integrated collector storage (ICS). 

Photo courtesy of Katharine Kent, The Solar Store

(right) Unglazed flat plate collector. 

Photo courtesy of NREL
p.6 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

supplemental heat coming from the element to 

meet domestic needs. Cooler water from the bottom 

of the tank is circulated through the collector 

when solar energy is available to provide heat. 

This would be the only “water heater tank” serving 

the household.

Double Tanks: In a double tank system, one 

tank provides storage for solar heated fluid. This 

tank takes water directly from the solar collector 

and does not contain a heating element. The tank 

is plumbed to a second tank that does contain a 

heating element or burner that can be used when 

no solar energy is available.

Delivering Hot Fluid Where it is Needed

Solar collectors heat a fluid that then transfers the 

heat from the collectors to the storage tanks. This 

process of getting the heat where it is needed requires 

heat transfer fluid, pumps, pipes, insulation, and 

sometimes, heat exchangers and expansion tanks.

Heat transfer fluid is typically either water or 

a combination of propylene glycol and water. 

Water is the best heat transfer fluid for holding 

and transferring heat. However, water does freeze. 

Propylene glycol, mixed with water, is the industry standard heat transfer fluid where freezing is 

a hazard. Propylene glycol is not toxic so heat 

exchangers designed for this fluid need only be 

single wall construction, depending on local code 

requirements. Toxic fluids require double wall heat 

exchangers. Commercially available propylene 

glycol for solar installations come packaged with 

dilution charts, showing how much glycol should 

be mixed with water to protect systems from freezing 

at predetermined temperatures. Using the leanest 

appropriate mixture saves pump wear and increases 

heat transfer capabilities.

Pumps circulate fluid through the solar system. 

Passive systems rely only on gravity and thermal 

stratification to deliver fluids where they are needed. 

In an active system, a pump circulates heat transfer 

fluid through pipes from the storage tank to the 

collector. In an active direct system that delivers 

solar heated potable water directly for domestic 

use, the pump must have a bronze or stainless 

steel housing and impeller because of oxygen 

from incoming water and venting. Steel and cast 

iron pumps would corrode, pass rust through the 

system, and eventually fail. In an active indirect 

system, a cast iron pump is acceptable as long as 

the heat transfer fluid is compatible.

Piping is the conduit through which heat transfer 

fluid travels. Piping must be properly sloped to 

allow for proper flow, dropping at lease 1/4 inch 

per linear foot. Copper pipe is the most common 

conduit. Other products, such as PEX, are under 

evaluation for specific applications (Burch, Heater, 

and Brandemuhl 2006). At present, PEX and other 

non-copper products are not recommended for use 

in solar thermal loops. Exposure to freeze-thaw 

cycles and potentially very hot fluids require copper. 

Various grades of copper are used for different 

portions of the solar system. Pipe joints are typically 

soldered but could include mechanical crimping 

and gasket connections. Keep pipe runs as short as 

possible. Long pipe runs will lose heat and hamper 

system performance.

Pipe insulation is important for energy performance 

and freeze protection. Many pipe insulations will 

not tolerate the temperature extremes possible in 

solar thermal systems or the exposure to sunlight. 

Because of these conditions, do not use polyethylene 

foam insulation sold for plumbing. Elastomeric 

insulation has an R-value of 3.5 per inch, is used 

for heating and cooling systems, and is preferred for 

exterior and interior applications. Fiberglass insulation, with an R-value of 3 per inch, is suitable for 

interior runs. Insulation should be carefully applied 

to fit around corners, gauges, and valves. Gauges 

and valves should be insulated to the extent possible. 

All insulation exposed to the weather should be 

jacketed with paint, PVC pipe, or aluminum to 

prevent deterioration from ultraviolet radiation 

and environmental conditions. Paint needs to 

be redone every three to five years. Do not run 

insulation through roof penetrations.

Propylene glycol is a non-toxic heat transfer 

fluid that provides freeze protection.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.7

Solar-Thermal Water Heating Chapter 3

The Tucson-Pima County Sustainable Energy 

Standard specifies that for passive collectors no 

more than 20 linear feet of pipe should separate 

integrated collector storage type collectors and 

storage tanks (www.tucsonmec.org/ses.htm).

Heat exchangers are always needed in propylene 

glycol systems but sometimes systems using water 

also use heat exchangers. Heat exchangers allow 

for heat to be transferred from the solar fluid to 

either the domestic hot water system, or a space 

heating system. Systems with heat exchangers are 

called “indirect” systems, because the fluid from 

the solar side is not intended to mix with domestic 

water. Two common designs in heat exchangers 

for hot water systems are coil-in-tank and wraparound systems. Heat exchangers reduce system 

efficiency by 10% to 20%. Some heat exchangers 

are incorporated into smaller tanks that tie into 

the domestic hot water tank. In these systems the 

smaller tank can be stacked on the main tank, 

saving floor space. 

Most indirect systems using a heat transfer fluid 

other than water have an expansion tank. These 

tanks allow for changes in fluid volume as temperature changes.

Controllers, Valves, and Gauges

Controllers determine when sufficient solar energy 

is available and directs the system accordingly. The 

main controllers function by controlling the pumps 

that push fluid through the system. Other controls 

work within the system as safeguards.

Differential Controller: This device is the most 

common controller and works with two sensors 

– one at or near the hottest point in the collector and 

another near the bottom of the storage tank. When 

the collector sensor finds that temperatures are 8°F 

to 4°F greater than the tank sensor, the controller 

starts the pump. These differential temperatures 

are pre-set by the installer in accordance with the 

specific characteristics of the installation. When 

temperature differences are less, typically 4°F, the 

controller stops the pump.

Photovoltaic Control: Another approach uses 

a photovoltaic module adjacent to and in the 

plane of the collector to provide DC power to a 

DC pump. The PV provider powers only when 

the sun shines. So, the pump only operates when 

solar energy is available. The critical part of this 

application is that the module and pump have to 

be matched properly for optimal operation (start, 

stop, flow, etc.).

(left) Rough-in plumbing for a solar thermal 

system. Photo courtesy of Heliodyne.

(right) Insulation ready for installation.

(bottom-right) A pre-packaged Heliodyne 

system takes up no more space than a water 

heater tank. Photo courtesy of Heliodyne.
p.8 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

(left, middle, right) Field-mounted gauges, 

pumps, and valves and an example of 

a prepackaged unit. Timer Controller: These systems are rarely used 

and none are certified by the SRCC. These systems 

are not recommended.

Valves serve many safety and control functions.

• Air vents expel and vent air from the system 

to prevent air locks and are located at the 

uppermost part of the system.

• Temperature and pressure relief valves release 

excessive pressure and temperature. Typically, 

only pressure relief valves are used in the 

collector loop. Combination pressure and 

temperature relief valves are required on 

domestic water heaters.

• Vacuum breakers prevent vacuum locks during 

drainage.

• Ball and gate valves isolate parts of the system. 

Ball valves are typically used for the solar loop.

• Drain valves are used to drain the solar 

system. Drain valves are also found on all 

water heaters.

• Check valves prevent thermosiphon heat losses 

and may be mechanical or motorized.

• Antiscald valves ensure that hot water is conditioned with cold water before being used for 

domestic use. Antiscald valves are more accurate 

than mixing valves and are a true “safety” valve. 

Mixing valves are more of an energy savings 

device than a safety valve. 

• Pressure gauges, temperature gauges, and 

flow meters monitor the system or allow for 

technicians to diagnose the system and for 

homeowners to determine that the system is 

indeed working.

• Freeze prevention valves open in cold weather 

to allow water to drain out of exposed collectors. 

Better freeze protection is available for systems 

in colder climates. These valves should only be 

used in typically non freezing climates with ICS 

or simple systems with pumps. 

• Some instruments provide information for 

diagnostics and maintenance.

Pressure gauge: All closed loop systems require a 

pressure gauge. On direct and indirect loop systems 

these gauges indicate if a leak has occurred.

Flow Meter: Flow meters allow owners and service 

people to determine if pumps are operating and at 

what rate. These meters should be located in the 

collector feed line, above the pump.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.9

Solar-Thermal Water Heating Chapter 3

Temperature gauges: Two gauges are usually 

plumbed, one for the collector feed line and one for 

the return line to allow for the visual verification 

of fluid temperatures.

Freeze Protection

Freeze protection prevents damage to system 

components from ice formation.

Draindown System: These systems are no longer 

in use and are not recommended. None are certified 

by the SRCC.

Drainback System: A drainback tank collects 

fluid that drains from the solar collector each time 

the pump turns off. The tank should be located in 

conditioned space and vertically close to collectors 

to reduce head pressure. The pump is controlled 

by a differential controller. Drainback systems are 

described more fully in the Solar Thermal Systems 

section, later on this page.

Water Flow: Water is circulated through the 

collector by a pump with a freeze switch. This 

method requires electric power and is not reliable 

when the power goes out, which requires manually 

draining the collector.

Freeze Prevention Valves: Freeze prevention 

valves open in cold weather to allow water to drain 

out of exposed collectors. Better freeze protection is 

available for systems in colder climates (Ramlow 

and Nusz 2006). 

Propylene Glycol: Propylene glycol systems were 

described earlier in the “Delivering Hot Fluid Where 

it is Needed” section on page 6. These systems 

include a mix of nontoxic propylene glycol and 

water. The nontoxic propylene glycol is an antifreeze. The ratio of the two fluids varies depending 

on the level of protection needed. These systems are 

more complex than other systems but offer a great 

method for freeze control in colder climates.

Solar Thermal Systems:

Putting the Pieces Together

Solar components may be combined in many ways 

to achieve efficient water heating. Systems can be 

quite simple, or very complex depending on the 

need for freeze protection, and the system design. 

This section describes common approaches to 

system design, starting with the simplest approaches. 

The very first part of the discussion talks about 

components that are common to all systems. These 

common components will not be included in 

the other discussions. Packaged systems hold the 

potential for labor savings and greater consumer 

acceptance and are also discussed up front.

Most systems require the following components:

• pressure relieve valves are important safety 

devices on all systems – some systems use 

combined safety and temperature relief valves

• piping to move heat transfer fluids from 

collectors to storage and to carry cold fluids 

to the collector

• insulation for the piping

• valves to isolate, bypass, and drain the 

solar system 

• air vents to allow air to escape the system

• insulation for storage tanks. 

Packaged systems can greatly simplify installation, 

save space, and make a more pleasing presentation 

to consumers. By pre-combining many components, 

packaged systems can also cut down on labor costs. 

Some systems combine controllers, sensors, pumps, 

gauges and valves. These systems also include 

insulated covers preformed to fit the components 

and pleasantly styled to look more like dashboards 

than boiler rooms. The covers can be easily removed 

and reused.

Solar water heating systems are described using 

four common terms:

Installers prepare to lift a solar panel 

onto the roof.
p.10 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

• Active systems use pumps to move fluids 

through the system.

• Passive systems rely on the buoyancy 

of warm water and gravity to move fluids 

through the system without any pumps.

• Direct systems heat water that feeds directly 

into the domestic hot water system. Direct 

systems always use potable water as the heat 

transfer fluid. In areas with dissolved minerals, carbon dioxide, or other water quality 

problems, these systems may require water 

softeners or other treatments. 

• Indirect systems have independent piping 

and use heat exchangers to isolate solar 

fluids from potable domestic hot water. 

Systems using propylene glycol must use heat 

exchangers, however, water may also be used 

in indirect systems with heat exchangers.

The following system descriptions include example 

illustrations of system designs. In practice, systems 

may be configured in many different ways.

(left, right) ICS mounted directly on roof deck and 

integrated with mission and cement tile systems. 

The photos were taken at a development in 

Thousand Oaks, California, in 2002. Photos 

courtesy of John Harrison of the SRCC and FSEC.

Probability of at Least One Pipe Freeze in 20 Years

Figure courtesy of Jay Burch of NREL.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.11

Solar-Thermal Water Heating Chapter 3

(left, right) ICS mounted directly on roof 

deck and integrated with mission and cement 

tile systems. The photos were taken at a 

development in Thousand Oaks, California, in 

2002. Photos courtesy of John Harrison 

of the SRCC and FSEC.

Integral Collector Storage (ICS) 

Passive Direct System 

ICS systems are passive and direct. The tank and 

collector are combined. Potable water is heated 

and stored in the ICS collector. As hot water is used, 

cold water fills the collector from the bottom. These 

systems work best when hot water demands are in 

the late afternoon and evening. Heat gained during 

the day may be lost at night if not used depending 

on local weather conditions. A check valve or the 

arrangement of pipe runs stops reverse thermosiphoning where heat is lost from the domestic hot 

water system to the night sky. These systems are the 

least expensive of solar thermal options and one 

of the most popular systems on the world market. 

However, they may only be used in areas that do not 

experience many hard freezes, such as the orange 

areas in the map on the previous page.

ICS collectors have more depth than flat plate collectors to accommodate integral tanks. Some builders 

have placed these collectors directly on the roof deck 

and built up around them with tile roof systems. The 

nearby photos offer an example of this approach.

Thermosiphon Passive Direct System

Thermosiphon systems are passive with a storage 

tank located higher than the solar collector. Some 

systems come prepackaged with tanks pre-mounted 

to collectors. In these systems the tank sits on the 

outside of the roof. Other systems have tanks located 

inside attic spaces above the collectors. These systems 

are direct, using potable water as the heat transfer 

TANKFreeze Prev. Valve

Drain Valve

By-pass

Valve

Drain

Valve

Drain Valve Shut-Off Valve

Pressure

Relief Valve

Air

Vent

Ball

Valve

Ball

Valve

COLD WATER IN HOT WATER OUT

Check Valve

Check

Valve

WATER

HEATER TANK

Freeze

Prevention

Valve

Drain Valve

Drain

Valve

Shut-Off

Valve

Pressure

Relief Valve

3-Way Ball Valve

COLD WATER IN

HOT WATER OUT

Check Valve

Isolation Valve
p.12 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

fluid. Water pipes and tanks containing water 

must be protected from freezing or located in a 

conditioned space in climates that freeze.

Thermosiphon Passive Indirect System

These similar to the thermosiphon systems described 

in the preceding section, however, these systems are 

equipped with heat exchangers within their tanks 

and may use propylene glycol or other non-freezing 

fluids for freeze protection. In warm climates, care 

must be taken to avoid stagnant conditions that 

can lead to the glycol overheating. In climates that 

freeze, the water pipes and tanks containing water 

must be in a conditioned space.

Draindown Active Direct Systems

These systems are not recommended.

Drainback Active Indirect Systems

Drainback systems use water as the heat transfer 

fluid. Some manufacturers recommend a mix 

of water and propylene glycol. All water in the 

collector and pipe lines drains from the system 

into a reservoir when the pump shuts off. The 

system is suited to most climates. These systems 

work best in warm climates because they also 

drainback when the system has met a maximum 

set temperature in the storage tank. This automatic 

safeguard against overheating avoids problems 

when hot water demand is very low, such as during 

(left) Recent Innovations: Davis Energy Group 

is working with SunEarth and NREL to develop 

polymer-based ICS. Photo courtesy of 

Jay Burch of NREL.

(right) Photo courtesy of Rheem Water Heating.

TANKFreeze Prev. Valve

Drain Valve

By-pass

Valve

Drain

Valve

Drain Valve Shut-Off Valve

Pressure

Relief Valve

Air

Vent

Ball

Valve

Ball

Valve

COLD WATER IN HOT WATER OUT

Check Valve

Check

Valve

Heat Exchanger

P/T

Relief

Valve

Drain Valve

Pressure Relief Valve

Shut-Off Valve

COLD WATER IN HOT WATER OUT

Drain

Wrap Around 

Heat Exchanger

Sight

Glass

Pump

Drain
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.13

Solar-Thermal Water Heating Chapter 3

vacations. These systems must be installed so that 

water will completely drain from the collector and 

pipes when needed. These systems work in cold 

climates because they drain when the pump is not 

operating so that the heat transfer fluid is protected 

inside conditioned spaces. The pump is controlled 

with a differential controller.

Controller–Based Active Direct Systems

Direct systems always use potable water as the heat 

transfer fluid. These systems circulate water from 

the main hot water storage tank to the collectors. 

Water is heated in the collectors and returned to 

the storage tank. These systems only operate when 

a pump is on. The pump controller directs system 

operation. Check valves are needed to stop reverse 

thermosiphoning. Freeze prevention valves offer 

insurance against freezing, but direct systems 

should not be used where hard and continuous 

freezing is a threat. A differential control turns 

the pump on when temperatures in the collector 

are 8°F to 4°F hotter than temperatures in the 

tank. Another approach is to use a photovoltaic 

module to power a DC (direct current – not to be 

confused with a “direct system”) pump. When the 

sun shines, the pump runs.

Propylene Glycol Active Indirect System

Propylene glycol makes solar collectors and pipes 

resistant to freezing. It is not as efficient as water 

as a heat transfer fluid, but these systems are 

recommended for use in climates with frequent 

or prolonged periods with temperatures below 

freezing. As active systems, pumps move the glycol 

through the system. Pumps may be activated with 

a differential control or a PV module. An expansion tank compensates for glycol expansion and 

contraction. Glycol systems must be indirect; that 

is, heat exchangers are required to transfer heat 

from the glycol to the domestic hot water system. 

These systems can be used in warmer climates, 

however, care must be taken to protect against 

stagnant conditions when the glycol may overheat. 

Propylene glycol must be changed every 10 to 15 

years, but overheating will cause degradation. One 

way to ensure against stagnation is to run the system 

whenever it is sunny. Large systems, or systems 

with periodic idle times, require a shunt load. This 

load may be a buried length of uninsulated pipe, 

or an outdoor radiator, or outdoor hot tub to take 

on excess heat from the solar system.

Builder Best Practices

Before installing solar equipment, be sure house 

designs, materials, and construction techniques 

are as energy efficient as possible. An integrated 

system design approach should be applied to your 

homes to ensure the maximum possible value 

for consumers, and profits for your company. An 

integrated system design can improve comfort, 

increase home durability, save money, and improve 

energy efficiency. Best practices and research reports 

for energy-efficient construction can be found at 

www.buildingamerica.gov.

P/T

Relief

Valve

Drain

Shut-Off Valve

Air Vent

Vacuum

Breaker

HOT WATER OUT

Drain

Drain

Check Valve

Tank

Controller

Circulator Pump

Pressure

Relief Valve

Freeze

Prevention Valve

Ball Valve

Ball Valve

Tank Sensor

Collector

Sensor

COLD WATER IN

P/T

Relief

Valve

Air Eliminator

Shut-Off Valve

Air Vent

Fill/Drain

Assembly

Check Valve

HOT WATER OUT

Heat Exchanger

Controller

Circulator Pump

Expansion

Tank

Pressure

Relief Valve

Pressure

Gauge

Tank

Sensor

Collector

Sensor

COLD WATER IN
p.14 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

Inviting solar thermal professionals to join your 

building team will bring experience and technical 

capability to help minimize system problems and 

maximize system performance. Many firms have 

been in business since the 1970s. Check out how 

long your potential installers and suppliers have 

been in business.

Installation companies should be familiar with 

SRCC collector and solar system ratings. Ask potential installers and suppliers to show you the SRCC 

labels for the systems they handle. Compare their 

systems with others in the SRCC directory which 

lists the performance of every system tested. Only 

install systems that have been SRCC certified. Note 

that Florida has its own certification requirement 

and the Florida Solar Energy Center has ratings, 

manuals, and other useful information. 

SRCC-certified systems require that an owners 

manual be provided to homeowners. Installers 

should show you this manual and production 

builders should incorporate it into the homeowners 

manuals and materials that you provide.

Solar thermal installers can be certified by 

NABCEP (North American Board of Certified 

Energy Practitioners). This process will have its 

initial test and candidates in autumn 2006. So, for 

now, certified installers will be hard to find. But, 

solar energy associations, community colleges, 

manufacturers, and others offer training. Ask 

installation companies what types of training 

their installers receive and if they plan to pursue 

NABCEP certification. Florida requires that installers have a solar contractor’s license.

Solar thermal installers and manufacturers can 

help with system design. Residential design is 

straight forward and experienced installers will 

know local climate constraints and availability 

issues. Work with installers to select the systems to 

be used in your houses. Select packaged systems 

where possible for the benefits of pre-engineering. 

Installers will know local code restrictions and 

permitting requirements.

Choose the simplest systems that will work in your 

climate. The Cold and Very Cold climate covers over 

half the area of the 48 conterminous states. Freezing 

is common in this climate zone and propylene 

glycol or drainback systems are recommended. 

Evacuated tube (heat pipe) systems are receiving 

more attention, but are expensive. Where snow 

accumulation is common, evacuated tubes are 

well enough insulated that snow may not melt 

off of them and may block solar heat gain. In the 

warmest of areas, where freezing is not an issue, 

ICS and water based thermosiphon and active 

systems work great. Everywhere except the warmest 

of areas, solar thermal systems must be designed 

to accommodate freezing, but there is flexibility 

in how this protection is achieved.

Provide space in home designs for pipe runs from 

solar collectors to storage tanks.Pipe slope can be 

critical in systems that rely on drainage for freeze 

protection. In these systems, pipes must drop at 

least 1/4 inch every linear foot. If pipes cross open 

areas, ensure that equipment installers will not 

expect to use those areas for access to HVAC or 

other equipment. If the pipes cross a path where 

they will get pushed out of the way, they may be 

pushed upward, creating a trap for flowing water, 

and establishing a freeze hazard. Pipe runs should 

be kept to less than 20 feet if possible.

Ensure there is adequate space in the utility area 

for solar storage tanks, pumps, valves, and pipes. 

Note that some packaged systems can sit on top of 

a single tank, taking up no extra floor space.

Insist that solar installers meet with other trades 

to work out equipment compatibility, supply, and 

installations issues. For example:

• Plumbers and solar installers need to be clear 

on who is providing which storage tanks and 

auxiliary heating systems, and when.

• Plumbers need to know that continuously 

operating, whole-house circulating pumps are 

incompatible with direct solar systems.

• Plumbers and installers need to inform each 

other about any problems with corrosive local 

water supplies.

• Roofers need to know what types of flashing to 

use, who will be installing it, and when.

• Trades requiring roof penetrations need to know 

what areas are off limits in order to reserve space 

“We pride ourselves on repeat business 

and good customer service. For us to do 

the installation with no experience would 

have been a warrantee and customer 

relations nightmare...The vendor has 

licensed plumbers and electricians 

specifically trained in solar installations. 

For us, this made the most sense.”

Rich Michal, Civano Project Manager 

for Pulte Tucson, in Arizona
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.15

Solar-Thermal Water Heating Chapter 3

and sunlight for the solar system.

• PV and solar thermal installers need to know 

what parts of the roof to use for their systems. 

Typically the truest southern exposure should go 

to the PV installation unless a western exposure 

is needed to reduce utility peak demand.

• For longer-term performance, landscape designers 

and installers need to keep the southern exposure 

unobstructed from trees and outbuildings.

After exterior sheathing is installed, solar piping, 

wiring, and mounts may be installed. Rough-in 

plumbing for the solar thermal system may be 

installed at the same time as the domestic water 

plumbing rough-in. While on the roof before 

finish roofing has been installed, the solar installer 

should spray paint on the underside of the roof 

the boundaries needed for the solar panels and 

sections of the roof that should be off limits to 

other penetrations that may cause shading.

Solar collectors that are to be integrated into the 

roof are installed directly to the deck before finish 

roofing. The term “integrated” can be confusing 

here. In this context integrated means to be made 

a part of the roof. The confusion may come with 

the name for ICS or integrated collector storage 

type collectors. In ICS collectors the storage tank 

is integrated with the collector.

Final solar equipment can be installed after the finished 

roof is installed and sheetrock has been installed. It may 

also be advantageous to wait until after interior and exterior painting. Waiting avoids problems with overspray 

on solar collector glazing or PV modules, and avoids 

blocking difficult to reach places behind storage tanks 

and equipment.

Production builders should be using a quality 

assurance process that includes pressurization tests 

for the house and duct work. Quality assurance 

should also include the inspection and testing of 

all solar thermal and PV equipment. Experience 

has shown that when inspections have been done, 

failure rates on solar thermal systems are very low, 

much less than 1%. Train your quality inspection 

staff or sub contractor, or hire a specialty sub 

contractor, to test and inspect solar systems. Local 

utilities may help with this function.

Solar Installer Best Practices

This document does not provide detailed technical 

best practices for installers. Other references, listed 

in the Additional Information section, can help 

with details. What this section does do is provide 

insights into working with production builders.

The largest market for solar thermal installers has 

traditionally been in retrofit situations. In retrofit 

settings, the installer takes whatever conditions 

they find and makes things work. Seldom do other 

trades get involved. In the production building of 

new residences, the emphasis should be on systems 

integration, optimal design, and interaction with 

other trades.

New construction provides an opportunity to 

optimize the equipment and installation process. 

Work with manufacturers to package systems that 

will have consumer appeal. Consumers value floor 

space over exposed pipes, valves, and gauges. Select 

packages that preserve floor space and maintain a 

tidy appearance. 

Take advantage of the bulk purchase opportunities 

afforded by production building. Work with the 

builder and manufacturer to ensure the lowest 

prices to production builders. Bear in mind that the 

builder has essentially taken much of the risk and 

marketing costs out of the solar systems installed 

on production homes.

Work with the builder and his or her designers to 

draw the solar system into the plans. System location may change with orientation and site access, 

but putting the system on the plans alerts other 

subcontractors, site supervisors, and inspectors that 

the systems are going in. The plans should include 

predetermined pipe runs between the collectors 

and the location of storage tanks. If needed, the 

plans should also indicate any structural additions 

added for easier or stronger installations. 

Production building incorporates factory-like 

processes in the field. It is not uncommon to 

have houses in various stages of construction as 

one looks down a street. Depending on the size 

of the project, it is possible that every trade that 

supports a particular builder will be represented 
p.16 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

on the job site every day, but working on different 

houses. Thermal solar installers will need to fit into 

this rhythm. It may be necessary to schedule crews 

to do pre-installations, collector installations, and 

interior component installations. Different crews may 

do these tasks simultaneously, or one crew may have 

different jobs at different times. Be clear with the site 

supervisor about demands for crew time.

Work with site supervisors, roofers, plumbers, and 

others to determine the best time to schedule and what 

materials to provide. Pay attention to other trades that 

will be working in the same spaces.

• Spray paint or otherwise mark roof areas 

before finish roofing is installed that need to 

be protected for mounting collectors and to 

maintain solar exposure.

• If collectors go in before painting is complete, 

cover them with plastic to protect against 

overspray. Wind may carry overspray from 

nearby houses so check the status of painting 

on neighboring houses. Remove the plastic when 

painting is complete or ensure that somebody 

has that responsibility.

• Protect pipe runs from other trades that may 

also need access to the same spaces or that may 

need to create runs of their own. 

• Label pipe runs so that they are not pushed up 

and out of the way, creating water traps and 

freeze hazards.

• Work with the builder or designer to establish 

pipe runs in plans to avoid conflicts and maintain slopes. Also add to the plans any structural 

changes that are needed for mounting.

• To avoid confusion, keep solar pipe runs away 

from other plumbing runs to the extent possible, 

especially in houses using copper pipes (rather 

than PEX or another product) for potable 

water system.

• Keep pipe runs away from the perimeter of the 

building or other locations where nailing or 

screwing will be occurring. High activity areas 

include kitchen and bath walls, and above 

doorways and windows that may be moved. In 

addition to avoiding damage, an added benefit is 

that interior locations are less likely to freeze.

Solar installers are a specialized trade within the 

construction industry and often combine functions 

of many traditional trades, such as designers, 

roofers, and plumbers. The design and installation 

of solar thermal systems requires a wide range of 

activities that often includes:

• Activities evaluating the building 

and roof orientation

• Roof work

• Plumbing rough-in, system component 

integration, and final equipment installation 

and start-up.

No one traditional trade combines all of these 

functions without significant training. Solar 

installers need to educate builders about the 

trade’s special products and needs that may require 

added expense.

Solar installers need to confirm solar exposure 

before mounting hardware on the roof. 

Provide quality assurance inspections. Work with 

the site supervisor. Learn from the inspections 

to improve future work. Utility and government 

programs that have involved evaluations have 

found that most system failures are related to 

craftsmanship rather than system design or material 

flaws (for example, FSEC 2006b). These types of 

problems tend to be related to shading, insulation, 

and system connections. Three solutions lend 

themselves to solving these types of problems: 

• Train installers in proper methods and materials.

• Select prepackaged systems that minimize 

onsite connections and insulation.

• Inspect installations and correct problems 

immediately.

In a study of solar thermal retrofits, FSEC staff discovered 

many problem areas related to craftsmanship (Harrison 

and Long 1998). These areas and some design issues 

are shown in the following table. The photos used in 

this table are from John Harrison of the SRCC and 

FSEC and originally appeared in the report indicated 

above, unless otherwise noted.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.17

Solar-Thermal Water Heating Chapter 3

The Wrong Way The Right Way

Always confirm that solar 

exposure is unobstructed. Shading 

is a critical flaw in installation.

Photo middle courtesy of Michael Baechler, PNNL.

Photo far right courtesy of Bill Guimey, Solargenix.

If local water is corrosive to 

copper, use treatments or 

indirect systems.

Photo left courtesy of Mahoney and Menicucci 

2002. Photo right courtesy of Michael 

Baechler, PNNL.

Efficient roof placement minimizes 

pipe runs and keeps pipes sloping 

downward. Keep pipe runs less 

than 20 feet if possible.

Bolts used in mounting must be 

secured and the mount must 

be sealed.
p.18 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

The Wrong Way The Right Way

Roof penetrations must be 

properly flashed and sealed and 

racks properly bolted.

All exposed wires, sensors, and 

insulation must be protected 

against ultraviolet sunlight and 

weather. Temperature sensors 

must be securely attached near 

the hot water exit from the 

collector.

Polyethylene foam insulation sold 

for interior plumbing will not stand 

up to high temperature or prolonged 

sunlight. Use elastomeric insulation 

for heating and cooling systems. 

Fiberglass insulation is suitable for 

interior runs. All insulation exposed 

to the weather should be jacketed 

with PVC pipe, or aluminum, or 

painted. Paint needs to be redone 

every three to five years.

Insulation should be carefully 

applied to fit around corners, 

gauges, and valves. 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.19

Solar-Thermal Water Heating Chapter 3

The Wrong Way The Right Way

Install air vents in a true 

vertical position.

Attic pipe insulation must be 

secured. Insulation on right is 

glued and mitered. Note that 

insulation abuts roof decking and 

does not penetrate it. The hole 

through the deck must 

be caulked.

Seal and hide penetrations 

through interior ceilings and walls 

for fire protection and to block air 

leaks. In new construction, these 

types of penetrations should 

be minimal.
p.20 / CHAPTER 3 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 3 Solar-Thermal Water Heating

Resources and References

ASHRAE Standard 93. “Methods of Testing to Determine the Thermal Performance of Solar 

Collectors,” and ASHRAE Standard 96, “Methods of Testing to Determine the Thermal Performance 

of Unglazed, Flat Plate, Liquid Solar Collectors.”

Aztec Solar. Undated. Solar Water Heating Systems, Solar Pool Heating Systems. Aztec Solar. 

www.aztecsolar.com.

Burch, Jay, Morgan Heater, and Mike Brandemuhl. 2006. “Northward Market Extension for 

Passive Solar Water Heaters By Using Pipe Freeze Protection with Freeze-Tolerant Piping.” Solar 

2006 Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, 

Boulder, CO.

Florida Solar Energy Center (FSEC). 2006a. Solar Water and Pool Heating Manual: Design 

and Installation & Repair and Maintenance. University of Central Florida, Orlando, FL. 

www.fsec.ucf.edu/en/industry/resources/solar_thermal/manual/index.htm.

Harrison, J., and S. Long. 1998. Solar Weatherization Assistance Program. FSEC-CR-1028-98, 

Prepared by the Florida Solar Energy Center for the Florida Department of Community Affairs, 

Tallahassee, FL, 25 August 1998. 

www2.fsec.ucf.edu/en/publications/html/FSEC-CR-1028-98/index.htm.

ISO 9806-1:1994. Test methods for solar collectors – Part 1: Thermal performance of glazed liquid 

heating collectors including pressure drop, ISO 9806-1:1994, International Organization for 

Standardization, Geneva, Switzerland. www.iso.ch/iso/en/ISOOnline.frontpage.

ISO 9806-2:1995. Test Methods for solar collectors – Part 2: Qualification test procedure, ISO 9806-

2:1995, International Organization for Standardization, Geneva, Switzerland. 

www.iso.ch/iso/en/ISOOnline.frontpage.

ISO 9806-3:1995. Test methods for solar collectors – Part 3: Thermal performance of unglazed 

liquid heating collectors (sensible heat transfer only) including pressure drop, ISO 9806-3:1995, 

International Organization for Standardization, Geneva, Switzerland. 

www.iso.ch/iso/en/ISOOnline.frontpage.

Lane, Tom. 2004. Solar Hot Water Systems: Lessons Learned 1977 to Today. Energy Conservation 

Services to North Florida, Inc. Gainesville, FL. www.ecs-solar.com.

Mahoney, Rod, and Dave Menicucci. 2002. Copper Corrosion Analysis of Civano Solar 

Collectors: Final Report. Prepared by Sandia National Laboratory for the U.S. Department 

of Energy, Washington, D.C.

Patterson, John. 2005. “Solar Hot Water: Simplified.” Home Power Magazine, June and July 2005.

Ramlow, Bob and Benjamin Nusz. 2006. Solar Water Heating. New Society Publishers, Gabriola 

Island, Canada.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 3 / p.21

Solar-Thermal Water Heating Chapter 3

Salasovich, Jim, Jay Burch, and Greg Barker. 2004. Pipe-Freeze Probability for Passive-Solar 

Water Heating Systems in the United States. Solar 2005 Conference Proceedings, edited by R. 

Campbell-Howe. American Solar Energy Society, Boulder, CO.

Solar Rating and Certification Corporation (SRCC). 2006. Directory of SRCC Certified Solar 

Water Heating System Ratings. SRCC, Clearlake, FL. www.solar-rating.org.

Solar Rating and Certification Corporation (SRCC). 2006. Summary of SRCC Certified Solar 

Collector and Water Heating System Ratings. SRCC, Clearlake, FL. Listings of SRCC rated solar 

collectors and systems are available at www.solar-rating.org/ratings/ratings.htm.

Solar Rating and Certification Corporation (SRCC). 2006. Operating Guidelines for 

Certifying Solar Collectors, SRCC Document OG-100-06. SRCC, Clearlake, FL. 

www.solar-rating.org.

Solar Rating and Certification Corporation (SRCC). 2002. Operating Guidelines and 

Minimum Standards for Certifying Solar Water Heating Systems, SRCC Document OG-300. 

SRCC, Clearlake, FL. www.solar-rating.org.

Solar Rating and Certification Corporation (SRCC). Accessed 2006. SRCC OG-300 Solar Water 

Heating System Installation Guidelines. Accessible at 

www.solar-rating.org/education/og300education.htm.

Solar Rating and Certification Corporation (SRCC). Accessed 2006. Training videos for solar 

thermal system installation and inspection are available from the SRCC at 

www.solar-rating.org/EDUCATION/video/srcc_video.html.

Tucson-Pima Metropolitan Energy Commission. 2005. Tucson-Pima County Sustainable 

Energy Standard. www.tucsonmec.org/ses.htm.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 4.

Photovoltaic Power Generation

Building America Best Practices Series

Homes with PV systems typically fit in with 

their neighbors.

Enjoying the dappled light filtering through a tree may be as close to understanding the physics of 

photovoltaic (PV) systems as most consumers will get. Tree leaves absorb solar energy for photosynthesis. 

Like leaves on a tree, PV systems produce energy from the sun. Even though the PV process is a phenomenal 

scientific breakthrough, the technology and its application are straightforward. Innovators around the 

world have taken much of the guesswork out of PVs, and research continues to improve efficiency, cost, 

and style. PVs are electric generators and must be properly designed and installed, but the technology 

is readily usable and effective.

Builders’ Brief

• PV cells, frames, wiring, and mounting hardware have 

all advanced to provide integrated systems that can be 

barely discernable on a house.

• Inverter reliability is improving with 10-year 

warranties available.

• Net metering allows consumers to receive credit for the 

power they produce that exceeds the amount they use.

• The National Electrical Code provides detailed guidance 

for PV installation.

• Solar PV installers can be certified by NABCEP; find out if 

they are or what their plans are for becoming certified.

• Incorporate solar information into the homeowners 

manuals that you provide.

• Select packaged systems where possible for the 

benefits of pre-engineering.

• Insist that solar installers meet with other trades to work 

out equipment compatibility, supply, and installation issues.

• Quality assurance inspections and tests will ensure that 

PV systems are properly working.

Installers’ Brief

• Use specialized knowledge to educate 

builders and other trades. New construction provides an opportunity to optimize 

the equipment and installation process.

• Take advantage of the bulk purchase 

opportunities afforded by production building.

• Work with site supervisors, roofers, plumbers, 

and others to determine the best installation 

sequence and schedule, what materials to 

provide, and how to avoid shading from vents 

and other roof penetrations.

• Confirm solar exposure before mounting 

hardware on the roof.

• Provide quality assurance inspections. 

• Many problems are related to 

craftsmanship – use quality assurance 

techniques to avoid problems.

• Work with the builder to develop 

inspection protocols.

• Correct installation and craftsmanship 

problems immediately.
p.2 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Photovoltaic Arrays

PV systems are made with semiconductors like the 

materials used for integrated circuits in computers. These semiconductors convert sunlight into 

direct current (DC) power, just like the electricity 

produced by batteries.

The wafers used to make the semiconductors are 

created from refined silicon (an element found in 

quartz and among the most common elements on 

earth). Traditionally PV cells have been made from 

waste silicon from the computer industry. Now that 

PV is becoming a larger market share, more silicon 

production facilities are coming online.

The most basic part of many PV systems is the 

Cell. A cell is typically a small silicon square (or 

rounded off square). Each cell generates about 

0.5V. In comparison most small batteries like AAA 

or watch batteries are 1.5V. Cells are combined to 

create a PV Module or Panel.

A module is a standalone piece that is enclosed 

between sheets of tempered glass or plastic to 

protect the cells. PV modules should be listed to 

UL Standard 1703. Modules are installed in a set 

called a PV array.

An array is designed to generate a specific amount 

of energy. There can be one, a few, or very many 

modules in an array.

PV cells are one of three types: mono-crystalline, 

multi-crystalline, or amorphous (thin-film).

• Mono-crystalline (or Single-crystalline) 

cells are grown from a single silicon wafer. They 

are the most efficient type of PV cell. Because of 

the way they are grown, mono-crystalline cells 

are rounded. An early industry innovation was 

(top) Reach for the sky!

(bottom) PV cells have grown more diverse 

and efficient. This photo was taken at the NREL 

outdoor test facility and shows both 

mono- and multi-crystalline cells.

Recent Innovations: Modules are on 

the market that are made to replace or 

supplement roofing components. These 

systems are described later in this 

chapter and are called building 

integrated PV.

PV Building Blocks – The Basics

Every house that is connected to an electric utility has a main service panel, an electrical meter and a 

line to the grid. Power flows from the grid through the meter to the panel where it is distributed through 

the wires in the house. When PV or some other form of on-site power generation is added, additional 

power from that source will also flow to the Main Service Panel to be distributed throughout the house. 

Simple grid-tied PV systems have similar additional components that will connect between the PV and 

the main service panel.

A PV installation is an electrical project, and usually a roofing project. Much work has been done with 

proper procedures, National Electrical Code (NEC) applications, and proposed NEC changes. A good 

source of information on these topics is www.nmsu.edu/~tdi/. One suggested publication available 

on that web site is Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested 

Practices (Wiles 2005). References in this chapter will often refer to portions of the NEC as described 

in the NEC 2005 Handbook published by the National Fire Protection Association (NFPA 2005). The 

North American Board of Certified Energy Practitioners (NABCEP) certifies PV installers. The NABCEP 

library is a good source of reference material (www.NABCEP.org).

PV ARRAY

DC

Disconnect

Inverter

DC Grounding

Electrode

Conduit

Existing AC Grounding

Electrode System

AC

Disconnect

Utility

Disconnect

Utility Service

Entrance

Main Load Center

+

-

+

-

L1

L2

L1

L2

N

Schematic diagram of a typical residential PV system. Adapted from Wiles 2006a.

Residential PV System
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.3

Photovoltaic Power Generation Chapter 4

This display of amorphous (thin) PV film shows 

its flexibility.

Talking Shop – Staying Current

Photovoltaics are electric generators. The name is taken from a combination of light (photo) 

and electric force (volt). Electric basics apply and here are some of the basic electrical terms. 

Mathematically, the first three terms are related: Volts = Watts/Amps

A volt is the unit of measurement of force in an electrical circuit that causes current to flow. 

It is electrical “pressure” analogous to water pressure. Volt is abbreviated V and sometimes E. 

Voltage will always cause current to flow from a place of higher voltage (higher pressure) to 

one of lower voltage. One volt is the amount of force needed to produce one ampere of current 

in a circuit having a total resistance of one ohm. 

Amperes or amps refer to the rate of current – or electron flow – through a wire. Amps are 

abbreviated A or sometimes I (for intensity). In terms of water, amps are similar to gallons 

per minute. 

Watts show the rate at which electrical energy is produced (or used). Watts are the power. Watts 

are abbreviated W. We frequently see the abbreviation kW for kilo Watts – one thousand Watts. 

A Watt is an amount of electrical power that is equal to one Amp under the pressure of one volt.

Resistance is a measure of the degree to which an object opposes the passage of electrical 

current. The resistance of a wire depends on the material it’s made of, the thickness (cross 

section) of the wire, the length the current has to travel on the wire and the temperature of the 

wire. Resistance is abbreviated R and measured in ohms or Ω.

Direct Current is the type of current produced by generators such as batteries or PV modules. 

It flows in one direction and produces little variation in voltage. Many household items are run 

on direct current – flashlights, computers, MP3 players, cameras. 

Alternating Current is current that alternates between negative voltage and positive voltage 

with a regular cycle. Almost all electricity produced by U.S. electric utilities is AC and alternates 

60 times a second (60 Hertz). Most large household appliances run on alternating current.

to trim the cell sides to pack more cells closer 

together in modules. 

• Multi-Crystalline (or poly-crystalline)

cells are made up of variously oriented, small 

individual crystals that have been cast in a 

block. They range in color from bright blue to 

black. With their shape and crystalline structure, 

the multi-crystalline cells with small crystals 

resemble dark granite countertops. Cells made 

with larger crystals resemble the structure of 

oriented strand board, but are glossier. Multicrystalline cells are rectangular and closely 

butted into modules. Their larger surface area 

and denser packaging make up for the small 

difference in efficiency between multi-crystalline 

and mono-crystalline cells, leaving them essentially equivalent in generating efficiency.

• Amorphous (or thin-film) modules are made 

by depositing a very thin film of semiconductor 

onto a substrate (glass or plastic). This technology 

does not use individual crystals and the substrate 

can be flexible. These modules are approximately 

half as efficient as the mono- or multi-crystalline 

modules, but also currently cost about half 

as much.

Recent Innovation: Thin film is the 

newest of the PV technologies and 

should help reduce manufacturing 

costs as well as materials costs for 

future products. Some of today’s thin 

film products are described later in this 

chapter in the section BIPV Systems: 

Putting the Pieces Together.
p.4 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

The Grid

For most homes, the source of power is the grid. 

The grid is a common name for the electric utility 

companies’ transmission and distribution systems 

(wires and substations) that link power plants to 

customers through high power transmission line 

service. The power on this line is AC. Most PV installed 

on new homes will be grid-tied (also known as 

Utility-interactive) – or attached directly to the grid 

through the homeowner’s electrical service.

Grid Tied and Battery Backup

Standalone PV systems use special inverters and 

batteries to store power that is generated by the PV 

system. This adds major cost and design complexity 

to a PV system. Unless there is a very specific regular 

need for battery backup, or a home is being built 

on a site more than half a mile away from any 

electric utility, Building America recommends 

grid-tied systems. Essentially, grid-tied systems 

use the grid as a battery. These systems provide 

renewable resources to the homeowner and to the 

utility buying the excess power. However, when 

Residential inverter with backup batteries stored 

inside the box. Photo courtesy of Leif Juell, 

Alternative Power Enterprises, Inc.

Net Metering – Getting Credit For the Sunshine

In most states if the homeowner’s PV array produces more power than the homeowner is using, the 

extra power is sent back to the grid and the homeowner will be credited by the local utility for that 

power. This credit for excess power is called Net Metering. At least 40 states allow net metering.

How does net metering get set up?

Any net metering will require special arrangements with your local utility. Forms will need to 

be filed with the utility to start a net-metering account. Not all utility meters are capable of 

net metering; in some cases special meters will replace the standard meter, in other cases an 

additional meter will need to be installed to show the flow of the energy going to the utility. 

Your solar installer should be familiar with the forms and hardware requirements of the utility.

How much power can I send back? 

Each state has different requirements and allows different sized systems to qualify for net 

metering. In some states only major utilities are required to accept net metering. Some states 

only require the utilities to accept a limited amount of energy back from consumers. Some 

utilities offer net metering even when it is not required by the state.

How much credit will the utility give?

The amount of money paid for the energy varies widely: from the price the utility pays to make 

energy themselves to the highest price a consumer might pay based on Time of Use. In most 

states credits are earned each month based on kWh and are applied to the next bill.

What happens at the end of the year?

Usually there is some kind of “true up” at the end of the year or billing period. The “year” is 

either defined as the end of the calendar year – December 31, or the year since you contracted 

with the utility. In California, at the end of the year since you connected to the grid, any extra 

credits earned go back to the utility. In Colorado, at the end of the calendar year, the utility 

must pay the customer for any extra credits at the utility’s average hourly incremental cost 

for the year. 

Check www.dsireusa.org and www.irecusa.org/connect/index.html for the latest information for 

your state and pointers to your local utility’s net metering website.

The Bottom Line

“Even based on a PV system cost of 

$18,000 to $20,000 for a PV system 

bundled with energy efficiency improvements, if that cost is included in a 30-year 

mortgage with a 6.5% mortgage rate, the 

annual utility bill savings is usually greater 

than the annual increase in mortgage 

cost. When we compared the incremental 

mortgage cost to annual energy savings, 

we showed a positive cash flow.”

David Springer, Davis Energy Group
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.5

Photovoltaic Power Generation Chapter 4

the grid is not functioning (there is a blackout), 

the grid-tied PV system does not provide power 

to the house. Facilities that offer emergency 

services during disasters are good candidates 

for battery backup systems. Candidates would 

include clinics, fire stations, police departments, 

and dispatch facilities.

Inverter

In many respects the inverter is the most complex 

component in a PV system. An inverter takes DC 

current and shapes it into AC current. With a gridtied system the inverter “listens” to the AC current 

being delivered to the house and “echoes” the sine 

wave shape and timing of the wave of power being 

delivered. This way the PV power that is received by 

the house looks just like grid power. When more 

power is generated than is needed by the house, 

the extra power will blend seamlessly back into the 

grid for use by other houses or electrical loads in 

the utility system.

If the utility goes down and there is no power 

coming from the grid, the inverter will turn 

off since there is nothing to echo. This feature 

helps to ensure the safety of linemen working to 

fix the grid. Unless there are batteries involved 

in the PV system, no power will be available to 

the household when the grid is down. This may 

be surprising to homeowners, since their system 

will be capable of generating power, but without 

batteries and a special inverter to switch to the 

battery back up no solar power will be available to 

use until the grid comes back up and the system 

automatically restarts.

As the most complex part of the system, the inverter 

literally takes the heat of converting DC to AC 

power. Like other electronic equipment, inverters 

must dissipate heat. Inverters may be designed for 

either indoor or outdoor installations, but indoor 

installations are more common and provide better 

protection. It is important to plan on space for 

the inverter to be located near the main electrical 

panel. Inverter innovation has made large technical 

strides in the last 10 years. Inverters are becoming 

more efficient, durable, and versatile, and some 

can handle multiple strings of PV modules with 

varying voltages.

Grid-tied inverters should meet UL Standard 1741.

Grid tied inverters. One mounted on a California 

garage wall, the other in a Maryland basement. 

The remote display can be placed anywhere 

in the house for consumers to keep tabs on 

power production. Web-based services are also 

available to monitor PV system performance. 

Builders need to plan ahead to save space for 

the inverter and breakers.

Recent Innovations: Inverters with 

10 year warranties are now available in 

the U.S. European style non-grounded 

inverters are allowed by the 2006 NEC 

(NEC 690.35) code, although not all 

jurisdictions have adopted the most 

recent versions of the code. Remote 

sensors allow consumers to read 

inverter output anywhere in their house.
p.6 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Wires and Connections

Wire sizing is very important as a safety feature of 

PV systems. The photovoltaic contractor, electrician, 

or engineer must properly size the array, the wire, 

and the inverter. The correct type of wire will have to 

be chosen as well. Here is some of the information 

that should be considered for wire sizing: 

The size of wire needed for a PV installation depends 

on the amperage the wire needs to carry and the 

distance it must travel. There are three things that 

can affect wire size: voltage, temperature, and wire 

type. For the same amount of wattage, if you can 

raise the voltage on a wire, the number of amps 

will decrease and the wire size can be reduced. 

Wire length affects voltage. The longer the wire, 

the more voltage will be “lost” along the way.

In other words, the higher the pressure, the less 

flow you need to create the same power (Amps 

=Watts/Volts). This is why the electric utilities 

transmit power across the U.S. at such high voltages; otherwise the cables would be huge. With 

the high prices of copper, aluminum, and conduit, 

properly sized wire is a huge cost savings. For new 

homes, PV systems with batteries are restricted to 

no more than 48V, unless energized parts are not 

accessible during routine battery maintenance 

(NEC 690.71(B)(1). But grid-tied systems without 

batteries are almost always higher voltage and can 

go up to 600V while still meeting the National 

Electrical Code (NEC 690.7C).

The most common types of wire are copper and 

aluminum. Copper has a greater conductivity than 

aluminum and can carry more current than an 

aluminum wire of the same size. It is also more 

expensive. Aluminum is less reliable in smaller 

gauges and is not permitted by NEC for interior 

home wiring. Another variable of wire type is 

insulation. The insulation covering of a wire can 

protect the wire from water, heat, or sunlight. 

Depending on the coverings available, conduit 

may be required to protect the wire. Exposed wire 

should be water and sunlight resistant. Smaller 

wire will require smaller conduit.

PV arrays are made up of PV modules connected 

together. There are two ways to connect those 

modules—in series and in parallel.

Photos of finished (top left) and roughed-in 

exterior junction boxes (right) offer an example 

of how roof flashing attaches to these PV 

system components.

(bottom left) Connectors

Recent Innovations: “Plug and play” 

cable systems have made wiring faster 

and more durable. These cables are 

made to snap together, much like stereo 

or computer component cables have 

worked for years. Some manufacturers 

have also made grounding wires easier 

to install by providing pre-mounted 

cables. If the wires are accessible after 

the modules are installed, the connectors 

must have a mechanical connection to 

prevent accidental opening. Accessible 

junction boxes are required if PV module 

placement makes wire connections 

inaccessible (NEC 690.34).
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.7

Photovoltaic Power Generation Chapter 4

• In series, voltages add up but amperage stays 

the same. Two 12V at 3A modules wired in series 

will give 24V at 3A. In essence, the two modules 

run one after the other and the “pressures” add 

up while the “rate of flow” stays the same.

• In parallel, voltages stay the same but amperages 

add up. The same two 12V at 3A modules wired in 

parallel will produce 12V at 6A. The two modules 

effectively run side by side, and the “pressures” 

are even, but the “rates of flow” at the end 

add up.

• A row of modules wired in series is known 

as a string. Strings of modules can be paralleled together in junction boxes (combination 

boxes) nearby (before the inverter) to reduce 

the number of wires that are connected to the 

house or each string can have its own inverter 

and be combined on the AC side of the system 

(after the inverters).

Wire color coding is a safety issue and a code issue. Wire 

colors on the DC side and AC side are the same.

• The grounded conductor or neutral must be 

white or gray (or marked with those colors). 

Remember this line can carry power.

• The equipment ground must be green, green 

with yellow stripes, or bare.

• The hot-ungrounded conductor may be any 

other color, usually red or black.

Overcurrent Protection

NEC requires that all ungrounded conductors in a 

PV system be protected by overcurrent devices. These 

devices protect the wire from electrical current that 

exceeds the wire’s amperage limits (ampacity). It is 

possible to have excess electrical current on both the 

DC side as well as the AC side. Circuit breakers or 

fuses that are used on the DC side must be UL listed 

and DC rated for the application. These breakers or 

fuses are not intended to protect equipment from 

damage, but to protect the wire from overheating 

and potentially causing fires. Code specifies the 

correct sizes of overcurrent protection based on the 

ampacity of the wire used, its insulating material, 

and the temperature.

Disconnects

All homes require at least one disconnect. Electric 

power from the utility enters a home through either 

an overhead or underground feeder. Before this feeder 

gets into the house, it usually first goes through a 

billing kilowatt-hour meter and then the service 

entrance disconnect. In many jurisdictions, the main 

disconnect may be immediately inside the home at 

the point of first penetration as allowed by the NEC 

(Section 230). A growing number of jurisdictions 

require that a service entrance disconnect must be 

located on the outside of the house. In all cases 

this disconnect must be readily accessible. These 

requirements were established many years ago to 

allow fire response personnel to quickly shut off 

power to a building so that firefighters can safely 

enter the building and cut holes in walls, ceilings 

and roofs in life threatening situations.

Some BIPV systems tie into a junction box that 

was installed during the rough-in stage 

of contruction.

12V DC

3A

12V DC

3A

12V DC

6A

12V DC

3A

12V DC

3A

24V DC

3A

12V DC

6A

12V DC

3A

12V DC

3A

24V DC

3A
p.8 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Exterior disconnect.

In homes with PV systems, the NEC (section 690.14) 

requires supplementary disconnects in addition 

to the main feeder disconnect. One required PV 

disconnect is between the PV arrays and the inverter. 

If the attic is readily accessible with permanent 

stairs, and the PV is on the roof, this disconnect 

may be near the point where the output wire 

from the PV array first enters the house. Or, the 

disconnect may be right next to the inverter if 

the DC conductors are in a metallic raceway or 

pre-assembled metal clad cable. Some inverters 

have incorporated a disconnect switch into a box 

attached to the inverter.

The NEC requires that each piece of PV equipment 

have disconnect switches allowing service providers 

to disconnect the equipment from all sources 

of power. For example, an inverter must have a 

disconnect between it and the array, and between 

the inverter and the panel. The disconnects may 

be circuit breakers or switches (Section 690.17). 

DC-rated switches are expensive; therefore, the 

ready availability of moderately priced DC-rated 

circuit breakers with ratings up to 125 volts and 

110 amps may be a good choice for use in all 12-, 

24-, and 48-volt systems. When properly located 

and used within their approved ratings, circuit 

breakers can serve as both the disconnect and an 

overcurrent device.

In grid-tied systems, the number of disconnects 

depends on the complexity of the system. In a 

simple system there would be disconnects on both 

sides of the inverter, in addition to the main feed 

disconnect required on all houses. In more complex 

systems, there may be disconnect switches for each 

string of arrays, sub-array disconnects, main PV 

disconnects for each inverter, sub-panel and AC 

disconnect (you can only have one AC disconnect 

per utility service). If there are multiple inverters 

they must be combined in a dedicated subpanel 

that feeds one AC disconnect) and a main feed 

AC disconnect.

Disconnect switches must be rated to carry appropriate levels of current and have appropriate voltage 

and interrupt ratings (NEC Section 110.3(B)). 

Recent Innovation: Modern inverters may also 

include integrated DC disconnect switches. In 

these systems, a separate DC side disconnect may 

not be required. 

Main Electrical Panel

Usually power from the inverter is pushed (backfed) 

into the main service panel of a house through a 

circuit breaker. The number of amps that can be 

pushed through is dependent on the original size 

of the electrical panel (load center). The sum of 

the rating of all breakers supplying power to a 

panel must not exceed 120% of the panel rating. 

The backfed PV breakers and the main breaker 

supply power to the panel (NEC 690.64B). For 

example a panel rated at 100A with a 100A main 

breaker can have 20A additional backfed from a 

PV system.

If the system being installed is larger than 20% 

of the panel rating, there are other ways to 

connect to the main panel, but these require specific 

electrical design.

Grounding

NEC 2005 requires any PV system carrying more 

than 50V to be grounded (NEC 690.41), unless 

specific requirements are met (found at NEC 

690.35). These types of systems are common 

in other countries. Also, PV systems must have 

their equipment grounded—even at only 12V 

(NEC 690.43). Grounding limits problems due 

to lightning and other line surges and makes the 

system safer for people working on and around 

the system.

There are two types of grounding—equipment 

grounding and system grounding. 

• Equipment grounding is done to prevent shock 

when touching metal parts that don’t usually 

carry electricity (for example the frames of the 

modules, the junction boxes, appliances). If any 

of the exposed metal is touched by a live wire 

the metal becomes electrified as well – this is 

called a ground fault. A person who touches 

this live part will complete the circuit and be 

shocked. To solve this problem all exposed metal 

parts are wired to the grounding electrode. The 

grounding system must connect every exposed 

Recent Innovations: As of NEC 2005, 

ungrounded systems are permitted 

(not required) in the United States. 

(NEC 690.35) PV installations in Europe 

and Japan have been ungrounded 

for decades, but this is new technology for North America. Allowing this 

technology will bring smaller, lighter, less 

expensive inverters from Europe. The 

inverters don’t need internal isolation 

transformers so they weigh less. This 

change requires the use of listed PV wire 

technology—double insulated single 

conductor wires. Use of ungrounded 

systems will require training on the 

installer/electrician side and the inspector side of solar installations.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.9

Photovoltaic Power Generation Chapter 4

non-current-carrying part of the installation to 

ground. The equipment ground wire is either 

green, green with yellow stripes, or bare. 

• System grounding takes one current-carrying 

conductor and attaches it to ground. On the DC 

side that is the negative or positive (depending 

on the inverter and module specifications) 

conductor (white or gray wire); on the AC side it’s 

the neutral conductor (white or gray wire). The 

closer the grounding connection can be to the PV 

source the better the protection from surges due 

to lightning.

• When servicing you must be able to remove a 

module without breaking the system ground 

circuit. Some modules on the market are 

not compliant with this code issue. Ensure 

that modules for your job meet this code 

requirement. 

BIPV Systems: A New Way of

Putting the Pieces Together

Fundamentally, all PV systems have similar components and work in similar ways. At the beginning 

of this chapter was a diagram of a generic system. 

Although systems work in similar ways, they do 

have different architectural styles and engineering 

methods for how they are integrated with a house in 

order to take advantage of the unique characteristics 

of module materials.

Even though their use is more widespread, PV 

systems have become much more difficult to spot 

on rooftops. Building integrated systems are literally 

built into the building and have the same profile 

as nearby materials. 

Most PV systems still mount on racks, but many of 

these systems have such a low profile they appear to 

be thin skylights. A review of products available in 

the U.S. can be found in the November 2005 issue 

of Energy Design Update (EDU 2005). Mounting 

systems that place PV arrays very close to the roof 

surface, but not actually integrated into the roof, 

are described in Chapter 6: Solar System Mounts. 

More traditional rack systems are also described.

BIPV stands for Building Integrated Photovoltaics. 

These systems represent a major innovation in 

incorporating PV into residential architecture. 

BIPV systems are PV arrays that also serve as 

an integral part of the building. The PV arrays 

usually replace other parts of the shell – typically 

roofing material.

Recent Innovations: Module 

manufacturers are providing grounding 

screws and pre-installing cables to 

ease installation.

Recent Innovations: Building 

Integrated and direct mount systems 

hide most hardware, are difficult to 

spot, and use the array to cover most 

roof penetrations, helping to keep 

penetrations out of the direct weather.

Standard Fire Ratings for Roof Coverings – UL 790

Three classes of fire exposure are described:

Class A roof coverings are effective against severe fire test exposures. Under such exposures, roof 

coverings of this class afford a high degree of fire protection to the roof deck, do not slip from 

position, and are not expected to produce flying brands (burning objects). 

Class B roof coverings are effective against moderate fire test exposures. Under such exposures, 

roof coverings of this class afford a moderate degree of fire protection to the roof deck, do not slip 

from position, and are not expected to produce flying brands. 

Class C roof coverings are effective against light fire test exposures. Under such exposures, roof 

coverings of this class afford a light degree of fire protection to the roof deck, do not slip from 

position, and are not expected to produce flying brands. 
p.10 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Cement Tile Systems

Perhaps the most popular integrated system in 

the U.S. is made up of PV modules that are sized 

and mounted to replace cement tiles. The most 

common systems use mono- or poly-crystalline 

cells. The PV tiles are installed on roofs in a way 

that blends in with cement tiles. The PV tiles follow 

the contour of the roof in exactly the same way as 

do the cement tiles. Electrical connections are made 

between each tile. In some cases a single module 

will replace a set of three or four tiles, reducing the 

number of connections. Many of these tiles, when 

installed according to manufacturer specifications, 

are Class A fire resistant.

The PV arrays weigh less than the cement tiles 

they replace. But the roof must be engineered for 

the correct weight and any supporting structure is 

done in advance. Since these products are replacing 

roofing material and are the first line of defense 

against the elements, they should be compliant 

with local and national roofing requirements. Some 

BIPV products have been tested by UL as a Listed 

roofing material under UL 790 (Class A Fire) and 

UL 997 (110 wind rating), as well as UL 1703 (PV 

Module). In addition the ICC recently established 

acceptance criteria to provide guidance for the 

evaluation of BIPV roof panels (ICC 2006). Builders 

should ask installers or other suppliers to confirm 

that BIPV systems meet these standards.

Each manufacturer has specific requirements for 

its product. One product selected as an example 

is the SunPower SunTile. These PV tiles are placed 

on top of an underlayment that covers the roof 

deck. The underlayment helps to provide Class A 

fire rating. The following text and photos describe 

the installation sequence for this product.

Photo numbers correspond to paragraph numbers. 

Not all paragraphs have a corresponding photo. 

∂After framing but before insulation and sheetrock 

are installed the house is prewired for the PV 

array. Metallic armored cable is run from a loose 

junction box placed near the roof to the point 

where the inverter will be installed. Rough-in 

boxes are installed as end points for the cable. 

The inverter is installed and lines are run to the 

shutoff on the AC side and to the main panel. 

This product is lighter than the tiles replaced, 

so no extra structural support is needed.

Here are some of the 

currently available cement 

tile type PV systems:

EnergyTile – BP Solar

GEPV-055 – GE Energy

MyGen | Meridian – Kyocera

ND-62RU1 – Sharp Solar

SolarSave – Open Energy Corporation

SunSlates – Atlantis 

SunPower

(photo series) Cement tile system 

step-by-step installation

Photo numbers correspond to paragraph 

numbers. Not all paragraphs have a 

corresponding photo.

∂ ∑ ∏
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.11

Photovoltaic Power Generation Chapter 4

(photo series, continued) Cement tile system 

step-by-step installation

∑Roofers install cement tiles in all areas except 

where the PV array will go. The PV crew installs 

underlayment over the roofing felt to achieve a 

Class A fire rating. 

∏Before installing any PV modules, the crew 

checks for proper solar exposure. In this case 

the crew determined that the house next door 

would shade the system as originally designed. 

The crew adjusted by moving the location for 

the array farther up the roof. This adjustment 

required removing some of the cement tile 

battens near the ridge and installing a new 

course of cement tiles at the base of the array. 

πBrackets are installed for the first run of PV tiles. 

All brackets are sealed to the underlayment with 

butyl tape.

∫PV tiles are installed row by row. Each row is 

tested for proper power production as the PV 

tiles are installed. The entire array is grounded 

through the inverter back to the main panel. 

Plug and play cables and connectors wire 

together the modules.

aAny penetration left over from removing obstructive nails or a screw that did not seat or for any 

other reason is sealed with caulk. 

oA tube that is combined with flashing and a seal 

guides the positive, negative, and ground wires 

through the roof. An additional seal is provided 

with caulking. The last PV tile covers the wire 

receiver.

ΩThe junction box that was left hanging loose at 

the top end of the interior wiring is now attached 

at the point where the wire receiver penetrates 

the decking. The PV wires are hot as soon as the 

array is installed, so wires from the PV should 

not be wired into the interior wires until the 

system is ready to accept the electric current. 

æWiring can be connected to the inverter 

AC disconnect and the main panel. The AC 

disconnect is located outside within sight of 

the main service panel for access by utility and 

emergency crews.

ø An example of the finished product is the model 

home at Grupe’s Carsten Crossing in Rocklin, 

California.

∫

π o ø

“When Premier Gardens’ homeowners 

started moving into their homes in fall 

2004, their September energy bills 

averaged $20 while their neighbors 

were paying around $70. The homes 

are nearly identical in size and price 

but the Premier Homes sport advanced 

energy-saving features and a 2.2-kWh 

photovoltaic tile system on every roof.”

According to ConSol, a U.S. Department of 

Energy Building America Team Partner.
p.12 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Thin Film PV Laminate 

for Raised Seam Metal Roofs

One interesting place to put solar is on a metal 

standing seam roof. This laminate on soft plastic 

rolls out to fit between the seams. While this does 

not replace the metal on the roof, it is directly 

attached with glue during installation of the roof. 

The electrical connections are made under the roof 

ridge (an easily accessible place for maintenance). 

The systems are easy to install with no additional 

structural support required. The system is produced 

by Uni-Solar Laminates – Uni-Solar Ovionics.

Examples of installations of metal standing seam 

roof laminate systems follow. Photo numbers correspond to paragraph numbers. Not all paragraphs 

have a corresponding photo. 

∂After framing but before insulation and sheetrock 

are installed the house is pre-wired for the PV 

array. Metallic armored cable is run from a loose 

junction box placed near the roof to the point 

where the inverter will be installed. Rough-in 

boxes are installed as end points for the cable. 

The inverter is installed and lines are run to the 

shutoff on the AC side and to the main panel. No 

extra structural support is needed for this product. 

Preparation may include providing conduit races 

through the peak to run wires. 

∑The metal roof must have steel pans that are at 

least 16” wide. They must be flat surfaced with 

no pencil beading or decorative stippling.

∏The pans must be cleaned well to the manufacturer’s specifications. 

πThe laminate is installed onto the pans before 

the pans are installed on the roof. The laminate 

comes in pre-cut rolls and comes with the glue 

already adhered to one side. Peel the protective 

covering and adhere the laminate to the pan. 

Make sure there are no bubbles. This job could be 

completed in a shop to maintain a clean surface 

and to keep materials out of the weather.

∫Install the pans on the roof normally with the 

wires facing the peak. 

aThere are no penetrations in the pans with this type 

of solar array, reducing the possibility of leaks.

oThe wires are connected along the ridge of the 

roof and covered later by the ridge cap. The 

∂ ∑

(photo series) Metal standing seam roof 

laminate systems step-by-step installation.

(above) Photo courtesy of Leif Juell, 

Alternative Power Enterprises, Inc. 

Photo numbers correspond to paragraph 

numbers. Not all paragraphs have a 

corresponding photo.

Photo courtesy of Decker Homes. Photo courtesy of Decker Homes.

π
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.13

Photovoltaic Power Generation Chapter 4

NEC requires that wires penetrating the roof 

be inside metal conduit.

ΩPV wires are hot as soon as the array is installed, 

so wires from the PV should not be wired into 

the interior wires until the system is ready to 

accept the electric current.

æWiring can be connected to the inverter AC 

disconnect and the main panel. In this example, 

the AC disconnect is located outside for access 

by utility and emergency crews.

ø An example of a finished home using Uni-Solar 

Laminates.

Non-Roof BIPV

South facing walls can be covered in PV vertically 

or can be slanted to act as window shading and 

PV at the same time.

Thin-film PV can be set between two sheets of 

tempered glass to make a filtered window or filtered 

skylight that also collects power. This runs about 

three times more expensive than regular PV but 

can make a powerful architectural statement.

Mono- or poly-crystalline PV can also be set between 

sheets of glass to create a dappled effect, blocking 

the majority of sunlight to make electricity, but 

allowing shaded light through. This reduces solar 

gain to the interior of the building while producing 

electricity.

(photo series) Metal standing seam roof 

laminate systems step-by-step installation. 

Photo courtesy of Decker Homes.

Photo courtesy of Leif Juell, 

Alternative Power Enterprises, Inc. 

(top) Photo courtesy of Decker Homes.

(bottom) Photo courtesy of Leif Juell, Alternative Power Enterprises, Inc. 

∫

a

æ

This house from the Solar Decathlon incorporated thin film PV 

in its windows. Photo courtesy of Wendy Butler-Burt of the U.S. 

Department of Energy.

ø
p.14 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Shingle Systems

Shingle systems are similar to the thin-film laminate 

product. Shingle systems take advantage of thin film 

PV and can replace asphalt shingles (Heckeroth 

and Perkins 2006). This lighter weight plastic 

replacement for shingles comes in relatively long 

strips to replace courses of asphalt shingles and 

reduce the number of electrical connections.

One currently available amorphous asphalt shingle 

replacement is the Uni-Solar Shingle made by 

Uni-Solar Ovionics. These PV shingles are applied 

over a fire-resistant membrane. 

Builder Best Practices

Before installing solar equipment, be sure your 

designs, materials, and construction techniques 

are as energy efficient as possible. An integrated 

system design approach, saving at least 30% 

whole house energy use, should be applied to 

your homes to ensure the maximum possible value 

for consumers, and profits for your company. An 

integrated system design can improve comfort, 

increase home durability, save money, and improve 

energy efficiency. Best practices and research reports 

for energy-efficient construction can be found on 

www.buildingamerica.gov.

Inviting photovoltaic professionals to join your 

building team will bring experience and technical capability to help minimize system problems 

and maximize system performance. Your team 

will need to include a solar designer, installer, 

and electrician. Sometimes this can be the same 

person. Usually the solar designers are also the 

installers. Often solar design firms also employ 

master electricians to review their designs. The 

solar design firm should be familiar with which 

jurisdictions you’ll need permits from, how to 

contact the local utility for grid-tied systems, and 

how to get rebate information.

PV installers can be certified by NABCEP (North 

American Board of Certified Energy Practitioners). 

Solar energy associations, community colleges, 

manufacturers, and others offer training. A listing 

of coursework is available at www.irecusa.org. Ask 

installation companies what types of training their 

installers receive and if they plan to pursue NABCEP 

certification. Find out more about NABCEP at 

(left) ∂ Using a template provided by the 

manufacturer, the crew marks and drills holes 

for the solar shingle wiring to be pulled through 

the roof. The holes are under the shingles, but 

should be caulked or otherwise weather sealed. 

(middle two photos) ∑∏ These systems use 

plastic grommets to line penetrations and a 

plastic raceway acts as a junction box for the 

wires. Check with local code officials to ensure 

these components comply with local code.

(right two photos) π∫ In this house there are 

two strings, with one inverter per string. There is 

a combiner box on AC side (after the inverters). 

The photo shows the two AC disconnects, the 

inverters, and the main panel. The PV wires are 

hot as soon as the array is installed, so wires 

from the PV should not be wired into the interior 

wires until the system is ready to accept the 

electric current. Systems should be 

tested prior to final hook up.

All photos courtesy of Decker Homes.

∂ ∑

π

∏ ∫
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.15

Photovoltaic Power Generation Chapter 4

www.nabcep.org/pv_installer.cfm. The NABCEP 

system installer study guide is a good reference as 

well as helping installers prepare for the certification test (NABCEP 2003).

Electrical work on the AC side may be done by 

electricians rather than solar installers (who also 

may be electricians), or by the solar installers if 

needed. An electrician is needed for the interconnection to the utility grid.

The design for the system will include the type 

(BIPV or rack mounted) and number of modules, 

the size and type of wire, number of inverters, 

and location of all components. Designers should 

provide space for wiring runs and for mounting 

inverters and shut-offs. Make sure the plan has 

been reviewed by an electrician. You will need good 

drawings for the local utility, jurisdiction and crew. 

Locations for the main panel, shut-offs, signage, 

and the inverter should be clearly indicated on 

plans. Often these components are mounted on a 

single board for ease of access.

A photovoltaic firm should know what permits 

are required. In some jurisdictions only electrical 

permits are needed. In others, the permit systems 

can be more complicated. Some jurisdictions give 

priority attention or reduced fees for projects that 

include solar features. Because this system will be 

a grid-tied system, the local utility must approve 

it. The photovoltaic design firm should know how 

to get this done.

Choose systems that match your architectural style 

and are easy to install. Avoid systems that require 

multiple penetrations through the roof deck or 

that involve multiple separate arrays. Multiple 

arrays are possible, but may involve adding more 

than one inverter.

Standardized design packages with pre-engineered 

mounting systems and integrated components offer 

advantages over custom designs. These systems 

tend to include documentation such as drawings 

and instructions that aid with permitting and 

inspections. Pre-engineered systems require less 

installation time and cost (Dunlop Undated).

Once the PV system has been properly sized and 

the design has been committed to the plans, 

ensure that contract documents stipulate the 

specifications of the equipment and the installation requirements for the installer, including 

responsibility for quality assurance and corrections. A sample Statement of Work can be found at 

www.consol.ws/pdf/pv3sow.pdf, and in Appendix I. 

ConSol, the company that developed this sample 

Statement of Work, leads a Building America team, 

and has worked on several ZEH communities 

using PV and a high level of energy efficiency.

As the roof is being framed, additional structure 

to support the PV can be installed, but typically 

should not be needed. Although not needed structurally, backing material may be added to allow 

for easier installation and more secure lag bolt 

connections.

Insist that PV installers meet with other trades to 

work out equipment compatibility, supply, and 

installations issues. For example:

• Roofers need to know what types of flashing to 

use, who will be installing it, and when. Roofers 

also need to know if BIPV will be used that will 

replace sections of the roof.

• Trades requiring roof penetrations need to 

know what areas are off limits for vents or 

other elements that may shade the PV. This 

coordination issue was the number one area of 

difficulty identified by PV installers interviewed 

for this document.

• PV and solar thermal installers need to know 

what parts of the roof to use for their systems. 

Typically the truest southern exposure should 

go to the PV installation.

• For long-term performance, landscape 

designers and installers need to keep the 

southern exposure unobstructed from trees and 

outbuildings. 

• Painters and stucco crews need to take all steps 

necessary to avoid overspray.

SheaHomes offers an example of a well-integrated 

solar installation. A report on the Scripps Highland 

project found there “were no issues whatsoever 

Home with PV shingle system. Photo courtesy of 

Decker Homes.

Trades requiring roof penetrations need 

to know what areas are off limits for 

vents or other elements that may shade 

the PV. This coordination issue was the 

number one area of difficulty identified 

by PV installers interviewed for this 

document.
p.16 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

regarding roof penetrations (and any leaks as a 

result of)” at the project. The report notes that 

the systems were installed with a roof penetration flashing system, the design of which was 

supported by the roofing company involved in 

the installation. “That, in all likelihood, made a 

substantial difference in the success of the project, 

by engaging the existing roofing subcontractor in 

the decision-making process, and calling upon 

the company’s expertise in roofing and flashing 

techniques (Nelson 2005).”

After exterior sheathing is installed, solar mounts 

and junction boxes may be installed. While on 

the roof, the solar installer should spray paint 

the boundaries needed for the PV modules and 

sections of the roof that should be off limits to 

other penetrations that may cause shading or that 

will be blocked by the array.

The best time to install PV modules will depend 

on the product being used and accommodations 

worked out with trades. It may be advantageous 

to wait until after exterior painting. Waiting avoids 

problems with overspray on solar collector glazing 

or PV modules.

Production builders should be using a quality 

assurance process that includes pressurization tests 

for the house and duct work. Quality assurance 

should also include the inspection and testing of 

all solar thermal and PV equipment. Experience 

has shown that when inspections are done, failure 

rates on solar thermal systems are very low, much 

less than 1%. Train your quality inspection staff or 

sub contractor, or hire a specialty sub-contractor, to 

test and inspect solar systems. Local utilities may 

help with this function. Inspection guidance for 

codes officials (which should be readily adaptable 

for quality assurance) is available at www.irecusa.

org. A detailed testing protocol has been developed 

by the National Renewable Energy Laboratory and is 

available at www.nrel.gov/docs/fy03osti/30301.pdf. 

A quality assurance checklist, developed by ConSol, 

a team leader for Building America, is available at 

www.consol.ws/pdf/PV4Checklist.pdf and in 

Appendix I. Sources for other checklists are listed 

at the end of the PV Installer Best Practices in the 

next section. 

PV Installer Best Practices

This document does not provide detailed technical 

best practices for installers. Other references, listed 

in the Additional Information section can help with 

details. What this section does do is provide insights 

into working with production builders. 

Work with the builder and his or her designers to 

draw the PV system into the plans. System location may change with orientation and site access, 

but putting the system on the plans alerts other 

subcontractors, site supervisors, and inspectors 

that the systems are going in. The plans should 

include predetermined locations for inverters and 

cut off switches. If needed, the plans should also 

indicate any structural additions added for easier 

or stronger installations. 

Production building incorporates factory-like 

processes in the field. It is not uncommon to have 

houses in various stages of construction as one 

looks down a street. Depending on the size of the 

project, it is possible that every trade that supports 

a particular builder will be represented on the job 

site every day, but working on different houses. PV 

installers will need to fit into this rhythm. It may 

be necessary to schedule crews to do pre-installations, array installations, and interior component 

installations. Different crews may do these tasks 

simultaneously, or one crew may have different jobs 

at different times. Be clear with the site supervisor 

about demands for crew time.

Work with site supervisors, roofers, plumbers, and 

others to determine the best points in time to be 

in a house and what materials to provide. Pay 

attention to other trades that will be working in 

the same spaces.

• Spray paint roof areas before the finish roof is 

installed that need to be protected for mounting 

modules and to maintain solar exposure.

• If arrays go in before house painting is complete, 

cover them with plastic to protect against overspray. Wind may carry overspray from nearby 

houses so check the status of painting on 

neighboring houses. Remove the plastic when 

painting is complete or ensure that somebody 

has that responsibility.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.17

Photovoltaic Power Generation Chapter 4

• Work with the builder or designer to establish 

wire runs in plans to avoid conflicts. Also add 

to the plans any structural changes that are 

needed for mounting.

As noted, the area to be used for the PV array 

should be outlined on the roof deck, before finish 

roofing is installed, with orange paint. The solar 

designer should walk the edges of the PV array 

location—especially the corners—with the 

“Solar Pathfinder” or other shade analysis device 

to make sure there are no obstructions during 

the critical solar window (9am – 3pm) before 

applying paint on the deck. The painted area 

should extend to the south beyond the actual PV 

footprint to avoid the installation of any components (vents or stacks) that may cast a shadow 

on the array. Plumbers, electricians, roofers, vent 

installers, and any other relevant trades should 

be informed that the outlined area is off limits 

to penetrations.

If stand-offs are needed for a rack mounted system, 

they should be installed and flashed before the 

final roofing material is installed.

If part of the roofing material is BIPV, the base 

roofing felt or other membrane material should 

be installed first. The BIPV can then be installed 

and final wiring done. There may be minor finish 

work edging the BIPV. 

Rack mounted systems require roofing to be 

completed before installing the system. Installers 

can compensate with plastic wedges for modules 

that are slightly out of square and roofs that aren’t 

perfectly flat. 

Each row of modules should be tested as arrays are 

installed to isolate any loose connections, ground 

faults, or faulty modules.

Cover the installed PV arrays with tarps or drop 

cloths during external painting of the house. Check 

the status of nearby house painting. Wind can carry 

overspray from a neighboring house. Overspray 

on the modules can greatly reduce their power 

generation.

Provide quality assurance inspections. Work with 

the site supervisor. Learn from the inspections to 

improve future work. Have the electrician do a 

commissioning check before the last connection 

is made (between the PV and the DC breaker). 

Inspection guidance for codes officials (which 

should be readily adaptable for quality assurance) 

is available at www.irecusa.org (Brooks Engineering 

2006) and at the Southwest Technology Development Institute at www.nmsu.edu/ntdi (Wiles 

2006a and b). An onsite commissioning process 

has been published by the National Renewable 

Energy Laboratory (Barker and Norton 2003). A 

quality assurance checklist developed by ConSol, 

a team leader for Building America, is available at 

www.consol.ws/pdf/PV4Checklist.pdf and in 

Appendix I. A checklist designed specifically for 

compliance with the NEC has been developed by 

John Wiles (2006).

Gather a homeowner packet of information, 

including homeowner/installation guides from 

the PV manufacturer, the inverter manufacturer 

and from any monitoring systems that have been 

installed. Make this information part of the builder’s 

homeowners manual.

An evaluation of Florida experience suggests a 

number of reliability problems can be attributed 

to the quality of installation and workmanship of 

contractors, primarily due to the limited workforce and experience. Often these problems can 

be attributed to the lack of good plans, drawings 

and instructions for the installation. In other cases, 

the limited knowledge, skills and experience among 

contractors have resulted in poor quality installations (Dunlop undated, and Wiles, Brooks, and 

Schultze 2006). The following table lists a set of 

measures that field inspectors have found to be 

problem areas. 
p.18 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Always confirm that solar 

exposure is unobstructed. 

Shading is a critical flaw 

in installation.

(left) Photo courtesy of NREL. 

(right) Photo courtesy of 

Heidi Stewart of PNNL.

Roof penetrations must be 

properly flashed and sealed.

Photos courtesy of

 Namaste Solar Electric

Wire connections must be 

properly installed. New “plugand-play” wires systems help 

solve this problem.

(left) Photo courtesy of John Wiles of 

SWTDI. (right) Photo courtesy of 

Kurt Johnson of SunPower

Electrical materials (lugs, screws, 

wires) selection is critical for 

a safe and durable system. In 

the picture to the left, indoor 

rated materials were used for an 

outdoor grounding application.

(left) Photo courtesy of 

John Wiles of SWTDI

The Wrong Way The Right Way
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.19

Photovoltaic Power Generation Chapter 4

The Wrong Way The Right Way

Materials must be properly 

installed. Wires must fit lugs. 

Use lugs listed for proper 

environment.

Photos courtesy of John Wiles of SWTDI.

Testing as arrays are installed 

allows for isolating problem 

panels and troubleshooting the 

overall system. A non-functioning 

array might as well be constantly 

facing the night sky.

(left) Photo courtesy of NASA. (right) Photo 

courtesy of Kurt Johnson of SunPower.

Service providers must be 

able to disconnect each piece 

of serviceable equipment in 

the PV system, such as arrays 

and inverters. In simple grid 

tied systems there will be a 

DC disconnect between the 

modules and the inverters and 

an AC disconnect between 

the inverters and the panel. 

Components need to be placed 

in readily accessible locations.

(left) Photo courtesy of John Wiles of SWTDI.

Arrays must be protected from 

construction activities, including 

paint overspray.

(right) Photo courtesy of NREL.
p.20 / CHAPTER 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 4 Photovoltaic Power Generation

Long Term Maintenance

PV systems have very simple long term maintenance. These systems should last at least 20 years. Here 

are the basic steps homeowners need to follow:

• Yearly cleaning of the PV modules or rely on seasonal rain,

• Occasional snow removal – depending on the climate (do not use metal objects to clean glass),

• If any wires are exposed, yearly checking for evidence of hungry critters (like squirrels), and 

• Maintaining a performance log to watch for major variations in energy production (non-weather 

related) to track potential problems. Systems that include web-based monitoring can provide 

this service.

Resources and References

California Energy Commission (CEC) lists of Eligible Equipment 

www.consumerenergycenter.org/erprebate/equipment.html

NABCEP – North American Board of Certified Energy Practitioners 

www.nabcep.org

IREC – Interstate Renewable Energy Council

www.irecusa.org

Southwest Technology Development Institute, New Mexico State University

www.nmsu.edu/~tdi/

SEI – Solar Energy International 

www.solarenergy.org

Namaste Solar Electric 

www.namastesolar.com

FSEC – Florida Solar Energy Center 

www.fsec.ucf.edu

NREL – National Renewable Energy Laboratory, Solar Research

www.nrel.gov/solar/

Barker, G., and P. Norton. 2003. Building America System Performance Test Practices: Part 

1 – Photovoltaic Systems. NREL/TP-550-30301. Prepared by the National Renewable Energy 

Laboratory for the U.S. Department of Energy, Golden, CO. www.nrel.gov/docs/fy03osti/30301.pdf

Brooks Engineering. 2006. Inspector Guidelines for PV Systems. Prepared for the Renewable 

Energy Technology Analysis Project of the Pace Univeristy Law School Project. Available at 

www.irecusa.org/articles/static/1/binaries/InspectorGuidelinesDraft9.pdf

Dunlop, Jim. Undated. Reliability and Experience in the Florida PV Buildings Program. Florida 

Solar Energy Center, Cocoa, FL
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 4 / p.21

Photovoltaic Power Generation Chapter 4

Energy Design Update (EDU). 2005. “New Products: Photovoltaic Roofing.” Energy Design 

Update, November 2005. Aspen Publishers, New York. www.aspenpublishers.com

Heckeroth, Stephen and Daniel Perkins. 2006. “The Future of Photovoltaic Roofing Products.” 

Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, 

Boulder, CO.

ICC Evaluation Service, Inc. 2006. Proposed Acceptance Criteria For Building-Integrated 

Photovoltaic (BIPV) Roof Panels. AC365. Whittier, CA. www.icc-es.org

National Fire Protection Association. 2005. NEC 2005 Handbook: NFPA National Electrical 

Code, International Electric Code Series. Edited by Mark Earley, Jeffrey Sargent, Joseph Sheehan, 

and John Caloggero. National Fire Protection Association, Quincy, MA.

Nelson, Les. 2005. Scripps Highlands; A SheaHomes Zero Energy Home Project in the San Diego 

Area. Prepared by Western Renewables Group for the Sacramento Municipal Utility District.

North American Board of Certified Energy Practitioners (NABCEP). 2003. Study Guide 

for Photovoltaic Systems Installers and Sample Examination Questions. Originally prepared 

for the U.S. Department of Energy and Sandia National Laboratories by the Southeast Regional 

Experimental Station and the Florida Solar Energy Center, Cocoa, FL.

Rudin, Arthur and Edgar Becerra. 2006. Designing Residential PV Systems to Meet Local Wind 

Loads and Building Codes. Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. 

American Solar Energy Society, Boulder, CO.

Russell, Scott. 2004. “Solar Electric Systems Simplified.” Home Power, Issue 104, December 2004 

and January 2005. www.homepower.com

Wiles, John. 2006a. Photovoltaic Electrical Power Systems Inspector/Installer Checklist. Available at 

www.nmsu.edu/~tdi/

Wiles, John. 2006b. “Code Corner: Working with Inspectors: What Your Checklist Should Include.” 

HomePower, Issue 113, June & July 2006. www.homepower.com. Also at www.nmsu.edu/~tdi/

Wiles, John. 2006c. “Achieving the Art of the Possible.” July-August 2006. IAEI News, International 

Association of Electrical Inspectors. www.IAEI.org. Also at www.nmsu.edu/~tdi/

Wiles, John. 2006d. “The 15-Minute PV System Inspection: Can you? Should you?” May-June 2006. 

IAEI News, International Association of Electrical Inspectors. www.IAEI.org. 

Also at www.nmsu.edu/~tdi/

Wiles, John, Bill Brooks, and Bob-O Schultze. 2006. “PV Installations, A Progress Report.” 

Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, 

Boulder, CO.

Wiles, John. 2005. Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested 

Practices. SAND-2005-0342-N, Prepared for Sandia National Laboratories by the Southwest 

Technology Development Institute at New Mexico State University, Las Cruces, New Mexico. 

(electronic version was published in 2006) www.nmsu.edu/~tdi/
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems -JUNE 2007 CHAPTER 5 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 5.

Planning and Orientation

Building America Best Practices Series

Low Riders: Builders and homeowners prefer 

collectors and arrays that hug the roof line.

The prime real estate for PV arrays and solar thermal collectors is the portion of a roof facing south. Although 

this scenario is the best, there is plenty of latitude for both the tilt and the direction (azimuth) of arrays and 

collectors. Surface tilt angles and azimuth angles can be varied over a considerable range without substantially 

reducing the amount of available annual solar radiation (Christensen and Barker 2001). This is especially 

true for locations with low latitudes and typical low-angle roof tilts (i.e., 20° to 30°).

Information in this chapter is similar for both solar thermal and PV systems. This chapter reviews planning 

and orientation information for solar installations. Site assessments are not difficult. Solar installers 

should insist on conducting site and house-plan assessments before contracting to perform work on a 

particular community. It is highly recommended that installers coordinate with other trades that can 

impact their roof space, such as plumbers, to ensure that no obstacles will be placed in the way of the 

solar installation. Some installers have found it helpful to physically mark-off the area on the roof that 

is reserved for the solar collector(s). Installers should also confirm that there are no shading problems 

at the time of collector or array installation. Builders and designers can do their own assessments to 

confirm findings or to improve house designs or siting plans. 

Builders’ Brief

• South is best, but solar orientation and tilt are forgiving for PVs and solar thermal.

• Use low riders - add solar equipment close to the roof and at the same angle as the roof.

• Consider sites other than the roof of the house to locate solar equipment.

• Design for the climate with efficient windows and appropriate overhangs. 

• Free web-based tools offer modeling and design guidance.

• Design communities to avoid shading solar collectors and arrays.

• Carefully use trees to shade streets (reduce heat-island effects) and south or west windows for free cooling. 

• Choose shorter deciduous trees that will not shade solar collectors.

Installers’ Brief

• Plan ahead with builder to minimize 

shading and location problems from 

vents and chimneys.

• Plan ahead with builder to ensure roof 

area for collectors.

• Assess shading to help decide if solar 

is right for a community.

• Assess shading before installing 

collectors or arrays to confirm location.

• Give builders a copy of the sun chart 

or site evaluation for their community. 

• Free web-based tools offer modeling 

and design guidance.
p.2 / CHAPTER 5 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 5 Planning and Orientation

There is great deal of flexibility in where collectors 

and arrays may be installed. While it is possible to 

provide an optimal tilt that is different from that 

of the roof, there is little penalty in putting solar 

equipment parallel to and close to roof decks, 

and installations close to the roof will realize 

minimum wind loads. This configuration appears 

much like a skylight, and some products allow 

actual integration into the roof. In PV systems, 

this flexibility helps to explain the attractiveness 

of building-integrated systems. 

In addition to roofs, solar equipment may also be 

mounted on racks sitting on the ground or on the 

roofs of sheds, carports, or other outbuildings. All 

of the same rules apply for site evaluation.

The rule of thumb is to install PV arrays and solar 

thermal collectors in direct sun with no shade 

during the peak solar window (approximately 

9:00 AM to 3:00 PM). However, in situations where 

utilities experience significant afternoon or early 

evening peaks in the summer, it may be preferable 

to face PV arrays more to the west to take advantage 

of late afternoon sun – this can be coupled with 

time-of-use electricity tariffs that can make this 

more cost-effective to the homeowner. This is less 

important for solar thermal collectors because of 

their ability to store up heat in tanks.

Shading 

Shading is likely to have the largest impact on 

overall PV system performance. Even a small 

percentage of shading on a PV array surface can 

have a much greater effect on overall array output 

than obtaining its optimal tilt or azimuth. Collectors are more intolerant of shading than arrays. 

Several external and uncontrollable factors can 

cause array shading, including trees, plumbing 

vents, chimneys, nearby buildings, poles, towers 

and the like. Shading of an installation can also 

be caused by parts of the building on which the 

array is mounted, and sometimes even from the 

module or support hardware. The expected growth 

of nearby trees and new construction should 

be considered. 

(left) The BP Integra PV system (above)

hugs the roof line.

(right) These solar thermal collectors and 

PV modules are about four inches off the 

roof on standoff mounts.

N 

Deciduous 

Trees 

Shrub Shading of

Lower Wall

Windbreak Shrubs 

North Side Shading from Evening and Morning Sun

Careful landscaping can preserve roof-top solar exposure and provide 

shading to help control solar gain through windows.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 5 / p.3

Planning and Orientation Chapter 5

(left) This solar thermal system is ground 

mounted. Photo courtesy of Leif Juell, 

Alternative Power Enterprises, Inc.

(right top) To preserve a traditional appearance, 

Tindall Homes locates its PV systems away from 

the house on sheds. Photo courtesy of John 

Moyniham of Bald Eagle Solar.

(right bottom) This solar collector and PV array 

are subject to shading by a nearby structure.

Photo courtesy of NREL.

A simple rule of thumb is that any potential shading 

structure should be twice as far away from the PV 

array as it is tall. In addition, a detailed evaluation 

of the southern horizon can be used to predict 

shading issues arising from things that are not part 

of the home. Several devices are available for this 

analysis, and are discussed below. Shading should 

be evaluated as part of the design phase to ensure 

that a site is suitable for solar. Shading should 

also be evaluated at the time of solar equipment 

installation to ensure the prime roof area is selected 

and that there are no shading issues that were not 

considered.

Site evaluations use sun charts or digital tools to 

assess how obstructions, such as trees, buildings, 

or chimneys, will fall between the installation and 

the sun at various times of the year. Sun charts 

are available at no cost from the University of 

Oregon on the web at http://solardata.uoregon.

edu/SunChartProgram.html. A sample U. of O. 

sun chart is shown below. Solar thermal and PV 

installers should have equipment to simplify site 

evaluations. In short, the equipment provides a 

way to add sources of shading to the sun chart. 

Anywhere a potential obstruction crosses into the 

solar window, it blocks critical solar energy.

D D

H

H

Any potential shading structure should be twice as far away 

from the PV array as it is tall (D = 2 * H))

The sun chart shows where the sun will be in the sky 

at a particular time of day each month.

Each of the blue lines represents the path of the sun 

during a particular month. Only half a year is needed, 

because the year is symmetrical. The red lines show 

the time of day.

Custom sun charts are available on the web from 

the University of Oregon at http://solardat.uoregon.

edu/download/temp/50651026.pdf. The green 

area superimposed on the chart shows the annual 

solar window in which shading would be especially 

detrimental. The summer solstice is the longest day 

of the year. The winter solstice is the shortest.

Sun Charts

Summer Solstice

WINTER Solstice
p.4 / CHAPTER 5 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 5 Planning and Orientation

The Solar PathfinderTM is a commercially available 

site evaluation tool. The Solar Pathfinder reflects 

the image of surrounding obstructions onto a small 

plastic dome. Beneath the dome is a specific sun 

chart for an area. Using the reflections, the person 

conducting the evaluation outlines the shape of 

the obstructions on the chart to create a written 

record of the obstructions.

The Solmetric SunEye is a commercially available product for site evaluation. The hand-held 

device includes an integrated fish-eye lense and 

digital camera. It automatically detects shading 

obstructions and 

produces sun charts 

or projections of 

monthly or annual 

solar access shown 

on bar charts. 

More information 

is available at 

www.solmetric.com.

New approaches 

based on digital 

photography are also being developed. The 

Sacramento Municipal Utility District (SMUD) 

developed a software tool that analyzes digital 

images taken from a rooftop site inspection and 

calculates shade impacts for input into existing PV 

system performance software (Bartholomy, Sloan, 

and Bertolino 2006). The product is currently being 

used internally at the utility. 

Additional information on site evaluation is available at the SRCC web site at www.solar-rating.

org/EDUCATION/criteria/collector/6_5_13.htm. 

Orientation

If you can set your compass for due south, adjust 

for the difference between true north and magnetic 

north, and find an unobstructed view of the sun, you 

have prime solar real estate. However, if you can’t, 

there is still lots of solar energy available. In all of 

the conterminous states, even at 60° off due south 

(southeast or southwest) at least 90% of the energy 

is still available with proper tilt and no shading. In 

all but the coldest portions, at 90° off due south 

(due east or due west), at least 80% of the energy is 

still available with the proper tilt and no shading. 

However, energy produced from a west-facing PV 

array may be worth more to utilities.

Sometimes due south is not an option because 

hillsides, highways, or views force communities to 

face certain directions; or when towering mountains, buildings, or towers block access to the sun. 

Utilities may even prefer that PV arrays be situated 

toward the west to gather more late afternoon sun 

to match their peak demand, rather than the more 

intense midday sun that would produce maximum 

power. When due south is not an option, it is likely 

that at least one elevation of your homes will be 

struck with adequate solar energy to pursue solar 

technologies. In fact, as mentioned in the first 

section, west-facing PV arrays may be the orientation of choice in locations with summer-afternoon 

peaking electric utilities.

Tilt

The optimal tilt of an array or collector doesn’t 

need to be all that optimal. The very best tilt will 

depend on the latitude of the house and regional 

climate conditions affecting typical cloud cover. But 

there are other factors as well: mountains to one 

side of the house and snow cover all can effect the 

optimal tilt of a solar array or collector.

Most of the United States has an optimal tilt of 

about 30-36 degrees. At a standard 6/12 roof pitch, 

(22.5 degrees) at least 95% of available solar energy 

can be absorbed in all of the conterminous U.S. 

(Christensen and Barker 2001). In Alaska, collectors 

or arrays will still be struck by more than 90% of 

the available energy at standard roof tilts.

The following table converts roof pitches to 

degrees of tilt.

Approx. roof pitch Approx. tilt in degrees

Flat 0°

2 in 12 8.5°

4 in 12 17°

6 in 12 22.5°

12 in 12 45°

Vertical wall 90°

The Solar Pathfinder is used in the 

field to evaluate and document shading. 

Photo courtesy of Heidi Steward of PNNL.

43°

AZIMUTH

TILT

36°

30°

24°

N

Sun chart from the Solar Pathfinder

Tilt and Azimuth determine the extent to 

which a surface is exposed to the sun.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 5 / p.5

Planning and Orientation Chapter 5

Roof tilt and southern orientation (azimuth) is quite flexible for the entire U.S. (Adapted from Christensen and Barker 2001). The map 

identifies optimal tilt angles for the shaded regions on the map. The charts show the percentage of solar energy available in each of 

the regions as the tilt and azimuth (orientation) change. For example, in the portion of the country where the optimal tilt angle is 30° 

(most of the country), at an azimuth of 0° (due south) the tilt can run from flat (0°) all the way to 55° and still receive 90% to 100% 

of available energy. If the tilt is at the optimum of 30° the azimuth could vary to about 65° either east or west and still receive 90% to 

100% of the available energy.

-90 -60 -30 0

Azimuth

Optimal Tilt Angle of 42°

Optimal Tilt Angle of 36°

Optimal Tilt Angle of 30°

Optimal Tilt Angle of 24°

ALASKA - Optimal Tilt Angle of 48°

HAWAII - Optimal Tilt Angle of 18°

Tilt

0

30

30

60

90

60 90

-90 -60 -30 0

Azimuth

Tilt

0

30

30

60

90

60 90

-90 -60 -30 0

Azimuth

Tilt

0

30

30

60

90

60 90

-90 -60 -30 0

Azimuth

Tilt

0

30

30

60

90

-90 -60 -30 0 60 90

Azimuth

Tilt

0

30

30

60

90

0.5 - 0.6

0.6 - 0.7

0.7 - 0.8

0.8 - 0.9

0.9 - 1.0

60 90

-90 -60 -30 0

Azimuth

Tilt

0

30

30

60

90

60 90

42°

36°

30°

24°
p.6 / CHAPTER 5 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 5 Planning and Orientation

Modeling Performance 

and System Sizing

Part of the site assessment, design, and decision 

making may include modeling solar performance. 

This modeling may or may not include economic 

analysis. The tools listed here are free web-based 

models and estimators. 

The RETScreen® International Solar Water Heating 

Model can be used world-wide to evaluate the 

energy production, life-cycle costs, and greenhouse 

gas emissions reduction for three applications: 

domestic hot water, industrial process heat and 

swimming pools (indoor and outdoor), ranging in 

size from small residential systems to large-scale 

commercial, institutional and industrial systems. 

The model contains a database of essentially all 

commercially available solar thermal collectors. 

The model is free, but registration is required. 

The model can be accessed at www.retscreen.net. 

This site also includes models for evaluating PV 

systems and other renewable and energy-efficient 

technologies.

The California Energy Commission maintains an 

extensive website with much information about 

PV systems. One feature is a list of modules that 

qualify for that State’s rebate program. This list is 

available at www.consumerenergycenter.org/cgibin/eligible_pvmodules.cgi. There is also a list of 

qualifying inverters at www.consumerenergycenter.

org/erprebate/documents/2002_tax_credit/2003-

03-03_APPR_PV_LIST.PDF#search=%22photovolta

ic%20model%22. The site also includes a feature to 

help find California installers at www.consumerenergycenter.org/erprebate/database/index.html.

A PV system sizing model called the Clean Power 

Estimator is available at www.consumerenergycenter.org/pv4newbuildings/schematicdesign.html.

PVWATTS is a free model available from NREL that 

calculates electrical energy produced from a gridconnected PV system. Access to the model is available at 

http://rredc.nrel.gov/solar/codes_algs/PVWATTS/.

Another web-based resource is Find Solar. This site 

has energy calculators for photovoltaic and solar 

domestic hot water and pool/spa heating. The site 

is sponsored by the American Solar Energy Society, 

Solar Electric Power Association, Energy Matter 

LLC, and the U.S. DOE. A PV solar estimator meant 

to help roughly identify price, savings, and system 

size can be found at www.findsolar.com/index.

php?page=rightforme.

For a listing of free and available-for-purchase 

energy models, including solar design tools, see 

DOE’s Building Technology Program web site at 

www.eere.energy.gov/buildings/tools_directory.

Site Planning

Better understanding of available solar energy and 

improvements in window technologies have done 

much to increase flexibility in site planning while 

still giving consumers the value of solar energy. Still, 

site planning should take advantage of southern 

window and roof exposures. Lay out lots, trees, 

houses, and community buildings being careful to 

avoid shading neighboring roofs. Orient community 

and private pools to allow for solar water heating 

and include the solar systems as part of initial 

construction. Allow enough roof area facing south 

for both solar thermal and PV systems. The CEC 

suggests that the rough sizing requirements for PV 

are about 100 sq. ft. for each kilowatt of system 

capacity for crystalline technologies and 175 sq. 

ft. for each kilowatt of thin film PV products. Solar 

thermal systems will likely require one or two 

collectors requiring about 32 sq. ft. each.

Windows

Positioning buildings to get the maximum amount 

of sun means selecting windows and overhangs to 

help manage the solar energy. Thoughtful design 

for your climate and site will increase value for 

consumers by making the sun an ally. Windows 

should be selected to manage the quantity of solar 

heat gain allowed into the house. In cold climates, 

it may make sense to use windows with a high solar 

heat gain coefficient. These windows will allow 

solar heat gain to help heat the house in winter 

where summer heat gain is not important. These 

windows are also valuable for winter heating in 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 5 / p.7

Planning and Orientation Chapter 5

mixed climates where they can be shaded by well 

designed overhangs during summer months.

Where sun is ample and cooling dominates 

utility bills, windows with low solar heat gain 

coefficients and high visible light transmittance 

will help to block both infrared and ultraviolet 

light while allowing visible light into the spaces. 

These windows will protect furniture, carpeting, 

and other surfaces from fading and will greatly 

increase occupant comfort.

The Efficient Windows Collaborative operates a 

web site that can help designers and consumers 

choose windows. The web site includes a tool that 

allows users to analyze energy costs and savings for 

windows with different ratings. Visit the web site at 

www.efficientwindows.org/index.cfm.

The Web site also has fact sheets with comparisons 

for each state. These fact sheets could make effective 

marketing tools. Also described on the web site is a 

book entitled Residential Windows: A Guide to New 

Technologies and Energy Performance (Carmody 

et al. 2000), which offers homeowners, architects, 

designers, and builders a fascinating look at the 

state of the art in window technology. 

Cool Neighborhoods Have Shade 

Tree preservation brings many benefits, one of which is increased salability. Native trees 

are most beneficial to the environment. The NAHB reports in its survey of buyers, What 

21st Century Home Buyers Want, that over 80% of respondents in the West rated trees as 

essential or desirable (2002b, page 61). In 1992, the Florida Solar Energy Center (FSEC) 

estimated that a treed lot in Florida may increase the value of a home by as much as 20%. 

American Forests and the NAHB (1995) found that mature trees may add from $3,000 to 

$15,000 to the value of a residential lot.

Trees also bring value by providing shade. It is far better to prevent solar energy from 

reaching a house with a heavy air conditioning load than to attempt to manage it once it 

enters, with the additional consideration of solar heating in the winter. Shade trees can block 

summer sunlight before it strikes windows, walls, and roofs, dissipating absorbed heat to the 

air where it can be carried away by the breeze. However, when photovoltaic and/or water 

heating systems will be used, trees must be placed not to shade these systems. This dualfunction can often be achieved by carefully selecting the variety of tree for height and width 

as well as being deciduous.

Truly cool neighborhoods have trees. A study in Florida has shown that a subdivision with 

mature trees had cooler outside air with less wind velocity than a nearby development 

without trees (Sonne and Viera. 2000). The development with a tree canopy had peak 

afternoon temperatures during July that were 1.1°F to 3.1°F ( ± 0.7°F) cooler than the site 

without trees. The total effect of shading, lower summer air temperature, and reduced wind 

speed can reduce cooling costs by 5% to 10% (McPherson et al. 1994).

For reducing cooling requirements, trees are most effective when carefully located to cast 

shade on the roof, windows, walls, and air conditioners, and when located on the side of 

the home receiving the most solar exposure. Shade to the southwest and west is especially 

important for blocking peak solar gain in the summer in late afternoon. Depending on 

the species, trees more than 35 feet from the structure are probably too far away for shade. 

Plants too close to air conditioners or heat pumps can plug coils. Be careful not to shade 

solar equipment. Energy-efficient windows are comfortable to 

sit near and provide protection for furniture 

and window treatments.
p.8 / CHAPTER 5 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 5 Planning and Orientation

Example of window overhang in Florida. 

Overhangs

Another consideration is intentional shading. 

Overhangs help to shed water and provide shade 

at the appropriate times of the year. One advantage 

to using overhangs is that they can be designed 

to allow solar gain in the winter. Low SHGC glass 

blocks the sun year round. Overhangs should 

be sized to account for differences in the angles 

of the sun during winter and summer. Precise 

overhang dimensions should be calculated for each 

latitude. Free and low-cost computer programs 

and tools are available to help. For example, a 

free program telling you the angle of the sun 

for any point in the country is available at www.

susdesign.com/sunangle/. Latitude, longitude, 

and elevation data can be obtained at www.

wunderground.com. Overhang dimensions can be 

calculated at www.susdesign.com/overhang/index.

html. Click on Software Tools on the lower right 

side. A low-cost sun angle calculator is available 

from the Society of Building Science Educators at 

www.sbse.org/resources/sac/index.htm.

Seeing Your Way Through Windows

High-performance windows can be an easy way to achieve ENERGY STAR qualification. 

Efficient windows will add expense to your project, but will provide tremendous value in 

comfort, durability, and energy savings. High-performance windows add so much to energy 

efficiency that smaller cooling and heating equipment can often be specified, which may 

recapture much of the cost. A voluntary rating system developed by the National Fenestration 

Rating Council (NFRC) provides performance information for about half the windows sold. 

The NFRC label contains ratings for the following features. You can find more information 

about the NFRC on the Web at www.nfrc.org.

• U-factors take into account the entire window assembly and rate how well the window 

prevents heat from passing through the window. The lower the U-factor the better the 

window performs at stopping heat flow. U-factors are the inverse of R-values used to 

measure the effectiveness of insulation. U-factor values for windows generally fall between 

0.20 and 1.2.

• SHGC is the solar heat gain coefficient, which measures how well the window blocks heat 

caused by sunlight. The lower the SHGC rating the less solar heat the window transmits. 

This rating is expressed as a fraction between 0 and 1.

• Visible transmittance (VT) measures how much light comes through a window. VT is 

expressed as a number between 0 and 1. The bigger the number the more clear the glass.

• Air leakage through a window assembly is included on most manufacturers’ labels, but is 

not required. The AL rating is expressed as the equivalent cubic feet of air passing through a 

square foot of window area (cfm/sq.ft.) The lower the 

AL, the less the window leaks. A typical rating is 0.2.

• Another optional rating is Condensation Resistance 

(CR), which measures the ability of a product to 

resist the formation of condensation on interior 

surfaces. The higher the CR rating, the better that 

product is at resisting condensation formation. CR 

is expressed as a number between 1 and 100, with 

a higher value representing more resistance to the 

formation of condensation.

Winter

Sun

Summer

Sun

21o

4 ft.

66o

Sun angle and overhang 

recommendations for windows

in representative cities

Winter

Sun

Summer

Sun

22o

4 ft.

67o

Winter

Sun

Summer

Sun

34o 77o

Winter

Sun

Summer

Sun

31o 74o

Portland, Oregon Minneapolis, Minnesota

Louisville, Kentucky Albuquerque, New Mexico
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 5 / p.9

Planning and Orientation Chapter 5

Overhangs also provide protection from rain, hail, 

and the effects of overheating and ultraviolet radiation on siding and windows.

Builder Best Practices

Conduct site assessments to ensure that solar energy 

will not be obstructed.

There is a great deal of latitude in the direction 

and tilt of collectors and arrays. Consider solar 

installations for all houses and communities. Most 

likely, some roof surface or ground area will have 

an adequate exposure.

Keep solar collectors and arrays close to the roof 

line. However avoid placement too close to the 

peak or the eaves.

• Take into account the climate and 

orientation in selecting windows. 

• Free web-based software exists for designing 

overhangs. Add overhangs to your designs for 

protection from rain, snow, and sunlight.

• Use free web-based models to verify solar 

installation performance and costs.

• Design communities and landscaping to 

avoid shading solar equipment.

• Save native trees to encourage cooling while 

avoiding shade on solar equipment.

• Consider adding the shading analysis sun 

chart to your homeowners manuals.

Installer Best Practices

• Conduct site evaluations of shading to ensure 

that communities have viable solar exposure.

• Help builders assess the economics and 

performance of solar installations by using 

models to analyze performance.

• Ensure unobstructed solar exposure before 

choosing locations for – or installing – solar 

collectors or arrays. 

• Provide copies of site assessments to builders, 

including sun charts. These materials may be 

used for marketing or may be passed on to 

home purchasers.

References and Resources

American Forests and the National Association of Homebuilders. 1995. Building Greener 

Neighborhoods: Trees as Part of the Plan. NAHB, Washington, D.C.

Bartholomy, Obadiah, Brent Sloan, and Jon Bertolino. 2006. “Development of a Digital Shade 

Analysis Tool for PV Siting.” Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. 

American Solar Energy Society, Boulder, CO.

Carmody, John, Stephen Selkowitz, Dariush Arasteh, and Lisa Heschong. 2000. Residential 

Windows: A Guide to New Technologies and Energy Performance. W.W. Norton and Company, 

New York. www.wwnorton.com/npb/welcome.htm

Christensen, C.B. and Barker, G.M. 2001, “Effects of Tilt and Azimuth on Annual Incident Solar 

Radiation for United States Locations,” Proceedings of Solar Forum 2001: Solar Energy: The 

Power to Choose April 21 – 25, Washington, D.C.

McPherson, G.E., D.J. Nowak, and R.A. Rowntree (eds). 1994. Chicago’s Urban Forest 

Ecosystem: Results of the Chicago Urban Forest Climate Project. U.S. Department of Agriculture, 

Forest Service, Northeastern Research Station, www.f.fed.us/ne/newtown_square/publications/

technical_reports/pdfs/scanned/gtr186a.pdf
p.10 / CHAPTER 5 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 5 Planning and Orientation

National Association of Home Builders. 2002b. What 21st Century Home Buyers Want: 

A Survey of Customer Preferences. NAHB, Washington, D.C. www.BuilderBooks.com

Sonne, J.K. and R.K. Viera. 2000. “Cool Neighborhoods: The Measurement of Small Scale Heat 

Islands.” Proceedings of the 2000 Summer Study on Energy Efficiency in Buildings, American 

Council for an Energy-Efficient Economy, Washington, DC. 

www.fsec.ucf.edu/bldg/pubs/pf363/index.htm

Viera, R.K., K.G. Sheinkopf, and J.K. Sonne. 1992. Energy-Efficient Florida Home Building, 

third printing. Florida Solar Energy Center, FSEC-GP-33-88, Cocoa Beach, FL.

SRCC site evaluation information: 

www.solar-rating.org/EDUCATION/criteria/collector/6_5_13.htm

Solarmodeling software: www.retscreen.net/

California Energy Commission list of qualifying PV modules: 

www.consumerenergycenter.org/cgi-bin/eligible_pvmodules.cgi

California Energy Commission list of qualifying inverters: 

www.consumerenergycenter.org/erprebate/documents/2002_tax_credit/

2003-03-03_APPR_PV_LIST.PDF#search=%22photovoltaic%20model%22

California Energy Commission list of installers:

www.consumerenergycenter.org/erprebate/database/index.html

California Energy Commission PV system sizing model called the Clean Power Estimator: 

www.consumerenergycenter.org/pv4newbuildings/schematicdesign.html

PV solar estimator meant to help roughly identify price, savings, and system size can be found at:

www.findsolar.com/index.php?page=rightforme

DOE’s Building Technology Program.

www.eere.energy.gov/buildings/tools_directory

The Efficient Windows Collaborative.

www.efficientwindows.org/index.cfm

A free program telling you the angle of the sun for any point in the country.

www.susdesign.com/sunangle/

Sun charts are available at no cost from the University of Oregon on the web at: 

http://solardata.uoregon.edu/SunChartProgram.html

Information on the Solmetric SunEye is available at:

www.solmetric.com

NREL’s PVWATTS model for grid-connected PV systems is available at:

http://rredc.nrel.gov/solar/codes_algs/PVWATTS/
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 6 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 6.

Rack-Mounted Systems

Building America Best Practices Series

Solar collectors mounted on a standing seam roof. 

Photo courtesy of Leif Juell, Alternative Power 

Roof Penetrations and Mounts Enterprises, Inc.

Atop many automobiles are roof-top rack systems 

that carry everything from kayaks to bicycles. These 

systems are pre-engineered to carry these loads at 

highway speeds and their modular pieces are easily 

installed. Think of the hardware for mounting solar 

collectors and arrays as roof racks for houses. The 

best systems are pre-engineered to carry loads and 

use matched hardware.

Of course roof-top mounts for solar equipment 

must also protect the house from water intrusion. A 

recent study of one of the first ZEH communities that 

incorporated both solar thermal and PV technologies, reports that absolutely no problems have been 

reported related to water leakage (Nelson 2005). 

Flashing systems are described in this chapter.

Building integrated systems tend to either attach 

directly to the roof deck and/or use proprietary 

mounting systems. Three of these types of systems 

are described in Chapter 4: Photovoltaic Power 

Generation, and a roof deck-mounted approach 

for ICS is described in Chapter 3: Solar-Thermal 

Water Heating.

Two references are important to acknowledge 

as resources for this chapter and for designers. 

The first is a 2005 evaluation of roof-mounting 

approaches for solar thermal systems prepared by 

the Davis Energy Group, titled Zero Energy Homes 

Solar Thermal Collector Mounting Evaluation. 

Another good reference for flashing all roof systems 

is the National Roofing Contractors Association 

(NRCA 2006) guidance document, entitled: The 

NRCA Roofing and Waterproofing Manual, 

Fifth Edition. The document is available online at 

www.nrca.net.

Structural Loads

There are two structural concerns, dead load, the 

weight of the systems bearing on the roof, and live 

loads, the intermittent loads created by wind, snow, 

and maintenance people. Collectors should never 

be supported by roof sheathing between structural 

members. This is particularly important for ICS 

collectors, because they are heavy when full of 

water, although problems have been rare. Over 300 

ICS systems were installed on low income housing 

during a Florida program and no structural changes 

had to be made to any of these homes (Harrison 

2006). Before installation, installers did make sure 

that the roof was in good condition, with good 

trusses, and no sagging.

Nonetheless, the project structural engineer or 

truss designer should be involved early in the 

design process. Even if not needed to accommodate 

the load, additional framing may be added as a 

convenience for easier solar installations even if 

structural loads are within limits. The BP Integra 

system described later in this chapter used this 

approach. If modifications are needed, they should 

Builders’ & Installers’ Brief

• Roof top mounts can place solar 

thermal and PV systems very close to 

the roof surface.

• If needed, such as on a flat roof, 

mounts can also place solar systems 

at optimal angles.

• Ensure systems are engineered for 

dead loads and wind uplift. 

• Install standoff mounts before roofing 

is installed to allow for proper flashing 

and sealing.

• If house roofs are not available, mount 

solar systems on outbuildings or 

ground mounts.
p.2 / CHAPTER 6 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 6 Rack-Mounted Systems

be installed during framing. Solar is offered as an 

option to allow for future installations. If solar is 

not actively offered as an option, but the builder 

wants the houses to be Solar Ready, then any needed 

modifications should be installed in all houses.

Dead loads are typically minimal in PV arrays, no 

more than 5-10 lbs/ft2. However, the loads are often 

transferred to the rooftop through mounting devices 

that concentrate the array dead loads onto small 

surface areas of the roof or individual load bearing 

members. These conditions can significantly add 

to the loading conditions of a single truss, rafter, 

joist, decking or other roof component. Live loads 

can be large in magnitude, but are intermittent, 

and attributed to wind, snow, and maintenance 

personnel. Most PV modules are rated for dead 

loading of 50-55 lbs/ft2, or equivalent to the pressure of constant 110-120 mph winds (Barkasi and 

Dunlop, 2001). 

Designing mounting systems for wind uplift is 

more critical in areas subject to hurricanes and 

excessive wind speeds. Manufacturers of collectors, 

modules, and mounting systems typically have their 

mounting systems pre-engineered for worst-case 

wind loads (DEG 2005). In parts of the world that 

are vulnerable to hurricanes or extreme wind 

storms, the collector and its mounting structure 

need to be able to withstand intermittent wind 

loads up to 146 miles per hour. This corresponds 

to a pressure of about 75 pounds per square foot 

(FSEC 2006). Rudin and Becerra (2006) describe 

approaches for analyzing severe wind loads.

Wind loads may be greater near the roof ridge. 

Mounting collectors or arrays near the ridge may 

increase wind loads on the equipment (FSEC 

2006). Similarly, locating collectors and arrays in 

from eaves may reduce wind loads (Rudin and 

Becerra 2006).

Good engineering cannot make up for poor installation. It is easy to miss structural members when 

fastening mounting systems to the roof. Care must 

be taken to insure that fasteners are correctly 

positioned. Failure of a bolt to torque down is a 

clear indication the structural member has been 

missed. Also, bolts shorter than those recommended 

by the manufacturer should not be used. Mounting 

systems can be secured to structural blocking placed 

between rafters/trusses if the layout of rafters/trusses 

do not align with the desired collector location. All 

bolts securing collectors or modules to racks or 

brackets must be securely tightened.

Fire Ratings

As a rule, solar collectors are not UL-listed roofing 

products. The easiest way to achieve the Class A 

UL rating required by building codes is to apply 

Class A composition shingle roofing under all 

collectors. Some PV systems have been fire rated. 

Many modules require an underlayment to achieve 

(left) Added lumber makes PV module 

installation easier. The added cross piece in this 

photo is located just below the wire penetration.

(right) Copper flashing for pipe. 

Photo courtesy of John Harrison of 

the SRCC and FSEC
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 6 / p.3

Rack-Mounted Systems Chapter 6

(left) Standoff mounts located beneath 

the collector receive some protection from 

the elements.

(right top, bottom) L brackets used on 

composition roofs. Roof photo compliments of 

Joseph Wiehagen of the NAHB Research Center.

a Class A rating. The ICC Evaluation Service recently 

established acceptance criteria to provide guidance 

for the evaluation of BIPV roof panels as roofing 

components (ICC 2006). Builders should ask 

installers or other suppliers to confirm that BIPV 

systems meet these standards. 

Roof Penetrations, Flashing, 

and Roof Attachments

With the exception of raised-seam metal roofs, 

most all roof types require penetrations for rack 

mounts. In the best installations, standoffs, lag 

screws, or bolts tie into structural members. All 

brackets should have butyl tape or a high-quality 

caulking such as polyurethane or polysulfide, to 

seal any bolt penetrations and under struts, brackets, 

or mounting feet.

If standoff mounts or other brackets can be installed 

before the roofers install the finished roof, roofers 

can more easily shingle or tile around the flashing, 

and may install the flashing for the mounts. This 

approach helps to ensure that the roof warranty 

is intact. Solar installers need to coordinate with 

roofers prior to the installation to ensure proper 

flashing materials are on hand and installation 

procedures have been worked out.

Solar collectors require copper piping to carry 

fluid. Pipes must have insulation, jacketing, and 

flashing. Flashing may be either a roof boot or 

a copper cap. An advantage of the copper cap, a 

pipe flashing frequently used in solar installations, 

is that it should incorporate a separate port for 

sensor wiring. 

PV systems require roof penetrations for wires. 

Both internal and external junction box systems 

were described in Chapter 4: Photovoltaic Power 

Generation.

In both PV and solar thermal systems, where 

mounting brackets or other penetrations may 

be mounted under the collector or module, the 

solar equipment itself affords some protection 

from the weather.

Composition Shingle Roofs

Mounting systems can be secured over comp 

shingles with or without flashing. Where flashing 

is not used, L brackets, mounting feet or a strut 

are bolted directly to the roof surface. The roof 

is sealed by applying a high-quality caulking 

such as polyurethane or polysulfide to the bolt 

penetration and under the mounting foot or strut, 

which is bolted through the sheathing to the rafter 

or truss below. A mounting rack, or the collector 

itself, is then bolted to the foot or strut. A hanger 

bolt can also be used in this fashion by running 

the lag screw end into the roof structure so that 

only the machine screw thread is showing, and 

bolting a washer to the roof with sealant applied 
p.4 / CHAPTER 6 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 6 Rack-Mounted Systems

underneath. These mounting methods are preferred 

for retrofit applications, but can also be used for 

new construction.

Stanchions and hanger bolts can be used with 

flashing at the mounting points. Both the bolt 

and the stanchion are applied before the roofing 

is installed. The lag screw end of the hanger bolt is 

threaded directly into the structure. The stanchion 

is lag-screwed to the roof structure (into a truss or 

rafter). After these are placed, a flashing is applied 

over the bolt or stanchion. Hanger bolts are preferred 

due to their low cost and quick installation, but 

should not be used with ICS systems for structural 

reasons. Stanchions may be flashed with roof boot 

type flashing (see figure below).

Tile Roofs

There are two general methods for mounting collectors to tile roofs: flush mounting and suspended 

mounting. The flush mounting method is identical 

to methods for installing over composition shingle. 

This method requires that the entire portion of the 

roof beneath the collector be covered with composition shingles. Lathe strips are then nailed to the roof 

(left) Roof boots can be used with stand off 

or stanchion type mounts. 

(right) Flat plate collectors flush mounted with 

tile surround. Photo courtesy of John 

Harrison of the SRCC and FSEC.

Lag-Bolted L Brackets (Diagrams courtesy of SRCC 1998)
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 6 / p.5

Rack-Mounted Systems Chapter 6

Stanchion Mount with Tile Roof

up to the sides of the collectors for hanging tile. 

While this method provides an attractive built-in 

appearance, the comp roofing is penetrated by 

nails when the lathe is installed, compromising 

the integrity of the roof, particularly below the 

collectors. Application of a Bituthene underlayment 

below the comp roofing can provide insurance 

against leakage but increases cost. 

Flush mounting examples are also described in 

Chapter 3: Solar Thermal Water Heating.

Another method for flush mounting that reduces 

the risk of roofing penetration is to build up a 

raised section of roof (or curb) that matches the 

footprint of the collectors, and to install flashing 

around the perimeter of the curb. The top of the 

curb is roofed with composition roofing and the 

collectors are mounted as they would be over 

composition shingles. The high cost of building 

the curb and installing roofing and flashing makes 

this method less desirable to builders. An advantage 

of this system is that mounting penetrations are 

made into the curb, not through the roof.

With standoff mounts, collectors or modules 

are supported above the tile. While providing a 

higher profile, this method appeals to builders and 

contractors because it follows typical construction 

procedures and does not require that roofers make 

two appearances, one to apply composition roofing 

and a second to install tile. Supports can be installed 

before the tile and flashed, or the tile can be drilled 

to accept hanger bolts on which racks or rails are 

installed. Drilling through the tile is less desirable 

because the water seal depends on caulking at the 

hanger penetration, and the risk of breaking tile is 

greater. Installing stanchions or hanger bolts and 

flashing before the tile is placed is preferred, since 

trusses or rafters are more easily located and there 

is less risk of breaking tile. Penetrations through the roof decking are not 

needed for mounts if curbs are installed as 

shown on this flat roof.

Figures adapted from Davis Energy Group 2005.

Hanger Bolt Mounting with Flashing/Round Tile Roof
p.6 / CHAPTER 6 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 6 Rack-Mounted Systems

Flat Roofs

Curb mounts work well for flat roofs. Elevated racks 

are often used on flat roofs to provide an appropriate 

angle for the collector or module. Racks may be 

mounted on curbs or standoff mounts. Another 

reason for using racks in colder climates is to place 

modules and collectors above snow levels. Curb 

systems were discussed earlier and are described 

in the NRCA manual.

Standing Seam Metal Roofs 

S-5 clips attach to raised seam metal roofing and do 

not require a roof penetration. Laminate PV systems 

are described in Chapter 4: Photovoltaic Power 

Generation. Information on S-5 clips is available 

at www.unirac.com/s5.htm. As an alternative to 

clamping on PV modules, laminate material may 

be glued directly to metal roofing. One idea from 

laminate systems may work well for any PV module 

or collector. Unisolar recommends that wiring for 

the laminate PV be run to the roof ridge where it 

is directed into the house. A ridge cap covers the 

penetrations. An example of this type of system is 

included in Chapter 4.

Structural Insulated Panel Roofs

As part of a study of affordable ZEH in Tennessee, a 

process was worked out for installing racks on roofs 

made with structural insulated panels (Christian 

2006). The report is available on the Building 

America web site at www.buildingamerica.gov.

Rack Systems

The traditional method to install solar arrays is 

on rack-based systems. These can be attached to 

roofs or on poles or on the ground. There are many 

manufacturers that make universal mounting 

systems. Mounts are best attached before the final 

roofing so that installers or roofers can install 

flashing to reduce the chance of leaks. 

• Collectors and arrays are sometimes mounted 

away from the main house. The rack systems 

are similar to roof mounts, but the base is 

sometimes mounted on the ground. Systems 

are also sometimes mounted on out-buildings, 

such as sheds. These systems are mentioned in 

this chapter and the Tindal Homes Case Study 

provides an example of shed mounts.

(left, middle) Both PVs and solar collectors are 

mounted on racks on the flat roofs of these 

Tucson houses in the Armory Park community. A 

case study on this community is included in this 

document. Photos courtesy of John Wesley Miller.

(right top) S-5 clips attached to a standing 

seam metal roof. Photo courtesy of 

Bill Guiney of Solargenix.

(right bottom) S-5 mini clip holding a solar 

module. Photo courtesy of Jeff Christian of ORNL.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 6 / p.7

Rack-Mounted Systems Chapter 6

Low-Profile Mount

Many PV systems come with arrays, racks, and clips 

that are designed to mount together. One method of 

reducing the visual effect of a solar array is to make 

the mounting system as close to the roof, and as 

small, as possible. The BP Integra frame sits directly 

over an asphalt shingle roof with no standoffs. A 

variety of modules from the manufacturer can be 

inserted into this frame.

All major PV manufacturers produce PV modules 

that can be mounted in low-profile racks.

Rack Systems

Solar collectors and many PV modules work with 

universal rack systems. Most of the roof-installed 

rack-based systems will sit only a few inches above 

—and parallel to—a pitched roof. This is known as 

a stand-off mount. These are visually unobtrusive 

and the extra air flow beneath the array allows for 

slightly greater performance. If needed, a rack-based 

system can be tilted at a different angle than the 

underlying roof, but this approach may make the 

panel more visible above the roof.

(left series of three) Installation of the BP Integra 

System, a low-profile mount. Photos courtesy of 

Joseph Wiehagen of the NAHB Research Center.

(middle) Completed BP Integra PV system on the 

Maximum Efficiency Greenland Home in BelAir, 

Maryland, built by Bob Ward Companies.

(right top and bottom) One PV company installs 

rails to their modules in the shop to help with 

transport and to ease mounting on the roof.

(right) Rails are often mounted on the roof with an L bracket or 

stand-off mount. Collectors and modules are then attached to the rail. 

Earlier photos in this chapter showed these types of systems.
p.8 / CHAPTER 6 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 6 Rack-Mounted Systems

Ground mounts imbedded in concrete. 

Photos courtesy of Leif Juell, Alternative 

Power Enterprises, Inc.

Resources and References

Barkazi, Stephen F and James P. Dunlop. 2001. “Discussion of Strategies for Mounting 

Photovoltaic Arrays on Rooftops.” Proceedings of Solar Forum 2001: Solar Energy: The Power 

to Choose April 21 – 26, 2001. Washington, D.C.

Christian, Jeff. 2006. How to Build Small Affordable Houses That Use 30% Less Total Energy in the 

Mixed-Humid Climate, Prepared by Oak Ridge National Laboratory for the U.S. DOE., Oak Ridge, TN.

Florida Solar Energy Center (FSEC). 2006. Solar Water and Pool Heating Manual: Design 

and Installation & Repair and Maintenance. University of Central Florida, Orlando, FL.

www.fsec.ucf.edu/solar/install/solarmanual.htm

Davis Energy Group (DEG). 2005. Zero Energy Homes Solar Thermal Collector Mounting 

Evaluation. Prepared by the Davis Energy Group for the National Renewable Energy Laboratory, 

Davis, CA.

Ground Mounts

Ground mounts are rack systems installed on or 

in the ground. Many ground mount systems are 

similar to roof mounts, except they are fixed in 

concrete footings rather than roof trusses. The 

lower edge of ground-mounted collectors and 

arrays should be high enough to clear vegetation 

and accumulated snow, and to avoid splashing and 

soiling, and standing water. Some systems use a 

single pole for the mount. These systems minimize 

concrete footings but must be sized appropriately 

for the load.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 6 / p.9

Rack-Mounted Systems Chapter 6

Harrison, John. 2006. E-mail to Michael Baechler dated Monday, September 25, 2006. The e-mail 

partially reads as follows: “Over 300 ICS systems were installed on low income housing during 

the SWAP program and no structural changes had to be made to any of these, just so the roof was 

in good condition, that is, good trusses, not sagging, etc. Since the weight is distributed over four 

mounting points there is usually no problem even for these units.” Mr. Harrison is with the Solar 

Rating and Certification Corporation and the Florida Solar Energy Center, Cocoa, FL.

Harrison, J. and S. Long. 1998. Solar Weatherization Assistance Program, FSEC-CR-1028-98. 

Prepared by the Florida Solar Energy Center (FSEC) for the Florida Department of Community 

Affairs. www.fsec.ucf.edu/solar/projects/swap/swap.html.

ICC Evaluation Service, Inc. 2006. Proposed Acceptance Criteria For Building-Integrated 

Photovoltaic (BIPV) Roof Panels. AC365. Whittier, CA. www.icc-es.org

National Roofing Contractors Association (NRCA). 2006. The NRCA Roofing and 

Waterproofing Manual, Fifth Edition. NRCA, Rosemont, IL. www.nrca.net

Nelson, Les. 2005. Scripps Highlands: A SheaHomes Zero Energy Home Project in the San Diego 

Area. Prepared by Western Renewables Group for the Sacramento Municipal Utility District.

Rudin, Arthur and Edgar Becerra. 2006. Designing Residential PV Systems to Meet Local Wind 

Loads and Building Codes. Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. 

American Solar Energy Society, Boulder, CO.

www.unirac.com/s5.htm – Information on S-5 clips and other rack components.

Solar sheds provide unobstructed southern 

exposures and put PV systems where they 

are not a visible part of the house. A case 

study about Tindall homes is available in this 

document. Photo courtesy of Bald Eagle 

Solar Technology.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 7 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 7.

Worker Safety

Building America Best Practices Series

Sunglasses, hardhats, and harnesses protect 

this crew from glare and falls. Builders must 

recognize that, ultimately, they may be held 

accountable for compliance with worker safety 

regulations. Although not required by regulation, 

protection for workers from solar exposure is 

important. Photo courtesy of NREL.

OSHA (2005) lists the standards most frequently 

included in the agency’s citations in FY 2004 as 

the following:

1. Scaffolding 

2. Fall protection 

(scope, application, definitions) 

3. Excavations (general requirements) 

4. Ladders 

5. Head protection 

6. Excavations 

(requirements for protective systems) 

7. Hazard communication 

8. Fall protection (training requirements) 

9. Construction 

(general safety and health provisions) 

10. Electrical 

(wiring methods, design and protection). 

Most of these standards are relevant to solar 

installations.

Falls

Fall hazards are the most common serious issue 

in construction. OSHA regulations for fall protection 

are covered in Part 1926, Subpart M. The regulations 

for fall protection apply to any work conducted 

greater than 6 feet above the ground.

OSHA offers the following tips to avoid fall hazards:

• Identify and evaluate fall hazards, 

including slick surfaces created by 

weather or jobsite activities.

• Mitigate any hazards you can – cover holes, 

keep the job area as clean as possible.

• Use appropriate equipment to prevent falls.

• Make sure fall-protection equipment is in 

good working order.

OSHA offers the following control measure suggestions to mitigate the most serious hazards for which 

employers have been cited most often:

Builders’ & Installers’ Brief

• Ultimately, the builder may be 

responsible for jobsite Occupational 

Safety and Health Administration 

(OSHA) violations.

• Falls are the number one cause of 

worker injury in house construction.

• Fall protection regulations apply to 

any work situation greater than 6 feet 

above ground.

• Do as much work as possible on 

the ground.

• Encourage protection against 

exposure to the sun’s rays.

• PV modules are energized whenever 

struck by light. Workers must be 

protected from electrical hazards.

• Solar thermal installers work with 

plumbing processes that include open 

flame. Precautions must be taken to 

protect workers and structures from 

flame and hot solder.

The Occupational Safety and Health Act of 1970 (the Act) generally covers all employers and employees 

in the U.S., including U.S. Territories. The Federal Occupational Safety and Health Administration 

(OSHA) administers and enforces the act. OSHA sets standards and conducts inspections to help ensure 

safe workplaces. The Act provides for penalties including fines and imprisonment depending upon the 

violation. States with their own plans can have different penalties.

Standards applicable to construction are contained in Title 29 of the U.S. Code of Federal Regulations, 

Part 1926, Safety and Health Regulations for Construction (29 CFR 1926).
p.2 / CHAPTER 7 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 7 Worker Safety

• Determine if any of the work (even a small 

portion) can be performed at ground level 

or if a crane can be used to lift assembled 

portions (e.g., sections of roofing) into place, 

eliminating or reducing the number of 

workers exposed to the risk of falling.

• Tether or restrain the worker so he or she 

cannot reach the edge thereby eliminating 

the fall hazard.

• Consider the use of aerial lifts or elevated 

platforms to provide better working surfaces 

rather than having workers walking top 

plates or beams.

• Erect guardrail systems, warning lines, or 

control line systems to protect workers from 

falls off the edges of floors and roofs.

• Place covers over holes as soon as they are 

created if no work is being done at the hole.

• Use safety net systems or personal fall arrest 

systems (body harnesses).

Not only can people fall off roofs, tools and equipment can fall as well making the site unsafe for 

people below. Keeping an uncluttered workspace 

can reduce both the risk of falling tools and the 

risk of tripping on misplaced tools. 

Attics

Solar installations (both PV and solar thermal) can 

require working in attic spaces. Attic environments 

generally call for protection from insulation: breathing masks, eye protection, clothing that protects 

skin from loose insulation and roofing nails that jut 

into the attic space. Attics can get very hot—make 

sure workers are adequately hydrated. 

It is important to know where there is enough 

support to hold the weight of a person as well as 

any tools or equipment being used in the attic 

space. Finding the ceiling joists or trusses may 

be difficult with blown insulation, but is critical 

to maintaining a pristine ceiling. Care must be 

taken not to damage ductwork or existing wiring. 

Careful sequencing of worker access to the site can 

avoid some of these hazards. For example, do not 

have insulation installed until all solar, electrical, 

plumbing, and HVAC work is complete. Task 

lighting will probably be needed for work.

Electrical

PV installers are doing electrical work with “hot” 

(energized) equipment. PV modules are live with 

even minimal amounts of light hitting them. Panels 

should be covered until they are installed. Opaque 

covers over the panels will reduce the amount of 

power produced—it must always be assumed they 

are energized.

(left) Photovoltaic installers have attached 

mounting rails to the PV modules in the shop. 

This saves time on the roof and provides 

for easier shipping. 

(right) This photovoltaic installation crew wears 

safety harnesses and hard hats for protection.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 7 / p.3

Worker Safety Chapter 7

Foot protection should not only have impact and 

compression resistance, it should also be rated EH 

for electrical hazard or electrical shock resistance

as specified in OSHA guidelines. Electrical hazard 

footwear is manufactured with non-conductive 

electrical shock-resistant soles and heels. It is 

intended to provide a secondary source of protection against accidental contact with live electrical 

circuits, electrically energized conductors, parts 

or apparatus. 

The North American Board of Certified Energy 

Practitioners (NABCEP 2005) notes that the 

following sections of the OSHA rules apply to PV 

installation sites:

• Subpart I – Tools, Hand and Power

• Subpart K – Electrical

• Subpart X – Stairways and Ladders.

Plumbing

Solar thermal installers often deal with plumbing 

equipment and processes, such as using torches for 

soldering or possible exposure to very hot water or 

steam. These hazards can not only injure workers, 

they can damage roofs and other structural and 

finish materials. Dripping solder can damage 

unprotected skin, as well as newly installed flooring 

or paint.

NABCEP (2006) notes solar thermal installations 

are also covered by the following OSHA rules:

• Subpart P – Tools, Hand, and Portable 

Power Tools

• Subpart Q – Welding, Cutting, Brazing.

Lifting and Handling

PV modules for solar thermal collectors are heavy 

and the metal surrounding them can get very hot 

in the sun. If a module is dropped, jagged edges 

can be dangerous. Gloves can help protect workers 

from these hazards. Hard hats should be worn 

whenever there is a hazard of materials falling 

from above. 

Roof-mounted solar systems require lifting large 

parts onto roofs creating lifting hazards. Solar PV 

systems can be large and ungainly and involve 

many pieces. Solar thermal collectors are heavier 

and may require more than one person or machinery to lift onto a roof. Even ground-level work on 

a solar PV system can require heavy lifting: some 

inverters weigh over 150 pounds and may require 

two people to lift to their mounting places.

The National Institute for Occupational Safety 

and Health (NIOSH) recommends that employers 

and workers minimize their risk of back injury by 

developing and implementing a comprehensive 

ergonomics program. A program of this nature 

would focus on prevention (www.cdc.gov/niosh/

homepage.html).

The Labor Occupational Health Program at University of California Berkeley has created a checklist to 

help reduce lifting hazards (http://socrates.berkeley.

edu/~lohp/graphics/pdf/cBACKS.pdf). This list is 

based on California regulations, but is sensible in 

any state. The list helps define for builders what 

lifting hazards are. These include: 

• Heavy loads including 20-pound objects that 

are lifted repeatedly and 50-pound objects 

that are lifted at one time. 

• Bulky or awkward objects

• Loads whose weight may suddenly shift

• Objects that must be lifted from above 

shoulder level

• Objects that must be lifted from the floor

• Objects that cannot be held close to the body.

The checklist also provides guidance to help reduce 

lifting hazards. Some of the recommendations 

include the following:

• Encourage workers to stretch and warm 

up before lifting and to take frequent 

stretch breaks.

• Train workers on lifting methods.

• Use mechanical lifting devices (fork lifts, 

hoists, cranes, and block and tackle).

• Ensure that manual lifting and carrying 

devices (dollies, hand trucks, pry bars, and 

hooks) are available and in good condition.
p.4 / CHAPTER 7 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 7 Worker Safety

• Split up materials to reduce weight.

• Deliver materials as close as possible to the 

work site.

• Divide lifting tasks among workers or use 

team lifting.

• Store heavy materials that must be lifted 

manuallyabove the ground, no lower than 

knee height. (This limits the height of the 

lifting required, and reduces pressure on the 

spine.)

• Store heavy materials where there is enough 

space to lift them safely, without reaching 

or twisting.

Responsibility for Violations

Employers are responsible to ensure that the 

requirements of the Act are met. However, in most 

situations this could be confusing when there 

might be a general contractor, subcontractors, and 

even third-tier subcontractors. OSHA ultimately is 

looking at who has control of the jobsite.

According to part 1926.16(a), prime contractors 

and subcontractors may agree who is responsible 

for items such as first aid, etc., on the jobsite, but 

legal responsibility cannot be abdicated. “In no case 

shall the prime contractor be relieved of overall 

responsibility for compliance with the requirements 

of this part for all work to be performed under 

the contract.” Parts 1926.16(c) and (d) address 

joint responsibility among prime contractors and 

subcontractors. Details can be found at: www.osha.

gov/pls/oshaweb/owadisp.show_document?p_

table=STANDARDS&p_id=10605.

Injured workers, even if they work for a third-tier 

subcontractor, may have a claim against the prime 

contractor in certain circumstances. In some states, 

general contractors may have to pay claims for 

injuries when subcontractors and third-tier subs 

have no workers’ comp insurance.

Enforcement

OSHA has 10 regional offices and many area offices. 

A list of the offices is provided at www.osha-slc.

gov/htmol/RAmap.html. Section 18 of the Act 

allows states to adopt their own standards under 

supervision of OSHA. According to OSHA’s website 

(www.osha.gov), “There are currently 22 States 

and jurisdictions operating complete State plans 

(covering both the private sector and State and 

local government employees) and 4 – Connecticut, 

New Jersey, New York, and U.S. Virgin Islands 

– which cover public employees only.” When OSHA 

grants final approval to a state under Section 18(e) 

of the Act, it “relinquishes its authority to cover 

occupational safety and health matters covered 

by the State.” It is very important, therefore, to be 

aware of states that have their own OSHA programs: 

www.osha.gov/fso/osp/faq.html#oshaprogram.

Since resources are limited, “targets” are used to 

determine sites that will be inspected. “Targets” 

include past bad performers. In addition, 

“programmed inspections” are conducted which 

focus on high-hazard groups/industries that have 

the highest injury rates. When certain circumstances 

occur, such as a fatality, a complaint, or a referral, 

an “unprogrammed inspection” may be conducted. 

Local enforcers may also just “drive by” job sites.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 7 / p.5

Worker Safety Chapter 7

Resources and References

29 CFR 1926. Title 29 of the U.S. Code of Federal Regulations, Part 1926, Safety and Health 

Regulations for Construction. Occupational Safety and Health Administration. http://www.osha.

gov/pls/oshaweb/owastand.display_standard_group?p_toc_level=1&p_part_number=1926

National Association of Homebuilders (NAHB) and the Occupational Safety and Health 

Administration (OSHA). 1999. NAHB-OSHA Jobsite Safety Handbook, Second Edition. Home 

Builder Press. Washington, D.C. at www.osha.gov/doc/jobsite/.

U.S. Department of Health and Human Services, Center for Disease Control & 

Prevention, The National Institute for Occupational Safety and Health (NIOSH)

www.cdc.gov/niosh/homepage.html 

NIOSH Fact sheet on Back Belts

www.cdc.gov/niosh/backfs.html

“The first thing we do is check the roof 

and make sure it is safe to work there.”

Jason Fisher, Aurora Energy, 

Annapolis, Maryland 

Head Protection 

• Workers must wear hard hats when overhead, 

falling, or flying hazards exist, or when danger of 

electrical shock is present. 

• Inspect hard hats routinely for dents, cracks, 

or deterioration. 

• If a hard hat has taken a heavy blow or electrical 

shock, you must replace it even when you detect 

no visible damage. 

• Maintain hard hats in good condition; do not 

drill; clean with strong detergents or solvents; 

paint; or store them in extreme temperatures. 

Eye and Face Protection 

• Workers must wear safety glasses or face 

shields for welding, cutting, nailing (including 

pneumatic), when working with concrete and/or 

harmful chemicals, or when exposed to 

flying particles. 

• Eye and face protectors are designed for 

particular hazards so be sure to select the type 

to match the hazard. 

• Replace poorly fitting or damaged safety glasses.

• Safety glasses or face shields are worn when 

workers are exposed to any electrical hazards 

including energized electrical systems.

Foot Protection 

• Residential construction workers must wear 

shoes or boots with slip-resistant and punctureresistant soles. 

• Safety-toed shoes are worn to prevent 

crushed toes when working with heavy rolling 

equipment or falling objects. 

Hand Protection 

• High-quality gloves can prevent injury. 

• Gloves should fit snugly. 

• Glove gauntlets should be taped for working 

with fiberglass materials. 

• Workers should always wear the proper gloves 

for the job (for example, heavy-duty rubber 

for concrete work, welding gloves for welding, 

insulated gloves and sleeves when exposed to 

electrical hazards). 

Fall Protection 

• Use a safety harness system for 

fall protection. 

• Use body belts only as positioning 

devices—not for fall protection.

Jobsite Safety Regulations 

Adapted from the NAHB-OSHA Jobsite Safety Handbook (1999), Second Edition at 

www.osha.gov/doc/jobsite/ and the OSHA Pocket Guide, 2005.
p.6 / CHAPTER 7 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 7 Worker Safety

Electronic Library of Construction Occupational Safety & Health (eLCOSH), funded by NIOSH

www.cdc.gov/elcosh/index.html

State of California, Department of Industrial Relations, Division of Occupational 

Safety and Health (DOSH) enforces California Occupational Safety & Health Administration 

(Cal/OSHA) regulations

www.dir.ca.gov/dosh/dosh1.html

Labor Occupational Health Program, School of Public Health, University of California 

at Berkeley. A community outreach program that addresses health and safety needs in nearly 

every industry. They have publications, training programs, a free library, and a telephone reference 

service. They are geared toward safety in California but have references at a federal level as well. 

Some of their information is in multi-lingual format.

www.lohp.org

http://socrates.berkeley.edu/~lohp/graphics/pdf/cBACKS.pdf follows Cal/OSHA code, but is a great 

checklist to help reduce lifting hazards. 

North American Board of Certified Energy Practitioners (NABCEP). 2005. NABCEP Study 

Guide for Photovoltaic System Installers and Sample Examination Questions Revision 3. 

Prepared for the U.S. Department of Energy and Sandia National Laboratories. 

www.nabcep.org/Monticello/userfiles/File/PVStudyGuide093006FINAL.pdf

North American Board of Certified Energy Practitioners (NABCEP). 2006. Nabcep

Study Guide for Solar Water and Pool Heating System Installers and Sample Questions With 

Answer Key, Version 1. Prepared for NABCEP by the Florida Solar Energy Center and Energy 

Conservation Services. 

www.nabcep.org/Monticello/userfiles/File/NABCEPSolarThermalStudyGuideVersion1.0.pdf

Occupational Safety and Health Administration (OSHA). 2005. OSHA Pocket Guide 3252-05N 

2005. U.S. Department of Labor, Washington, D.C.

www.osha.gov/Publications/OSHA3252/3252.html

Solar Energy International (SEI). 2004. Photovoltaics: Design and Installation Manual. New 

Society Publishers, Gabriola Island, British Columbia, Canada 

www.solarenergy.org
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 8 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 8. 

Solar Ready

Building America Best Practices Series

Making a home Solar Ready means providing the 

plumbing, wiring, and structural changes needed 

to support solar thermal collectors and PV modules. 

These modest upgrades make future installations 

much easier, less costly, and more durable.

Building America experience and market research 

suggests that when it comes to ZEH, communities that make the technology part of the house 

package, rather than an option, do the best job of 

marketing solar. However, solar ready is a small 

step for builders who want to get started, but are 

not ready to commit to full installations. 

Making a home solar ready helps to retain the 

advantages of new construction, such as avoiding 

after-market roof penetrations, and will help builders comply with programs that require offering 

solar features to consumers.

Perhaps the most important step in using 

solar energy is the site evaluation and design. 

Site planning that exploits and protects solar 

exposure is critical to making a home and 

community solar ready for both PV and solar 

thermal technologies.

Clearly label all end points for wires or pipes so 

subcontractors, homeowners, maintenance workers, 

and solar installers know their purpose and where 

the materials are located. Similar information 

will be needed for the location of structural reinforcements. This information should also include 

the intended placement for potential equipment, 

such as arrays, collectors, tanks, inverters, and 

switches. Diagrams and notes should be included 

in the homeowner’s manual. In addition, a copy 

of the wiring notes and diagrams should be left 

in the electrical panel. Post a sign or label on the 

electrical panel door indicating that the home is 

SOLAR READY.

See the respective chapters on PV and solar thermal 

installations and site planning and orientation 

for more details.

Design the home as if PV were 

going to be installed. Here are 

some elements to include:

• Design the orientation and pitch of the southernmost facing roof to maximize solar gain, 

although there is a great deal of flexibility in 

both the direction and angle.

• Design the roof vents, chimneys, gables or other 

obstructions to sit to the north side of the planned 

array. Do not shade the part of the roof where 

a potential PV array or solar thermal collector 

could be installed.

• Ensure that the roof structure is strong enough. 

Design structural support into the roof to handle 

the weight of a rack-mounted system.

• Design space for inverters and disconnects near 

the main service panel.

Builders’ & Installers’ Brief

• Use the techniques found throughout 

this document to make homes 

solar ready.

• Making provisions for solar installation 

up front will make future installations 

easier, less costly, and more durable.

Plan for solar at the earliest stages of site 

design and construction.
p.2 / CHAPTER 8 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CHAPTER 8 Solar Ready

• Make sure the main service panel has space to 

handle a power input breaker.

• Pre-wire or install empty metal conduit from the 

roof to near the main service panel to handle wires 

from the future array to the future inverter. 1” 

conduit would support most residential systems. 

A conduit will also be needed from the inverter 

location to the main service panel. If you are 

preparing a very large house you may need to 

run two or more conduits from the roof.

• Provide enough room in the breaker box for a 

double-pole 30 A breaker (solar electric feed).

• Provide a vertical wall area to mount an inverter 

in the mechanical area of the house.

• Minimize the distance (wire run) from the array 

to the inverter.

• Install an electric disconnect switch for a 

potential future solar electric system.

• If stand-off mounts or racks are needed, install 

them before the final roofing material is installed 

to ensure proper flashing. 

Preparing for solar thermal:

• Design the orientation and pitch of the southernmost facing roof to maximize solar gain, 

although there is a great deal of flexibility in 

both direction and angle.

• Design the roof vents, chimneys, gables, or other 

obstructions to sit to the north side of the planned 

array. Do not shade the part of the roof where 

a potential PV array or solar thermal collector 

could be installed.

• Ensure that the roof structure is strong enough. 

Work with your designer or structural engineer 

to ensure adequate structural support. Note that 

in some designs structural lumber is added as 

a convenience for easy installation rather that 

to actually support additional load.

• Install 3/4” copper pipe for both cold and heated 

water from the roof to the space where hot water 

storage tanks would be located. The pipe will 

need to be capped and accessible on the top. The 

bottom should dead end until the solar system 

is installed. Insulate the pipe as described in 

Chapter 3: Solar-Thermal Water Heating.

• Run sensor wires parallel with copper pipe. 

Electric cable may be needed for a potential 

pump.

• Allow space near the water heater for necessary 

equipment including hot water tanks, valves, 

pumps, heat exchangers, expansion tanks and 

other needed equipment.

• If stand-off mounts or racks are needed, install 

them before the final roofing material is installed 

to ensure proper flashing. 

(left) Structural changes may be added to ensure 

adequate support or just to make installation easier.

(right) Set off mounts installed before roofing to 

allow for proper flashing. Photo courtesy of Namaste.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 8 / p.3

Solar Ready Chapter 8

Resources and References

Lubeliner, Michael, Andrew Gordon, Adam Hadley, and Michael Nelson. 2004. 

“Introducing ‘Solar Ready’ Manufactured Housing.” Proceedings of the 1994 ACEEE Summer 

Study on Energy Efficiency in Buildings, American Council for an Energy-Efficient Economy, 

Washington, D.C.

Seiter, Doug. 2006. “Are You Solar Ready.” Home Builder, July 2006.

(left) Pre-plumbing for solar thermal collectors is 

especially important in inaccessible areas.

(right) Pre-wiring or installing empty conduit allows 

for the easy installation of PV systems. A junction box 

with some flexibility can be moved to the appropriate 

location to match a future PV array.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 9 / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Chapter 9.

Looking Back, Looking Ahead

Building America Best Practices Series

(top) America’s second satellite in space may have 

launched the PV industry. Photo courtesy of NASA.

(bottom) Work continues through the night at the 

Solar Decathlon in Washington, D.C. Photo courtesy of 

Byron Stafford, NREL.

Feeling the Heat

The hot box was first tested by a Swiss scientist at 

the dawn of the American Revolution (1760s). In 

1891 Clarence Kemp combined the glass-covered 

hot box with a black metal tank to create the 

Climax Solar-Water Heater. Even before Kemp, metal 

collectors and tanks similar to some modern pool 

heaters were in use. At the turn of the 20th century, 

a third of the homes in Pasadena, California, were 

equipped with Kemp’s panels (Butti and Perlin 

1980). In 1909, William J. Bailey patented the 

“Day and Night” thermosyphon solar water heater 

(Butti and Perlin 1980). With the panel sitting 

on the roof, and a separate storage tank in the 

attic, these systems held heat through the night 

much better than Kemp’s exposed tanks. After 

World War II half of Miami, Florida, homes had 

solar thermosyphon water heaters and over 80% 

of newly constructed homes in the area had them 

installed (Lane 2004).

This chapter reviews the refinements in solar technologies over the last century. Solar thermal systems 

have been around longer than radio, longer than refrigerators, and longer than automobiles. Builders 

can take comfort in the proven nature of this technology. In addition to looking only at the past, also 

included is a review of entries in the 2005 Solar Decathlon. These houses, many of which went on to 

become residences, show how the newest engineers and designers are approaching zero energy homes. 

And finally, a short summary is provided of the homes featured in the case studies at the end of this 

document. These examples of today’s near zero energy homes that cut utility bills at least 50 percent are 

located across the United States and range from individual custom homes to entire communities.

Solar technologies have been around a long time. Butti and Perlin (1970) describe the use of south 

facing glass by Romans, Greeks, and later Europeans to capture the sun’s heat. Ancient civilizations in 

the Americas, such as the Pueblo Indians (and Spanish colonialists when they arrived) took advantage 

of solar orientation to heat and cool their homes. A summary of Butti and Perlin’s work and more recent 

Perlin documents are available at www.californiasolarcenter.org/history_solarthermal.html. 

Builders’ & Installers’ Brief

• Solar technologies are mature systems 

that have been continually upgraded 

since their inception.

• Solar thermal systems have been 

commercially available in the United 

States since the 1890s.

• PV systems saw breakthrough 

discoveries and applications in the 

1950s with the space race and their 

first use on houses in the 1970s.

• The Solar Decathlon shows what 

today’s students are thinking about 

tomorrow’s houses.

• Building America case studies show how 

today’s leading builders are installing 

Kemp’s 1891 Climax Solar Water Heater. solar thermal and PV into today’s ZEH.
p.2 / CHAPTER 9 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 9 Looking Back, Looking Ahead 

Modern solar thermal systems and companies in 

the United States have been around since the 1970s. 

Interest in solar started picking up after the oil crisis 

that developed during the OPEC (Organization 

of Petroleum Exporting Countries) oil embargo 

of the U.S. after the Arab-Israeli war in 1973. In 

that same year the University of Delaware built 

Solar One, the first residence outfitted with PVs 

(www.lib.udel.edu/ud/spec/findaids/boer/index.

htm). The house had a grid-tied PV system and 

had a net metering arrangement with its utility. 

It was also outfitted with solar-thermal collectors 

used for space heating.

Another war along the Israeli-Lebanese border 

and a revolution in Iran disrupted oil supplies 

and began pushing prices up again in 1978. This 

time, 40% federal tax credits were enacted for solar 

thermal installations. The tax credits proved both 

blessing and curse to the emerging solar industry. 

Solar thermal technologies were not well developed 

and a quickly growing market brought in many 

new companies that had little experience with 

the technology or the installations. Memories of 

failed systems from that era still haunt installers, 

builders, and consumers. However, many systems 

installed in the 1980s still perform.

Finding the Light

William Grylls Adams and Richard Evans Day 

discovered in 1876 that light shined on solid selenium would produce an electric current (Perlin 

1999). Over 75 years later, scientists at Bell Laboratories inadvertently made a more efficient solar 

cell that, with refinement, could power electrical 

equipment. Sputnik in 1957 and the subsequent 

race for space turned the new photovoltaics from 

novelties to power sources. Vanguard 1, launched 

in 1958 as America’s second artificial satellite, 

is the oldest manufactured satellite still orbiting 

earth, and was the first to use photovoltaics (Green 

and Lomask 1970). It continued to transmit for 5 

years, until 1964. In comparison, America’s first 

satellite, Explorer 1, which was equipped with a 

nickel cadmium battery, had power to transmit 

for 105 days. (See www.nasm.si.edu/research/dsh/

artifacts/SS-vanguard.htm).

With more than a century of technical innovation 

in the solar industry, and with widespread use in 

times and places of energy scarcity, another point 

becomes clear. As an energy source for consumers, 

solar competes with natural gas and electricity. 

Electricity cost and availability is dependent on 

coal, oil, water flow and other factors facing 

Progress on development of the International 

Space Station can be traced through the 

addition of PV systems. The latest installment 

came in September 2006 (top right). 

Photos courtesy of NASA. 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 9 / p.3

Looking Back, Looking Ahead Chapter 9

environmental, economic, and political pressures. 

American history, and trends in Japan, Australia, and 

Europe, show that cheap and abundant fossil fuel 

energy squelches the rate at which solar thermal 

is installed.

However, fossil fuels and electricity are no longer cheap 

or always abundant. Revolutions, wars, and hurricanes 

have created long lines for gasoline. Droughts, market 

manipulators, endangered species, and poor planning 

have resulted in electricity price spikes and rolling 

brownouts. With the price and availability of energy 

commodities becoming more uncertain, prospects 

for solar installations are looking brighter.

As a commercially viable product, solar power 

was born in the U.S. However, the rest of the world 

has caught on and surpassed the U.S. market. 

One exception is building-integrated PV systems. 

Building-integrated systems were developed in the 

U.S. and have had a real impact on ZEH development over the last five years. However, the largest 

markets for both solar thermal and PV are now in 

China and Europe.

The good news for the U.S. solar industry is that the 

technologies that have grown in foreign markets 

are starting to make their way to the U.S. market. 

Some of these products involve innovative packages 

of solar thermal components and advances in 

PV inverters.

A Glimpse of the Future

The Solar Decathlon is a collegiate team competition to build energy-efficient solar houses. Twenty 

teams competed in 2005 from colleges and universities across the U.S. as well as Puerto Rico, Canada 

and Spain. Fourteen teams from across the U.S. and 

Puerto Rico competed in 2002. The teams’ solar 

houses use the newest products and technologies on 

the market. As a tribute to the teams’ innovation and 

as a glimpse into the designs of tomorrow, here is a 

brief gallery of some of the 2005 Solar Decathlon 

houses. For more information on the Solar Decathlon, visit www.eere.energy.gov/solar_decathlon/. 

All Decathlon photos are courtesy of DOE 

unless noted.

The Solar Decathlon is a competition sponsored 

by the U.S. Department of Energy’s (DOE’s) Office 

of Energy Efficiency and Renewable Energy. The 

American Institute of Architects (AIA), American 

Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), BP, Sprint and NAHB 

partnered with DOE as title sponsors.

(left) Pittsburgh Decathlon Team home—a 

joint effort of Carnegie Mellon, the University of 

Pittsburgh, and The Art Institute of Pittsburgh.

(right) University of Missouri-Rolla and Rolla 

Technical Institute Decathlon home. Photo 

courtesy of Stefano Paltera, Solar Decathlon.
p.4 / CHAPTER 9 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 9 Looking Back, Looking Ahead 

The Pittsburgh Decathlon Team is a joint effort 

of Carnegie Mellon, the University of Pittsburgh, and 

The Art Institute of Pittsburgh. The home literally 

reaches out to the sun, with its north and south 

walls tilting 12 degrees to the south. The tilted north 

wall is made of sheets of polycarbonate, a strong, 

insulating, translucent plastic, with embedded 

glass beads.

University of Missouri-Rolla and Rolla 

Technical Institute – “Our way of expanding 

solar is making it more visually acceptable,” says 

University of Missouri-Rolla student Allison Arnn. 

Above all else, this team wanted to build a house 

in which any traditional Midwesterner might feel 

at home. 

University of Maryland – Student Luming 

Li, and house architect of the design they chose, 

originally envisioned a house “floating” over a 

field of water, describing it as “anchored to the 

earth, yet touching it lightly.” To marry that vision 

with the practicality of transporting the house to 

the National Mall, the students chose to rest the 

house on a field of stone. Their iterative design 

process led to a final design with “very clean and 

simple” lines. The home’s PV system—comprising 

51 charcoal-gray BP Solar panels—adds to its 

aesthetic appeal. Student Tom Serra said, “We 

made a statement by integrating the panels into 

the home’s design, not hiding them.”

University of Michigan – Inspired by designs 

from the aircraft and automobile industries (in 

which the external skin of an object supports some 

or most of the load on the structure), University of 

Michigan team chose aluminum for the house’s 

exterior. Beeson notes that “Aluminum is not an 

energy-efficient material to produce, but it lasts 

and doesn’t lose any value when recycled.” 

University of Colorado’s winning entry. 

Using natural materials was one of the team’s five 

major design goals, along with innovation, energy 

efficiency, modularity, and accessibility. The result 

is a sustainable, attractive solar home built almost 

entirely of recycled and natural materials.

In chilly Montreal, the location of the Concordia 

University and Universite de Montreal, the 

appearance of the sun in winter is a welcome sight 

for more than one reason. “We hope to use weather 

prediction and smart controls as much as possible 

to effectively control the home,” says Mark Pasini, 

Canadian Decathlon team project manager.

(left) University of Maryland decathlon home. 

Photo courtesy of Paul Norton, NREL. 

(middle top, bottom) University of Michigan 

decathlon home with an aluminum exterior. Photo 

courtesy of Stefano Paltera, Solar Decathlon.

(right top) University of Colorado’s 

winning entry to the Solar Decathlon.

(right bottom) Concordia University and Universite 

de Montreal decathlon home. Photo courtesy of 

Wendy Butler-Burt, Department of Energy.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 9 / p.5

Looking Back, Looking Ahead Chapter 9

To help with designing the automation system 

and other aspects of the house, team members 

designed their own software to simulate the thermal 

behavior of the house. The software combines all 

the unique components of the house, including 

the automated blinds and the thermal storage. 

Phase-change materials and a wall of water placed 

adjacent to window glass serve as thermal storage 

and perpetuate the house’s invisible-technology 

design approach.

Although the Universidad Politecnica de 

Madrid’s home has its share of high technology, the 

primary design objectives were to make it attractive 

and comfortable, so that it would appeal to anyone. 

You shouldn’t have to be in love with gadgets to 

enjoy this flexible Mediterranean-style home. Many 

of the controls are designed to work automatically. 

“Designing those controls, understanding when the 

various space conditioning and lighting systems 

should operate, and connecting sensors to them 

to allow them to operate automatically was the 

most exciting part of the project,” said engineering 

student Álvaro Gutiérrez.

The Washington State University students knew 

that, as the only team from the Northwest, their 

participation in the 2005 Solar Decathlon gave them 

a unique opportunity to showcase local products and 

technologies. Student and team fundraising leader 

Andrea Read said, “We wanted to keep our house true 

to the green that people associate with our area.”

Sometimes when you try to solve a transportation 

problem, you end up refining an exciting new 

mobile home design. That’s what happened to the 

team from Virginia Polytechnic Institute and 

State University. Faculty advisor Joe Wheeler 

says, “We wanted to be able to transport our home 

to Washington intact so we could spend the five 

days in D.C. fine-tuning and testing it, rather than 

reconstructing the building.” The result is a unique 

synthesis of manufactured housing principles and 

innovative transportation solutions.

California Polytechnic State University

students decided to take the simplicity concept as 

far as they could. You will not see a lot of high-tech 

gadgets on this house, nor is the building elaborate 

in form. Not only will this help ensure it will fit on 

one truck, but it fits well with their dedication to 

passive architectural design strategy. “Ours is an 

architectural strategy for performance and comfort 

that encourages the use of the building itself,” says 

Sandy Stannard, a faculty adviser on the team. 

(left) Universidad Politecnica de Madrid 

decathlon home.

(middle) Washington State University decathlon 

home. Photo courtesy of Wendy Butler-Burt, 

U.S. Department of Energy.

(right top) Virginia Polytechnic Institute and 

State University decathlon home. Photo 

courtesy of Byron Stafford, NREL.

(right bottom) California Polytechnic State 

University decathlon home. Photo courtesy 

of Byron Stafford, NREL.
p.6 / CHAPTER 9 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 9 Looking Back, Looking Ahead 

Samples of the 

Best of Today’s ZEH

Builders all over the United States are making 

breakthroughs in the design and construction of 

ZEH. All of these homes incorporate solar technologies with high levels of energy efficiency. Few 

homes have met the goal of generating as much 

power as they consume over the course of a year. 

But, the builders showcased in the case studies 

contained in this document have worked with their 

solar partners and Building America to streamline 

installations and demonstrate the effectiveness of 

ZEH technologies for both energy effectiveness and 

consumer acceptance.

The 13 case studies presented at the end of this 

document tell the stories of some of the nation’s 

largest builders like Centex and Pulte, regional 

production builders like Clarum and Bob Ward 

Companies, a custom builder, and even affordable 

housing builders like Habitat for Humanity.

Bob Ward Companies’ Maximum Efficiency 

Greenland in BelAir, Maryland – Bob Ward 

Companies took its popular Greenland house model 

and decided to see just how efficient it could be 

made. The builder, an energy-efficiency pioneer 

in Maryland, started with a basement foundation 

of precast high-density concrete walls with an 

interior layer of rigid foam insulation plus R-19 of 

fiberglass bat, and went up with advanced framed 

upper walls and a whopping R50 blown fiberglass 

ceiling insulation, plus foam sealing of all band 

joists, top and bottom plates and wall penetrations. 

A whole house fan and fresh air intake ensure air 

quality in the super-tight structure, which Bob 

Ward has kept open for a year to showcase the 3kW 

photovoltaic system, solar hot water system, and 

super-efficient lighting and appliances for regional 

builders, realtors, and architectural students.

Centex Avignon in Pleasanton, California 

– Builder of over 350,000 homes, Centex has 

committed to efficiency on its Avignon development, 

the first all-solar, zero-energy community to be 

built in Alameda County. The 3.5 kW PV systems 

use SunPower integrated Suntiles, which match the 

dimensions of the cement roof tiles they replace 

to blend in seamlessly with the roofing. Other 

energy-saving measures like R-49 attic insulation 

and R-15 wall insulation, high-efficiency windows 

and appliances, caulking, sealing, and independent 

air leakage testing help ensure energy savings of 

up to 70% for home owners.

Clarum Homes’ Vista Montana in Watsonville, California – The largest ZEH development 

to date when completed in 2005, Vista Montana 

includes 257 single-family homes and townhouses 

along with 132 solar-powered apartments, plus a 

14-acre park, and an elementary school. This is 

one of several PV-powered, energy-efficient developments the innovative builder has constructed in 

the Bay area with more on the way in southern 

California and Arizona. Clarum has committed to an 

Enviro-Home green package designed to be ZEH.

CARB Cold Climate Homes in Hadley, Massachusetts, and Madison, Wisconsin – With 

assistance from the Consortium for Advanced 

Residential Buildings (CARB), two homes built in 

the cold climate offer examples of solar thermal 

and photovoltaic systems. CARB’s modeling and 

monitoring has helped quantify solar energy 

contributions and identify installation hardware 

and techniques to greatly improve performance. 

Based on energy-efficiency features and the solar 

thermal system, the Massachusetts house would 

consume 33% less energy than the Building America 

benchmark, and 41% less when the photovoltaic 

system is added in. During critical summer peaking 

months, this house generated more electricity than 

it consumed. With its energy-efficiency features 

and solar thermal system, the Wisconsin house 

is 43% more efficient than the benchmark. Both 

homes shelter families of four. The Massachusetts 

solar water heating system provided 61% and 

the Wisconsin system provided 63% of hot water 

needs. Both homes result in positive cash flows 

for homeowners. 

Georgia Department of Natural Resources 

SIPS Cottage in Okefenokee, Georgia – Full 

blast air conditioning might seem the only way to 

tame the heat and humidity of Georgia’s Okefenokee 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 9 / p.7

Looking Back, Looking Ahead Chapter 9

Swamp but DOE’s Building America researchers 

helped put together a home that takes advantage 

of passive solar and cooling design elements to cut 

energy use by 43%. By maximizing cross ventilation 

using sun-blocking overhangs like long screened 

porches and adding the heat-shielding power of 

structural insulated panels, the home’s 4.1-kW 

photovoltaic system is able to more than meet all 

of the home’s heating and cooling load in all but 

the two coldest months of the year.

Grupe Carsten Crossings, Rocklin, California 

– Central California production builder Grupe 

used today’s zero energy home designs to help 

market its homes in a volatile Sacramento area 

housing market. The builder decided to make 

solar standard on its 144-home development, 

along with rigid foam exterior building wrap, 

tankless water heaters, SmartVent night ventilation 

cooling, high-efficiency appliances, and lighting. 

The 2.4-kW solar system was composed of flexible 

tiles that blend with the roof’s cement tiles for 

nearly invisible installation.

Habitat for Humanity Denver Metro’s ZEH 

in Wheat Ridge, Colorado – This near zero 

energy demonstration home is so well insulated 

- with extra thick double stud walls sandwiching 

three layers of R-13 fiberglass batt, R-60 in the 

attic and R-30 in the floors, that the homeowners 

stay cozy through Denver winters with baseboard 

heaters in the bedrooms and a small direct-vent 

natural gas system in the living room. An energy 

recovery ventilation system retains heat while 

providing fresh air. The home is equipped with 

a 4-kW PV system plus three solar thermal water 

collectors on a drain-back system with a 200-gallon 

tank that provide nearly all of the family’s electric 

and hot water needs.

13 Solar Best Practices Case Studies

Tindall Homes

Princeton, NJ

Bob Ward Companies

BelAir, MD

Georgia Department of Natural Resources

Okefenokee, GA

Habitat for Humanity

Louden County, TN

Pulte Homes - Civano

Tucson, AZ

John Wesley Miller Companies

Tucson, AZ

Clarum Homes

Watsonville, CA

Centex Homes

Pleasanton, CA

Premier Homes

Sacramento, CA

Grupe-Carsten Crossings

Rocklin, CA

Garst House

Olympia, WA

Habitat for Humanity

Metro Denver

Wheat Ridge, CO

CARB Cold Climate Houses

Hadley, MA and Madison, WI
p.8 / CHAPTER 9 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

Chapter 9 Looking Back, Looking Ahead 

Habitat for Humanity Loudon County’s Five 

Test Homes in Tennessee – Loudon County’s 

Habitat for Humanity affiliate teamed with DOE’s 

Oak Ridge National Laboratory to build five near 

zero energy homes. The Lab has done extensive 

energy analysis on the houses, each of which 

has a different mix of energy-efficiency features 

including structural insulated panel walls and roofs, 

geothermal or air-to-air heat pumps, metal roofs, 

and 2 or 2.2 kW photovoltaic systems. Volunteer 

labor showed that energy-efficiency measures 

like draft-stopping and air sealing aren’t hard 

to learn. Total utility bills range from $0.30 to 

$1.00 per day.

John Wesley Miller Companies’ Armory Park 

del Sol in Tucson, Arizona – This southwestern 

style development includes rooftop solar panels 

for an integrated solar water heater and a 1.5-kW 

photovoltaic power system standard on each of its 

99 units. Steel-reinforced masonry walls with rigid 

insulation under a three-coat stucco finish, R-38 

ceiling insulation, and low-emissivity dual-pane 

windows ensure a tight thermal envelope and 

high-efficiency appliances and ducts in conditioned 

space help reduce energy usage. 

Premier Homes Premier Gardens in 

Sacramento, California – Similarly sized and 

priced neighborhoods in a Sacramento subdivision 

provided an interesting test bed for zero energy 

homes. Premier Homes’ development outshone 

its neighbor with average annual utility bills of 

about $400 compared to $800 for the neighboring Energy Star homes and $1000+ for standard 

construction homes. 2-kW PV systems and rigid 

foam exterior house wrap, well insulated ducts, and 

high-efficiency appliances, windows, and lighting 

made the difference.

Pulte Homes’ Civano Neighborhoods 2, 

3, and 4, in Tucson, Arizona – When huge 

production builder Pulte Homes took over as master 

developer of neighborhoods 2, 3 and 4 of the Civano 

development near Tucson, it agreed to the energy 

efficiency, solar, and sustainability requirements 

of the “new urbanist” planned community. Using 

Building America research and lessons learned 

from other builders of Civano Neighborhood 1, 

Pulte selected a workable combination of active 

closed-loop solar thermal water heaters to meet the 

5% solar requirement and an efficiency package 

it calls Pulte platinum to meet the energy savings 

requirement of 50% over local code. The package 

includes “cathedralized” application of blown 

insulation along the roof line of the attic to provide 

conditioned space for the ducts and air handler 

as well as air leakage testing, high-performance 

closed-combustion gas appliances, and use of a 

drainage plane, flashing, and other water management details to provide superior energy performance 

as well as safety and durability for the 1200 to 1500 

homes Pulte plans to build.

The Garst House near Olympia, Washington 

– It may be hard to believe solar can work in the 

cloudy, damp Pacific Northwest but home owner 

Sam Garst teamed with Building America and a 

building science-minded builder and architect 

to showcase just how green you can get in the 

evergreen state. The house sports a 4.5-kW photovoltaic system, radiant heat and hot water from a 

ground source heat pump, advanced framing, a 

foam-insulated slab foundation, and Icynene spray 

wall and ceiling insulation, together with other 

green features like a greenhouse for passive solar 

heat, a rainwater cistern, construction recycling, 

fly-ash concrete, low VOC finishes, and bamboo 

and recycled tire flooring. 

Tindall Homes’ Legends at Mansfield in 

Columbus, New Jersey – New Jersey builder Mark 

Bergman pioneered the first all-solar development 

of market-rate homes in New Jersey, with 39 homes 

built to be at least 60% more efficient than code. 

The heavily insulated, tightly sealed homes use 

energy-efficient appliances and lighting to cut 

energy use. To ensure maximum solar gain for 

his 2.64-kW photovoltaic systems, he located the 

panels on detached garden sheds that could be 

located anywhere on the lots for ideal orientation 

to the sun.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 CHAPTER 9 / p.9

Looking Back, Looking Ahead Chapter 9

Resources and References

Butti, Ken and John Perlin. 1980. Golden Thread: Twentyfive Hundred Years of Solar 

Architecture and Technology. Cheshire Books. Palo Alto, CA. Excerpt posted on 

www.californiasolarcenter.org/history_solarthermal.html. Accessed on 15 May 2006.

DOE’s Energy Efficiency and Renewable Energy’s Solar Decathlon 

www.eere.energy.gov/solar_decathlon/

Green, Constance McLaughlin and Milton Lomask. 1970. Vanguard: A History. 

NASA SP-4202. National Aeronautics and Space Administration. Washington, D.C. available at 

www.hq.nasa.gov/office/pao/History/SP-4202/cover.htm. Accessed on 15 May 2006.

Lane, Tom. 2004. Solar Hot Water Systems: Lessons Learned 1977 to Today. Energy Conservation 

Services of North Florida, Inc. Gainesville, FL.

National Air and Space Administration 

www.nasa.gov

National Air and Space Museum 

www.nasm.si.edu/research/dsh/artifacts/SS-vanguard.htm

Perlin, John. 1999. From Space to Earth – the Story of Solar Electricity. Excerpts posted on 

www.californiasolarcenter.org/history_pv.html. Accessed on 15 May 2006.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: Bob Ward Companies 

– Maximum Efficiency Greenland

BelAir, MD 

Building America Best Practices Series

For the production home builder, the prospect of 

zero energy construction poses a lot of questions; 

the best way to find the answers may be simply 

to try it. That’s what Bob Ward Companies of 

Baltimore, Maryland, decided to do when a U.S. 

Department of Energy Building America team 

approached them about building a super-efficient 

solar-powered home.

The resulting demonstration home, completed in 

June 2006, sports 22 photovoltaic panels and two 

thermal panels on the roof, enough to produce 4000 

kWh of electricity each year and most of a family 

of four’s domestic hot water. Inside, the home is 

packed with a host of additional high-performance 

and energy-saving features.

The home is a joint project between Bob Ward 

Companies, a Building America team led by the 

National Association of Home Builders Research 

Center (NAHB), and the Maryland Energy Administration. Although this was Bob Ward Companies’ 

first experience with solar, the company already 

had an excellent reputation for energy-efficient 

construction. Bob Ward Companies was one of the 

first ENERGY STAR® builders in Maryland and has 

committed to building all of its homes - about 200 

per year—to ENERGY STAR criteria. 

The house won a 2007 Silver 

Energy Value Award for moderate 

climate custom homes.

“We chose Bob Ward because we 

wanted a local builder who was 

interested in energy efficiency 

and who had enough capacity to effect some 

change. Bob Ward Companies was very interested 

in doing this as a learning experience to find out 

about solar and other new products they could offer 

buyers and as an opportunity for their trades to get 

experience,” said Joe Wiehagen, a senior research 

engineer at NAHB Research Center.

“We did the Maximum Efficiency Greenland to 

see what technologies would be effective in terms 

of how much energy they would save and how 

much they would cost. We were looking at how 

cost effective solar and advanced energy efficiency 

could be for the average guy. You can put as much 

solar as you want on a $2 million house. But we 

are building for the average consumer buying 

a $400,000 or $500,000 house, so we wanted to 

see what enhancements we could put into that 

house without breaking the buyer’s bank,” said 

Joe Gregory, a production manager for Bob Ward 

Companies’ residential business.

“You can put as much solar as you 

want on a $2 million house. But we are 

building for the average consumer buying 

a $400,000 or $500,000 house, so we 

wanted to see what enhancements we 

could put into that house without 

breaking the buyer’s bank.” 

Joe Gregory, a production manager for Bob 

Ward Companies’ residential business

BUILDER PROFILE

Builder’s Name: Bob Ward Homes

Where: Baltimore, MD

Founded: 1983

Employees: 50

Homes Per Year: 200

Energy Efficiency Status: 

All ENERGY STAR homes since 

ENERGY STAR’s inception

Solar Status: First solar home

Development: 

Maximum Efficiency Greenland - 

Bel Air, MD

Size: 1 home

Price: $500,000

A Zero Energy Showcase

Photo courtesy of the U.S. Department of Energy.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Bob Ward Companies – Maximum Efficiency Greenland

The NAHB Research Center conducted energy-efficiency testing during construction and is conducting 

performance monitoring of the energy use, solar PV, 

and hot water production, as well as the heating, 

cooling, and ventilation systems for a full year before 

the home is sold and occupied. NAHB Research 

Center also helped with consumer education materials like posters and brochures explaining the solar 

systems and energy-efficiency measures. 

“We want to get as much educational value out of 

the house as we can this year, while the displays 

are set up and we are doing monitoring,” said 

Gregory. “We did two open houses. The first was 

at rough-in stage, the second was at the final 

construction stage in June. We hosted a tour for 

the local green building network in July 2006 and 

another tour in September for the technical high 

school and community college building and energy 

efficiency programs. We have several displays set up 

throughout the house to tell people what’s inside 

the walls and about the mechanical systems and 

the extra insulation. Several local builders have 

come by to look at the house during construction 

and since we’ve completed it.”

“The Maximum Efficiency Greenland model was a 

research house for us and for other builders in the 

area. We are hoping to get a few more to jump on 

board with the energy-efficiency improvements,” 

said Gregory. “You have to prove to builders and 

to home buyers that it can be done, and that 

it’s worthwhile. We will start offering solar as an 

optional upgrade after we get all of the data from 

NAHB Research Center. We want to come up with 

cost savings to show potential buyers.”

“We used one of our standard house designs, not 

a special design, in a development where we have 

four lots. We didn’t have to do anything special to 

the lot, we just made a minor adjustment in the 

home’s orientation on the lot to improve the roof’s 

solar gain,” said Gregory. “One thing we wanted 

to know is whether we can make solar work as an 

option here on the East Coast where a builder often 

has to submit plans two or three years before they 

build; at that stage you won’t know which home 

buyers are going to ask for solar,” he concluded. 

Solar System

The 3-kW roof-mounted PV system consists of 22 

63-inch by 31-inch Integra modules manufactured 

by BP Solar. “The DC output of the system is rated 

at 3850 watts and it may hit 3 kilowatts of AC in 

full sun,” said Wiehagen. “The panels rise no more 

than two inches above the roof’s surface, a very 

low profile for a system not integrated into the 

roofing material,” Wiehagen noted. The panels 

also use a unique bracket that can be bolted to 

the roof’s sheathing instead of into the trusses. 

Each bracket can accommodate two panels if the 

panels are butted against each other. “It was a pretty 

quick installation,” said Wiehagen. “The installers 

installed one panel every 15 minutes.” 

The NAHB Research Center helped the builder 

locate an installer. They chose Aurora Energy LLC, 

a solar contractor that has worked throughout the 

Mid-Atlantic states since 1994 installing PV systems 

for homes, businesses, and government clients 

including the White House and the Pentagon. 

The house also features two roof-top 29-sq-ft StiebelEltron thermal collectors. Copper tubing transports 

the heated fluid from the roof to an 80-gallon 

storage tank in the home’s basement. The closed 

loop system contains antifreeze so the system will 

operate in all seasons. The solar thermal system 

preheats the water, greatly reducing demand on the 

home’s Seisco electric instant-on water heater.

“We used our regular electricians and plumbers 

to work with Aurora Energy,” said Gregory. “The 

PV installers are not permitted to go into the panel 

box. The electrician has to do the cabling from 

the inverter to the panel box. Our electrician ran 

the cables into the attic so Aurora could make the 

connection,” Gregory added. 

Energy Efficiency Measures

Solar power was just one of the building innovations 

that Bob Ward was interested in trying out. For 

the home’s full basement with nine-foot ceilings, 

they tested insulated concrete wall panels made by 

Superior Walls. The wall and foundation system 

consists of a 2-inch layer of high-density concrete 

Key Features

3kW roof-mounted photovoltaic system 

Two solar hot water panels installed 

on roof, to preheat 80-gallon 

hot water tank

Superior Wall Foundation - prefabricated 

basement wall panels of 2-inch layer of 

high-density concrete, steel-reinforced 

concrete studs, and 2-inch layer of solid 

foam insulation in between for R-12 

wall. R-19 fiberglass bat can be added 

between studs.

2x4 16-inch on center upper walls with 

optimum value engineering framing 

techniques: 3-stud corners, ladder 

nailers where interior partitions intersect 

exterior walls, insulated headers 

Thermal ply sheathing with a 

1-inch layer of rigid foam insulation 

taped at joints 

R22 blown fiberglass in walls

R50 blown fiberglass in ceiling

Ducts in conditioned space

Cross-over vents for all bedrooms

Passive fresh air intake to return air 

filter; auto-on cycling whole house 

and bathroom exhaust fans 

Air source heat pump, 9.3 HSPF, 

19 SEER air conditioner

High-performance low-e 

argon-filled windows

ENERGY STAR lighting in 90% of 

fixtures; ENERGY STAR appliances

Significant air sealing package: 

foam-sealed band joists, top and

bottom plates, windows, and wiring

and plumbing penetrations

Blower door and duct blaster tests 

conducted by NAHB
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Bob Ward Companies – Maximum Efficiency Greenland CASE STUDY

with steel rebar tied to concrete studs with a 2.5-

inch layer of foam in between, for a foundation 

wall R value of 12.5. There is room to add an 

additional R-19 of insulation between the studs. 

The system doesn’t require concrete footers and 

installs on a gravel base. The basement comes 

sheet-rock ready to finish, with 2x6, 24-inch on 

center steel-reinforced concrete studs in place 

that are pre-drilled with access holes for wiring 

and plumbing. 

The NAHB Research Center suggested the exterior 

wall sheathing detail. Instead of solid wood sheathing on the upper floors, the exterior walls consist of 

a one-eighth-inch thick layer of laminated fibrous 

board sheathing that is covered with a 1-inch-thick 

layer of extruded polystyrene foam board made by 

Dow. These layers go on the exterior side of the 

studs, under the stone or wood siding, to prevent 

thermal bridging. The taped foam board serves 

as an air barrier so house wrap is not needed. 

This layer also moves the dew point surface to 

the outside of the framing member reducing the 

potential for condensation and moisture damage 

within the wall cavity. 

The foam board is applied after carpenters put 

up the framing. “We ordered it in 9 ft lengths so 

that the joints didn’t line up anywhere there was 

a joint in the Energy Brace or the top of the walls. 

Every joint beneath was covered by a solid piece of 

foam. All of the foam-board seams were covered 

completely with tape at all joints,” said Gregory.

“This is the first time we had used it. We don’t 

know any other builders locally who are using 

it. The blower door test score for the Maximum 

Efficiency Greenland model was about 1285 cfm 

at 50 Pa, which is about 600 cfm lower than we 

are used to. (The blower door test score was 0.2 air 

changes per hour at natural pressure.) We plan to 

work the new sheathing in to all of our houses this 

year,” said Gregory who noted that ”when the cost 

of OSB went up so much because of the hurricanes, 

this (Energy Brace-foam insulation combination) 

came in at almost the same cost as OSB.“

The builder used Optimum Value Engineering 

framing details including three-stud corners, ladder 

nailers where interior partitions intersect exterior 

walls, non-load-bearing headers on non-load 

bearing walls, and insulated headers on load 

bearing walls. In addition to careful caulking 

and sealing of all wall penetrations, all band joists 

and top and bottom plates were foam sealed, as 

were windows, wiring, and plumbing. Bob Ward 

also used blown-in glass fiber insulation in the 

walls and ceiling, totaling R-15 in the 2x4 walls, 

R-23 in the 2x6 walls, and R-49 in the attic, which 

is six more inches of ceiling insulation than they 

typically install.

All of the ducts were located in conditioned space. 

Ducts to the second floor were run in interior 

partitions or through the first floor ceiling joist 

bays. All of the ducts were taped and a duct leakage 

test showed a score of 83 cfm. The super high-

(left) The two solar thermal panels provide heat 

for most of a family of four’s hot water needs 

and the 22 photovoltaic panels should produce 

4000 kWh of electricity each year.

(right) The 22 BP Integra photovoltaic panels 

snapped into place quickly using special 

brackets that fit to the panel’s I-beam-shaped 

edges. The brackets are screwed to the roof 

sheathing not the trusses and one bracket sits 

between each two panels. The panels were 

installed by an experienced PV contractor, 

Aurora Energy. Photo courtesy of Joseph 

Wiehagen of the NAHBRC.

“It was a pretty quick installation. 

The installers installed one panel 

every 15 minutes.” 

Joe Wiehagen, a senior research engineer 

at the National Association of Home Builders 

Research Center, a Building America partner.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Bob Ward Companies – Maximum Efficiency Greenland

efficiency HVAC equipment includes a 9.3 HSPF 

Trane air source heat pump and a 19 SEER air 

conditioner with a variable speed air handler and a 

two-speed compressor. The air handler is located in 

the basement and draws fresh air from the outside. 

The Maximum Efficiency Greenland model uses 

a manifold plumbing system with PEX flexible 

piping. The centrally located manifold reduces 

wait time for hot water to distant fixtures and 

minimizes the amount of hot water left standing 

in the piping. 

To further cut energy load, the home was outfitted 

with ENERGY STAR appliances, ceiling fans, highperformance windows, and an extensive efficient 

lighting package. 

“This home is 50% to 55% better than a codecompliant house in this area, based on current codes 

(Maryland complies with the 2003 IEC building 

energy code),” said Gregory. 

Health, Durability, Sustainability

With the external foam insulation, the house is 30% 

tighter than Bob Ward’s traditional ENERGY STAR 

homes, in fact it’s so tight they were worried about 

the indoor air quality. “That’s why we included the 

whole house ventilation system, to make sure we 

maintain good indoor air quality,” said Gregory. 

The multi-port exhaust fan provides bath and 

kitchen exhaust and low-level whole house ventilation. “It cycles on for 20 minutes every hour, pulling 

fresh outside air in through a filtered intake to the 

furnace to provide make-up air for the system,” said 

Gregory. Transfer grills above the bedroom doors 

ensure an adequate return air pathway.

Dollars and Sense

The state of Maryland requires utilities to net 

meter PV systems so that homeowners can sell 

surplus power back to the grid. The power is sold 

at the going rate with no extra incentive for selling 

at peak. 

Wiehagen said that the system cost was about $8 

per watt, reflecting a discount from BP; Wiehagen 

noted that a more typical price would be $10 per 

watt; the general cost for installing a 3-kW AC 

system would be about $31,000-39,000 including the panels, the inverters and wiring, and the 

installation costs. 

Along with the $2,000 Federal tax credit, the state of 

Maryland is offering a grant program that includes 

up to $2,000 for solar water heating and a $3,000 

rebate to the home owner for PV (or 20% of the 

cost, whichever is less). 

Electricity rate increases of 38% to 72% announced 

in spring 2006 provide a market-driven incentive 

to seek alternatives. 

Bottom Line

“This was Bob Ward’s first near zero energy house. 

We found out we can do it. We just hooked up the 

solar in June. We all stood there and watched the 

electric meter spin backward,” said Gregory.

“We’ve got a much better idea of how to build 

a more efficient house. Several of these energy 

efficiency improvements we’ll carry over to our 

production houses. We intend to make the whole 

house ventilation and external foam insulation a 

part of our standard homes. The solar package is 

something we will offer as an optional upgrade.

We will offer both photovoltaic and solar thermal 

water heating,” Gregory said.

(top) The photovoltaic array is mounted on 

the back side of the house. The solar thermal 

collectors are to the left.

(bottom) During construction, sales staff 

toured the home to learn about its solar and 

high-performance energy-efficiency features. 

Here they get a lesson in insulated concrete and 

steel wall foundation panels. Photo courtesy of 

Joseph Wiehagen of the NAHBRC.

“This was Bob Ward’s first near zero 

energy house. We found out we can do 

it. We just hooked up the solar in June. 

We all stood there and watched the 

electric meter spin backward. My advice 

for builders considering solar is to find a 

good installation contractor and go for it.” 

Joe Gregory, a production manager for the 

residential side for Bob Ward Companies 

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

Centex Avignon

Pleasanton, CA 

Building America Best Practices Series

Centex, one of the nation’s largest home builders, is 

constructing the first, zero-energy community to be built 

in Alameda County. The development called Avignon, 

is located in Pleasanton, California. Model homes 

opened in June 2006. All 30 homes in the development 

feature energy-efficient construction topped by a 3.5-kW 

photovoltaic system on every roof.

Centex worked with ConSol, leader of the BIRA 

Building America consortia, on the energy-efficient 

design and the PV systems. The PV panels are 

integrated as part of the roof and are similar in 

depth to the cement roof tiles they replace. The 

panels are a product called SunTile,® provided 

and installed by PV manufacturer PowerLight 

(now called SunPower). 

“By first constructing the most energy-efficient 

homes and then adding state-of-the-art renewable 

resources, each home in Avignon will be constructed 

to be 25% more energy efficient than required by the 

strict California energy codes; have a 70% energy 

savings on the annual electric bill; and draw no 

more than 1kW from the utility during summer 

peak time (the hottest time of the day),” said 

Jeff Jacobs, Director of Community Development, 

Centex Homes, Bay Area Division.

Solar Systems

“We commend Centex’s vision in providing solar 

electric systems as a standard feature on all of 

their new homes at the Avignon community in 

Pleasanton. Solar seamlessly powers homes and 

dramatically reduces a homeowner’s electric bills, 

while producing completely emissions-free energy. 

High quality, newly built homes provide the absolute 

best time to install solar,” said Howard Wenger, 

Executive Vice President of SunPower, which is 

based in Berkeley, CA.

SunPower installs the integrated roofing system and 

predicts the 3.5-kW DC photovoltaic power should 

provide most of the home’s annual electricity needs. 

The homes are hooked up to the local utility grid 

so homeowners can draw electricity when they 

need it. Any excess electricity produced by the 

system is sold back to the utility for homeowner 

credit. A unique feature of the SunPower system 

is an ongoing monitoring service that SunPower 

provides, enabling the company to track each 

home’s power output to ensure everything is in 

working order. Homeowners can track the progress 

themselves through a website that posts each home’s 

power production data.

BUILDER PROFILE

Builder’s Name: 

Centex, Northern California Division

Where: 

San Francisco Bay Area, California

Founded: 1950, Dallas, Texas

Development: 

Avignon, Pleasanton, California

Size: 30 units

Square Footage: 3,671-4,035 square 

feet (4 to 5 bedrooms, 3 to 4 baths)

Price Range: 

Around $1,000,000

The 1st Zero-Energy New Homes Community in Alameda County
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Centex Avignon

Energy Efficient Features

The homes at Avignon meet the rigid energyefficiency guidelines of ConSol’s ComfortWise®

program with properly designed heating and air 

conditioning systems, Andersen 400 Series HP 

low-emissivity spectrally selective glass windows, 

and tightly sealed air ducts. The homes are independently inspected for quality and performance 

of the insulation, caulking and sealing, windows, 

and heating and cooling ductwork. Inspections and 

tests are performed by ComfortWise home energy 

raters who are certified and monitored by either 

CalCerts or the California Home Energy Efficiency 

Rating System (CHEERS), both certified by the 

California Energy Commission.

Additional energy-saving features at Avignon 

include R-49 attic insulation, with R-30 above 

the garage and within cantilevers, and R-15 wall 

insulation. Mechanical systems include two 14 

SEER ACs with TXV (a 3-ton unit and a 3.5-ton 

unit) and a .92 AFUE furnace. Two on-demand 

tank-less water heaters with .82 energy factor 

should produce up to 8.5 gallons of hot water per 

minute, while saving up to 30% in energy costs 

per year over a standard water heater. 

This is not the first time Centex has worked with 

ConSol. The Building America partner worked 

with Centex on several past projects including 

Windemere development in San Ramon where 

Centex is building 800 homes to the ComfortWise 

energy efficiency standards. According to ConSol, 

other Centex ComfortWise developments include 

communities in Paso Robles, Atascadero, San Luis 

Obsipo, Hanford, Claremont, Lake Elsinore, Corona, 

Murieta, and Fontana. 

Centex has also worked with the Davis Energy 

Group, another Building America partner, to build 

three high-performance demonstration homes in 

Livermore and San Ramon. The experience taught 

the builder how to integrate solar thermal, PV, and 

energy efficiency into production buildings. 

Rob Hammon, a principal at ConSol, pointed out 

that energy efficiency is a key element in designing a 

near-ZEH. “The house’s overall energy use first must 

be dramatically reduced through a combination of 

super-efficient features and advanced construction 

practices. The use of these energy-saving building 

methods ensures that the addition of a relatively 

small photovoltaic (PV) solar system (typically 

2.4 kilowatts in capacity) can effectively lower 

the electricity usage of a house by half or more 

compared to a typical new home,” Hammon said 

in a Solar Today article (May/June 2005).

Hammon noted that a typical house has 20% to 

30% duct leakage. In a near-ZEH, ductwork is sealed 

and super-insulated or placed in the conditioned 

space. Spectrally selective glazed windows reflect 

the sun’s heat in summer and reduce heat loss in 

Key Features

3.5-kW DC photovoltaic integrated 

roofing system from SunPowerTM

ComfortWise® package by ConSol

Properly designed heating 

and air conditioning systems

Andersen 400 Series HP Low-e 

spectrally selective glass windows

Tightly sealed air ducts

Independent inspection of insulation, 

caulking and sealing, windows, and 

heating and cooling ductwork

R-49 attic insulation with R-30 

above garage/cantilever

R-15 wall insulation

Two on demand tankless water 

heaters with .82 energy factor 

3 Ton and 3.5 Ton 14 SEER AC with TXV

.92 AFUE furnace

(left) J.D. Power rated Centex as the top builder 

in customer satisfaction in the San Franciso 

Bay area.

(right) All Avignon homes will incorpoprate 

3.5 KW PV systems.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Centex Avignon CASE STUDY

winter. Carefully designed HVAC systems account 

for bends and turns in ductwork, register locations, 

duct length, connections and airflow. Other ways 

to “tighten up” residential energy consumption 

include improved ceiling and wall insulation, 

energy-efficient appliances and the use of fluorescent lighting. “All of these efforts are combined in 

a whole-house approach to designing and building 

the ZEH,” said Hammon.

Dollars and Sense

Incentives are available to builders and to home 

owners. In January 2006, the California Public Utilities Commission (CPUC) adopted a program–the 

California Solar Initiative (CSI)–to provide more 

than $3 billion in incentives for solar projects with 

the objective of providing 3,000 MW of solar capacity 

by 2017 from residential and commercial projects 

combined. Homeowners will receive $2.50/Watt

AC for residential systems, with the incentives 

awarded as a one-time, up-front payment based 

on expected system performance. Several counties 

offer incentives to builders including free technical advice and waiving of fees on solar projects; 

some counties offer rebates to homeowners on 

solar equipment.

There is also the federal $2,000 tax credit for 

homeowners who purchase solar electric and 

solar water heating systems as well as a $500 tax 

credit for those who purchase energy-efficient 

equipment like furnaces, air conditioners and 

water heaters. Also, many utilities in California 

offer a rebate for energy-efficient construction, 

usually $500 per house.

“We are typically spending $1,000 to $1500 per 

house to get to 20% above code. But we can market 

these homes at a premium,” said Jacobs. Centex 

predicts homeowner energy bills at Avignon will 

be reduced by up to 70% each year.

“I don’t expect any builder to lose money,” said 

Jacobs. “You may have a desire to be a good 

steward of the environment but you also have to 

be responsive to your stockholders. There are strong 

environmental and societal reasons for building 

energy-efficient homes. But strong, sustainable 

building practices also help a builder differentiate 

themselves in a competitive marketplace, while 

still keeping focused on the bottom line. The 

American public has proven over and over that 

they are willing to pay more for it (energy-efficient 

construction).”

“We need to educate the buyer. If you are building 

houses and you start including photovoltaics, and 

tankless water heaters, and high-performance 

construction, your buyers are going to enjoy living 

in those homes because of lower operating costs, 

increased comfort, etc. We just need to educate 

homeowners to see what they are getting. The 

message they need to hear is ‘You pay more but 

you get more,’” said Jacobs.

About Centex Homes

Dallas-based Centex Homes (www.centexhomes.com) is one of the nation’s leading home 

builders, operating in more than 90 U.S. markets in 25 states and delivering 33,387 homes in 

the United States in 2005. The company is a subsidiary of Centex Corporation (NYSE: CTX), 

a Fortune 250 company. Centex Corporation (www.centex.com), founded in Dallas in 1950, 

is one of the nation’s premier companies in home building, financial services, home services 

and commercial contracting. Centex ranks No. 1 in its industry on FORTUNE magazine’s 2005 

list of “America’s Most Admired Companies.” Centex has been ranked “highest in customer 

satisfaction with new home builders in the San Francisco Bay Area” by JD Power 

and Associates in both 2005 and 2006.

About SunPower

SunPower Corporation (formerly known 

as PowerLight) is a leading global provider 

of grid-connected solar electric power 

systems. SunPower’s turnkey solutions for 

commercial, government and residential 

customers feature a full line of proprietary 

solar products and technologies designed 

to optimize energy output and project 

economics. Recognized by Inc. Magazine

for five consecutive years as one of 

the 500 fastest growing privately held 

companies, SunPower designs, builds and 

operates many of the largest solar electric 

systems in North America and Europe. For 

more information about SunPower and its 

products and services, please visit 

www.sunpower.com.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Centex Avignon

The Bottom Line

“I think it’s our social responsibility to do it and 

it’s not that hard to do. It’s not 20 or 30 things you 

have to do, it’s a handful of changes you need to 

make,” said Jacobs. “With the energy codes out 

there (in California) everyone is already building 

a good house; with a few more things you can 

build a great house.” 

With construction quality like Centex is providing 

at Avignon, Jacobs feels he can assure buyers, “You 

are going to love it the day you move in because 

it’s a great house. You are going to love it a year 

from now because we thought about comfort 

and operating cost.” Jacobs suggests to builders, 

“You want buyers to be happy about it 5 or 6 

years from now. You want buyers who will say ‘I 

talked to my friends who bought a house from a 

different builder and they don’t have everything 

I do with this house.’” For Jacobs, word of mouth 

recommendations like that make zero energy 

construction completely worth the effort.

(left top) Centex built one of the nation’s first ZEH in 

Livermore, California, in 2002. The homeowners had 

not had to pay an electrical bill through 2004

(left bottom) Centex included solar water heaters and 

PV modules in the demonstration houses.

(right) This garage display shows how a solar-thermal 

system, storage tank, and instantaneous water heater 

are combined into a water heating package.

All photos above courtesy of NREL.

Centex Demonstrates Zero Energy Homes for Building America Research

Centex has conducted some cutting edge research on zero energy homes working with 

the Davis Energy Group, a Building America partner. With their help, Centex completed 

a 3,080 sq ft home in Livermore, California, in 2002. As of 2005, homeowners had yet to 

pay an electric bill and had 45% lower natural gas bills for space and water heating than 

comparable homes in the area. The Livermore home featured both PV and solar thermal 

systems. Two Centex model homes in San Ramon, completed in 2004, reduced energy by 

70%, cutting the homeowners’ annual energy bills by $1900 each. Assuming that the total 

cost of the zero energy package is included in the mortgage and amortized at 6% for 30 

years, the incremental annual cost is $1,440, or $480 less than what the annual utility bills 

would have been, resulting in a positive cash flow for the home owners. All three homes 

featured the NightBreeze ventilation system for evening cooling, a variable-speed air handler 

for space heating, radiant barrier roof sheathing, extensive insulation and air sealing, a 

2.4 or 3.6-kW PV array, and a solar hot water heater. For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems -JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

Clarum Homes – Vista Montaña

Watsonville, CA 

Building America Best Practices Series

In 2003 Bay area production builder Clarum Homes 

partnered with Building America to build the 

nation’s largest zero-energy home community, 

Vista Montaña, in Watsonville, California, near 

Santa Cruz. The development of 177 single-family 

homes, 80 townhouses, and 132 apartments opened 

in August 2003 and sold out in its first year. Clarum 

initially advertised prices of $379,000 to $499,000 

but some units sold for as much as $600,000. Every 

home sports a 1.2 to 2.4 kW photovoltaic system on 

the roof and a slew of energy-efficiency measures 

throughout in a package of zero energy features 

that Clarum offered standard at Vista Montaña.

Clarum is a leader at zero energy home construction. The builder installed its first solar system 

in 1999 and opened its first zero energy home 

in 2000. In August 2001 Clarum announced the 

opening of its first zero energy home development, 

Cherry Blossom, in Watsonville. Each one of the 

31 single-family homes came with a 3.2-kwh PV 

system and energy efficient features as standard 

equipment. Clarum also made zero energy construction standard on its Shorebreeze IV community of 

20 single-family homes, which opened June 2003 

in East Palo Alto.

“I was first introduced to the solar and green building methods at a national homebuilder conference 

in Atlanta in 1999,” said John Suppes, founder and 

president of Clarum Homes. “I came back and 

immediately started incorporating the ideas into our 

communities so that we could offer more efficient 

homes and give our homebuyers the opportunity 

to actually produce electricity in the midst of this 

energy crisis we were facing. I feel very strongly 

about the need to promote sustainable energy 

sources.” He made a commitment in 2001 that 

all of the homes built by Clarum Homes would be 

designed and built using photovoltaic systems and 

as many “green” building features as they could 

afford to include. 

Clarum partnered with ConSol, leader of the Building Industry Research Alliance (BIRA) Building 

America team, on both Shore Breeze IV and Vista 

Montaña and the developments included Clarum’s 

Enviro-Home green building and energy-efficiency 

features designed to save homeowners 60% to 90% on 

their whole house energy usage. Clarum is working 

with BIRA and the Davis Energy Group, another 

Building American partner, on four highly efficient 

demonstration homes at Borrego Springs.

BUILDER PROFILE

Builder’s Name: 

Clarum Homes www.clarum.com

Where: Palo Alto, California

Founded: 1994

Employees: 35-50

ZEH Commitment: 

Committed to all sustainable, energy 

efficient construction since 2001.

Development: 

Vista Montaña, California

Size: 177 single-family homes, 

80 townhouses, 132 apartments

Square footage: 3-5 bedrooms, 

10 different floor plans

Price Range: $379,000 to $600,000

Nation’s Largest Zero Energy Home Community 

a Winner in Watsonville

Clarum’s Vista Montaña in Watsonville, 

California, near Santa Cruz, is the largest 

zero-energy home community in the nation, 

with 177 single-family homes, 80 townhouses, 

and 132 apartments. The all-solar development 

opened in August 2003 and sold out in the 

first year. Photo courtesy of Consol.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Clarum Homes – Vista Montaña

“Clarum is the first builder to sign a memorandum of understanding saying they will commit to 

the California Zero Energy New Home criteria,” 

said Bruce Baccei, the BIRA project manager 

for ConSol.

“We have a commitment to high-performance 

houses and we have a commitment to the environment,” said Suppes. “Since 1999, we have been 

dedicated to building sustainable communities.”

Energy Efficient Features 

Clarum partnered with ConSol and others to develop 

its Enviro-Home package of energy efficiency and 

solar power features, designed to reduce homeowner 

energy bills by up to 90%. Each Enviro-HomeTM 

has been professionally designed, certified, and 

inspected to reduce energy consumption and use 

sustainable resources while improving comfort. The 

program has also earned the U.S. Environmental 

Protection Agency’s ENERGY STAR® seal, ConSol’s 

ComfortWiseSM designation, and the California 

Building Industry Institute’s California Green 

Builder certification. 

In addition to a solar electric home power system, 

each Enviro-HomeTM in the Vista Montaña community features a tankless on-demand water heater, 

and a high-efficiency furnace as standard features. 

The homes also feature a foam-wrapped building 

envelope, increased insulation, radiant roof barrier, 

advanced HVAC technology, tightly sealed ducts, 

and low-E energy-efficient windows. Ceiling fans, 

fluorescent light bulbs, water conserving plumbing 

fixtures, and water conserving landscaping are 

also incorporated, providing homeowners further 

utility savings.

The Enviro-HomeTM features that are included 

as standard equipment will provide more than 

$20,000 of added value to homebuyers at no cost, 

says Suppes. 

In addition to its energy-efficient features, the 

Enviro-HomeTM incorporates sustainable building 

materials, such as engineered lumber, recycled 

decking material, and fiberglass doors, and offers 

recycled content carpet, bamboo flooring, cork 

flooring, and environmentally friendly paint as 

optional items.

Key Features

1.2 to 2.4 kw photovoltaic system

Tankless water heater with 

0.82 energy factor

Foam wrapped walls

Radiant roof barrier

Low-E, U-factor 0.4, SHGC 0.4 windows

90% AFUE furnace with a 

programmable thermostat

Tightly sealed ducts

Low-flow showers

Ceiling fan outlets

ENERGY STAR appliances

Florescent lighting

Clarum markets its homes with the EnviroHome package, which combines high energy efficiency with sustainable building practices.

Schematic courtesy of Clarum Homes. 

Clarum is building four zero energy research 

homes at Borrego Springs, California. 

Photos courtesy of Clarum Homes. 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Clarum Homes – Vista Montaña CASE STUDY

Clarum is building four zero energy research 

homes at Borrego Springs, California. 

Polystyrene slab edge insulation helps to 

carefully control heat gains and losses.

Photos courtesy of Clarum Homes. 

Extreme Heat Meets Extreme Cool

Showing the ingenuity that can pay big dividends for a production home builder, Clarum is 

branching out into the Anzo Borrego desert with four test homes that could help Clarum offer 

homes that beat the heat and high energy costs at a cost to Clarum that will still ensure profits 

as the Bay area builder reaches into hotter, drier locales.

Clarum partnered with Building America partners ConSol and the Davis Energy Group to 

build four super-efficient demonstration homes in Borrego Springs where temperatures 

routinely soar past 100 degrees F 6 months of the year. 

“These demonstration homes in Borrego Springs provide an opportunity to try out new 

products that could be economically viable in the regular and affordable housing markets 

we serve,” explained Suppes.

The four homes use an identical floor plan sporting three bedrooms and three baths in 2,000 

sq ft of living space and Clarum installed identical 3.2-kW Kyocera photovoltaic solar systems 

on each home. The PV panels mount to the standing seams of the homes’ metal roofs so 

there are no roof penetrations. The homes also have several energy-efficiency features in 

common including tankless water heaters, rigid polystyrene insulation around the foundation, 

and ENERGY STAR appliances and fluorescent lighting. Heat gain from the sun is kept to 

a minimum through use of a radiant roof barrier, low-emissivity windows, five-foot shade 

overhangs over the homes’ perimeters, and shade screens on the windows and doors of all four 

homes. But there are some unique differences between the homes, including three different 

kinds of exterior wall systems, three different cooling systems, and two kinds of space heating. 

The demonstration project homes showcase two types of advanced wall systems – rigid foam 

insulated thermal mass concrete walls, in this case a Dow product called Styrofoam T-MASS, 

and structural insulated panels (SIPS), as well as 16-inch-on-center 2x6” lumber framing on 

one house for comparison.

The homes are equipped with three different cutting-edge cooling systems. Two of the homes 

feature Speakman OASys two-stage evaporative coolers; the third home features both a Freus 

water-cooled condenser (which cools indoor air as well as the floor) and a NightBreeze night 

ventilation cooling system; and the fourth home features a Lennox 20.5 SEER air conditioner. 

The cooling systems were designed to accommodate both the hot-dry conditions that prevail 

most of the summer and the hot-humid weather that accompanies the monsoon season in late 

summer. Three of the homes are also equipped with under-floor radiant heating.

Building America partner Davis Energy Group designed the heating and cooling systems for 

the homes, which were completed in May 2006. Davis is working with ConSol to monitor 

energy use through summer 2007 to collect two cooling season’s worth of data, one without 

occupants and one with. They hope to collect data on cost, construction schedule, production 

feasibility, energy efficiency, product lifecycles, embodied energy, and cost and energy savings. 

Clarum hopes at least one of the homes will show a 90% reduction in cooling energy.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Clarum Homes – Vista Montaña

Solar Systems

AstroPower supplied the photovoltaic panels on 

the solar electric power system for Vista Montaña. 

The systems range in size from 1.2 to 2.4 kilowatts 

and enable homeowners to generate their own 

electricity, reduce their utility bills, and protect 

the environment. Additional panels were offered 

as upgrades if homeowners wanted to generate 

even more electricity.

Suppes advised builders contemplating adding 

solar to just try it. “Put them on. Have the PV 

manufacturer come out and train your subs to put 

the panels on correctly, and use your existing subs; 

you’ll save a lot of money that way.”

Dollars and Sense

Clarum works with Building America to use their 

cost and energy savings analysis to point to the 

most cost-effective combination of features for 

the climates it builds in. Once a cost-effective 

combination is chosen, economies of scale can be 

achieved through volume purchasing and training 

of subcontractors.

The Bottom Line

“Solar electric power adds value to the homes we 

build,” said Suppes. “By giving homeowners the 

tools they need to generate their own electricity, 

we’re enabling them to save money on their utility 

bills. We’re also differentiating our homes in the 

marketplace. We set out to provide exceptional 

value for our customers by adding solar power, 

and in the process we did something exceptional 

for our business.” 

For more information visit: 

www.buildingamerica.gov

Clarum is building four zero energy research 

homes at Borrego Springs, California. 

Photos courtesy of Clarum Homes. 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: 

CARB Cold Climate Homes

Hadley, MA and Madison, WI 

Building America Best Practices Series

Two houses built with assistance from CARB, the 

Consortium for Advanced Residential Buildings, 

demonstrate the potential of solar water heating and 

photovoltaic electric generation in the US cold and 

very cold climates. CARB is one of six U.S. Department 

of Energy Building America research teams.

One home built in Hadley, Massachusetts, in 

partnership with Western Massachusetts Electric 

Company (WMECO), uses photovoltaic panels and 

a solar domestic hot water system in combination 

with energy-efficient construction. Another house, 

built by Veridian Homes in Madison, Wisconsin, in 

partnership with the Wisconsin Focus on Energy 

program, uses two roof-top solar hot water collectors 

to help heat household water. 

Energy-Efficient Features

WMECO Home – Hadley, Mass

The Hadley, Massachusetts, home was completed in 

Spring 2004 and has had two full years of energy 

use monitoring. CARB’s analysis found that the 

home would consume 33% less energy than the 

benchmark Building America home, or 41% less 

if the solar electric energy were included. First year 

electrical savings were over 66%, most likely due to the 

lack of air conditioning, the inclusion of fluorescent 

lighting, and the energy consciousness of the home 

owners. The Hadley home still achieved a HERS 

rating of 90.4, based on the rating system in place 

prior to July 2006.

Veridian Welcome Home – 

Madison, Wisconsin

The Madison, Wisconsin, prototype home, constructed 

by Veridian Homes, was also completed in 2004. The 

home is 40% more energy efficient than a home 

built to Wisconsin’s Uniform Dwelling Code and 43% 

more efficient than the Building America benchmark. 

The prototype home included a monitor that shows 

homeowners’ current and past electrical use at the 

house, as well as peak and off-peak usage, so they can 

make adjustments to keep utility bills lower.

Veridian, Wisconsin’s largest home builder with 600 

homes a year, has committed to constructing all of 

its homes to Wisconsin ENERGY STAR® Homes and 

Green Built criteria. Veridian Homes was named the 

2004 ENERGY STAR Partner of the Year by the US 

Environmental Protection Agency. The company 

HADLEY HOUSE PROFILE

Builder’s Name: Mark Hopf

Where: Hadley, MA

Built: Spring 2004

Development: 1 demonstration home 

with solar photovoltaic electric generation 

and solar thermal water heating

Square footage: 4,000 square feet 

(4 bedrooms, 3.5 baths, including an 

in-law apartment)

Key Features:

• 2x6 stick frame construction with 

dense packed cellulose insulation

• Loose fill cellulose R-41 attic, 

R-30 in vault

• Double pane, low-e windows 

• Oil boiler with an AFUE of 86%, 

no air conditioning

• Fluorescent or compact 

fluorescent lights

• Energy Star or equivalent appliances

• 2.6-kW photovoltaic system

• Solar thermal water heating

• Hydronic heating

• No air conditioning

Two Houses Demonstrate Solar Potential in the Cold Climate 

CARB conducted energy analysis on this 

home in western Massachusetts, which uses 

both solar water heating and photovoltaic power 

to cut energy use by 41% off the Building 

America benchmark.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY CARB Cold Climate Homes

was awarded the 2007 Energy Value Builder of the 

Year Award and the Gold Award for cold climate 

custom homes from the National Association of 

Home Builders Research Center. 

Besides the environmental benefits 

of building energy-efficient homes, 

Veridian president David Simon said 

it’s good for business. He said the 

company’s commitment to energy 

efficiency attracts customers and 

also saves money by using fewer 

materials. “The key to a lot of this 

is proper implementation,” he said. 

“We wanted to make it easier for 

our customers to give back to the 

environment.”

Solar Systems

The Massachusetts home has a 2.6-kW photovoltaic 

system on the roof. The PV system provided an 

annual average of 7.3 kWh/day out of the house’s 

average consumption of 9.7 kWh/day, for a solar 

fraction of 76% of the home’s electricity demand 

On average, during summer peak energy demand 

periods – 6:00am to 10:00pm weekdays in June, 

July, August, and September – the home did not 

consume any utility power and was a net generator 

of 1.4 kW, compared to a typical home that would 

consume an average of 5.1 peak kW. This pattern 

can be very beneficial to utilities by helping them 

to avoid purchasing the most expensive sources of 

peaking power. The following figures shows how 

the Massachusetts PV system performed. 

The Wisconsin prototype home was built by 

Veridian Homes, Wisconsin’s largest home 

builder and winner of a 2005 National Green 

Building Award from the National Association 

of Home Builders, and the 2007 Builder of the 

Year Energy Value Award and a Gold Energy 

Value Award from the NAHB Research Center.

Electric Power Profile - Three Days in August

8/1/04 0:00 8/1/04 12:00 8/2/04 0:00 8/2/04 12:00 8/3/04 0:00 8/3/04 12:00 8/4/04 0:00

Date & Time

Net Power from Utility (W)

AC PV Power (W)

House Load (W)

-2,000

-1,000

0

1,000

2,000

3,000

4,000

0

Jan ‘05

Feb ‘05

Mar ‘05

Apr ‘05

May ‘05

Jun ‘05

Jul ‘05

Aug ‘05

Sep ‘05

Oct ‘05

Nov ‘05

Dec ‘05

2

4

6

8

10

12

14

16

Average Daily Electricity

Average Daily Energy (kWh)

Month

Consumption

Generation

MADISON HOUSE PROFILE

Builder’s Name: Veridian Homes

Where: Madison, WI

Development: The Welcome Home in 

Grandview Commons, a single prototype 

home with solar thermal water heating

Square footage: 2,324

4 bedrooms, 2.5 baths

Key Features:

• Advanced framing for 34% lumber 

savings and enhanced insulation

• Low-e argon filled windows

• Compact and sealed duct system 

• Properly sized HVAC equipment

• Direct or power-vented mech. equipment

• Exterior foundation insulation that 

extends to the sill plate

• Spray foam insulation in the rim 

and band joists

• Blown-in fiberglass insulation: R-23 

in walls and R-50 in ceiling

• “Smart” vapor retarder

• Ventilation system capable of 

complying with ASHRAE Standard 62.2

• Return air pathway ventilation 

transfer grilles 

• Compact fluorescent lighting and 

ENERGY STAR rated appliances

• Solar thermal water heating

• Instant. gas water heater as back-up 

• Elec. commutated furnace motor

• 2-ton 13 SEER air conditioning

• Electric load monitoring system

Figure 2. Electricity generation and 

consumption on an average day in 

each month of the year.

Figure 1. Hourly power generation and consumption at the Hadley, Massachusetts, house over three 

days in August 2004. One of these days, August 2, 2004, was the hottest day of the year.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

CARB Cold Climate Homes CASE STUDY

Both homes used solar thermal water heating 

systems. The systems were similar in that both 

feature two flat-plate collectors on the roof that 

circulate 50% propylene glycol antifreeze solutions 

to heat exchangers in the basement, where heat is 

transferred to 80-gallon hot water storage tanks. 

The systems differ in the controls used for the 

flow of water from the roof-top heater to the hot 

water tank. 

The Massachusetts home uses a dedicated photovoltaic module to power a direct-current pump to move 

the antifreeze solution. The Massachusetts system 

works whenever the sun is shining brightly regardless 

of the fluid temperatures in the collectors and in the 

storage tank. In addition to the solar storage tank, 

the Massachusetts home has an auxiliary oil-fired 

boiler with an indirect water heater tank. 

The Wisconsin system relied on a control system 

that uses two AC electric-powered pumps regulated 

by a differential controller. AC electric power is the 

typical type of power that comes from utilities. The 

controller senses temperatures at the tank and 

at the solar panels. If the panels are hotter than 

the tank, the AC-powered pumps are activated. 

Additional hot water is provided by an on-demand 

(tankless) gas water heater. Monitoring showed that 

the circulating pumps on this system used electric 

power equivalent to 24% of the fuel cost savings 

offered by the home’s solar thermal system.

The Massachusetts solar water heating system 

provided 61% of the domestic hot water for the 

home’s family of four. The Wisconsin system 

provided 63% of hot water needs for its family 

of four. CARB’s monitoring uncovered important 

lessons for both systems.

At the Hadley, Massachusetts, home, a timercontrolled recirculating pump intended to provide 

more immediate hot water to the bathrooms caused 

significant cooling of the water in the auxiliary 

tank, prompting the oil boiler to turn on repeatedly, 

even when the solar tank was hot.

At the Wisconsin home, a poorly configured 

tempering valve caused significant losses of solar 

hot water. Tempering valves are found on most 

solar hot water systems to prevent scalding water 

from flowing out of faucets. The tempering valve 

is usually located after the auxiliary water heater 

as the hot water enters the distribution plumbing. 

However, on this system, the valve was located 

between the solar tank and the auxiliary heater. 

And the valve was set at 100°F rather than 125°F 

as recommended by CARB. This combination led to 

a tremendous amount of lost solar energy because 

the valve was cooling down the solar-heated water 

every time hot water was used. Solar performance 

increased when the valve was reset to 125°F and 

the solar water tank was insulated.

Figure 3. The Massachusetts home’s solar water heating system uses a dedicated photovoltaic 

module to power a direct-current pump to move the antifreeze solution through the solar collectors 

to the basement storage tank. The system provided 61% of annual hot water.

Figure 4. The Wisconsin home’s solar water heater provided 63% of 

the home’s annual hot water after adjustments were made to the tempering 

valve and the storage tank was insulated.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY CARB Cold Climate Homes

Dollars and Sense

The following table shows energy savings, 

incremental costs of measures, and the effects 

of the measures on monthly loan payments and 

energy bills. 

Hadley, MA Madison, WI

Added Costs Dollars # Dollars +

Solar PV $26,445 $0

Solar Thermal $7,808 $6,493

Energy Efficiency $5,848 $7,025

Total $40,101 $13,518

Incentives $11,370 $3,205

Net Costs $28,731 $10,313

Increased Monthly 

Mortgage*

$191 $68

Savings

Solar PV $430 $0

Solar Thermal $172 $86

Energy Efficiency $1,985 $777

Annual Total $2,587 $863 

Monthly Savings $216 $72 

Affect on Cash Flow

Net Monthly 

Increased Cash Flow 

+$25 +$4

# 2006 analysis and energy costs

+ Based on builder’s costs and 2004 analysis and energy costs

* 7% loan amortized over 30 years

Both houses show a positive affect on cash flow. 

When mortgage payments and energy bills are 

considered together, the Massachusetts home comes 

out $25 ahead every month and the Wisconsin 

home comes out $4 ahead. Since the time of these 

analyses, utility rates have continued to rise and 

the consumer benefits have increased. 

The Bottom Line

The systems evaluated in these prototype homes work 

well, providing over 60% of the water heating load in 

each home. Solar water heating will become more 

cost-effective when initial costs come down. As CARB 

noted, “commissioning of solar thermal systems is key 

for good operation, and without [CARB’s] monitoring, 

the homes would be consuming considerably more 

fossil fuel for water heating.”

The PV system on the Massachusetts house was very 

effective at cutting peak demand for electricity in 

the summer.

Two key points can be drawn from the CARB analysis. First, energy efficiency is more cost effective to 

homeowners than solar and should be the first choice 

in investing. When evaluating the solar and energyefficiency features as a package, it is the energy 

savings from the efficiency measures that dominates 

the benefits. 

Second, although the solar systems did not pay for 

themselves outright, when considered as a package 

with energy efficiency, and when cash out of pocket 

expenses are taken into account, homeowners can 

come out ahead with these homes. 

“It can be done inexpensively,” said David Simon, 

president of Veridian Homes, which built the 

Wisconsin prototype home in 2004. “Eventually 

others will follow because it’s the right thing 

to do.”

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: Georgia Dept. of 

Natural Resources – SIPS Cottage

Okefenokee, GA 

Building America Best Practices Series

It takes solid building science principles to design 

a building that can stand up to the heat and 

humidity of Georgia’s Okefenokee Swamp. The 

U.S. Department of Energy’s Building America 

program has helped design a SIPS-insulated 

cottage that can handle the weather and provide 

near-zero energy bills too, thanks to a roofmounted solar electricity system. The Ultra Low 

Energy Suwanee River Administration Building 

matches form and function to its southeast Georgia 

location for performance that is near zero energy. 

The 1,700-sq-ft building incorporates structural 

insulated panels, energy-saving appliances, and 

passive solar and cooling design elements to cut 

energy use by 43%. Thanks to super-efficient 

features like these, the home’s roof-mounted 

solar panels more than meet heating and cooling 

loads in all but the coldest months of January 

and February. 

“The SIPS cottage is an excellent example of what 

builders can achieve when they put sound building 

science principles to work. This house would be an 

outstanding performer even without the solar panels,” 

said George James, manager of the DOE Building 

America programs new construction program.

The Georgia Department of Natural Resources 

certainly appreciates the low energy bills. The 

department is using the cottage to house Georgia 

Parks Department staff offices at the Okefenokee 

National Wildlife Refuge. The house was built in 

2003 in partnership with the U.S. Department of 

Energy’s Building America program. Building 

America’s Building Science Consortium team 

got involved at the design and planning stage, 

working with the State Parks Department’s architect. 

Building Science Consortium performed Manual J 

calculations, evaluations during different construction stages, building air leakage and duct leakage 

tests, and indoor pressure differentials. 

“This was a prototype home to explore what 

would be needed to get to the 40% or better level 

in the hot, humid climate, even without PV,” 

said Armin Rudd, a project lead with Building 

Science Consortium.

Form and Function

The home’s L-shape is the most effective design 

for bringing day light and natural ventilation to 

every room in the house. High ceilings, dormer 

BUILDER PROFILE

Builder’s Name: 

Collaborative project of the Georgia 

Department of Natural Resources Parks 

Recreation and Historic Sites Division, 

the U.S. Department of Energy Building 

America Program, the U.S. Department 

of the Interior, the National Park Service, 

Southface Energy Institute, Building 

Science Corporation, and Canthan 

Construction Co.

Where: Okefenokee National 

Wildlife Refuge, Georgia

Development: Pilot house

Size: 1,700 sq. ft.

(2 bedroom, 2 bath, 1 loft)

With its energy-saving and solar energy features, 

the home is calculated to save $812 per year or 

69% over a similar sized home built to the Building 

America benchmark (roughly the 1993 Model Energy 

Code, plus lighting, appliances, and plug loads).

All photos and figures courtesy of 

Building Science Corporation.

Solar Power Finds a Home in Okefenokee
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Georgia Department of Natural Resources – SIPS Cottage

windows, an open interior, and deep wrap-around 

porches maximize passive cooling and natural 

lighting. Windows that can open are strategically 

placed all around the house to promote natural 

ventilation, which is enhanced with ceiling fans and 

mechanical ventilation to bring fresh, filtered air 

to the heating and cooling system. Deep overhangs 

and retractable awnings block out the heat gain 

from direct overhead summer sun, but let light in 

from the lower winter sun.

The home’s second-story dormer windows act as 

chimneys, encouraging a stack effect by providing 

an exhaust route for hot air rising through the 

home’s open interior. This upward moving air 

helps draw cool air in from the screened porches 

on the first floor.

Envelope a Key to Energy Savings

The home’s location near Okefenokee Swamp in 

southeast Georgia dictates a greater concern for 

cooling than heating. The passive cooling techniques 

are supplemented with a high-efficiency 14 SEER 

air conditioner with a two-stage compressor and a 

variable-speed, electrically commutated (ECM) air 

handler motor, plus a separate dehumidifier. An 8.95 

HSPF air source heat pump and a high-efficiency 

gas fireplace provide heat when it’s needed. Both 

the furnace and the air conditioner are controlled 

by a smart, programmable thermostat, further 

boosting the HVAC system’s efficiency. And not an 

ounce of heating or cooling is wasted because the 

ducts are insulated and located in a crawlspace 

that is sealed, conditioned, and insulated with R-7 

1.5-inch XPS foam board.

The Georgia Ultra Low Energy House ensures a 

tight building envelope with structural insulated 

panels. These very solid wall components sandwich 

extruded polystyrene between sheets of oriented 

strand board for panels that are straighter and 

stronger than structural timber with superior 

insulation properties and less thermal bridging. 

The builders used 6.5-inch-thick panels valued at 

R-22 in the walls and R-38 in the home’s cathedral 

ceilings. High-performance low-emissivity windows 

and extra attention to caulking and sealing details 

add to envelope performance to reduce air changes 

to 2.5 sq. in. leakage per square foot of building 

envelope. A highly reflective white standing seam 

metal roof minimizes solar heat gain to the home’s 

interior. All of these features combined resulted in 

a HERS rating of 91.5 and energy savings of 43%, 

not counting the photovoltaics. 

ENERGY STAR appliances and lighting further 

decrease electric load. Even the home’s ceiling fans 

were thoughtfully chosen for cooling effect. The 

Key Features

4.1 kW photovoltaic system

Passive solar design using deep 

overhangs, retractable awnings, and 

solar screens on windows

Ducts in conditioned space

Mechanical ventilation with motorized 

damper to bring fresh air to air handler 

unit and circulate indoor air

Envelope – R-38 structural insulated 

panels (SIPS) in roof and R-23 SIPS panels 

for walls, and sealing details to achieve 

0.25 cfm 50/ft2 thermal enclosure

Windows – high-performance 

low-emissivity Argon-filled fiberglass 

framed windows, U=0.35, SHGC=0.33

Integrated HVAC system

Air conditioner – high-efficiency, 

variable speed, 14 SEER air conditioner

8.95 HSPF air source heat pump

Roofing is aluminum standing 

seam metal roof painted white for 

maximum heat reflection 

Insulated ducts are located in the 

crawlspace and are sealed, conditioned, 

and insulated with R-7 1.5 inch XPS 

foam board, duct leakage is less than 

5% and none is to unconditioned space

Hot water heater is 0.94 EF 

electric with R-8.5 wrap

Separate stand-alone dehumidifier

Lighting is 80% fluorescent

ENERGY STAR appliances

The home’s L-shaped design, numerous openable 

windows, and screened porches encourage cross 

ventilation. The open interior and second-story loft 

windows help create a stack effect, drawing cooler air in 

through porches while hot interior air rises and escapes 

through second-story windows. These natural cooling 

features, together with high-performance ceiling fans 

and a white metal roof that minimizes solar heat gain, 

help reduce the home’s reliance on air conditioning. 
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Georgia Department of Natural Resources – SIPS Cottage CASE STUDY

blades on the fans used throughout the home have 

a slight twist that enables them to move air nearly 

50% more efficiently than conventional blades and 

they tend to operate more quietly with less wobble. 

The fans come with a dimmable fluorescent light 

and a programmable remote control as well, to 

encourage their use only when occupants are 

around to appreciate the benefits.

Solar Systems

The house’s steep pitched roof sports 40 photovoltaic panels to produce electricity and is capable 

of supporting a 4-ft by 8-ft solar thermal panel, 

should one be added for water heating in the 

future. The 4.1-kW photovoltaic system with 40 

EC-102 panels provides 6,405 kWh of electricity 

per year, meeting two-thirds of the home’s total 

demand of 9,529 kWh for heating, cooling, hot 

water, and plug load. Because the system is tied to 

the grid, it relies on the grid instead of batteries for 

backup power. Any surplus electricity produced by 

the photovoltaic system is sold back to the utility, 

i.e., the meter runs backward. 

A 4-ft by 8-ft thermal hot water panel was evaluated 

to provide the building’s estimated 2,022-kWh hot 

water load. The evaluation was conducted by Building America’s Building Science Consortium, which 

recommended a passive, integrated system that 

relies on thermo-siphoning or density differences 

due to temperature differences to move potable 

water through the system instead of pumps, valves, 

or a controller. According to Building Science 

Consortium, this is a very simple, yet sophisticated 

solar water system with a good track record in 

the field. On the Georgia house, hot water from 

the roof panel would circulate to the standard 

50-gallon storage tank of the electric water heater. 

One solar thermal panel would be adequate to 

supply most of the hot water needs for a family of 

four, depending on weather and the hot water use 

of the occupants. The integrated system is designed 

for temperate climates with limited likelihood of 

freezing temperatures but it does include the two 

freeze protection systems required by the Solar 

Rating Certification Corporation: the high mass 

4-inch tubes and the drain-down system. It is rated 

for 20°F for an 18-hour period.

Dollars and Sense

The 4.1-kiloWatt photovoltaic system costs about 

$8 per watt, or approximately $32,000 for the 

whole system installed. The PV system should be 

virtually maintenance-free during its 20+ years 

of expected operation. 

Building Science Consortium used the DOE2.1Ebased EnergyGaugeUSATM software to calculate the 

The Ultra-Low-Energy Suwanee Administration 

Building takes advantage of passive solar 

techniques such as deep overhangs, porches, 

and awnings over windows to keep out high 

summer sun and let in low winter sun. 

Passive Cooling

Key elements of passive cooling include:

Deep wrap-around porches and window 

awnings for maximum shading and lots of 

indirect daylighting

Highly reflective white standing-seam 

metal roof cladding

Numerous operable windows located 

for cross ventilation and high ceilings 

(for stack effect ventilation)

Mechanical ventilation to draw cool air from 

porch through filter to air handler air intake 

where it is mixed with conditioned air

High-performance ceiling fans

All of these features work together to 

reduce the need for mechanical cooling 

and electric lighting.

The home’s roof accommodates 40 photovoltaic panels in a 4.1-kW power system that meets all of the home’s energy needs in all but 

the two coldest months of the year. A 4-ft by 8-ft solar thermal panel would meet nearly all of the hot water needs of a family of four.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Georgia Department of Natural Resources – SIPS Cottage

energy savings for the house as built and with two 

other, more efficient, heating and cooling systems. 

As built, the house cuts energy use by 43% compared 

to a similarly sized home built to the Building 

America benchmark (which is roughly equivalent 

to the CABO 1993 Model Energy Code, although 

the benchmark also includes lighting, appliances, 

and plug loads). Building Science Consortium 

calculated an annual energy cost for the house of 

$1,067, representing a $335 savings over a home 

built to the benchmark guidelines. Those savings 

don’t count the PV. When the 4-kiloWatt photovoltaic 

system is added to the calculation, annual energy 

costs drop to $590 for a savings over benchmark of 

$812 or 69%. The house achieved a Home Energy 

Rating System (HERS) score of 91.5.

These calculations were based on the home as built 

with a 13.5 seasonal energy efficiency ratio (SEER) air 

conditioner and an 8.5 heating seasonal performance 

factor (HSPF) air source heat pump. If the home’s 

heating and cooling were upgraded to an 18 SEER 

air conditioner and a 10 HSPF air source heat pump, 

the home would have achieved savings of 47% over 

the Building America benchmark (and 72% savings 

with PV) and a HERS score of 92.8. With a ground 

source heat pump of 26 EER and 5 coefficient of 

performance (COP), energy savings would have 

been 51% without the PV and 77% with the PV with 

energy cost savings of $492 and $969. The HERS 

score would have been a whopping 94.4.

“The Georgia house definitely demonstrated 

that energy savings far above 30% are possible. 

This prototype is a great model to show builders 

that this kind of whole house design is a viable 

solution in the hot and humid climate zone. It 

could succeed on a community scale as well, if 

you have a motivated builder and buyers who 

care about energy efficiency and on-site power. 

It can also work in an economic climate that 

makes on-site power attractive, which is certainly 

already the case in some parts of the country, 

such as California,” said Rudd.

The Bottom Line

“Building America achieves superior performance 

by applying measures that work with the local 

climate. The principles that went into the design 

of the Georgia Ultra Low Energy House were 

sophisticated but not complicated. I would encourage any builder who is interested in near zero 

energy construction to talk to us and give it a 

try,” said James. 

Energy Costs and Savings compared to Building America Benchmark Home 

for Ultra-Low Energy Home as built and with two different advanced 

heating and cooling systems

FEATURE

Annual 

Energy 

Cost

Cost 

Savings over 

Benchmark

% Energy 

Savings over 

Benchmark

HERS* 

Rating

Building America Benchmark home $1,402 — — 82.4

As Built Home 

With 13.5 SEER, 8.5 HSPF air source heat pump $1,067 $335 43% 91.5

 With 4 kW PV $590 $812 69% —

Home with 18 SEER, 10 HSPF air source heat pump $1,001 $401 47% 92.8

 With 4 kW PV $524 $878 72% —

Home with ground source heat pump, 26 EER, 5 COP $910 $492 51% 94.4

 With 4 kW PV $433 $969 77% —

For more information visit: 

www.buildingamerica.gov

Source: Rudd, A, P Kerrigan, Jr, and K Ueno 

(Building Science Corporation). 2004. “What 

Will it Take to Reduce Total Residential Source 

Energy Use by Up to 60%?” In Proceedings of 

ACEEE Summer Study 2004, Pacific 

Grove, California.

*Based on HERS rating system in 

place before July 2006.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

Grupe – Carsten Crossings

Rocklin, CA 

Building America Best Practices Series

In the volatile California housing market, zero energy 

construction has helped Stockton area home builder 

Grupe to standout from the competition. “Zero 

energy has definitely helped us close deals,” said 

Mark Fischer, a senior vice president at Grupe. 

Sacramento’s new home market took a nosedive 

with sales dropping by up to 45% between 2005 and 

March 2006, just when the first 10 of the 144 homes 

at Grupe’s Carsten Crossings project were completed. 

“We sold 23 of our first 30 homes in the first three 

months, even though the market in Sacramento 

is very slow right now; it is the slowest housing 

market in the country. Our project is doing better 

than most of our competitors,” said Fischer.

The cost of doing business, and a major part of 

profitability, is driven by the time required to sell out 

a community. Reducing this time by selling houses 

faster has a significant affect on the builder’s costs. 

Mark Fischer reported at a builders conference that 

Grupe achieved a sales rate of 4.6 home sales per 

month versus 1.9 for their competitors, a rate 2.5 

times faster than their competition. Grupe has 

calculated that if only about 19% of their increased 

sales rate was due to energy efficiency, solar PV, and 

green features, the increased cost of $2.6 million in 

marketing and increased materials costs paid for 

them self. If the trend continues, Grupe will save 

a total of $14 million.

In this first solar development for Grupe, solar was 

made a standard feature on all 144 houses. “We 

certainly like the fact that it makes us unique, 

and we feel good about offering it because we 

think solar is the right thing to do,” said Fischer. 

Photovoltaics are only part of the equation. Grupe 

anticipates that Carsten Crossings homeowners will 

see annual utility savings of up to 70% more than 

homes built to the California energy code thanks 

to both the photovoltaics, and an impressive mix 

of energy-efficient features that are being offered 

as standard features by Grupe.

“Making solar a standard feature instead of an 

optional upgrade is the way to do it,” said David 

Springer of Davis Energy Group, which is a partner 

in the U.S. Department of Energy’s Building America 

program. Springer worked with Grupe on the 

Carsten Springs Project. “That’s been our experience 

on previous projects. Grupe was able to negotiate a 

much better deal with their contractors by making 

it standard across the project,” said Springer.

Other builders have found that when solar is 

offered as an upgrade, buyers will often choose 

BUILDER PROFILE

Builder’s Name: Grupe

Where: Stockton, CA

Founded: 1966, 50,000 homes 

built as of September 2006

Employees: 70

Development: 

Carsten Crossings at Whitney Ranch 

in Rocklin, CA

Size: 144 homes

Square footage: 2,168-2,755 sq.ft.

(3-5 bedroom, 3 baths)

Price: From $478,000 to $528,000

Number of homes per year: 

300 to 400 homes

Solar status: 

First zero energy development, an 

ENERGY STAR builder for 10 years

Zero Energy Sets Sacramento Area Builder Apart

Grupe chose to make photovoltaics a 

standard feature on every one of the 144 

homes it is building at Carsten Crossings 

in Rocklin, California.

Grupe’s Carsten Crossing 

Community won the gold 

award for moderate climate 

production homes in the 2007 

Energy Value Housing Award 

competition held by the National 

Association of Home Builders 

Research Center.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Grupe – Carsten Crossings

more immediately visible options like upgraded 

countertops or flooring. A RAND Corporation study 

done for Building America partner ConSol in 2006 

shows that the majority of buyers are interested in 

energy-efficient and green construction. But, as Bill 

Dakin of Davis Energy Group pointed out, it’s much 

easier to actually sell solar when it’s in the context 

of an all-solar community where it is included in 

the price of the home, than to sell the home buyer 

solar as a $15,000 to $20,000 upgrade perceived 

to be an extra out-of-pocket expense.

Carsten Crossings is the second largest community 

to meet the California Energy Commission Zero 

Energy New Homes initiative criteria and one of 

the largest all-solar communities in northern 

California. It is the first all-solar community for 

Grupe, a Stockton-based production builder producing 200 to 300 homes per year. 

“The Carsten Crossings project has been a positive 

learning experience for Grupe” said Lew Pratsch, the 

DOE Project Manager for Integrated Onsite Power.

Davis Energy Group (DEG), part of Building 

America’s Consortium for Advanced Residential 

Buildings (CARB) team, has helped Grupe on 

several aspects of the project, including selecting energy-efficiency measures, preparing 

bid specifications for the photovoltaic system, 

testing and inspections during construction, 

and long-term monitoring of energy use and 

production post construction. DEG also helped 

develop educational materials for staff and 

the public. 

Zero energy construction can be a great selling 

tool if sales staff know how to use it. “If you are 

going to put it in, be prepared to train your whole 

organization on why it’s a good deal, especially 

sales staff. You have to train them so that they can 

tell potential buyers why zero energy construction 

is so great,” said Fischer. 

To further the learning experience, Grupe turned 

the garage of one of its model homes into an energy 

efficiency and solar show room for training sales 

staff and educating potential buyers. It’s worked well. 

“Grupe’s sales staff is sold on solar; they are passionate 

about it,” said Bill Dakin of Davis Energy Group.

To learn more about the energy savings, Davis 

Energy Group and Building America conducted duct 

blaster and blower door testing on the homes to test 

air leakage in the ducts and whole house during 

construction. Davis Energy Group also monitored 

energy use in one occupied house for a whole year 

to evaluate heating and cooling usage and energy 

production from the PV system. 

The Solar System

For its solar system, Grupe chose to go with SunPower 

(known at that time as PowerLight), a manufacturer 

and supplier of commercial photovoltaic systems that 

had recently turned to the residential market with a 

roof-integrated product called SunTile. Rather than 

sitting on top of the roof like traditional solar panels, 

these integrated solar tiles, which are equivalent 

in size to a row of five concrete roof tiles, are used 

in place of some of the roofing tiles or shingles, 

Key Features

2.4 kW roof-mounted photovoltaic system

Tankless gas-powered hot water heaters

Energy-efficient windows

High-efficiency, variable speed 

furnace 90+AFUE

SmartVent automatic night 

ventilation cooling 

“FreshVent” continuous ventilation system 

Dual-zone equalizer two-zone 

heating and cooling system

Energy-efficient lighting

ENERGY STAR dishwasher

R49 attic insulation

Radiant barrier sheathing in 

attic ceiling to reduce cooling

1-inch rigid foam-wrapped building envelope

Ducts in attic covered with 

blown-in cellulose insulation

Wall insulation soy-based foam (option)

Homerun parallel piping manifold plumbing

Third-party duct and air sealing testing

SunPower integrated solar roof tiles blend in 

with surrounding roof tiles to provide up to 

2.4 kW of clean, quiet energy year round.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Grupe – Carsten Crossings CASE STUDY

in an overlapping pattern that blends in with the 

surrounding roofing materials.

“What really affects the power production of the PV 

cells is orientation toward the sun,” said Fischer. 

“We don’t limit ourselves to putting these tiles on 

the backs of our houses. We put tiles on the front, 

back, or sides of the houses, wherever they will get 

the most solar gain. They blend in so well with the 

cement tiles that buyers have no objection to seeing 

them. You almost can’t tell they’re there.”

SunPower also offers a complete turn-key package, 

including delivering and installing the tiles, 5 years 

of free post-installation performance monitoring, and an extensive warranty covering parts, 

workmanship and repairs.

“We had no difficulty at all working solar into the 

production schedule. The solar installation does 

not interfere with any other critical path in the 

construction process. It really doesn’t add any time 

for installation,” said Fischer. According to Fischer, 

it didn’t add time for extra inspections either. “The 

PV system was inspected while the city inspectors 

were already on site doing other inspections. That 

may vary by jurisdiction, but that was the case in 

Rocklin,” said Fischer.

Post-installation performance monitoring enables 

the installer to make sure each system is producing 

power. Homeowners can also access the information 

through a user-friendly website that lets them see 

how much power their PV system is producing 

on a given day, and how much greenhouse gas 

emissions from traditional power sources their PV 

system is displacing. 

By early summer 2006, 12 California developers 

had announced plans to use SunPower solar tiles 

in communities totaling hundreds of new homes. 

Centex Homes is installing 3.5-kw roof tile systems 

on $1 million-plus homes in its Avignon community 

in Pleasanton. Another developer, Lennar, plans to 

incorporate the solar roof tiles in 450 homes it is 

building in Roseville over the next two years. Victoria 

Homes expects to integrate solar roofs in hundreds 

of homes in a Victorville subdivision for first-time 

and middle-income buyers. In addition to these 

California developments, deals are expected in New 

Jersey, Colorado, and Arizona, which have all passed 

alternative-energy incentives, according to Bill Kelly, 

vice president of SunPower’s residential division.

Energy Efficient, Innovative, Green

Solar photovoltaics alone will never get a home 

to zero energy bills. A super-efficient building 

envelope and high-performance appliances are 

key to cutting energy costs. 

All of the Carsten Crossings homes feature energyefficient low-emissivity windows, energy-efficient 

lighting, tankless gas-powered “on-demand” hot 

water heaters with a parallel piping manifold, 

high-efficiency variable speed 90+ AFUE furnaces, 

“FreshVent” continuous ventilation systems (CVS), 

and dual-zone equalizers. 

To cut cooling costs, the homes will employ 

SmartVent automatic night ventilation cooling. 

The system uses a thermostat-controlled damper 

to automatically bring in cool filtered air when 

outdoor temperature drops at night. “Think of it as 

Plumbing manifold gets hot water to its 

destination faster.

Solar in California - A Snap Shot

The California Energy Commission 

reported in 2006 that 16,684 homes 

and businesses have installed rooftop 

solar units since 1981, and California 

produces 130 megawatts of solar 

power annually. This puts California 

third globally in solar production after 

Germany and Japan according to 

Bernadette Del Chiaro, clean energy 

advocate for Santa Monica-based 

Environment California. Still, the state’s 

solar production represents just a 

fraction of the 33,032 megawatts that 

California produces on average each 

year. The number of installations on 

rooftops is a mere sliver (0.1%) of the 

12.2 million homes and apartment 

buildings in California.

In 2005, California home builders 

received permits to build 154,853 

new single-family homes and 53,000 

new apartments and condominiums, 

according to the Construction Industry 

Research Board. But statewide, they 

have built only 1,500 to 1,600 new 

homes with solar systems already 

included according to the California 

Energy Commission.

Every home is equipped with a high-efficiency furnace and air conditioner plus the SmartVent ventilation system, which requires very 

little power to circulate cool night air through the home in the summer months.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Grupe – Carsten Crossings

an intelligent whole-house fan. It provides filtered 

outside air to a specific set point, say 65 degrees, 

to cool off the house at night without having to 

open the windows,” said Dakin. He added that 

DEG’s year-long monitoring should show just 

how much cooling savings is achieved with the 

SmartVent system. 

The attics are equipped with R-49 blown cellulose and 

the heating and cooling system ducts are wrapped, 

sealed, and buried in the attic insulation. The attic 

ceilings are lined with a radiant barrier to keep out 

heat. The 2x4" house walls are filled with blown-in 

fiberglass or soy-based foam insulation. In addition, all of the homes’ exterior walls are blanketed 

with a 1-inch-thick layer of rigid foam insulation. 

Duct and whole house air sealing is independently 

confirmed through duct blaster and blower door 

testing conducted by Davis Energy Group. 

“By using a Building America consultant like 

Bill Dakin, not only do we get third-party credibility,” said Fisher, “we ourselves become incredibly educated about the things we can do to save 

energy while building sustainable and beautiful 

communities” (as quoted in the San Francisco 

Chronicle July 2, 2006).

“The Grupe Company has been a leader in energy 

efficiency,” said Pratsch, who noted Grupe was 

among the first ENERGY STAR builders in its area 

to use blown-in insulation. “We hope the Carsten 

Crossings zero energy home project will provide a 

model that other builders will follow.” 

Dollars and Sense

In its first foray into an all-solar development, Grupe 

did get a leg up from the California Public Utilities 

Commission. In January 2006, the Commission 

approved a 10-year, $2.9 billion program to give 

homeowners or builders a $7,000 per home subsidy 

to add solar units to their homes. (The subsidy will 

decrease as program volume increases).

This brings Grupe’s cost for adding solar down to 

about $16,000, or $18,000 for solar plus all of the 

energy efficiency measures said Dakin. According to 

Springer, Grupe is absorbing some of the additional 

cost to offer the homes to buyers at competitive 

prices in a market that has softened recently. 

In addition to the $7,000 subsidy, homeowners get a 

$2,000 federal tax credit (which goes directly to the 

homeowner and not to the builder or developer), 

providing additional benefit to the homeowner.

Utility savings can range from $500 to $1,300 annually. Building America plans to verify these numbers 

by monitoring. According to Springer, even based 

on a PV system cost of $18,000 to $20,000 for a PV 

system bundled with energy efficiency improvements, 

if that cost is included in a 30-year mortgage with a 

6.5% mortgage rate, the annual utility bill savings is 

usually greater than the annual increase in mortgage 

cost. “When we compared the incremental mortgage 

cost to annual energy savings, we showed a positive 

cash flow,” said Springer.

According to SunPower’s vice-president Bill Kelly, 

PV systems add to the home’s resale value. And 

the peace of mind they provide is even harder to 

calculate. Californians who still vividly recall the 

rolling blackouts of the early 2000’s can rest easier 

with a clean, quiet, emissions-free power plant 

nestled into the roof over their heads. 

The Bottom Line

For Grupe, zero energy homes make a lot of environmental sense, but they also make sense from a 

business standpoint. “They have been selling better 

than comparable competitor’s homes,” said Dakin. 

“In fact, they are outselling the competition 2.5 to 1.” 

The faster sales rate translates into millions of dollars 

of greater profits for the builder—more than enough 

to pay for added material and marketing costs.

Said Grupe’s Fischer, “In a few years, you will see 

this everywhere.”

(top) Grupe is marketing the zero energy 

homes as GrupeGreen homes. With their bundle 

of energy-efficiency measures, the homes meet 

the criteria of Building America’s Zero Energy 

Homes, the California Energy Commission’s 

Zero Energy New Home (ZENH) Initiative, and 

the ENERGY STAR homes program. Grupe is 

also participating in the LEED (Leadership in 

Energy and Environmental Design) Homes 

Green Building certification program.

(bottom) Using a real-time monitoring system, 

the solar installer can check the PV system’s 

performance from a portable computer or 

Blackberry at any time.

“By using a Building America consultant like Bill Dakin, not only do we get third-party credibility, we become incredibly 

educated about the things we can do to save energy while building sustainable and beautiful communities.” 

Mark Fischer, a senior vice president at Grupe (as quoted in the San Francisco Chronicle July 2, 2006)

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: Habitat for 

Humanity – Metro Denver

Wheat Ridge, CO 

Building America Best Practices Series

Habitat for Humanity of Metro Denver has worked 

with the National Renewable Energy Laboratory 

(NREL) for 15 years to build energy-efficient homes. 

Habitat Denver deserved the high praise it received 

when it won the Affiliate of the Year award in 2005. 

Its many accomplishments include building an 

innovative, affordable home designed to produce as 

much energy as it consumes on an annual basis. 

Though other Zero Energy Homes (ZEHs) have 

been erected by for-profit builders, Habitat Denver is 

among the first Habitat affiliates to build one. Using 

only common construction materials, the strength 

and determination of its volunteers, and help from 

NREL, Habitat Denver built a 1,200-square foot, 

3-bedroom home capable of withstanding cold 

Colorado winters while cutting utility bills to a 

fraction of typical costs—an important benefit 

to homeowners with limited or fixed economic 

resources. Support for NREL’s work came from 

DOE’s Building America Program. Says Habitat 

Denver construction manager Bruce Carpenter: 

“Our philosophy is that it’s not fair to our families if 

their energy bill is higher than their mortgage.”

Roadmap to Success

Most ZEHs have been built and marketed to middleand high-income buyers. Habitat Denver wanted 

to prove that the concept could be brought to the 

affordable home market. To achieve this end, 

the Building America experts from NREL and 

the Habitat team came together to create specific 

construction guidelines in order to achieve energy 

and construction success. 

The teams agreed that construction techniques 

had to be replicable by other Habitat for Humanity 

affiliates, so all energy-efficiency technologies were 

carefully assessed for their ability to be used in the 

future as well as their commercial availability. 

Techniques were selected to be “volunteer friendly” 

to avoid overextending the schedule due to extra 

training or compromising construction quality 

from lack of specialized knowledge. 

Some ZEHs have been built with special operation 

requirements or complicated mechanical systems 

in order to maximize renewable energy use. Habitat 

Metro Denver felt that it would be a worthwhile 

tradeoff to sacrifice some energy-efficiency in 

BUILDER PROFILE

Builder’s Name: 

Habitat for Humanity, Metro Denver

Where: Denver, CO

Founded: 1979

Development: Wheat Ridge, Denver, CO

Square footage: 1,200 sq.ft.

(3 bedrooms)

Price: Labor and some items donated

Energy efficiency, solar hot water, and 

photovoltaics will provide affordable energy 

for this family. Photo courtesy of NREL. Affordable Energy Savings in a Habitat for Humanity ZEH
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Habitat for Humanity – Metro Denver

order to make their clients feel comfortable in 

their new home by making everything as simple 

and familiar as possible. 

Once the basic criteria were decided upon, NREL 

turned to simulation software to help the teams assess 

the final home design and select the best energyefficient technologies and construction methods. 

Achieving Zero Energy

The work came down to two main goals: lessening 

electricity consumption and creating a well-sealed 

house to deter energy loss common in standard 

construction. 

Construction, Heating, and Ventilation

To achieve a super-tight outer shell, double-stud 

walls were used. Fiberglass batts were placed within 

the stud cavities and sandwiched between the 

double-stud walls for a total wall R-value of 39, plus 

a thermal break between the studs. Exterior walls 

were finished with a vapor permeable housewrap 

and fiber-cement siding. Inside, the walls and 

ceiling included a polyethylene vapor barrier and 

drywall, which helped ensure a tight seal. In the 

attic area, raised heel trusses were designed to 

accommodate 2 feet of blown-in fiberglass, giving 

the ceiling an R-60 rating. 

Because the shell was super-insulated, heating 

requirements were low. Most standard heating 

systems produced too much heat. So a small 

direct-vent natural gas system was installed in the 

living room, and small electric baseboard heaters 

were added in the three bedrooms, each on an 

independent thermostat. 

The tight seal also required the home to be outfitted 

with a mechanical ventilation system. An Energy 

Recovery Ventilation (ERV) system was installed 

to exhaust air from the kitchen and bathroom 

and supply fresh air to the living room and the 

bedrooms. The warmth of the exhaust air heats the 

incoming air, significantly reducing heat loss due 

to ventilation and further reduces heating needs.

Windows 

Special attention was paid to the long south side of 

the home. Here, large windows were installed to invite 

in light and warmth. The glass chosen was double 

glazed, low-e (e stands for emissivity) (U-value=0.30 

BTU/hr-F-ft2) in order to reduce the heat loss through 

the windows. Deep overhangs were added to keep 

direct sunlight from entering the homes during the 

summer when it is not needed for heating.

PV and Solar Hot Water

To achieve net-zero energy use, the team turned 

toward the sun for renewable power. Discounting 

the expected natural gas usage, the electricity needs 

of the home were determined and a 4-kW grid-tied 

photovoltaic (PV) system was installed to meet 

these needs. The system is grid-connected and is 

expected to produce excess energy in the summer 

to balance out excess use in the winter, achieving 

net zero energy consumption. 

Next to space conditioning, water heating is the 

largest energy cost a family must face. To reduce this 

load, the team installed a solar hot water system to 

compliment the electricity savings achieved by the 

PV array. Three collectors, totaling 96 sq. ft., with 200 

gallons of water storage were mounted on the roof 

pitch, for an annual water heating savings of 88%. 

A natural gas tankless water heater was installed 

as a backup, only kicking in when the solar water 

tank falls below its 115 degree hot water set point 

temperature. The solar water heating system uses 

water as its heat transfer fluid and is a drainback 

system. The collectors completely drain any fluid 

when the pump turns off. 

The Bottom Line

“Building energy efficiency is something we’re 

committed to,” says Bruce Carpenter. “If it’s practical 

and affordable, it’s morally the right thing to do. We 

are often stewards of other people’s money—the 

donors and vendors who give us materials—so we 

have to weigh carefully the benefits of what we are 

doing with the initial cost. We go with what makes 

sense. And this makes sense.” 

Key Features

4-Kilowatt PV system 

96-sq ft Solar Hot Water Collector

and 200-gallon tank

R-60 Attic Insulation

R-30 floor insulation

Double-glazed, low-emissivity windows 

with high solar heat gain coefficient 

windows on the south and low solar heat 

gain coefficient in other orientations

Double-stud walls with three 

layers of R-13 fiberglass batts

Energy Recovery Ventilation (ERV) system

(see specific home features on p.3)

(top) Double stud wall construction; 

the cavity will be filled with insulation 

(bottom) Solar thermal collectors and PV panels 

may provide as much energy as the household 

consumes. Photos courtesy of NREL.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Habitat for Humanity – Metro Denver CASE STUDY

Feature Standard Denver 

Habitat Approach

Upgrade Upgrade 

incremental 

materials cost

Foundation Type Conditioned crawlspace 

with 2-inch slab on floor and 

continuous run 50 cfm fan

Ventilated crawlspace 

with insulated joists

Floor Insulation 2-inch extruded polystyrene 

foam (Dow Blueboard) on 

interior crawlspace walls R-9.8.

R-30 fiberglass batts $400

Walls 2x6 studs 24 inches on 

center with insulated headers

Double stud 2x4 24 inches 

on center

Wall Insulation R-19 fiberglass batts in wall 

cavity; taped 1-inch extruded 

polystyrene foam (Dow 

Blueboard) (R-2.5) exterior 

sheathing over OSB Total 

R-21.5

3 layers of R-13 (R-39 total) 

fiberglass batts with interior 

polyethylene vapor retarder

$2,100

Attic Insulation R-38 blown-in fiberglass with 

raised heel trusses

24 inches of blown-in 

fiberglass (R-60) with raised 

heel trusses

$415

Passive Solar Features Site and building elevation 

designed for solar gain

Long dimension oriented 

east-west, increased glazing 

on south side, reduced glazing 

on east, north, and west

$0

Windows Low-e vinyl windows South facing: 

U of 0.30, SHGC of 0.58

Others: 

U of .22 and SHGC of 0.27

$640

Siding Varies Fiber cement over housewrap Varies

Air Sealing Caulk all edges of OSB; 

caulk, foam, or sill seal 

all penetrations

Spray foam at penetrations $525

Blower Door Test None 0.15 ACH natural $0

Domestic Hot Water Direct power vent 

gas-fired heater

Solar thermal drainback with 

instantaneous gas heater 

backup

$7,068 

Space Heating Forced air furnace, 

Sealed ducts 

82% AFUE gas-fired 

space heater with electric 

baseboard – no ducts

$100

Air Conditioning None None $0

Photovoltaic None 4 KW PV system (24 Sharp 

NE165U1 modules and a 

Sunny Boy SB3800U inverter)

$17,489

Ventilation Kitchen and bath exhaust Energy recovery with 

dedicated ductwork

$783

Lighting Partial compact fluorescent 100% fluorescent $0

Total component upgrade cost = $29,120

The utility room is equipped with energyefficient appliances, the tank for the solar 

water heating system, and an energy recovery 

ventilation system. Photo courtesy of NREL.

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: Habitat for 

Humanity – Loudon County 

Lenoir City, TN

Building America Best Practices Series

Researching Energy Affordability 

For families on a limited income, a $200 utility bill 

could be as much as a fourth of monthly earnings. 

Habitat for Humanity affiliates are able to offer 

families low- or no-interest loans and very moderate 

home prices, thanks to volunteer labor, sweat equity, 

and donated materials. Unfortunately, affordability 

can still be an issue once the family moves in and 

starts paying utility bills in this era of rising gas 

and electricity prices. 

But what if the house had utility bills of under 

$1/day? What if the electricity meter even ran 

backwards sometimes? 

Thanks to sound energy-efficient building design 

and roof-mounted photovoltaic systems, four lucky 

Habitat families are experiencing the thrill of home 

ownership with homes that sometimes earn them 

money from their utility company. The homes are the 

product of a unique collaboration between the U.S. 

Department of Energy’s Building America Program 

teams, DOE’s Oak Ridge National Laboratory (ORNL), 

the Habitat for Humanity Loudon County Affiliate, 

and the Tennesse Valley Authority.

Since 2002, the partnership has built and monitored 

five near-zero-energy Habitat homes in Lenoir 

City, Tennessee, as a part of a zero-energy research 

study. These modest but pleasant 1,000- to 1,200-

square-foot colonials may look ordinary, but their 

energy bills aren’t. Their Habitat home owners are 

paying $25 or less per month, 50% to 70% less than 

their neighbors.

Habitat home owner Becky Clark was thrilled to 

receive her first electricity bill showing a credit of $35 

in one month. “We got paid! It’s like we’re our own 

little power plant,” said Clark, who had been paying 

$200 a month for utilities in her apartment.

The first of the five houses was completed in June 

2002 and was the first house in the Tennessee Valley 

Authority’s power distribution area to sell solar 

energy to the electric grid. 

Putting it all Together

The extraordinary savings are due to a combination 

of high-performance energy saving technologies, 

attention to construction details, and a design 

based on sound building principles, according to 

Jeff Christian, director of the Buildings Technology Center at Oak Ridge National Laboratory in 

Tennessee, a partner in DOE’s Building America 

homes program.

The houses use an airtight shell of structural 

insulated panels, which are made of rigid foam 

BUILDER PROFILE

Builder’s Name: 

Loudon County Habitat for Humanity

www.loudoncountyhabitat.org

Energy Champion: Linda Morrison, 

construction, volunteer, and 

communications coordinator

Where: Loudon, TN

Founded: 1993

Number of Staff: 3

Number of homes built to date: 

52 homes

Number of homes built per year: 

8 homes

Construction type: 

Wood frame over a crawl space

Energy efficiency status: 

First ENERGY STAR house in 2002, 

now all ENERGY STAR

The first house was completed in November 

2002 and was the first house in the Tennessee 

Valley Authority’s power distribution area to sell 

solar energy to the electric grid. Solar system 

costs dropped from $22 K for the first house to 

$15 K for the second and third house one year 

later. Photo courtesy of Jeff Christian of ORNL.
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Habitat for Humanity - Loudon County

sandwiched between two layers of plywood. The 

panels have superior insulation, strength, and 

sound proofing values, and come to the building 

site prefabricated for quick wall and roof assembly. 

The walls on the fourth Lenoir City home were 

installed in five hours, and the insulated roof was 

up in just three hours. 

Each house includes a number of energyefficiency technologies, and no two houses have 

the same combination. Some of the technologies 

are used in all five houses; some have been 

tried in only one dwelling so far. For example, 

three of the homes use air source heat pumps 

for heating and cooling. Two use a geothermal 

heat pump, which heats or cools inside air using 

a heat transfer fluid pumped through pipes laid 

5 feet underground where the temperatures 

stay about 55 degrees in winter and 70 degrees 

in summer. High-performance, double-pane, 

low-emissivity windows are located on the 

homes’ south-facing walls under deep overhangs 

to increase day light while cutting glare and 

solar heat gain. Heat gain is also cut through 

the use of infrared reflective paints on the 

exterior walls and reflective roofing materials. 

A mechanical ventilation system maintains 

much better than average indoor air quality. 

ENERGY STAR appliances donated by Whirlpool 

and compact fluorescent lighting add to the 

energy savings. 

The PV Power Plant

The most striking feature for home owners though 

may be the 2-kW solar photovoltaic system mounted 

on each home’s roof. The solar systems are connected 

to the local utility grid and the Tennessee Valley 

Authority (TVA) pays the home owners 15 cents 

per kWh for all of the solar power produced. That’s 

more than twice the rate TVA customers pay for 

traditionally generated electricity, but less than it 

costs the utility to install new, renewable generating 

capacity. The PV systems produce about 20% to 30% 

of the electricity used by each house annually. But 

on warm sunny afternoons when the PV system is 

producing more power than the house is consuming, 

a net-meter allows the surplus energy to flow into 

the utility grid. 

Roof Installation

Christian describes the PV system on house 3 as 

an example. “The PV system has 1.98-kWp (kiloWatt-peak) capacity and is comprised of twelve 

165-Watt multi-crystalline silicon modules. The 

(left) All five houses use structural insulated 

panels (SIPS) for super-efficient wall 

and roof construction. 

(right) The fourth house, at 1,200 sq feet with a 

walk-in lower level, has energy costs of 60 cents 

per day for energy. Energy costs for a similarsized, new conventional house in Lenoir City are 

$4 to $5 per day. Photos courtesy of 

Jeff Christian of ORNL.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Habitat for Humanity - Loudon County CASE STUDY

system is attached to the 26.6-degree tilted roof 

(6/12 pitch) and faces directly south. It consists of 

12 panels with overall dimensions of about 5 feet 

by 33 feet.” As is, the system can meet 24% of the 

total energy load. But according to Christian, “there 

is room on the roof for three to four times more PV 

modules, enough to meet all of the home’s energy 

needs, thus attaining zero energy status.” 

The roofing material for house 3 is continuous 

standing seam 24-gauge steel panels. The standing 

seams on the roof allow for the attachment of the 

photovoltaic system without any penetration into the 

roof using a clipping mechanism shown above.

Live-In Laboratories

ORNL is doing extensive tracking of energy use on 

the five homes. Results have varied from house to 

house, because they installed different combinations of insulation levels, space heating, and water 

heating technologies in each house. But, according 

to Christian, they are seeing improvements with 

every house. The average energy cost to operate 

the homes stands at $1 per day for the first house, 

$0.88 for the second, $0.79 for the third, and $0.75 

for the fourth, with a goal of $0.60 per day for the 

fifth. Energy costs for a conventional house in 

Lenoir City are $4 to $5 per day.

Solar electricity generation has ranged from 2,000 

to 2,600 kWh per year and the home owners have 

sent between 670 to 1220 kWh of this back to the 

grid, according to Christian’s year’s worth of data 

on each house. Electricity produced earned the 

homeowners between $300 to $390 or roughly 

half of their year’s electricity bills which ranged 

from $640 to $830. 

The long-term goal of DOE’s involvement, according 

to Lew Pratsch, DOE Zero Energy Homes project 

manager, is to make zero energy homes truly 

affordable for the average consumer. Pratsch 

predicts that within the next decade, zero-energy 

homes will become commonplace. 

In the meantime, the project has made believers 

at the Loudon County Habitat for Humanity. 

Loudon’s Habitat Construction Supervisor Todd 

Helton, who is also a union carpenter, was so 

impressed with the SIPs construction he wants 

to build his own house with SIPs panels. The 

affiliate has committed to building all of its 

houses to the ENERGY STAR level, which is a 30% 

more efficient building envelope than standard 

construction, and a significant step on the road 

to zero energy home construction. 

(left) An S-5 metal clip is used to attach the PV 

modules to the standing seam metal roof. 

Photo courtesy of Jeff Christian of ORNL.

(middle and right) Loudon County Habitat 

for Humanity pays attention to details like 

caulking and window flashing to improve energy 

efficiency and durability. Photo courtesy of Linda 

Morrison of Loudon County Habitat for Humanity.

Energy Saving Features

Features were varied among the five 

houses to test the effectiveness of each. 

Highlights include:

Walls: 4.5 or 6.5 inch SIPS

Roof: 6.5, 8 or 10 inch SIPS

Roofing: 24 gauge steel standing seam 

with 0.17 or 0.23 reflectivity

Crawlspace: unvented or 

mechanically vented

Heating and Cooling: 2-ton 17 SEER air-toair heat pump or geothermal heat pump

Ventilation: mechanical ventilation to return 

side of coil, CO2 sensor, bathroom exhaust

Ducts: inside conditioned space

Water heater: integrated heat 

pump water heater

Solar system: twelve 165-W multi-crystal 

silicon PV modules in a 12.68% efficient, 

1.98-kWp system or twenty 110-W polycrystalline modules in a 2.2-kWp system
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Habitat for Humanity - Loudon County

Costs

When materials and labor costs are factored in, the 

costs of building the five study houses (not including 

the cost of land and infrastructure, which is the same 

for all, and not including the cost of the PV systems) 

ranged from about $79,000 to $88,000. The cost of 

building a standard construction Habitat house of 

similar size in the same locale was about $59,300 

in 2005. With the cost of the PV systems included, 

the construction cost ranged from about $100,000 

to about $104,000. 

However, the cost of the PV systems has dropped 

considerably since the first house was built. Over 

the long term, the cost of PV systems is expected to 

continue to drop as production volume increases.

(left) Thorough air sealing and locating ducts 

in conditioned space are two ways the Loudon 

County Habitat affiliate improves the efficiency of 

its homes. Photo courtesy of Linda Morrison of 

Loudon County Habitat for Humanity.

(right) Solar energy provided 2,260 kWh per 

year for this second house built in 2004. 

Solar system costs dropped from $22K for the 

first house to $15K for the second and third 

house one year later.

For more information visit: 

www.buildingamerica.gov

The heat pump water heater shown here 

and the geothermal and air-to-air heat 

pumps provided significant energy savings 

for heating, cooling, and water heating. 

Figure courtesy of Jeff Christian of ORNL.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

John Wesley Miller Companies

Armory Park del Sol – Tucson, AZ 

Building America Best Practices Series

The southwestern architecture cleverly 

hides the rooftop PV and solar heater units 

from passersby. Armory Park del Sol is a 

neighborhood with wide streets, two parks 

and a community garden – all within walking 

distance of downtown Tucson.

A vibrant neighborhood within walking distance 

of a bustling urban center? A community garden, 

spacious sidewalks for bikers and pedestrians, and 

two public parks nestled between the houses? How 

about stylish homes with universal accessibility and 

cutting-edge energy efficiency? It may sounds too 

good to be true, but not if you live near Tucson, 

Arizona. Here, within walking distance of the downtown commercial and business district is the Armory 

Park Del Sol community, offering homeowners a 

place to live without the hassle, headaches, and 

expense of suburban life. State-of-the-art energy 

saving technology is standard in all the homes, 

including photovoltaic (PV) electric power-generating systems and solar hot water heaters.

“We were told it couldn’t be done,” chuckles 

John Wesley Miller, owner of John Wesley Miller 

Companies (JWM), which built the development, 

“But it’s done well.We’ve always been involved in 

pushing the envelope of energy-efficient building.” 

Miller sought help from the National Association of Home Builders (NAHB) Research Center, 

a Building America partner, to select features and 

construction techniques that ensure every house 

in the community exceeds the Model Energy Code 

by 50 percent or more. Standard homes in Armory 

Park del Sol are expected to use only 7 kWh per 

square foot per year.

The community also contains one of the first 

net-zero energy homes. This house produces nearly 

all the energy it uses on an annual basis. It uses 

only 4 kWh per square foot annually and the 

solar hot water system provides almost all of the 

homeowner’s hot water and home heating needs. 

Total energy costs in 2005 for the ZEH were about 

$15 per month—including all heating, cooling, 

lighting, and appliance use.

Solar Energy First

“In 1973, I became enthralled and passionate 

about solar energy; I love it,” says Miller simply. 

His passion has evolved into a homebuilding creed 

that puts solar energy first. 

For example, each of the 99 lots within the Armory 

Park del Sol was carefully configured to take full 

advantage of the sun. The desert-style house plans 

were chosen not only to be pleasing to potential 

buyers, but also because the flat roofs and parapet 

walls common to southwestern architecture are 

ideal for keeping PV and solar hot water panels 

“In 1973, I became enthralled and 

passionate about solar energy; I love it.”

John Wesley Miller

BUILDER PROFILE

Builder’s Name:

John Wesley Miller Companies

Where: Tucson, AZ

Founded: 1956

Development: 

Armory Park Del Sol, Tucson, AZ

Square footage: 977 to 2,026 sq. ft. 

(2-3 bedrooms and baths)

Price: $373,000 - $932,000

A Neighborhood Beyond the Norm
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY John Wesley Miller Companies – Armory Park del Sol

hidden. All homes were installed with wind-resistant, 

1.5-kW PV systems with programmable thermostats, 

backed by a 25-year guarantee. The Homeowners 

Association (HOA) restricts the placement and 

maximum height of trees to avoid adverse shading 

conditions that could interfere with the efficiency 

of the PV modules. 

In addition, each house is outfitted with a roofmounted Copperheart solar hot water collector, 

which combines thermal collection (i.e., water 

heated by the sun) and storage in a single unit. It 

is backed up by a Seisco tankless water heater to 

ensure hot water on demand. Parallel piping was 

installed to improve hot water delivery time as well. 

This hot water distribution system features small 

polyethylene (PEX) plastic pipes that branch off of 

the main pipe to each hot water use point, speeding 

up delivery time and reducing energy losses.

Insulation from the Elements

The interior comforts of a home can be difficult 

to shield from the extreme outdoor conditions 

found in Arizona. But JWM incorporates several 

best practices that protect against the temperature 

swings found in desert climates.

Masonry Construction

An Armory Park del Sol home has a masonry wall 

superstructure consisting of steel-framed walls, 

concrete, and exterior insulation, including a 3-coat 

stucco finish. This masonry construction, notes 

Miller, provides excellent thermal mass storage and 

insulation to protect the indoor environment from 

outdoor conditions. A side benefit for homebuyers 

is its sound-deadening properties.

In addition, the plumbing and electrical lines 

run inside the walls and ducts are in conditioned 

space—two factors that help reduce air leakage 

heating or cooling losses for a very tight house 

(2.9 ACH50).

HVAC System

JWM Companies works with a professional engineer to review house plans to assess the placement 

of ductwork and the proper sizing of HVAC equipment. At Armory Park del Sol, the ducts are sealed 

with mastic, tested for air leakage, and enclosed in 

soffits below the insulation along the central core 

of the house. Transfer grilles across doorways and 

a central return equalize air pressure throughout 

the house. The careful attention to the HVAC 

All homes come standard with a 1.5-kW 

photovoltaic system and solar hot water 

collector. (left) Photo courtesy of NAHBRC. 

(right) Photo courtesy of JWM.

Key Features

1.5-kW PV system with 

25-year guarantee

Copperheart solar hot water collector 

with 10-year guarantee

Seisco tankless water heater

R-38 ceiling insulation

Milgard dual-pane, low-E2 windows

with lifetime guarantee 

14 SEER high-efficiency heat pump

Masonry wall superstructure 

Copper water lines

Universal accessibility design 

with 3-foot-wide doors on singlelevel floor plans
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

John Wesley Miller Companies – Armory Park del Sol CASE STUDY

system and its placement further contribute to 

the tightness of the construction.

Windows

Inferior windows can contribute to air leakage or 

heat transfer, which is why low-emissivity dual-pane 

windows were chosen for Armory Park del Sol 

homes. The spectrally selective coatings on these 

windows protect occupants from the heat and glare 

of the daytime sun, while the low U-value of 0.31 

prevents indoor heat loss during the night. 

Working Together

Over the years, John Wesley Miller Companies has 

formed several beneficial relationships that enhance 

its business practices. Long-standing relationships 

have been formed with local subcontractors and 

periodic meetings are held with staff and trades to 

review building practices and discuss issues. This 

ensures that all parties are on the same page when 

working with new techniques or materials.

The company has also formed a strong bond with 

Tucson Electric Power (TEP), the local utility. TEP 

aggressively promotes renewable energy power 

systems by offering rebates and other incentives. 

During the building of Armory Park del Sol, TEP 

performed periodic quality inspections during and 

after the construction process, confirming that 

Armory Park del Sol homes will be easy on the 

utility grid. TEP also agreed to a billing cap, so 

that heating and cooling bills are guaranteed not 

to exceed $1 per day for 5 years (depending on the 

size of the house). The utility also offered rebates 

for solar systems of $2.40 - $3.00 per installed watt, 

for a total rebate of $3,600 - $4,500 per house. 

John Wesley Miller is a big believer in working 

with like-minded builders and others to achieve 

energy efficiency in homes. In addition to working 

with Building America, he is also involved with 

other national and local building organizations. 

“I’m currently working with a green building 

subcommittee on county building codes,” he says. 

“This is a volunteer program to create incentives 

for builders to do good things instead of penalizing 

them. Too long we’ve been fighting each other. It’s 

time to sit down at the table and work together to 

accomplish these common goals.”

The Bottom Line

Although energy-efficient building standards such 

as high-quality masonry, PV, and solar hot water 

systems ultimately save money for the homeowner, 

the up-front costs can sometimes cause buyers to 

turn away. This is often due to a misunderstanding 

or a miscommunication about the benefits and 

savings associated with the systems and techniques. 

Miller believes that education is the key to promoting sales of energy-efficient homes.

Notes Miller, “About 80% of our buyers looked us 

up on the web first. We probably have more Ph.D.s 

living in our little development than any other 

part of town. This doesn’t mean you have to be 

a genius to appreciate the homes we build, but it 

shows that education and a willingness to learn 

about energy efficiency can drive sales.”

The home’s A/C unit (center) and an integrated 

solar water and space heating system. Solar 

collectors provide space and water heating with 

backup heat provided by a tankless water heater 

(photo from NAHBRC).

Miller believes that education is the 

key to promoting sales of energyefficient homes. 

For more information visit: 

www.buildingamerica.gov

Copperheart Integrated Collector Storage water 

heaters are included on each JWM house. 

Photo courtesy of the Solar Store.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

Premier Homes – Premier Gardens

Sacramento, CA 

Building America Best Practices Series

Folks living in Premier Homes’ all-solar Premier 

Gardens development in Sacramento can’t stop 

talking about their low energy bills. And their 

neighbors are getting a little miffed.

Premier Homes built 95 entry-level homes in 

Rancho Cordova near Sacramento in 2004, across 

the street from 98 similar homes built by another 

builder. The homes are nearly identical in size and 

price but the Premier Homes are near zero energy 

homes with advanced energy-saving features and a 

2.2-kW photovoltaic system on every roof. And when 

Premier Gardens’ homeowners started moving 

into their homes in fall 2004, their September 

energy bills averaged $20 while their neighbors 

were paying around $70, according to ConSol, a 

U.S. Department of Energy Building America Team 

Partner that worked on the project. 

Both developments were designed for energy 

efficiency but the Premier homes are drawing on 

average 54% less power from the grid. The difference 

in net savings between the two groups of homes 

would have been even greater but the neighboring 

homes were built as SMUD Advantage homes, with 

cooling energy usage estimated to be 30% lower 

than a standard California Title 24-compliant home. 

If the neighboring homes had been standard Title 

24 homes (which are themselves more efficient 

than the national average), the savings difference 

would have been more than 60%, according to 

Bruce Baccei of ConSol who worked with Premier 

Homes and the Sacramento Municipal Utility 

District (SMUD) on the project. 

Premier Gardens is the Sacramento area’s first 

near zero energy home community designed to 

cut energy bills at least 50% and the first Premier 

community offering solar energy as a standard 

feature. Premier had offered solar as an optional 

upgrade on previous developments and the Roseville 

builder has been committed to energy-efficient 

construction for more than a decade.

“It is an opportunity to set ourselves apart as a 

small builder,” said John Ralston, vice president 

of sales and marketing for Roseville-based Premier 

Homes. “The market will be wanting more energy 

efficiency in California as time goes on and we 

want to stay ahead of it.” 

Premier hopes to differentiate themselves from other 

builders in a very competitive market dominated 

by large corporate production home builders, 

according to Rob Hammon of ConSol. The development was open for sales in August 2004 and the 

“Premier Gardens is a unique opportunity 

for first-time homebuyers to live in an 

extremely energy-efficient home that will 

provide them with a solid value, both now 

and in the years to come.”

Kevin Yttrup, President of Premier Homes

BUILDER PROFILE

Builder’s Name: 

Premier Homes

www.builtbypremier.com

Where: Roseville, CA

Founded: mid 1980s

Development: 

Premier Gardens - Sacramento, CA

Size: 95 homes

Square footage: 1,285 - 2,248 sq.ft.

(3 to 6 bedrooms)

Price range: $245,000 to $335,000

Number of homes per year: 70-90

Solar status: First all ZEH development, 

have offered solar in the past

A view of the 95 homes of Premier Gardens, 

all today’s zero energy. Photo courtesy of 

Sacramento Municipal Utility District. Side by Side But Energy Use Difference is a Mile Wide
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Premier Homes – Premier Gardens

last home was sold in December 2005, faster than 

nearby subdivisions.

Premier branded Premier Gardens as a “Premier 

ProEnergy Community” and said it was the first 

Sacramento area all-solar development to offer entrylevel buyers so many energy features as part of the 

standard package. “We are excited to bring the first 

standard “near zero energy” community to Sacramento 

and we are confident buyers will be amazed at the 

savings,” Kevin Yttrup, president of Premier Homes, 

told the media when Premier Gardens was announced. 

“Premier Gardens is a unique opportunity for first-time 

homebuyers to live in an extremely energy-efficient 

home that will provide them with a solid value, both 

now and in the years to come.”

While the builder next door made granite countertops standard, Premier chose to make the 

photovoltaic systems standard, along with a host 

of other energy-efficient features including highefficiency furnaces and air conditioners, tankless 

water heaters, high-performance windows, and 

better insulation. Homes in both developments 

sold for similar prices. 

All of the Premier Gardens homes meet the DOE 

Building America goal for today’s zero energy house 

with their 60% reduction in power drawn from the 

grid and reduced natural gas consumption. SMUD 

certified the homes as SMUD Solar Advantage 

homes, which means the homes exceed the current 

California Title 24 energy cooling requirements by 

as much as 30%. In addition, the homes met state 

ENERGY STAR® Homes requirements.

ConSol conducted air leakage testing of the ducts 

and whole house through its ComfortWise program 

as each house was completed in Premier Gardens.

The Sacramento Municipal Utility District (SMUD) 

tracked the electric bills of all the homes in both 

developments and collected data every 15 minutes 

on electric consumption at 18 homes in Premier 

Gardens and 18 of the neighboring community. 

SMUD also collected PV production data every 15 

minutes on the Premier Gardens homes. SMUD 

shared this data with ConSol, which evaluated 

it both for the Building America Program and to 

determine potential benefits to the utility. SMUD 

helped to subsidize the project at $7,000 per home 

and provided $20,000 in marketing support in hopes 

that this and future PV projects can help SMUD 

shave its summer afternoon load peaks.

For utilities dealing with peak load issues and for 

consumers who may face higher peak rates, the 

Premier Gardens project provides some tantalizing 

results. In July 2005, while Building America and 

SMUD were doing their research, Sacramento 

experienced its hottest July on record. With everyone 

turning on their air conditioners, the utility broke 

their all-time-peak demand record three days in a 

row. But, while the sun was high, the PV systems on 

the near zero energy homes cranked away and the 

Premier Gardens homes had peak demands that 

Key Features

2-kW GE Energy AC photovoltaic system

Tankless hot water heater and R-4 pipe 

insulation on all major hot water lines

An engineered heating and air 

conditioning system 

Furnace AFUE .91; AC SEER 14

Dual-pane, vinyl frame spectrally selective 

glass windows, with u-factor of 33-37 

and SHGC of .32-.35

Tightly sealed air ducts buried in attic 

insulation, duct blaster tested

Fluorescent lighting in all permanent fixtures

Insulation R-38 in attic, R13 batt to R-19 

in walls, 1” rigid foam house wrap, R4.2 

duct insulation

HERS score of 90 

(based on pre-July 2006 HERS system)

The unobtrusive integrated photovoltaic cells are 

placed for best solar orientation depending on the 

home’s orientation on the lot, whether that be on 

the front, side or back of the house. The integrated 

photovoltaic cells are barely noticeable.

0

Typical New Home ComfortWise/

ENERGY STAR Home

Premier, Building America

and ZEH

Other Energy Use

Water Heating

Space Cooling

Space Heating

Annual Energy Bill ($)

200

400

600

800

1,000

1,200

Annual Energy Bill Comparison

Thanks to energy savings 

and PV produced electricity, 

Premier Gardens home 

owners paid $600 less 

per year on their energy 

bills than homeowners 

in standard construction 

homes and $400 less than 

those in ComfortWise homes.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Premier Homes – Premier Gardens CASE STUDY

were 75% lower than their neighbors. “The ability 

of solar to level out air conditioning-driven peak 

demand makes it a desirable investment for utilities 

and for consumers who want to help decrease the 

likelihood of rolling blackouts and sky-high utility 

prices,” said Baccei.

“Zero Energy Homes provide multiple benefits—lower energy bills for the homeowner and 

reduced energy demand on hot summer days when 

electricity is more expensive and the power grid 

most utilized,” said Paul Bender, SMUD manager 

of power production.

Solar System

The 2.2-kW photovoltaic system installed on 

Premier Gardens’ homes is an integrated tile 

PV product manufactured by GE Energy called 

Gecko modules. The tiles are similar in dimension 

to cement roof tiles and lay on the roof shingle 

fashion to blend with surrounding roofing. The 

system consists of 48 GT-55 modules and a SMA 

Sunny Boy 2500 inverter. SMUD supplied each 

home with a PV meter to record the solar electric 

system’s energy output; this figure appears on the 

homeowner’s monthly electric bill along with their 

electricity usage. 

ConSol and SMUD reported in March 2006 that 

the PV systems were performing exceptionally well 

and consistently exceeding estimated kilowatt hour 

production by 10% over the course of the first year. 

The homes produced about 3,330 kWh per year 

out of a total average of 7,007 kWh consumed 

per household between September 2004 and 

September 2005.

The systems were installed by an installation 

company founded by Premier Homes’ owners. 

Premier liked the aesthetics of the roof-integrated 

PV panels and found homebuyer acceptance was 

high. Some home builders are hesitant to install 

PV systems on the fronts of homes. Others believe 

that the visibility of PV systems can be desirable 

for home buyers who want to “show off” their 

photovoltaic systems. 

Energy-Efficient Features 

and Innovations

“The first step in designing a near zero energy 

home is to significantly reduce the home’s overall 

energy use. This enables the home builder to 

install a smaller, less expensive PV system to meet 

the home’s electrical needs,” said Rob Hammon 

of ConSol.

Building America, through its team leader ConSol, 

provided an energy analysis to help Premier select 

energy-efficient measures for the five house plans 

featured in the community. Each home is equipped 

with a high-efficiency .91 AFUE furnace and a 

correctly sized SEER 14 air conditioner. Ducts are 

0 -1.0

12 1 2 3 4 5

AM PM

6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11

500

1,000

1,500

2,000

2,500

3,000

-0.5

-0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5 kW

Avg. High Temp = 98°F

Average 15 Minute Interval Peak Demand ZEH vs. Non-ZEH July, 2005

Avg. Min Temp = 65°F

System Peak MW

Average of ZEH Net Grid Load (kW)

Average of Power Produced by PV (kW)

Average of Non-ZEH Net Grid Load (kW)

Selling Solar

Some of Premier’s most dedicated solar fans 

are its sales staff. “I am their walking, living, 

breathing advertisement for solar out here,” 

said Sheri Gage, sales manager and owner 

of one of the first solar homes completed at 

Premier Meadows, a 65-unit Premier Homes 

development at Live Oak 50 miles north of 

Sacramento. 

“I’ve been in since December 2005, and my 

electric bills have ranged from a high of $70 

to a low of $1.60 per month (for a 1,990 sq 

ft home),” said Gage. “People have been 

walking into my sales office who are paying 

between $250 and $800 a month on their 

electric bills,” said Gage. 

PG&E has raised the rates several times 

in the last two years. In August 2006, they 

announced another rate increase in September with two more likely to follow.” 

To show home buyers they have a choice, 

Premier Homes has run a very successful 

campaign advertising $30 a month bills. “We 

did an analysis of the Premier Gardens homes 

for a 9-month period in 2005. All 95 homes 

averaged $30 per month,” said Don Rives, 

sales manager at Premier Homes Premier 

Gardens and now Premier Bay Drive Estates, 

another all solar Premier development. 

A look at peak demand in July shows 

how much lower the near zero energy 

home’s demand is than that of nearby 

energy-efficient houses without PV.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Premier Homes – Premier Gardens

tightly sealed and buried in the attic insulation 

for an insulation value equivalent to R-13. Each 

home has a tankless on-demand hot water heater 

so power isn’t wasted keeping a 60-gallon tank of 

water hot 24 hours per day, 365 days per year, and 

all of the major hot water lines are insulated with 

R-4 pipe insulation. 

The windows are high-performance, dual-pane, 

vinyl-frame spectrally selective glass windows. 

Fluorescent lights are installed in all of the recessed 

downlights and other installed light fixtures in the 

home. There is R-38 insulation in the attic and R-13 

batt insulation in the wall cavities. In addition the 

outside walls are sheathed in a 1-inch layer of rigid 

foam insulation, which takes the place of house 

wrap and provides an additional insulation and 

water barrier. The homes have received an average 

Home Energy Rating Score (HERS) of 90 (based 

on pre-July 2006 HERS rating system).

Even without the solar, the homes used 22% less 

energy than homes in SMUD’s service territory built 

to California’s Title 24 standard and 13% less than 

the homes in the neighboring development built 

to SMUD Advantage home standards.

Dollars and Sense

The PV systems and the energy-efficiency features 

together add about $10,000-15,000 to the cost of a 

home. SMUD contributed financially to the project, 

committing to provide Premier about $7,000 per 

home toward the cost of each PV system and $200 

per home for advanced energy-efficiency features. 

As previously stated, Premier priced the homes so 

the near zero energy homes cost no more than the 

neighboring homes. According to a RAND study, one 

of the Premier Gardens residents calculated that 

the homes in the two developments cost the same 

per square foot at the time he purchased his new 

home. Thus at Premier Gardens homeowners are 

getting “today’s zero energy homes” at prices that 

are competitive with the much less efficient homes 

of their neighbors. And the project has continued 

to generate positive press for Premier Homes.

The Bottom Line

Premier Homes took the success of its solar-powered 

energy-efficient homes down the road to Roseville, 

where the builder has offered the same features 

standard at another Premier ProEnergy community, 

Premier Oaks. The 49 homes at Premier Oaks are 

slightly larger than the Premier Gardens homes 

(1,800 to 3,300 sq ft) and expected savings are 

60%-63% above a home built to Title 24. 

Premier is also offering PV as a standard feature 

at its 35 -home Premier Bay Drive Estates in Yuba 

City, the first all-solar community in Yuba City, 

with homes up to 3,000 sq. ft. selling for $200,000 

and up.

Premier has become so convinced of the selling 

power of solar that in July 2006, half way through 

construction on its 65-home Premier Meadows 

development north of Sacramento, it switched 

from solar as an option to making solar a standard 

feature. “If we believe in this stuff we just have to 

do it,” said Premier sales manager Don Rives.

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

Pulte Homes – Civano

Tucson, AZ 

Building America Best Practices Series

Pulte Homes is putting building science to work 

in 1,500 energy-efficient homes at the Civano 

master planned community in Tucson, Arizona. 

Working with DOE’s Building America Program, 

Pulte Tucson has put together a solar water heating 

and energy-efficiency package that is helping new 

Civano residents to cut their utility bills while the 

building company turns a profit. 

Civano began as an idea proposed by local advocates 

and government officials in the 1970s called the 

“Solar Village.” Construction started in the late 

1990s and Fannie Mae took over as master developer 

in 2000. Civano’s “New Urbanist” design scheme 

attracted attention and Civano’s first phase of 

construction, Neighborhood 1, was voted the best 

new community in the Southwest by Sunset Magazine in January 2004. The New Urbanist design 

combines residential, commercial, community, 

and open spaces in a pedestrian-friendly layout 

punctuated by diverse southwest architectures and 

drought-tolerant landscaping. 

Before Neighborhood 1 was built, planners of 

the Civano Community organized a committee 

of local engineers, code officials, and equipment 

providers to write a set of stringent requirements that 

builders must comply with when they build in the 

community. The requirements specify that energy 

consumption of the building shell, mechanical 

systems, and domestic water heating will be 50% less 

than the energy consumed by a house built to the 

Tucson/Pima County Energy Code. This equates to a 

30% minimum reduction over the Building America 

benchmark. There is also a solar goal of meeting 

5% or 550 kWh per bedroom of the household’s 

energy needs with solar energy sources. 

Other sustainability goals include a 60% reduction 

in potable water; xeriscaping with native plants, 

on-site recycling of construction debris, and reduced 

transportation by having at least one job at Civano 

for every two homes on site. 

Builders were encouraged to experiment to meet 

the goals of the project and several approaches 

were tried by the eight different residential builders 

working in Neighborhood 1. These included passive 

solar design, advanced framing techniques, and 

construction with insulated concrete, straw bales, 

structural insulated panels (SIP), adobe, Integra 

block, and RASTRA (a lightweight product composed 

of 85% recycled polystyrene foam). Most builders in 

neighborhood 1 chose solar water heaters to meet 

Civano’s solar energy requirement.

“Pulte’s involvement in Civano is 

the next step up from the exemplary 

level of efficiency and whole-building 

systems design already standard for 

the production builder.” 

Armin Rudd, Building Science Corporation 

BUILDER PROFILE

Builder’s Name: 

Pulte Homes, Inc., Neighborhoods 2 – 4. 

Mixed builders in neighborhood 1.

Where: Nationwide

Founded: 1950, Detroit, MI

Number of Staff: 13,400 nationwide

Development: Civano - Tuscon, AZ

Size: 1,517 to over 2,180 sq. ft. 

(Two to four bedrooms and 

two to three bathrooms)

Price Range: 

$120,000 to $260,000+

Pulte is building more than 1,400 energyefficient homes in the Civano community of 

Tucson, Arizona. Pulte Brings Building Science to Civano
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Pulte Homes – Civano

Pulte entered the picture in 2003 taking Fannie 

Mae’s place as master developer for the second 

phase of construction at Civano, in Neighborhoods 

2, 3, and 4. Pulte is also the primary builder of 

these neighborhoods, which it calls Sierra Morado, 

where Pulte intends to build 1,400 to 1,500 homes 

over the next five years, joining the nearly 500 

homes already built in Neighborhood 1. Construction in these neighborhoods began in early 2005 

and prices in 2006 ranged from $120,000 to the 

upper $200,000s. As with its other communities, 

Pulte brings to this project an understanding of 

building science and experience at managing the 

construction process. 

“Pulte is being successful at Civano. They are using 

Building America building science concepts and 

are scientifically doing a much better job, a more 

advanced job, to make their homes affordable and 

efficient,” said Al Nichols, the professional engineer 

who evaluates builders’ plans for Civano. “We will 

analyze the utility billing data in Spring 2007. I 

think Pulte will have greater performance than the 

Neighborhood 1 homes. But the goal of Civano is 

much bigger than this project alone. It’s to show that 

you can have much greater performance anywhere 

without a lot of additional cost, and you can make 

money at it. The only way to survive in a depressed 

market is to build better homes.”

“Building America was very helpful in making 

decisions at the start of the project. We consulted 

with them on what kind of water heaters to install 

and what mechanical systems configuration would 

best meet the requirements,” said Rich Michal, the 

Civano project manager for Pulte Tucson.

Solar Systems

Building America research partners studied the 

water heating systems used in Neighborhood 1 (see 

sidebar). Pulte Tucson used this research to select 

a system for its Neighborhood 2-4 homes.

Pulte is installing a SunEarth Empire EP40 system 

with a 40-sq.ft. flat plate solar collector mounted on 

the roof that heats a glycol fluid in a closed-loop, 

active system. Active systems use an electric pump 

to push the solar fluid through the collector and 

down to a heat exchanger that transfers the heat 

to potable water in an 80-gallon Rheem Solaraide 

HE hot water tank. The system also has a natural 

gas backup heater. The tank is installed in the 

garage. Pulte engineers the roof trusses for adequate 

structural strength to enable home owners to add 

future photovoltaic panels if they choose.

Michal noted that Pulte had been concerned about 

home orientation on the lots for solar gain but 

Building America research eased those worries. 

Building America partner Building Science Consortium did a study of placement of the solar panels 

to see if they met the Civano requirement. Building 

Key Features

BUILDING ENVELOPE:

Ceiling R-22 cellulose 

Unvented attic w/ tile roof

Walls 2x6 @ 24 o.c. R-19 w/ R-4 EPS or 

Walls 2x4 R-13 @ 16 o.c. w/ R-4 EPS

Foundation slab, uninsulated

Windows Low-e2 U=0.39, SHGC=0.33

Infiltration 2.5 sq in leakage area

per 100 sf envelope

MECHANICAL SYSTEMS:

Heat 90% furnace in conditioned attic

Cooling 14 SEER

DHW 40 sf solar collector with solar tank

Natural gas backup

Ducts R-4, conditioned attic

Leakage; None (to outside)

5% of flow maximum

Totaline thermostat

Ventilation 45 cfm 10 min per hour

Pulte uses mechanical ventilation to bring fresh 

filtered air into the home and send humid air out 

for a healthy indoor living environment.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Pulte Homes – Civano CASE STUDY

Science Consortium found only a 16% difference 

in performance between south, east, and west roof 

elevations. “We found that the active closed loop 

system works well even if it is 90 degrees off of 

due south. The panels can even be due east or due 

west and they will still operate at an 80% efficiency, 

i.e., they will still meet the 550 kW-per-bedroom 

requirement,” said Michal.

Energy Efficiency

Builders in Neighborhood 1 tried several different 

construction techniques (including SIPS, insulated 

concrete, and even straw bale homes) to achieve 

the Civano energy efficiency goals. 

Building America partners IBACOS, Sandia National 

Laboratories, and the National Renewable Energy 

Laboratory tested several of the Civano Neighborhood 1 homes and energy subsystems to document 

their performance. IBACOS did field monitoring 

of nine homes with a variety of construction types 

including 2x6 wood framing, SIPs, steel framing, 

and straw bale, and found that one-third did not 

meet the heating and cooling energy requirements. 

These research organizations provided analysis and 

lessons learned from Neighborhood 1. 

“When Pulte agreed to come in as master builder of 

Neighborhoods 2-4, they said they would meet the 

Civano energy efficiency goals but they had their 

own way of doing it. They wanted to standardize 

production,” said Rudd.

Pulte settled on one approach—the “platinumlevel” home they had developed with Building 

America building science principles for use in 

other developments across the country (see sidebar 

on building science principles). Pulte Tucson had 

been working with Building America since the mid 

1990s according to Rudd and had already used 

its platinum-level approach at several Tucson 

developments.

“Pulte has shown leadership in energy efficiency 

in Tucson. For a span of 10 years every house 

we built in Tucson was a platinum-level house,” 

said Michal. “We have committed to platinum at 

Civano, even though our calculations show that 

the Pulte gold level would probably meet Civano’s 

energy requirements.”

“Pulte does their own blower door and duct blaster 

testing during construction to confirm that homes 

meet their platinum-level standard,” said Rudd.

With help from Building America research, 

Pulte selected closed-loop, active solar water 

heating units.

Solar Thermal Water Systems: Passive or Active, Direct or Indirect?

There are two ways of classifying the major differences among solar water systems—active 

versus passive and direct versus indirect. Active systems all have pumps that move fluid 

through the system. Passive systems have no pumps; they rely on gravity and the buoyancy 

of warm water to move fluid through the system. Indirect systems have two loops—one 

loop goes to the solar collector and contains a fluid (generally a water-antifreeze mix) 

that transfers heat well but has a very low freezing point. This fluid exchanges its heat 

content with potable water in a separate loop. Indirect systems are also called “closedloop” systems. Direct systems have only one loop of potable water that passes through 

the collector and flows directly into the tank. Active, indirect systems with antifreeze, or 

controls that drain water from collectors, work best in climates with freezing conditions. 

Many passive and/or integral systems are only appropriate for areas with no or only 

occasional mild freeze conditions. Passive, direct systems are less complicated and 

sometimes less expensive. But direct systems are dependent on high-quality water for 

efficient operation and reasonable service life. Key Building America 

Building Science Principles

Pulte adheres to these principles in its Platinum Level houses for high-performance 

homes that deliver energy efficiency, 

safety, comfort, health, and durability:

Superior energy performance; HERS 

rating of 88 or better, which always 

includes high-performance windows 

with low U-value and low SHGC.

All ducts and air handling equipment must 

be located inside the conditioned space.

All combustion appliances in the conditioned space must be sealed-combustion 

(furnaces, boilers, and water heaters).

Mechanical ventilation per ASHRAE 62.2, 

including kitchen range hoods and bath 

fans that exhaust directly to outside.

Performance testing (per ENERGY STAR 

testing regime) with building air leakage 

of 0.25 cfm50/ft2 surface area or less; 

duct leakage of 5% or less of the total 

air handling system rated air flow at 

high speed; and interzonal air pressure 

differences, when doors are closed, of 

3 Pascals or less.

Adherence to water management details 

including drainage plane, capillary 

breaks and flashings, and attention to 

climatic wetting and drying potentials.
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Pulte Homes – Civano

According to Michal, one of the biggest changes Pulte 

makes in construction techniques over standard 

practice is to place the mechanical equipment in 

conditioned space in the attic. “We use cathedralized 

insulation; in other words, we apply the insulation 

right up along the roof line instead of on top of the 

ceiling. We use a blown-in cellulose product. It is a 

mixture of recycled newspapers and a fire retardant. 

We staple a burlap type sheeting to the rafters, then 

blow in the insulation above the sheeting along 

the roof line to insulate the attic. We also apply it 

wet to the walls before sheetrocking; it sticks to the 

walls and dries in place,” said Michal.

Pulte has also chosen high-efficiency HVAC equipment as a standard feature in each home, including 

a SEER 14 air conditioner and a 90% AFUE sealed 

combustion gas furnace, with all ducts located 

inside the conditioned attic. Controlled mechanical 

ventilation is provided by a central fan with fresh 

outside filtered air provided to the air handler 

through a motorized damper. 

Dollars and Sense

BSC evaluated 11 Pulte house plans against the 

Building America benchmark using the EnergyGauge USA software and found the Pulte homes 

will reduce total energy costs by approximately 

$500 to $850 annually.

According to Michal, the solar water heaters qualify 

homebuyers for pretty substantial federal and state 

tax credits and Pulte works with the installers to 

ensure that the homebuyer gets the documentation 

needed to qualify for their tax credits. The state 

of Arizona offers a solar tax credit for 25% of the 

cost of an approved solar device or system, up to 

$1,000. The homebuyer would also qualify for 

federal tax credits.

Those incentives could be enough to sway buyers 

in a competitive Tucson first-time home buyer 

market that was very hot in 2005 and early 2006 

but has cooled considerably since. 

The Bottom Line

“In a really high-growth area, there is a lot of 

competition and a push to just get homes up 

and fast. You could build a cardboard box and be 

successful in the first-time home market here when 

it was really hopping. We’ve had the leadership that 

was committed to building to a higher standard, 

going to the higher level. We are motivated to go for 

the return customer,” said Michal. Michal, who lives 

at Civano, added his encouragement for builders 

contemplating solar. “I think it’s the future. If we 

want to sustain the growth in this industry, we’ve 

“Pulte is being successful at Civano. 

They are using Building America building 

science concepts and are scientifically doing a much better job, a more 

advanced job, to make their homes 

affordable and efficient.” 

Al Nichols, professional engineer who 

evaluates builders’ plans for Civano

Solar Water Heating Lessons Learned at Civano Neighborhood 1 

Many of the solar collectors and related copper pipes installed in Neighborhood 1 failed or 

experienced excessive pitting. The collectors were part of passive, direct systems that had city 

water flowing through them. Building America researchers found that the city water had CO2

and potassium levels and a nitrate/nitrite ratio just high enough to be aggressive in terms of 

potentially corroding and pitting copper. The copper corrosion properties of the water were 

theorized to be enhanced by higher temperatures. 

In Neighborhoods 2, 3, and 4, Pulte chose to use an active, indirect system where the fluid circulating 

through the solar collector is in a closed loop and is a combination of water and nontoxic antifreeze 

that does not have the city water’s corrosive properties. 

IBACOS, a Building America team leader, found other problems with the design of the original 

solar water heating systems. One problem was that pipe runs were as much as 120 feet from 

the collector to the tank in some homes. The Civano energy requirements have since been 

upgraded to require that rooftop collectors be installed within 20 feet of the storage tank.

(continued on next page)
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 5

Pulte Homes – Civano CASE STUDY

“The goal of Civano is much bigger than 

this project alone. It’s to show that you 

can have much greater performance 

anywhere without a lot of additional 

cost, and you can make money at it. 

The only way to survive in a depressed 

market is to build better homes.”

Al Nichols, professional engineer who 

evaluates builders’ plans for Civano

“We found that the active closed loop 

system works well even if it is 90 

degrees off of due south. The panels 

can even be due east or due west 

and they will still operate at an 80% 

efficiency, i.e., they will still meet the 

550 kW-per-bedroom requirement.”

Rich Michal, Civano project manager 

for Pulte Tucson

(continued from previous page)

IBACOS also found that some houses equipped with the original solar water heaters were 

using more water heating energy than homes without solar systems. It turned out that these 

high-energy-consuming homes had hot water recirculation systems, a feature that provides 

instant hot water at faucets and showers. Some timer settings had the pumps running around 

the clock. The pumps pushed hot water from the tank into the solar collectors at night where 

the water was cooled. On its trip back around the system, the cooled water was reheated and 

then recirculated. Homes that used a button-activated recirculation pump, where the pump 

only ran for about 90 seconds, did not see this energy usage problem.

Solar Water Heating Lessons Learned

Problem Solutions

Corrosion of copper pipes due to 

“aggressive” city water chemistry and 

high temperature

1. Add chemicals to soften water. 

2. Choose a solar thermal collector with single glazed 

top rather than double glazed top for less heat buildup

3. Choose a closed loop system where glycol solution 

passes through copper collector pipes rather than 

chemically aggressive local water.

Long pipe runs reduce effectiveness of 

passive water transport mechanisms.

1. Locate solar collector less than 20 feet from tank.

2. Use an active solar collector system with a pump to 

move liquid through system.

Recirculation unit increases energy 

demand from hot water up to 550% 

over homes with standard water heating.

1. Don’t use recirculation systems with single loop 

solar heaters.

2. Use recirculation system only with closed loop solar 

water heating systems.

“I’m aware of the problems previous builders had with the then-cheaper passive integrated 

solar water systems. One of the reasons we went with the product we did, and paid a premium 

for it, was because we didn’t want to have the warrantee issues,” said Michal. “When we were 

pricing systems in 2004, the passive integrated copper systems were less expensive. Now with 

the price of copper going through the roof, the passive systems are more expensive than the 

active systems we are using,” said Michal.

Pulte purchases the solar systems through a local vendor and has the vendor do the 

installations. “We had never done solar water heating installations before,” said Michal. “We 

pride ourselves on repeat business and good customer service. For us to do the installation 

with no experience would have been a warrantee and customer relations nightmare. We 

are construction managers, we subcontract out everything. We just make sure that our 

subcontractors do the job right. We have the quantity to get good pricing. I don’t think we even 

considered doing it ourselves. Even in a market the size of Tucson I don’t think you are going 

to find many plumbers and electricians who will have the expertise to do solar. The vendor has 

licensed plumbers and electricians specifically trained in solar installations. For us, this made 

the most sense.”

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study:

The Garst House 

Olympia, WA

Building America Best Practices Series

Sam Garst has dreamed of building a solar home ever 

since he worked on the original energy bill under the 

Carter Administration in the late 1970s. In May 2006, 

his dream came true when he and his wife moved into 

their custom-built 2200-sq-ft photovoltaic-powered 

home near Olympia, Washington.

“Our concept all along has been to do something stylistically attractive and green as well—

Something that could really showcase what is 

possible,” said Garst.

Michael Lubliner of WSU Energy Program, a Building America team member with the Industrialized 

Housing Partnership, met with the Garsts and their 

local, LEED-certified architect to brainstorm ideas 

for the home. Lubliner modeled the selected plans 

to analyze whole house energy use.

Planning Ahead to Cut Costs

Garst notes that planning ahead was critical 

to the project’s success. “With something this 

complex, you don’t want to make it up as you go. 

We tried to do this all on paper before we started 

pouring concrete. We had the architectural plan, 

the landscaping plan, the lighting plan, even a 

furniture plan. We knew how the systems were 

going to work together.” 

For example, with a landscape plan in hand they 

were able to move large boulders onto the site 

before they laid pipes, septic lines, and the house 

foundation. This minimized disruption to the site, 

saving time and money, and preventing headaches 

later on. This same thinking applied to duct work, 

plumbing lines, and photovoltaic arrays.

The Solar System

The Garsts installed a 4.5-kW, 24-panel solar electric 

system that has a 5,500 kWhs per year design 

capacity, or about 15 kWhs per day. 

Although some may question the wisdom of photovoltaic power in the cloudy Northwest marine 

climate, Garst said even on rainy days their system 

generates electricity. He reported that the system had 

generated 1.76 megawatts between mid February and 

mid May, traditionally a rainy season in Olympia. 

“Western Washington State gets around 30% less 

sunlight per year than Las Vegas but only slightly 

less than Dallas, Texas. Even here solar electricity 

makes sense,” said Garst.

BUILDER PROFILE

Owner: 

Sam and Christine Garst 

www.thegarsts.com

Where: Olympia, WA

Architect: 

Mort Stafford James Architects 

in Olympia

Builder: 

Barrett Burr of Polar Bear 

Construction, Olympia, WA

Project Start: 

Started building summer 2005

Project Complete: 

May 2006

Contractors install PV panels on the curved 

roof of this custom zero energy home near 

Olympia, Washington.

All photos courtesy of Sam Garst.

Zero Energy in the Pacific Northwest
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY The Garst House – Olympia, WA

Garst noted that while conventional wisdom says 

solar collectors should be oriented to true south, 

that is not the case where their house is located 

because days often start with a marine layer of 

fog that burns off by late morning. Calculations 

show 5% more sun after noon than before noon; 

thus, in western Washington state, the maximum 

power is generated with a southwest orientation. 

“The electric company also prefers this orientation 

because the greatest peak demand for electricity is 

on the sunniest, hottest summer days and in the 

afternoon,” said Garst.

The Garst system is tied to the power grid so their 

meter runs backward when it is sunny and pulls 

power from the grid at night and on cloudy days. 

He estimated the system will provide over 70% of 

their total designed power demand, with production sometimes exceeding demand, especially on 

sunny afternoons. To use a rule of thumb quoted 

by Lubliner, “for every 1 kW of installed solar 

capacity on your roof, you’ll save 1,000 kWh per 

year on your utility bill.” 

Regarding batteries, Garst said “If you are close to 

the grid, forget about batteries. They cost money, 

take up space, and require maintenance. The grid 

is our storage battery to use on those long winter 

nights and cloudy winter days.” 

Solar electric panels generate direct current or DC 

electricity that must be converted to alternating 

current or AC electricity. Garst had two inverters 

installed in the home, with 12 panels hooked up 

to each inverter. There is room to add eight panels 

to each, which would allow them to upgrade the 

system in the future with minimal rewiring.

Innovations and 

Energy-Saving Features

The Garsts are pleased with their solar power 

system but readily acknowledge there’s much 

more to saving energy than the PV panels. Garst 

advises home buyers and builders, “Before you 

consider solar, you need to spend the money on 

conservation. We have taken Herculean steps to 

reduce the demand, everything from installing a 

ground source heat pump for heating and hot water, 

to air-to-air heat exchangers on the ventilation 

system, to buying compact florescent bulbs and 

the most energy-efficient ENERGY STAR appliances 

on the market.”

The Garsts packed the house with energy-saving 

features from the bottom up. They insulated under 

and around the slab with rigid foam insulation. 

The foam is 2 inches thick on the sides of the slab 

for R-10 and 3 inches thick under the slab for R-15 

insulating value. A layer of plastic separates the 

foam from the gravel beneath the slab and serves 

as a moisture barrier to prevent moisture from 

coming up into the concrete. 

Garst explained why they added insulation under 

the slab. “You cannot add insulation to the floor 

later without totally ripping out the slab; the added 

cost during construction was minimal.”

The home has 2x6 24-inch-on-center framing, 

which uses 25% less lumber than 2x4 16-inchon-center walls. According to Building America 

research, because this advanced framing technique 

uses fewer studs, there are less thermal bridges in 

the wall, and the 2x6 studs provide a deeper wall 

cavity to hold more wall insulation. 

The Garst’s house builder Barrett Burr said that he 

first learned about advanced framing 20 years ago 

when he started out in the construction business 

as a framer. “Advanced framing is such a simple 

thing but very few people are doing it. I taught 

myself how to do it by reading a manual.” Burr said 

advanced framing is a selling point with customers. 

He said the performance characteristics are easy to 

point out to the customer and it’s easy to carry the 

energy saving concepts through to other items like 

high-performance windows, more insulation, and 

air sealing. “I would ask customers, ‘Have you ever 

heard of this?’ Many hadn’t but when I explain it 

to them, they realize that I want what they want, 

a well-constructed house.”

Burr added “Energy efficiency has been a selling 

point with my customers, something that sets me 

apart. People appreciate that I’m thinking out of 

the box in a way that makes sense to them and 

saves them money in the long run.”

Key Features

2,200 sq ft, 3 bedroom 2 bath, single level, 

with great room and greenhouse/sun room

Slab on grade, 2x6 24”o.c. 

Siding: Hardiplank, over a drainage plane

Roofing: 50-yr asphalt shingle

Slab insulated with Owens Corning 

Foamular rigid foam (ENERGY STAR and 

GreenGuard certified) 3” under slab for 

R-15 and 2” on sides for R-10. Foam over 

plastic sheet, over pea gravel.

Radiant heat, ground source heat pump, 

filtered air circulation system with sealed 

ducts in attic, centrally located to limit 

ducting required, none near windows, no 

AC installed but could be. Air handler 

in conditioned space.

Advanced framing with 2x6 24” o.c.

ENERGY STAR appliances and CFL lamps

Insulation: R-15 3” rigid foam board in 

floor, R-19 Icynene foam in the walls and 

R-19 Icynene plus >R-19 blown 

fiberglass in the ceilings. 

Windows: high-performance windows with 

U-factor of 0.33, solar heat gain coefficient 

of 0.33, visible transmittance of 0.53

Caulking of all seams, plumbing 

and wiring penetrations.

Advanced framing and a ground source heat pump 

for heat and hot water add to the homes energy 

efficiency. The photovoltiaic array should provide 

70% of the home’s electricity.
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

The Garst House – Olympia, WA CASE STUDY

Burr mentioned that advanced framing is just 

one of many good innovations to come along in 

recent years, and he added examples like house 

wrap, hot water pipe heat recovery systems, sealing 

around windows, and caulking the drywall to the 

studs to reduce mold and improve draft control. 

“That’s where the science part of it comes in, new 

products and new ideas come along and you learn 

a better way of doing things.” 

One of these new products is Icynene foam, a 

spray-in foam insulation product that completely 

fills the wall cavity and is especially good at filling 

corners and areas around piping and wiring. The 

Garsts used Icynene for walls and ceiling insulation. 

According to Sam Garst, the foam does not off-gas, 

does not shrink or settle, and resists mold growth. 

Garst said the R-value for Icynene is 3.5 per inch so 

a 6-inch wall will produce an insulation value of 

around R-19. In the ceiling, Burr sprayed foam to 

R-19 and then covered it with an R-19 equivalent 

layer of less expensive blown fiberglass insulation, 

to achieve a total of at least R-38. “Icynene doesn’t 

provide any more insulation value than blown 

fiberglass but it does provide air sealing as well,” 

said Garst. 

Michael Lubliner noted that “Hundreds of homes 

are now using it.” When we do blower door tests for 

building envelope air tightness, homes insulated with 

Icynene tend to be the tightest we’ve found.”

The Garst home uses radiant heat through the floor, 

an increasingly popular heating system that consists 

of pumping heated fluid through a series of pipes 

embedded in a layer of concrete under the floor 

coverings. The fluid is heated by a ground source 

heat pump. The Garsts have a 3-ton heat pump 

and 1800 feet of piping buried in a 5-foot-deep 

trench looped about their 0.75-acre lot. The ground 

source heat pump could also be used for cooling. 

Garst estimates the heat pump will cut electricity 

demand for home and hot water heating by 65% 

to 70% over standard equipment. 

The heat pump also heats an 80-gallon hot water 

tank. The house is equipped with an electric instanton hot water heater, which reduces the amount of 

water wasted while waiting for hot water to arrive 

from the water tank. It turns off automatically once 

hot water starts arriving from the tank. As an added 

measure, the hot water pipes are insulated.

The home takes advantage of passive solar heating 

in the green house, which is built into the southwest 

wall of the house and is tied to a thermostat. In 

the winter, if the temperature in the green house 

rises above 75 degrees, a fan will come on to pull 

the warm air into the rest of the house. 

All of the windows in the home are high-performance 

windows with a U-factor of 0.33, solar heat gain coefficient of 0.33, and visible transmittance of 0.53.

To further cut energy use, Garst installed a Thermal 

Energy Detective (or TED), a device that instantly 

tells the homeowner how much electricity the 

house is using. According to Lubliner this instant 

feedback is especially helpful for homeowners 

who want to manage their lighting, appliance, 

and miscellaneous electric loads. 

Health, Sustainability, 

and Durability

To help prevent mold problems, an inch air pocket 

is maintained between the house’s siding and the 

wall with a vent at the top and bottom to allow air 

to move through the wall to dry it out. Behind the 

air pocket, a housewrap drainage plane covers the 

sheathing. Also all of the wood was sprayed with 

a borax-based mold inhibitor. All of the windows 

are flashed. 

Ducts were installed to bring in fresh filtered air for 

ventilation and air circulation. The air handling 

system for the ventilation is in conditioned space 

in an insulated enclosure built in the attic above 

the pantry. It is centrally located to minimize the 

length of ducts needed and to make certain that the 

pressures are easier to balance within the system. 

The system has two HEPA filters: one on air coming 

in and one on recirculating air. An air-to-air heat 

exchanger is expected to capture up to 70% of the 

heating energy by transferring heat from the exiting 

inside air to the incoming outdoor air. 

Good ventilation helps to minimize humidity 

issues. There is a humidistat to control the amount 

of external air that comes in. The two bathrooms 

The home’s walls and ceiling received R-19 of 

Icynene foam, which provides excellent insulation 

and air sealing. 

Custom built home owner Sam Garst 

on insulation: “You really can’t overdo 

insulation. It is relatively cheap compared 

to other components of the house and 

you will pay for under-insulating for the 

life of the house.”

Some Environmentally 

Friendly Products Used 

in the Garst House

Anderson Renewal Line Windows

PEX and UPC instead of PVC piping

Bamboo flooring

Ecosurface flooring made 

from recycled tires

30% flyash concrete

5,000 gallon rainwater cistern

Low VOC paints, varnishes, 

and adhesives
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY The Garst House – Olympia, WA

and kitchen have fans that exhaust to the outside. 

The office room is also vented with an exhaust fan. 

And the attached garage is mechanically vented 

to keep car exhaust and chemical vapors from 

entering the home.

The Garsts sought to use products produced with 

environmentally sensitive ingredients or methods 

throughout the house. The Garsts used on-site 

recycling during construction and estimated that 

they diverted nearly 3,000 pounds of waste OSB 

from the landfill. This was chopped for reuse as 

landscaping chips and mulch. Other wood scraps 

were given away for wood burning stoves. Paper 

and cardboard were taken to the local recycling 

center. Roofing shingle scraps were taken to a 

recycling center in Tacoma where they are used to 

make highway underlay. Garst noted, “According to 

the 2004 California Statewide Waste Characterization Study, construction and demolition materials 

account for almost 22% of the waste stream going 

into our landfills.”

Dollars and Sense

According to Garst, “the financial returns from PVs 

are incredible. The $27,000 PV system earns me a 

$2,400 rebate from Puget Sound Energy, a $2,000 

federal tax credit, and 15 cents for every kilowatt 

hour I generate thanks to recent state legislation, 

plus all of the savings on my electric bill.”

The system will generate around 5,500 kWh per 

year. The first year return is 14.5%. The return on the 

balance remaining ($21,390), assuming rates remain 

constant, is 5.6%, guaranteed through 2014.

“Compared to mutual funds, this is a pretty solid 

investment. My question to new homeowners is, 

what’s the financial return on granite countertops 

and cherry cabinets?” said Garst.

Garst estimated that their total electric bill for 

heating, cooling, lights, and appliances should be 

less than $50 month. Lubliner did an Energy Gauge 

comparison of the Garst home to a similar home 

built to Washington State’s Energy Code (which is 

slightly higher than IECC 2005) and found that 

the typical home would use 33,500 kWh/yr while 

the Garst home would pull only 12,900 kWh/yr 

from the grid, a savings of 20,600 kWh/yr, or more 

than 60%. And that calculation doesn’t take into 

account the savings from ENERGY STAR appliances 

and lighting.

Bottom Line

“Before you consider solar, you need to spend the 

money on conservation,” said Garst. The Garsts 

invested in a ground source heat pump, high 

performance windows, high-quality insulation, wall 

and duct sealing, and super-efficient appliances 

and lighting. “Why spend more for a solar system 

when there are cheaper ways to conserve?”

Garst said the home qualifies for ENERGY STAR, 

meets the LEED gold star criteria, and also meets 

the Olympia Master Builders 5-star criteria with 

540 points, the highest score they’ve seen to date. 

“I think we all learned something on this project,” 

said Garst.

Garst said they accomplished their goal to build 

a better house, a house that is sensitive to the 

environment, and one that also looks high end. 

“It will have the wow factor.”

A solar greenhouse is among the green features 

that complement the solar and energy efficiency 

features and helped earn the house a 5-star rating 

and the highest score ever achieved under the 

Olympia Master Builders Built Green Program. 

Skylights in the Great Room add daylighting.

Solar Incentives by State

To find out about solar and renewable 

energy incentives in your state, see 

http://www.dsireusa.org/. The site also 

lists available federal incentives.

Custom-built home owner Sam Garst on costs and pre-planning: “In theory, basic green construction should not 

cost more than conventional construction. But to identify possible savings, it is important to hold a team meeting 

and review plans when changes can be made on paper. There are countless trade offs that can be made to 

arrive at the most economical set of plans. Changes on paper are quick and cheap. Changes with a construction 

crew on site are slow and costly.”

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Case Study: Tindall Homes – 

Legends at Mansfield

Princeton, NJ 

Building America Best Practices Series

Greener in the Garden State

New Jersey production home builder Mark 

Bergman’s houses were already so energy efficient 

they were achieving home energy rating (HERS) 

scores of 89 when he decided to add solar. In 2003, 

Bergman, who is the founder of Tindall Homes 

based in Princeton, New Jersey, linked up with 

the U.S. Department of Energy’s Building America 

team lead IBACOS to design a solar-powered model 

house for his Legends at Mansfield development 

with hopes of offering solar on all 39 homes in 

the development.

Before construction began on the Legends at Mansfield homes, IBACOS analyzed two “base case” 

homes built by Bergman and found that he was 

already achieving HERS scores of 89 (a HERS score 

of 86 is required to qualify for ENERGY STAR). 

“We started building ENERGY STAR five years ago. 

For the past two years we’ve built 50% to 55% better 

than code, almost twice as energy efficient as the 

New Jersey ENERGY STAR requirements (which is 

30% better than state code). We offer these energyefficient features standard on all our homes” said 

Bergman. “With solar added, our houses are getting 

energy savings of 60% plus,” said Bergman. 

Solar Systems

Each of the 12 homes in phase one of the 39-home 

development has a 2.64-kW photovoltaic system. 

The solar modules were made by Isofoton of Spain, 

the number two module manufacturer in Europe, 

according to solar contractor John Moynihan, 

owner of Bald Eagle Solar Technology, LLC. They 

consist of 16 165-watt panels on a single string to 

the inverter. Moynihan noted that it is a simple, 

inexpensive system, but that model is not being 

produced anymore so they will be choosing a 

different module for future homes.

Tindall Homes couldn’t change the house orientations on their lots, which had been approved two 

years prior to construction. The builder’s fear that 

PV panels visible on the front of the homes would 

be unacceptable to upper-end buyers required 

some rethinking of solar panel placement as only 

one-third of the homes in the development were 

appropriately oriented for installing the solar panels 

on the back roofs.

Moynihan, Bergman, and the construction foreman 

came up with a novel solution. Instead of putting 

the PV panels on the roof, they installed them on 

a garden shed that Moynihan designed and had 

built by an Amish carpenter from Lancaster, PA. The 

BUILDER PROFILE

Builder’s Name: 

Tindall Homes www.tindallhomes.com

Where: Princeton, NJ

Founded: 1986

Employees: 10

Number of homes per year: 40-50

Energy Commitment: 

All ENERGY STAR since 2001

Development: Legends at Mansfield

Size: 39 homes

Square footage: 3800 to 6000 sq ft, 

(4 and 5 bedroom, 3 to 4.5 bath)

Price range: $759,000 to $924,000

New Jersey builder Mark Bergman and solar contractor John Moynihan installed the PV panels on a shed 

that can be situated on each lot for maximum solar 

gain regardless of the home’s orientation. 

“Homeowners will get 15 times more in 

energy cost savings than what it costs to 

add these features to a home, and they 

will get these energy cost savings over 

the life of the home.” 

Mark Bergman, owner of Tindall Homes in 

Columbus, New Jersey
p. 2 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Tindall Homes – Legends at Mansfield

shed is a 1-story-high, 200 sq ft (12x16 ft) wooden 

structure, with double doors, two windows, a short 

pitched roof on the front, and a long, 40-degree 

sloped back roof that is completely covered with 

solar panels. The sheds are oriented on each lot 

for maximum solar gain. 

The inverter for the solar system is located in the 

home’s basement. Moynihan digs a trench and 

runs a buried wire from the shed to the house and 

through the wall to the inverter. 

“In a perfect world you could orient every home 

for perfect solar gain; we can’t do that, that’s why 

we went to the sheds,” said Moynihan, who hopes 

to market the sheds separately this year.

The Legends at Mansfield community is one of 

1,200 solar projects in New Jersey as of March 

2006, up from just six solar installations in 2001, 

thanks to a combination of rebates, financial 

incentives, and support provided by The New 

Jersey Clean Energy Program’s Customer Onsite 

Renewable Energy (CORE) program. According to 

the CORE website, 492 solar projects were funded 

in 2005 alone, a 75% increase over 2004. New 

Jersey now has 13 MW of installed solar capacity, 

generating 15,000 megawatt hours of electricity 

and reducing carbon dioxide emission by over 

18 million pounds, equivalent to removing 1,100 

SUVs from the road or planting 2,433 acres of trees, 

(www.njcep.com/index.html).

Due to the overwhelming interest in and requests 

for rebates, there have been starts and stops in 

rebate distributions and the New Jersey program 

announced in February 2006 that the rebate would 

drop to $4.35 per watt for solar PV systems with a 

capacity of 0 to 10,000 watts, the third drop since 

early 2005 when the program had been offering 

$5.50 per watt installed capacity. 

This and other limitations in implementation of 

the state’s rebate program have kept Bergman from 

fully realizing his plan of all solar at the Mansfield 

Road development to date. However Bergman has 

plans for a much more ambitious all-solar project 

that he hopes will meet with state approval—a 

1,500-unit community including single family 

homes, town houses, and apartments for various 

income levels located in Logan Township, across 

the river from Philadelphia. This will be a sustainable community with energy-efficient construction, 

green practices like water conservation, shared 

community spaces, and onsite work opportunities. 

Bergman plans to incorporate solar including 

larger scale solar on the main buildings to generate 

electricity internally for the community and he 

hopes to have the community certified for LEEDs 

(Leadership in Energy and Environmental Design) 

for neighborhood development. 

Energy Efficiency, Innovations

DOE’s Building America team led by IBACOS 

conducted a benchmark testing and inspection 

exercise on two of Bergman’s homes in June 

2003. Although IBACOS determined the energy 

efficiency rating of the two homes averaged a HERS 

score of 88, it was still able to identify some room 

for improvement: 

• upgrading from 2x4 16-in. on center to 

2x6 24-in. oc framing 

• upgrading from R-13 faced batt and R-3 

foam insulation in exterior walls to R-19 

blown or spray foam insulation

• upgrading from sheet metal and flex duct with 

27% leakage to sealing all ducts with mastic 

• using open-web floor joists and placing ducts 

in conditioned space

• replacing standard performance lights and 

appliances with energy-efficient models

• replacing the 75-gallon gas water heater with 

a tankless on-demand water heater

• using gas direct vent fireplaces instead 

of wood-burning fireplaces

• discontinuing the use of energy-wasting skylights.

In response to IBACOS’s suggestions, Tindall Homes 

built a pilot house at the Legends at Mansfield 

community in Columbus, New Jersey, that would 

be the model home for the 39-unit community. 

It features basement walls of a precast concrete 

foundation system with R-12.5 interior polystyrene 

insulation within the concrete wall cavities. There is 

Key Features

2.64 kW photovoltaic (PV) 

solar energy system 

HERS scores of 90-91

Exceeds the requirements of the NJ 

ENERGY STAR program 

Custom designed systems for 

maximum comfort and value 

High-efficiency, 2 units, 4-zone 

heating and air-conditioning 

High-efficiency tankless hot water heater 

Energy efficient low-E double pane windows 

Energy saving sill sealers 

Insulation: exterior walls R-19, Basement 

R-12.5, Vaulted ceilings R-30, Flat 2nd

floor ceilings with attic space above R-45 

Air tight construction and sealed ductwork 

Heat Recovery Ventilator (HRV) 

fresh air system 

Programmable digital clock thermostats 

Each house independently 

tested and inspected 

Certificate of Energy Efficiency 

issued to all homeowners

GE ENERGY STAR dishwasher

‘2 x 6’ exterior wall framing with 

R-19 insulation 

8 ft. concrete foundation wall system

Exterior perimeter drainage system 

Termite protection and certification 

Smoke and CO detectors 

per code requirements
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 p. 3

Tindall Homes – Legends at Mansfield CASE STUDY

a 3-inch-thick spray foam urethane insulation within 

the 2x6 exterior wall cavities making it a R-19 wall. 

The attic uses a combination of blown-in cellulose 

plus fiberglass batt insulation to achieve R-45. Greater 

sealing of penetrations together with the use of spray 

foam in the wall cavities helps achieve a continuous 

air barrier and an air-change rate of 0.10 ACH. A 

drainage plane layer is used over insulating foam 

sheathing and is correctly integrated with flashing, 

which is properly applied around windows and door 

areas to promote shedding of water. 

The house sports two optimally sized high-efficiency 

(92% AFUE) direct vent furnaces and 14 SEER 

condensing units. A direct vent gas tankless water 

heater provides hot water. The entire air distribution 

system is located in conditioned space with ducts 

traveling through an open web joist system. A 

central, fully ducted return system serves each floor 

with transfer grilles in bedrooms walls, allowing 

for the transfer of air from bedrooms to the return 

system. The total air distribution system air leakage 

target is 10% of system airflow, with no air leakage 

to the outside. A heat recovery ventilator provides 

balanced mechanical ventilation.

IBACOS ran EnergyGauge USA software version 

2.1 to calculate end-use and determined that the 

pilot home built to the design specifications (not 

including the contribution of the photovoltaic 

system) would save 46% with respect to the Building 

America benchmark house and 32% with respect 

to Bergman’s standard home for total end-use 

source energy. These savings rise to 54% and 43% 

when the contribution of the photovoltaic system 

is included. The pilot home and other PV homes 

built in the Legends at Mansfield community are 

achieving HERS scores of 90 and 91.

“The sales office is actively marketing the energy 

efficiency of Bergman’s homes; they state it in the 

first five sentences to the potential buyer,” said 

Moynihan, who added that he feels it sets Bergman 

apart as a home builder.

“Mark is a true pioneer, he has taken some risks. 

I don’t know of any other builder in NJ who has 

committed to all solar on a market-rate residential development. He really cares about energy 

efficiency. Mark is doing it because it’s the right 

thing to do,” said Moynihan.

Moynihan went on to share a story about the 

builder. “Mark got in an argument with one 

of his homeowners. The homeowner wanted 

80 incandescent can lights in his new house. 

Mark said ‘No, I can’t do that because it blows 

my energy efficiency rating for the house, and 

it’s the wrong thing to do. But we’ll give you as 

many fluorescent fixtures as you want.’ The guy 

was ready to walk away from his contract but 

Mark won him over. The trick is getting people 

to want it,” said Moynihan.

Dollars and Sense

“Homeowners will get 15 times more in energy cost 

savings than what it costs to add these features to a 

home, and they will get these energy cost savings 

over the life of the home,” said Bergman.

IBACOS estimated that cost savings (based on an 

average electricity rate of $0.101/kWh and a gas 

rate of $0.8798/therm) without including the PV 

were 32% or $1,122; with PV included cost savings 

were 43% or $1,511.

(left) Homeowners love the garden sheds; they 

also love the 50% to 60% energy savings they 

are getting from Bergman’s energy-efficient 

construction and the solar panels installed on the 

shed’s back roof.

(middle) It’s easy and safe to install PV panels 

for the 2.64-kW photovoltaic system on the low 

200-sq.ft structures. 

(right) The Building America team lead by IBACOS 

worked with Tindall Homes to build New Jersey’s 

first solar home development priced at market rates.

“We all want to make money but at some 

point as a society we have to evaluate 

what we are doing. Our homes cut energy 

use by 50%-55% over houses built to 

the state code. Over the lifetime of the 

house, our (Tindall) homes will save more 

in energy costs than the purchase price 

of the house. If we all did this, we could 

make a big difference.” 

Mark Bergman, owner of Tindall Homes in 

Columbus, New Jersey
p. 4 Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007

CASE STUDY Tindall Homes – Legends at Mansfield

The Bottom Line

“We all want to make money but at some point as 

a society we have to evaluate what we are doing. 

Our homes cut energy use by 50% to 55% over 

houses built to the state code. Over the lifetime of 

the house, our (Tindall) homes will save more in 

energy costs than the purchase price of the house. 

If we all did this, we could make a big difference,” 

said Bergman.

According to Moynihan, they are already making 

a big difference for Tindall home owners. “A 

homeowner called me up one Friday night. He 

and his wife had just bought one of our homes 

and he called me to tell that he had just got his 

electric bill and it was only $48 for the month. He 

said ‘this house is twice as big as my last house 

and my electric bill is half as much.’ A young 

guy like that should have something better to do 

on a Friday night then call his builder about his 

electric bill, but he was that excited about it,” said 

Moynihan.

“At the end of the day people need a place to live. 

For the public good, it would be nice if the place they 

live in doesn’t waste energy or pollute the environment and is sustainable,” said Moynihan.

Wiring for the photovoltaic system runs 

underground from the sheds to the houses.

Thermal Envelope Improvements

Added 1-time 

upfront cost

Annual savings 

to homeowner

Simple 

Payback

Superior Walls precast concrete basement 

walls with exterior rigid foam and R-13 

batts in wall cavities

$0 $209 33.5 yrs

Taped R-3 rigid foam sheathing on exterior walls $2000

R-18 spray foam urethane insulation in wall 

cavities instead of fiberglass batt

$5000

R-30 batt plus R-15 loose cellulose in ceiling $0

Drainage plane of plastic house wrap over foam 

sheathing and better window and door flashing

$0

Draftstopping at bathtubs, chases, behind the 

fireplace, and knee walls of exercise room 

and sealing of all penetrations

$600 $75 8 yrs

Floor joists switched from engineered 

wood to open web floor joists for ducts in 

conditioned space

$3000 $395 11.9 yrs

Engineered HVAC with 14 SEER, 92% AFUE 

and variable speed blower on two systems

$1000

Heat recovery ventilator $700

Tankless, gas-fired water heater $500 $86 5.8 yrs

Energy-efficient lighting and appliances $350 $243 1.4 yrs

PV Generation $5,000 

(after rebates)

$389 12.8 yrs

“We started building ENERGY STAR five 

years ago. For the past two years we’ve 

built 50% to 55% better than code, 

almost twice as energy efficient as the 

New Jersey ENERGY STAR requirements 

(which is 30% better than state code). 

We offer these energy-efficient features 

standard on all our homes. With solar 

added, our houses are getting energy 

savings of 60% plus,” said Bergman.

New Jersey builder Mark Bergman

Estimated costs, savings, and paybacks for efficiency improvements recommended 

by IBACOS for pilot house over builders’ standard practice 

(from a June 2004 report by IBACOS)

For more information visit: 

www.buildingamerica.gov
Building America Best Practices Series for High-Performance Technologies: Solar Thermal & Photovoltaic Systems - JUNE 2007 APPENDIX I / p.1

High-Performance Home Technologies: 

Solar Thermal & Photovoltaic Systems

Appendix I:

PV System Installation Checklist

Courtesy of ConSol

Building America Best Practices Series

ConSol leads the Building Industry Research Alliance, one of seven Building America consortia. 

For a complete listing of consortia and contact information see the back cover. 
Bringing you a prosperous future where energy is clean, abundant, reliable, and affordable

A Strong Energy Portfolio 

for a Strong America

Energy efficiency and clean, renewable 

energy will mean a stronger economy, 

a cleaner environment, and greater 

energy independence for America. 

Working with a wide array of state, 

community, industry, and university 

partners, the U.S. Department of 

Energy’s Office of Energy Efficiency 

and Renewable Energy invests in a 

diverse portfolio of energy technologies.

Research and Development 

of Buildings

Our nation’s buildings consume more 

energy than any other sector of the 

U.S. economy, including transportation 

and industry. Fortunately, the opportunities to reduce building energy use—

and the associated environmental 

impacts—are significant.

DOE’s Building Technologies Program 

works to improve the energy efficiency 

of our nation’s buildings through innovative new technologies and better 

building practices. The program

focuses on two key areas:

• Emerging Technologies 

Research and development of the 

next generation of energy-efficient 

components, materials, and 

equipment

• Technology Integration

Integration of new technologies 

with innovative building methods 

to optimize building performance 

and savings

For more information contact:

EERE Information Center

1-877-EERE-INF (1-877-337-3463)

www.eere.energy.gov

An electronic copy of this publication is 

available on the Building America Web 

site at www.buildingamerica.gov

U.S. Department of Energy

Energy Efficiency

and Renewable Energy

Building America Program

George S. James • New Construction • 202-586-9472 • fax: 202-586-8134 • e-mail: George.James@ee.doe.gov

Terry Logee • Existing Homes • 202-586-1689 • fax: 202-586-4617 • e-mail: terry.logee@ee.doe.gov

Lew Pratsch • Integrated Onsite Power • 202-586-1512 • fax: 202-586-8185 • e-mail: Lew.Pratsch@hq.doe.gov

Building America Program • Office of Building Technologies, EE-2J • U.S. Department of Energy • 1000 Independence Avenue, S.W. • 

Washington, D.C. 20585-0121 • www.buildingamerica.gov

Building Industry Research Alliance (BIRA)

Robert Hammon • ConSol • 7407 Tam O’Shanter Drive #200 • Stockton, CA 95210-3370 • 209-473-5000 • fax: 209-474-0817 • 

e-mail: Rob@consol.ws • www.bira.ws

Building Science Consortium (BSC)

Betsy Pettit • Building Science Consortium (BSC) • 70 Main Street • Westford, MA 01886 • 978-589-5100 • fax: 978-589-5103 • 

e-mail: Betsy@buildingscience.com • www.buildingscience.com

Consortium for Advanced Residential Buildings (CARB)

Steven Winter • Steven Winter Associates, Inc. • 50 Washington Street • Norwalk, CT 06854 • 203-857-0200 • fax: 203-852-0741 • 

e-mail: swinter@swinter.com • www.carb-swa.com

Davis Energy Group

David Springer • Davis Energy Group • 123 C Street • Davis, CA 95616 • 530-753-1100 • fax: 530-753-4125 •

e-mail: springer@davisenergy.com • deg@davisenergy.com • www.davisenergy.com/index.html

IBACOS Consortium

Brad Oberg • IBACOS Consortium • 2214 Liberty Avenue • Pittsburgh, PA 15222 • 412-765-3664 • fax: 412-765-3738 •

e-mail: boberg@ibacos.com • www.ibacos.com

Industrialized Housing Partnership (IHP)

Subrato Chandra • Florida Solar Energy Center • 1679 Clearlake Road • Cocoa, FL 32922 • 321-638-1412 • fax: 321-638-1439 • 

e-mail: subrato@fsec.ucf.edu • www.baihp.org

National Association of Home Builders (NAHB) Research Center

Tom Kenney • National Association of Home Builders (NAHB) Research Center • 400 Prince George’s Boulevard • 

Upper Marlboro, MD 20774 • 301-430-6246 • fax: 301-430-6180 • toll-free: 800-638-8556 • www.nahbrc.org/ 

National Renewable Energy Laboratory

Ren Anderson • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7433 • fax: 303-384-7540 • 

e-mail: ren_anderson@nrel.gov • www.nrel.gov

Tim Merrigan • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7349 • fax: 303-384-7540 • 

e-mail: tim_merrigan@nrel.gov • www.nrel.gov

Oak Ridge National Laboratory

Pat M. Love • P.O. Box 2008 • One Bethel Valley Road • Oak Ridge, TN 37831 • 865-574-4346 • fax: 865-574-9331 • 

e-mail: lovepm@ornl.gov • www.ornl.gov

Pacific Northwest National Laboratory

Michael Baechler • 620 SW 5th, Suite 810 • Portland, OR 97204 • 503-417-7553 • fax: 503-417-2175 • 

e-mail: michael.baechler@pnl.gov • www.pnl.gov

Produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory, a DOE national laboratory.

June 2007 • NREL/TP-550-41085

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June 2007 

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Technical Report 

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4. TITLE AND SUBTITLE

Building America Best Practices Series High-Performance Home 

Technologies: Solar Thermal & Photovoltaic Systems 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

M. Baechler and P. Love 

5d. PROJECT NUMBER

NREL/TP-550-41085 

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BET78004 

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Pacific Northwest National Laboratory 

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Richland, WA 

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Oak Ridge National Laboratory 

1 Bethel Valley Road 

Oak Ridge, TN 37831 

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PNNL-16382 

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National Renewable Energy Laboratory 

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Golden, CO 80401-3393 

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NREL 

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NREL/TP-550-41085 

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National Technical Information Service 

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14. ABSTRACT (Maximum 200 Words)

This document is the sixth volume of the Building America Best Practices Series. It presents information that is useful 

throughout the United States for enhancing the energy efficiency practices in the specific climate zones that are 

presented in the first five Best Practices volumes. It provides an introduction to current photovoltaic 

and solar thermal building practices. Information about window selection and shading is included. 

15. SUBJECT TERMS

building america; best practices; photovoltaic; solar thermal; climate zones 

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