Retrofitting Vegas: Implementing 

Energy Efficiency in Two Las 

Vegas Test Homes

S. Puttagunta

Consortium for Advanced Residential Buildings

April 2013
NOTICE

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 any of their employees, subcontractors, or affiliated partners 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. The views and opinions of authors expressed herein do not 

necessarily state or reflect those of the United States government or any agency 

thereof.

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
iii

Retrofitting Vegas: Implementing Energy Efficiency in 

Two Las Vegas Test Homes

Prepared for: 

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program 

Office of Energy Efficiency and Renewable Energy 

15013 Denver West Parkway 

Golden, CO 80401 

NREL Contract No. DE-AC36-08GO28308 

Prepared by: 

S. Puttagunta 

Steven Winter Associates, Inc.

of the 

Consortium for Advanced Residential Buildings 

61 Washington Street 

Norwalk, CT 06854 

NREL Technical Monitor: Cheryn Metzger 

Prepared under Subcontract No. KNDJ-0-40342-00 

April 2013 
iv

(This page left blank)
v 

Contents

List of Figures ............................................................................................................................................ vi

List of Tables ............................................................................................................................................. vii

Definitions ................................................................................................................................................. viii

Executive Summary................................................................................................................................... ix

Acknowledgments ...................................................................................................................................... x

1 Introduction ........................................................................................................................................... 1

1.1 Carmen .................................................................................................................................2

1.1.1 Building Envelope ...................................................................................................3

1.1.2 Mechanical Equipment ............................................................................................6

1.2 Sierra Hills ...........................................................................................................................8

1.2.1 Building Envelope ...................................................................................................9

1.2.2 Mechanical Equipment ..........................................................................................11

2 Research Goals................................................................................................................................... 13

3 Design Specifications and Energy Modeling................................................................................... 14

3.1 Carmen ...............................................................................................................................14

3.2 Sierra Hills .........................................................................................................................16

4 Implementation ................................................................................................................................... 19

4.1 Air Sealing .........................................................................................................................20

4.2 Heating, Ventilation, and Air Conditioning .......................................................................23

4.2.1 Carmen ...................................................................................................................25

4.2.2 Sierra Hills .............................................................................................................28

5 Final Performance Modeling ............................................................................................................. 32

5.1 Carmen ...............................................................................................................................32

5.2 Sierra Hills .........................................................................................................................35

6 Cost Analysis...................................................................................................................................... 39

7 Conclusions ........................................................................................................................................ 44

References................................................................................................................................................. 46
vi 

List of Figures

Figure 1. Projected foreclosure rates by state......................................................................................... 1

Figure 2. Exterior photo of the Carmen home.......................................................................................... 2

Figure 3. Ceiling leakage points at the Carmen home ............................................................................ 4

Figure 4. Top plate of interior walls cut out for electrical runs into partition walls............................. 4

Figure 5. Discovery of poor insulation in the kitchen kneewall............................................................. 5

Figure 6. Haze between the window panes is evidence of a broken hermetic seal............................. 6

Figure 7. Lack of air sealing around exterior doors ................................................................................ 6

Figure 8. From left clockwise: supply plenum located in the vented attic, roof-mounted packaged 

furnace/AC, and insulation unwrapping from flex duct because the exterior vapor barrier had 

deteriorated........................................................................................................................................... 7

Figure 9. Atmospheric gas water heater located in the attached garage ............................................. 8

Figure 10. Exterior photo of the Sierra Hills home .................................................................................. 8

Figure 11. (Left) Top plate corner leakage; (center) kitchen exhaust ducting through interior wall 

without backdraft damper; (right) leakage around garage door from lack of weather stripping . 9

Figure 12. Leakage in ceiling plane......................................................................................................... 10

Figure 13. Poor insulating of partially vaulted ceiling kneewalls ........................................................ 10

Figure 14. Interior wall cavities that are directly communicating with the attic................................. 11

Figure 15. Rooftop packaged furnace/AC located at the Sierra Hills home ....................................... 12

Figure 16. Atmospheric water heater located in the garage of the Sierra Hills home ....................... 12

Figure 17. Specification optimization analysis during the design stages of the Carmen home ...... 16

Figure 18. Specification optimization analysis during the design stages of the Sierra Hills home . 18

Figure 19. Field training flyer................................................................................................................... 20

Figure 20. Examples of air sealing at the Carmen home ...................................................................... 21

Figure 21. Existing package furnace/AC unit being craned off of the Sierra Hills home .................. 23

Figure 22. New outdoor heat pump unit being installed at the Sierra Hills home.............................. 24

Figure 23. Spot ERVs installed in both homes to provide balanced whole-house ventilation......... 24

Figure 24. The radial HVAC design for the Carmen home.................................................................... 26

Figure 25. Radial HVAC system as installed at the Carmen home ...................................................... 26

Figure 26. Mastic being applied to inside of flexduct jacket before being slipped over and secured 

to a branch takeoff elbow with compression bands....................................................................... 27

Figure 27. Initial radial HVAC design for the Sierra Hills home ........................................................... 29

Figure 28. Relocating pressure boundary to bring ductwork into conditioned space. On the left is 

the existing configuration; the right image shows the new configuration................................... 30

Figure 29. Pressure boundary being moved up to the bottom of the scissor trusses to allow ducts 

to remain within the building envelope............................................................................................ 30

Figure 31. Final energy savings prediction for the Carmen home ...................................................... 34

Figure 32. Cumulative contribution to total energy savings, by measure and end use, for the 

Carmen home...................................................................................................................................... 35

Figure 33. Final energy savings prediction for the Sierra Hills home ................................................. 37

Figure 34. Cumulative contribution to total energy savings, by measure and end use, for the Sierra 

Hills home............................................................................................................................................ 38

Unless otherwise noted, all figures were created by CARB.
vii 

List of Tables

Table 1. Final Estimated Performance of the Carmen and Sierra Hills Homes ................................... ix

Table 2. Existing Conditions at the Carmen Home.................................................................................. 3

Table 3. Existing Conditions at the Sierra Hills Home ............................................................................ 9

Table 4. Inputs of Economic Analysis .................................................................................................... 14

Table 5. BA Proposed Specifications at the Carmen Home ................................................................. 15

Table 6. BA Proposed Specifications at the Sierra Hills Home............................................................ 17

Table 7. BA Revised Specifications at the Sierra Hills Home............................................................... 17

Table 8. Least Cost Optimization Specifications at the Sierra Hills Home ......................................... 18

Table 9. Air Sealing Results at the Carmen Home................................................................................. 22

Table 10. Air Sealing Results at the Sierra Hills Home ......................................................................... 22

Table 11. Air Balancing Results at the Carmen Home .......................................................................... 28

Table 12. Verification of Suitable Return Air Pathways at the Carmen Home.................................... 28

Table 13. Air Balancing Results at the Sierra Hills Home..................................................................... 31

Table 14. Verification of Suitable Return Air Pathways at the Sierra Hills Home............................... 31

Table 15. Pre- and Post-Retrofit HERS Indexes for the Vegas Retrofits............................................. 32

Table 16. Summary of Specifications at the Carmen Home ................................................................. 33

Table 17. Summary of Specifications at the Sierra Hills Home............................................................ 36

Table 18. Comparison of Annualized Energy-Related Costs Based on Length of Mortgage and 

Analysis Period................................................................................................................................... 39

Table 19. First Costs of Efficiency Measures at the Carmen Residence ............................................ 41

Table 20. First Cost of Efficiency Measures at the Sierra Hills Residence......................................... 42

Table 21. Final Estimated Performance of the Two Test Homes ......................................................... 44

Unless otherwise noted, all tables were created by CARB.
viii

Definitions

AC Air conditioner

ACH50 Air changes per hour at 50 Pascals

AFUE Annual fuel utilization efficiency

ASHP Air source heat pump

BA Building America

BARA Building America Retrofit Alliance

BEopt Building Energy Software

Btu/h British thermal units per hour.

CARB Consortium for Advanced Residential Building

CFL Compact fluorescent lamp

cfm Cubic feet per minute

EPS Expanded polystyrene foam

ERV Energy recovery ventilator

HERS Home Energy Rating System

HSPF Heating Season Performance Factor

HVAC Heating, Ventilation, and Air Conditioning

in. w.c. Inches of water column

IR Infrared

kWh Kilowatt-hour

LAMEL Lighting, appliances, and miscellaneous electric loads

LED Light-emitting diode

NSP Neighborhood Stabilization Program

RESNET Residential Energy Services Network

SEER Seasonal energy efficiency ratio

SPB Simple payback
ix

Executive Summary

In 2009, Nevada received nearly $40 million in Neighborhood Stabilization Program funds from 

the U.S. Department of Housing and Urban Development. The purpose of this funding was to 

stabilize communities that have suffered from foreclosures and abandonment. In an effort to 

provide guidance to local officials and maximize how effectively this Neighborhood 

Stabilization Program funding is used in retrofitting homes, the Consortium for Advanced 

Residential Buildings (CARB) provided design specifications, energy modeling, and technical 

support for the Building America Retrofit Alliance (BARA) team and its local partners—Better 

Building Performance, Nevada ENERGY STAR® Partners Green Alliance, and Home Free 

Nevada—for two retrofit test homes. One home was to demonstrate a modest retrofit and the 

other a deep energy retrofit.

The Carmen and Sierra Hills homes demonstrate how cost effectively energy-efficient upgrades 

can be implemented in the hot, dry Southwest climate. The homes were used as an educational 

experience for home performance professionals, building trades, remodelers, and the public. Infield trainings on air sealing, HVAC upgrades, and insulating were provided to local contractors 

during the retrofit. BARA documented these retrofits through a series of video presentations, 

beginning with a site survey and concluding with the finished remodel and test out. 

Through this project, CARB has provided two robust solution packages for retrofitting homes 

built in this region between the 1980s and early 1990s without substantially inconveniencing the 

occupants. The Building America solution packages for the two test homes were fairly similar

(though the Carmen home did have a solar thermal water heating system) and achieved the 

targeted energy savings (over the pre-retrofit home) of 30% or more at the Sierra Hills home and 

50% or more at the Carmen home. The lower savings level at the Sierra Hills home was 

primarily a result of mechanical equipment updates that were performed over the past decade.

The final estimated performance of these homes is summarized in Table 1. 

Table 1. Final Estimated Performance of the Carmen and Sierra Hills Homes

Home

Source 

Energy 

Savings

Annual 

Utility 

Savingsa

Annualized 

Energy Related 

Cost Savingsb

Home Energy Rating 

System Index

Pre-Retrofit Post-Retrofit

Carmen 51% $1,138 $845 126 66

Sierra Hills 34% $480 $321 98 61 a $0.1175/kWh +$10 monthly charge, $0.7666/therm + $9 monthly charge

b 30-year mortgage, 4.0% loan interest rate, 1.6% inflation rate, 3.0% discount rate (real), 0% fuel 

escalation rate

The solution packages focused on air sealing the building envelope where accessible and 

replacing windows with double-pane low-e retrofit windows. This reduced solar heat gain and 

allowed rough openings to be better air sealed. Another essential strategy was to simplify the 

design and distribution of the high efficiency HVAC systems for optimum system performance. 

This included bringing the ductwork into conditioned space. 
x 

Acknowledgments

Steven Winter Associates, Inc. acknowledges the U.S. Department of Energy Building America 

program and its funding and support of development of this technical report as well as research 

that informed it. A special thanks to Annette Bubak, Brandon Kephart, and Kelly Thomas of 

Better Building Performance, Richard Chitwood of Chitwood Energy Management, and Darren 

Harris, Tami Svarfar, and Don Whipple of the BARA team.
1 

1 Introduction

In 2009, Nevada received almost $40 million in Neighborhood Stabilization Program (NSP) 

funds from the U.S. Department of Housing and Urban Development to stabilize communities 

that have suffered from foreclosures and abandonment. Nevada suffered the highest rates of 

foreclosure in the nation between 2008 and 2009 (see Figure 1). 

Figure 1. Projected foreclosure rates by state

Nevada used this funding to develop a renovation program that purchases foreclosed properties, 

performs audits on the homes to assess code compliance, energy efficiency, and health issues, 

and implements the recommended repairs from these inspections. These homes are then resold to 

qualifying buyers or held by housing authorities for rental.

A key change in the program requirements since 2011 was a focus on neighborhood-scale 

retrofits. The program requires that multiple homes in the same neighborhood be retrofitted. 

Tens of thousands of homes were built in this region over the past decades with hardly a nod 

toward energy efficiency. With a desire to make these homes affordable (low first cost) and 

sustainable (low operational costs), the focus has shifted from finishes, aesthetics, and curb 

appeal to home performance. Over the years, the U.S. Department of Energy’s Building America

(BA) program has provided support for this performance-based, whole-house remodeling 

approach and has educated the industry and homeowners about economically sound measures 

and strategies that result in energy-efficient, healthy, comfortable, and durable homes. 

In an effort to maximize how effectively this NSP funding is used to retrofit homes, the 

Consortium for Advanced Residential Buildings (CARB) provided design specifications, energy 

modeling, and technical support for the Building America Retrofit Alliance (BARA) team and its 

local partners—Better Building Performance, Nevada ENERGY STAR® Partners Green 

Alliance, and Home Free Nevada—for two retrofit test homes. Two homes in the Las Vegas 
2 

NSP were selected as test homes to demonstrate how cost-effective energy efficiency upgrades 

could be incorporated into these retrofits. These two demonstration homes were used as an 

educational experience for home performance professionals, building trades, remodelers, and the 

public. In-field trainings on air-sealing, heating, ventilation, and air conditioning (HVAC) 

upgrades, and insulating were provided to local contractors during the retrofit. BARA 

documented these retrofits through a series of video presentations, beginning with a site survey 

and concluding with the finished remodel and test out. 

The two test homes, the Carmen and Sierra Hills, are located in an area with one of the greatest 

number and highest percentage of foreclosed homes in the city. In this area, more than 11% of 

the existing housing stock is in foreclosure, equating to more than 8,100 homes, many of which 

are vacant or abandoned. 

The original scopes of work and cost estimates for the proposed NSP retrofits of these two 

homes were provided to CARB. After doing an initial energy audit of both homes, CARB 

performed energy modeling of the home conditions, the NSP proposed specifications, and CARB 

recommended specifications to achieve 30%–50% source energy savings over the existing 

conditions. Though some structural and cosmetic improvements were also included, this effort 

focused on the energy improvements and associated costs. 

1.1 Carmen

The Carmen home is a 1,521-ft2

 ranch built in 1983. This single-family detached home has three 

bedrooms, two baths, and an attached garage. At the height of the housing boom, it was valued 

as high as $285,000,1

 but now its estimated value is $97,400.2 The price range for homes in this 

neighborhood is $70,000–$130,000. The home was dated, but its overall condition was livable

after a thorough cleaning and repair of a couple broken windows. 

Figure 2. Exterior photo of the Carmen home

 

1 Based on information from www.zillow.com for July 2006. 2 Based on information from www.zillow.com for February 2012.
3 

Table 2 provides a summary of the Carmen home’s conditions. 

Table 2. Existing Conditions at the Carmen Home

Building Component Existing Condition

Foundation Slab-on-grade, uninsulated

Above-Grade Walls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III)

Attic Vented attic (gable vents), R-24 fiberglass batts (grade III) at 

ceiling plane

Kneewalls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III)

Windows Aluminum double pane, clear (assumed U-0.76, SHGCa

-0.67)

Cooling 

Roof-mounted Carrier packaged forced air furnace with cooling unit 

(Model 48KL042300BE), 40.5 kBtu/h cooling capacity, 

R-22 refrigerant, SEERb 8.5/EERc 8.0 (poorly maintained)

Heating

Roof-mounted Carrier packaged forced air furnace with cooling unit 

(Model 48KL042300BE), 60 kBtu/h heating input, natural gas, 76% 

AFUEd (poorly maintained)

Ductwork R-2 ductwork in vented attic, exterior vapor barrier in poor condition 

and unwrapping in various locations

Ventilation Kitchen exhausted to exterior and bathroom exhaust fans

Hot Water 

Reliance 50-gal atmospheric water heater, natural gas, 

0.55 EFe (Model 8 50 NKRTO, tank likely replaced in 1997 

based on serial number)

Lighting Mostly incandescent light bulbs except fluorescent 

lighting in kitchen

Appliances Original Tappan appliances from 1980s a SHGC = solar heat gain coefficient

b SEER = seasonal energy efficiency ratio

c EER = energy efficiency ratio

d AFUE = annual fuel utilization efficiency 

e EF = energy factor

1.1.1 Building Envelope

The Carmen home uses 2 × 4 wood framing at 16 in. on center with R-11 fiberglass batt cavity 

insulation. This was not a gut rehab, so the wall insulation was evaluated using infrared (IR) 

thermal imaging. There was the typical leakage commonly found in residential homes. Figure 3

provides an overview of the various leakage points between the conditioned living space and the 

attic.
4 

Figure 3. Ceiling leakage points at the Carmen home

IR thermal imaging revealed that many of the interior uninsulated partition walls were 

communicating with the attic. Penetrations in the top plates to accommodate electrical wiring 

were the most common culprit for this leakage pathway. Figure 4 shows two instances in which 

electrical wiring resulted in interior wall cavities that directly communicated with the attic air. 

These sections were not air sealed, and often did not have ceiling insulation, because it had been 

pulled or cut back. 

 

Figure 4. Top plate of interior walls cut out for electrical runs into partition walls

The ceiling insulation was Kraft-faced fiberglass batts installed with inset stapling. This was 

done for ease of installation before the ceiling drywall was installed. Unfortunately, this 

installation technique creates an air space between the ceiling drywall and the insulation. If air 

does not move in this space, it can be beneficial in terms of thermal resistance, but that is nearly 
5 

impossible to accomplish. The result was ceiling insulation that was performing significantly 

worse than its rated R-value because of the convective airflow cavity.

In general, kneewalls were performing poorly, mostly because unsupported batts had been 

dislodged, leaving uninsulated vertical bays. Figure 5 shows the kneewall at the transition from 

the kitchen to dining room. The IR camera showed that the bay to the left of the supply register 

had surface temperatures close to the attic temperature. Further investigation in the attic revealed 

that this section of the kneewall was not insulated because the fiberglass batt had fallen down. 

The whole top portion of this kneewall is hot, because all the batts are poorly installed and attic 

air is leaking between the batt and drywall, significantly reducing the insulation’s performance. 

Figure 5. Discovery of poor insulation in the kitchen kneewall

The window in the front corner bedroom was broken and temporarily boarded up. Further 

inspection revealed that the hermetic seal of several dual-pane windows had been compromised. 

This broken seal creates a pathway for moist air to enter this dead air space. When the window 

Missing kneewall 

insulation

Air conditioning being 

supplied at high-wall 

register

Air leaking between 

insulation and drywall
6 

surface temperature is lower than the dew point of the air, condensation forms. Over time, 

mineral deposits and a permanent white silica haze are visible (see Figure 6). 

Figure 6. Haze between the window panes is evidence of a broken hermetic seal

When door trim was removed, there was no evidence of prior air sealing between the exterior 

door jamb and the rough opening (Figure 7). This is a common source of air infiltration. In some 

instances, fiberglass batts are stuffed into this opening. This adds some slight insulation value, 

but is still not an air barrier.

Figure 7. Lack of air sealing around exterior doors 

(Image courtesy of Building Media, Inc.) 

1.1.2 Mechanical Equipment

The original HVAC system in the Carmen home was a packaged furnace/air conditioner (AC) 

located on the rear roof. It was more than 28 years old; its effective life expectancy is anticipated 

to be 15–18 years, so it was well past due for a replacement.

This furnace unit had a heating capacity of 60 kBtu/h with a seasonal gas heating efficiency of 

76% AFUE. On the cooling side, this 3.5-ton AC had a seasonal energy efficiency ratio (SEER) 
7 

rating of 8.5 but was poorly installed and maintained, so the actual delivered efficiency was 

likely closer to an equivalent SEER 5 equipment rating. Ductwork was run from this exterior unit 

through the roof deck and was distributed throughout the home through ceiling registers located 

in the vented attic. The flexible ductwork was in very poor condition with significant 

deterioration of the exterior vapor barrier and in some instances, the insulation had unwrapped 

from the inner duct liner. Images of this HVAC system are shown in Figure 8. 

The domestic hot water system is a 50-gal atmospheric, natural gas water heater located in the 

attached garage. The rated EF for this unit is 0.55. Based on its serial number, it was likely 

replaced in 1997. Though not original to the home, this unit is past its effective life expectancy 

of 11–13 years. 

Figure 8. From left clockwise: supply plenum located in the vented attic, roof-mounted 

packaged furnace/AC, and insulation unwrapping from flex duct because the exterior vapor 

barrier had deteriorated
8 

Figure 9. Atmospheric gas water heater located in the attached garage

1.2 Sierra Hills

The Sierra Hills home is a 1,131-ft2

 ranch built in 1991. This single-family detached home has 

two bedrooms, two baths, and an attached garage. Though dated, the overall condition of the 

home was livable and better than the Carmen home. At the height of the housing boom, this 

home was valued as high as $256,000,3

 but now its estimated value is $79,100.4 As this home is 

only half a mile from the Carmen home, the neighborhood price range is the same ($70,000–

$130,000). 

Figure 10. Exterior photo of the Sierra Hills home 

Table 3 provides a summary of the conditions in the Sierra Hills home. 

 

3 Based on information from www.zillow.com for March 2007. 4 Based on information from www.zillow.com for February 2012.
9 

Table 3. Existing Conditions at the Sierra Hills Home

Building Component Existing Condition

Foundation Slab-on-grade, uninsulated

Above-Grade Walls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III) + 

1 in. EPS* foam

Attic Vented attic (gable vents), R-24 fiberglass batts (grade III) at 

ceiling plane

Kneewalls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III)

Windows Aluminum double pane, clear (assumed U 0.76, SHGC 0.67)

Cooling 

Roof-mounted Tempstar packaged forced air furnace with cooling 

unit (Model PGF336060K00A1), 35 kBtu/h cooling capacity, 

R-22 refrigerant, SEER 13/EER 11

Heating

Roof-mounted Tempstar packaged forced air furnace with cooling 

unit (Model PGF336060K00A1), 60 kBtu/h heating input, natural 

gas, 79.6% AFUE

Duct Work R-4 ductwork in vented attic

Ventilation Kitchen exhausted to exterior and bathroom exhaust fans

Hot Water GE 40-gal atmospheric water heater, natural gas, 0.56 EF (Model 

GG40T6A, tank likely replaced in 2000 based on serial number)

Lighting Mostly incandescent light bulbs except fluorescent lighting in 

kitchen

Appliances Original General Electric appliances from 1990s * EPS = expanded polystyrene

1.2.1 Building Envelope

This home uses 2 × 4 wood framing at 16 in. on center with R-11 fiberglass batt cavity insulation

and 1 in. of EPS on the exterior. This was not a gut rehab, so the wall insulation was evaluated 

using IR thermal imaging. There were the air bypasses typically found in existing homes at the 

top and bottom plates, around windows and doors, and at penetrations of lights, smoke alarms, 

registers, and attic hatches in the ceiling plane. The IR images in Figure 11 and Figure 12 show 

that the surface temperature variation across the drywall was approaching 15°F. 

Figure 11. (Left) Top plate corner leakage; (center) kitchen exhaust ducting through interior wall

without backdraft damper; (right) leakage around garage door from lack of weather stripping 
10 

Figure 12. Leakage in ceiling plane 

(Image courtesy of Building Media, Inc.) 

Even though the kneewalls in this home were better than the Carmen home, there still were some 

issues (see Figure 13). Whenever there is complicated framing, batt insulation is difficult to 

install effectively. In addition, to achieve the rated performance of the batt insulation, an attic 

side air barrier should be included to minimize air movement through or around the insulation. 

Once again, the framing evidenced in Figure 13 would make establishing a continuous attic side 

air barrier challenging. 

Figure 13. Poor insulating of partially vaulted ceiling kneewalls 

(Image courtesy of Building Media, Inc.) 
11 

Compared to the Carmen home, the Sierra Hills home has more variation in the ceiling plane 

with a mix of flat and semi-vaulted ceilings throughout the home. This has led to several interior 

wall cavities directly communicating with the attic air (Figure 14). 

Figure 14. Interior wall cavities that are directly communicating with the attic 

(Image courtesy of Building Media, Inc.) 

1.2.2 Mechanical Equipment

The HVAC system for the Sierra Hills home was a packaged furnace/AC located on the rear 

roof. It was anticipated that the HVAC equipment would be comparable to the Carmen house 

system, but the packaged HVAC system was likely replaced in late 2007 or early 2008 (verified 

with the serial number on the unit: G071141225). For Tempstar units, the second and third 

number/letter of the serial number represents the year the unit was manufactured and the next 

two numbers represent the week of the year. This was an unforeseen challenge, as the efficiency 

of this unit was not suitable to achieve the energy efficiency goals of this project. Also, more 

than 10 years of usable lifespan remained, so the cost benefit versus the incremental savings 

benefit was significantly minimized. 
12 

Figure 15. Rooftop packaged furnace/AC located at the Sierra Hills home

(Image courtesy of Building Media, Inc.) 

Domestic hot water was provided by an atmospheric 40-gal natural gas water heater. Again, the 

serial number (GENG 0700123945) of the water heater was used to estimate the install date of 

this equipment. For General Electric water heaters, the first two numbers refer to the month and 

the second two numbers refer to the year. So this unit was manufactured in July 2000. It was 

likely installed shortly after manufacturing, so the water heater was likely replaced in early 2001. 

Therefore, this unit has basically reached its effective life expectancy of 11–13 years. 

Figure 16. Atmospheric water heater located in the garage of the Sierra Hills home 

(Image courtesy of Building Media, Inc.) 
13 

2 Research Goals

The overarching question addressed by this research is: 

• What solution package(s) can be readily implemented in hot, dry climate homes to 

achieve a 30% plus and a 50% plus energy savings home compared to the BA B10 

Benchmark? 

More specific questions: 

• Is the selected solution package for each home commercially viable? Where are 

opportunities to reduce costs in these solution packages? 

• What are the specific gaps to achieving the solution package at a production scale (cost, 

risk adversity, implementation complexity, etc.)? 

Questions specific to this study: 

• Based on the results of these test homes, what other energy efficiency measures and 

solution packages should be considered? 

• What are the market interest and consumer reactions, developer and builder reactions and 

feedback loops, and stakeholder enthusiasm for replicating the package? 

• How effectively does each energy efficiency measure meet its specific cost and 

performance targets? How effective is each when integrated into a whole-house 

package?
14 

3 Design Specifications and Energy Modeling

All energy modeling was performed using BEopt (Building Energy Optimization) v1.2 software 

developed by the National Renewable Energy Laboratory. For the economic analysis, the 

economic values in Table 4 were used. In general, the NSP scopes of work focus on HVAC 

equipment, water heaters, kitchen appliances, and updating finishes (paint, caulk, etc.). The NSP 

replacement equipment typically meets or slightly exceeds the federal minimum efficiency 

levels.

Table 4. Inputs of Economic Analysis

Economic Variables Modeling Inputs

Project Analysis Period 15 years

Inflation Rate 1.6%

Discount Rate (Real) 3.0%

Loan Period 15 years

Loan Interest Rate 4.0%

Electricity Rate – NV Energy $0.1175/kWh + $10.00 monthly charge

Natural Gas Rate – Southwest Gas $0.7666/therm + $9.00 monthly charge

Fuel Escalation Rate 0.0%

3.1 Carmen

Based on the goals of achieving 50% source energy savings over the pre-retrofit performance of 

the Carmen home, CARB performed optimization analysis. The primary focus was on air sealing 

the building shell and bringing efficient HVAC equipment within the building envelope. Based 

on the optimization analysis, the following specifications (see Table 5) were proposed to the 

project team. The building infiltration target for this home was 4.5 ACH50. The base proposed 

specifications resulted in a 52.2% source energy savings over the pre-retrofit conditions. If a 

solar thermal system is included, the source energy savings increases to 53.9%. 

Because the first costs of solar thermal systems are quite high, the hot water system was 

evaluated with and without this feature. In addition, programmable thermostats that are set back 

or up during the workday and overnight were included as an additional option. Numerous studies 

(such as Gunshinan 2007) conclude that programmable thermostats do not save money, because 

homeowners do not know—or care to know—how to properly set their schedules. Therefore, the 

project team wanted to have the proposed base package meet the efficiency targets even if these 

two items were not incorporated. 
15 

Table 5. BA Proposed Specifications at the Carmen Home

Building Component Proposed Upgrade

Above-Grade Walls Air seal any penetrations in exterior walls with spray foam

Attic Unvented attic, R-30 closed cell spray polyurethane foam 

at roof deck

Windows Simonton vinyl double pane, low-e retrofit windows 

(U 0.26, SHGC 0.23)

Cooling/Heating

Lennox XP21-024 ASHPa with CBX40UHV-036 air handler (SEER 

18.5/9.2 HSPFb), 25.6 kBtu/h cooling capacity, 24.2 kBtu/h heating 

capacity, R-410A refrigerant with TXVc valve

Ductwork Compact distribution design, R-6 ductwork in unvented attic, sealed 

with mastic

Ventilation

Kitchen and bathroom fans exhausted to exterior, Panasonic 

WhisperGreen 80 cfm fans with delay off timers in bathrooms, 

Panasonic WhisperComfort spot ERVd

Hot Water Solar thermal water heating system (40 ft2 of collectors) with 80-gal 

preheat tank with tankless water heater backup (0.84 EF)

Lighting All CFLs

e or LEDsf

Appliances ENERGY STAR appliances a ASHP = air source heat pump

b HSPF = heating seasonal performance factor

c TXV = thermostatic expansion valve

d ERV = energy recovery ventilator e CFL = compact fluorescent lamp

f LED = light-emitting diode
16 

Figure 17. Specification optimization analysis during the design stages of the Carmen home

3.2 Sierra Hills 

With a source energy savings target of 30%, the Sierra Hills project can more effectively be 

adopted in hot, dry climate zone, such as the Las Vegas retrofit market. The Sierra Hills 

specifications were geared to efficiency improvements that can be made to existing homes 

without disrupting or substantially inconveniencing the occupants. Based on the optimization 

analysis, the specifications in Table 6 were proposed to the project team. The building infiltration 

target for this home was 4.0 ACH50. The base proposed specifications resulted in a 30.6% 

source energy savings. Nearly identical efficiency savings would be achieved with a mini-split 

heat pump HVAC system. 
17 

Table 6. BA Proposed Specifications at the Sierra Hills Home

Building Component Proposed Upgrade

Above-Grade Walls Air seal any penetrations in exterior walls with spray foam

Attic Vented attic, R-49 blown insulation at ceiling plane

Windows Apply low-e film to existing windows (SHGC 0.43)

Cooling/Heating

Mitsubishi mini-split heat pump MXZ-4A36NA (SEER 16/8.5 

HSPF) + 4 MSZ-(A,FD) indoor units (9,9,9,9), 35.4 kBtu/h cooling 

capacity, 36.0 kBtu/h heating capacity, R-410A refrigerant

Ductwork –

Ventilation

Kitchen and bathroom fans exhausted to exterior, Panasonic 

WhisperGreen 80 cfm fans with delay off timers in bathrooms, 

Panasonic WhisperComfort spot ERV

Hot Water Natural gas premium tank water heater (0.67 EF)

Lighting All CFLs or LEDs

Appliances ENERGY STAR appliances

After discussions with the project team, a couple changes were made to the design specifications 

(see Table 7). There was concern about the durability of the low-e film on the existing windows. 

Therefore, more expensive double-pane, low-e replacement windows were specified. The project 

team was also concerned about the aesthetics of the wall-mounted mini-split heat pumps and 

chose a more conventional ducted HVAC system. To minimize the energy impact of having an 

HVAC system in the vented attic, the air handler was to be located in a closet of the secondary 

bedroom. The new distribution ductwork would still be located in the vented attic, but would be 

properly air sealed with mastic and insulated with R-8 duct insulation. 

Table 7. BA Revised Specifications at the Sierra Hills Home

Building Component Proposed Upgrade

Windows Simonton vinyl double-pane, low-e retrofit windows 

(U 0.26, SHGC 0.24)

Cooling/Heating

Lennox XP17-024 ASHP with CBX40UHV-036 air handler (SEER 

17.2/9.5 HSPF), 25.2 kBtu/h cooling capacity, 22.4 kBtu/h heating 

capacity, R-410A refrigerant with TXV valve

Ductwork Compact distribution design, R-8 ductwork in vented attic, 

sealed with mastic

If the minimum cost point on the BEopt optimization curve was the target, the specifications in 

Table 8 would replace those in Table 6 and Table 7. The lowest cost option with the same 

efficiency percentage would be achieved with no air sealing, a SEER 15/8.5 HSPF ASHP, and a 

tankless water heater. The fact that no air sealing is being advocated shows the limitations of 

modeling as the enhanced comfort achieved by minimizing drafts in the building are not 

accounted for in the annualized energy related cost. 
18 

Table 8. Least Cost Optimization Specifications at the Sierra Hills Home

Building Component Proposed Upgrade

Building Infiltration No air sealing efforts

Attic Less attic insulation, R-30 blown insulation at ceiling plane

Windows Keep original clear, double-pane windows

Hot Water Natural gas tankless water heater (0.84 EF)

Figure 18. Specification optimization analysis during the design stages of the Sierra Hills home

After completing this retrofit, the project team is now considering evaluating mini-split heat 

pumps in its next retrofit project. The primary reason for this renewed interest was based on 

inquiries about the technology from tour visitors at the Carmen home. 
19 

4 Implementation

There is no better way of learning than by doing. Therefore, the project team partnered with 

Richard Chitwood, founder of Chitwood Energy Management, to provide five hands-on training 

sessions for local contractors. Mr. Chitwood is an expert in energy-efficient residential building 

construction, diagnostic testing, and performance evaluation. CARB worked with Mr. Chitwood 

on the content of the courses and what details to include in the training to ensure that the 

efficiency goals would be met. 

The five sessions focused on shell sealing, HVAC, and insulation. There were two shell sealing 

sessions, one at the Carmen home and one at the Sierra Hills home. Similarly, there were two 

HVAC sessions. There was only one insulation session at the Sierra Hills home, because the 

Carmen home used spray polyurethane foam that was installed by a local contractor. This 

insulation session was essentially a follow-up to the air sealing session and focused on insulating 

kneewalls and vented attics. Also, there was training on maintaining proper ventilation in vented 

attics through the proper installation of baffles that allow airflow from soffit to rigid vent, even 

when high levels of ceiling insulation are installed. 
20 

Figure 19. Field training flyer

The BARA team documented the retrofits to the two selected homes through a series of short 

video presentations, beginning with the initial site survey and concluding with the test-out of the 

finished energy efficiency retrofits. 

4.1 Air Sealing 

Over the two-day air sealing sessions at each project home, the attendees worked with Mr. 

Chitwood to air seal all accessible openings, joints, and cracks to maintain a continuous pressure 
21 

boundary (see Figure 20). A blower door and an IR camera were used during the session to 

qualitatively identify air leakage pathways and to quantitatively measure the air sealing efforts. 

Figure 20. Examples of air sealing at the Carmen home

(Small images courtesy of Building Media, Inc.) 

Even though the Carmen home was to be insulated with closed cell spray polyurethane foam at 

the roof deck, the ceiling plane was still air sealed to minimize the transfer of air between the 

actively conditioned (living space) and unconditioned (attic) areas. When testing with the blower 

door, the pressure of the attic space was only one third the pressure of the rest of the home. 

Therefore, it did not significantly add to the conditioned volume that the HVAC system needs to 

address, but was still within the thermal envelope negating the thermal losses associated with 

being in a conventional vented attic. 

Table 9 and Table 10 provide the initial and final building infiltration test results, as well as the 

impact of specific leakage pathways to the overall leakage of these homes. As mentioned in 

Section 4, the Carmen home was targeting a building infiltration rate of 4.5 ACH50 and the 

Sierra Hills home was targeting a rate of 4.0 ACH50. Both homes were lower than the target 

goals at 3.2 ACH50. This level of building tightness is impressive in existing homes, considering 
22 

that the exterior walls were not touched other than sealing visible penetrations through them. 

This level of airtightness is 36% better than U.S. Environmental Protection Agency’s ENERGY 

STAR v3.0 Certified New Homes requirement of 5 ACH50 in climate zone 3. 

Table 9. Air Sealing Results at the Carmen Home

Building Component

Building 

Infiltration 

(CFM50)

CFM

Reduction

Test-In 2,241 (9.8 ACH50) –

Range Hood Sealed 2,099 142

Dryer Vent Sealed 2,052 47

Door to the Garage Sealed 1,806 246

Fireplace Sealed 1,623 183

Front Door Sealed 1,271 352

Laundry Room Exhaust Fan & Attic Hatch 1,205 66

Patio Door Sealed 1,199 6

Miscellaneous Electrical and Plumbing Leaks Sealed 1,134 65

Converting to Unvented Attic and Replacing the 

Existing Windows 725 409 

Test-Out 725 (3.2 ACH50) –

Table 10. Air Sealing Results at the Sierra Hills Home

Building Component

Building 

Infiltration 

(CFM50)

CFM 

Reduction

Test-In 1,043 (6.1 ACH50) -

Range Hood Sealed 1,006 37

Door to the Garage Sealed 966 40

Front Door Sealed 897 69

Three Exhaust Fans Sealed 798 99

Attic Hatch 752 46

Patio Door Sealed 729 23

Miscellaneous Electrical and Plumbing Leaks Sealed 605 124

Replacing the Existing Windows 590 15

Test-Out 590 (3.2 ACH50) –

Additional leakage testing was performed to see how well the garages were isolated from the 

living space to minimize the potential for carbon monoxide from cars and atmospheric natural 

gas water heaters from entering the homes. Using a guarded blower door method to bring the 

garage to the same building pressure (50 Pascals) as the home, the leakage between the garage 

and living space can be determined. The leakage in this interstitial wall was minimal in both 

homes. For the Carmen home, only 8 cfm50 was associated with leakage to and from the garage.

For the Sierra Hills home, 37 cfm50 was associated with leakage to and from the garage. 
23 

4.2 Heating, Ventilation, and Air Conditioning

CARB provided the HVAC design for both homes using the Air Conditioning Contractors of 

America’s Manual J (room-by-room load calculations), Manual S (equipment sizing and 

selection), Manual T (air distribution design), and Manual D (ductwork sizing). The initial 

designs focused on compact distribution systems based on a central trunk and branch system. 

Based on typical regional installation practices, this was redesigned to a radial system with each 

supply duct running back to the supply plenum. Manual dampers were specified for each supply 

duct run so the system could be balanced after startup.

Another common regional practice is the use of a furnace/AC HVAC system combination, but 

this made little sense because the heating demand for homes in this climate is low. CARB 

recommended switching to ASHPs to provide cooling and heating through a vapor compression 

cycle. This also allows the heating system capacity to be better matched to the heating demand.

Even the smallest capacity furnaces (40,000 Btu/h) are oversized by 200%. Two-stage and 

modulating furnaces add complexity to the systems (ductwork would still need to be designed for 

maximum capacity airflow, resulting in lower supply velocities at part load caused by oversized 

ductwork), and therefore were avoided in these homes. 

 

The existing packaged furnace/AC units were located on the roofs. In the case of the Carmen 

home, this unit was removed with a crane, the roof was patched, and the new outdoor heat pump 

unit was located in the backyard. For the Sierra Hills home, the project team decided to maintain 

the location of the outdoor unit, by placing the new outdoor heat pump on the roof (see Figure 

22). This resulted in added cost for a crane (see Figure 21), but simplified running the refrigerant 

line sets to the indoor air handler unit. 

Figure 21. Existing package furnace/AC unit being craned off of the Sierra Hills home 

(Image courtesy of Building Media, Inc.) 
24 

Figure 22. New outdoor heat pump unit being installed at the Sierra Hills home 

(Image courtesy of Building Media, Inc.) 

For ventilation, both homes had Panasonic 80 cfm WhisperGreen exhaust fans located in the 

bathrooms for local spot ventilation to remove excess moisture from showers. The kitchen ranges 

also had exhaust hoods that were ducted to outside to remove cooking contaminants from the 

home. These homes were extensively air sealed, so additional whole-house ventilation was 

provided in the form of a Panasonic 40-cfm WhisperComfort ERV (see Figure 23). CARB has 

researched this point source (Arena 2011) to verify that the units do not short-circuit (supply air

is directly exhausted before being distributed throughout the home because the supply air and 

return air are close together). 

Figure 23. Spot ERVs installed in both homes to provide balanced whole-house ventilation 

(Image courtesy of Building Media, Inc.) 
25 

4.2.1 Carmen

During the training course, the attendees did some initial testing of the HVAC system before 

removing it and installing the new unit. They determined that the delivery velocity of its

distribution air was very low. This allows for temperature stratification year round, which means 

the HVAC system runs longer in an attempt to achieve comfort in the occupied areas of the 

home. 

The attendees were trained on the design, installation, and commissioning of the HVAC system. 

Figure 24 shows CARB’s design of the Carmen HVAC system as a radial distribution system.

Once in the field, Mr. Chitwood felt the supply air in the kitchen was not necessary and could be 

adequately supplied from the dining room. CARB had reservations about eliminating this kitchen 

supply air because of the large internal gain loads of the laundry and kitchen. Also, the dining 

room supply is a high wall supply (see Figure 4) throwing toward the north end of the home 

(which is opposite to the kitchen and laundry room) on the south end of the home. Though a mild 

day, testing during the training session showed little temperature difference between the kitchen 

and dining room. 

The other field modification made to the HVAC design was to eliminate the return ductwork for 

the master suite. The door to the master bedroom was a 5-foot double door set, so the door 

undercut was calculated to provide a sufficient return air pathway. This left only the central 

return in the hallway outside the bedrooms. The as-installed HVAC layout is shown in Figure 25. 

There has to be a reason or purpose, not just because...

CARB designed the ventilation systems for these homes without exhaust fans in the 

laundry rooms. The homes originally had laundry room exhaust fans, but CARB 

recommended removing them and patching the ceilings to eliminate unnecessary 

envelope penetrations. 

During the training courses, the entire class said “it is code, you have to put a fan in a 

laundry room without a window.” To prove their case, they spent the next hour looking 

it up. In the end they determined that it was not required. As Mr. Chitwood stated, “We 

so often see something over and over and think it must be code. It was a wonderful 

lesson for the class.” 
26 

Figure 24. The radial HVAC design for the Carmen home

Figure 25. Radial HVAC system as installed at the Carmen home
27 

CARB calculated the cooling and heating loads during the design process to be 19,411 Btu/h and 

19,163 Btu/h, respectively. A 2-ton two-stage ASHP was specified to meet these loads. But as 

the retrofit was being undertaken, air sealing and building specification goals were exceeded, so 

the actual building loads were lower than predicted. Therefore, the two-stage ASHP was locked 

on first stage unless the house was 8°F from the set point, so it operates as an approximately 1.5 

ton unit. The class recalculated the duct design based on the final system controls configuration 

(full-stage lock out) and the in-field revisions to the duct layout (elimination of the dedicated 

kitchen/laundry supply). Once the target airflows were determined, the attendees worked on best 

practice installation methods for the various HVAC components (see Figure 26). 

Figure 26. Mastic being applied to inside of flexduct jacket before being slipped over and secured 

to a branch takeoff elbow with compression bands 

(Image courtesy of Building Media, Inc.) 

Session attendees extensively commissioned the HVAC system. The external static pressure drop 

of the HVAC system was 0.27 in. w.c., well below the manufacturer’s specified maximum (0.5–

0.7 in. w.c.). The lower external static pressure allows the electronically commutated fan motor 

to provide the required airflow with less resistance and therefore, less power draw. 

The total duct leakage was measured to be 23 cfm at 25 Pascals. This equates to 2.6% leakage 

based on system airflow. Though the source of the remaining total duct leakage was not

identified during the training, this was likely primarily around the air handler unit. The duct 

leakage to outside was measured to be negligible. 

The individual supplies were balanced using the manual dampers at each supply branch takeoff. 

As shown in Table 11, overall balancing of each supply register was within ±3% of the design 

flow rates. This was achievable because of the compact distribution design and tight ductwork. 
28 

Table 11. Air Balancing Results at the Carmen Home

Room Design 

(cfm)

Final 

(cfm)

Deviation

(%)

Dining/Kitchen 283 278 –2

Living Room 164 168 2

Master Bedroom 181 185 2

Bedroom 2/Office 98 98 0

Bedroom 3 146 141 –3

Total 868 870

The return air pathway for the central return system was confirmed by measuring the pressure 

difference between bedrooms with closed doors and the main living space. Industry standards, 

such as the Environmental Protection Agency’s ENERGY STAR v3.0 Certified Homes program, 

require this pressure difference to be ≤ 3.0 Pascals or additional return air pathways installed 

(jump ducts, transfer grilles, etc.). The Carmen home met this requirement (see Table 12).

Table 12. Verification of Suitable Return Air Pathways at the Carmen Home

Room Pressure Differential 

(Pascals)

Master Bedroom 0.9

Bedroom 2/Office 0.6

Bedroom 3 3.0

4.2.2 Sierra Hills

Similar to the Carmen home, attendees of this HVAC training session were trained on the design, 

installation, and commissioning of the HVAC system. Figure 27 shows CARB’s initial design of 

the Sierra Hills HVAC system as a radial distribution system. Once in the field, Mr. Chitwood 

again felt the supply in the kitchen was not necessary and could be adequately supplied from the 

living room (as the two rooms are open to each other). CARB had reservations about eliminating 

this kitchen supply due to the internal gain load of the kitchen and the distance of the supply 

throw to adequately reach the kitchen from the living room. 

The other field modification made to the HVAC design was to move the air handler unit from the 

bedroom closet to the hall closet. This was originally not an option based on feedback from the 

project team, but was deemed necessary to provide adequate clearances for ductwork. This also 

allowed ductwork to be moved inside the pressure boundary. The framing of the attic allowed for 

the pressure boundary to be relocated to the bottom cord of the scissor trusses (see Figure 28).

This simplified the ceiling insulation installation (as this eliminates the varying ceiling heights 

caused by the kneewalls) and creates a space for the ducts to be located inside the building 

envelope (see Figure 29). 
29 

Figure 27. Initial radial HVAC design for the Sierra Hills home
30 

Figure 28. Relocating pressure boundary to bring ductwork into conditioned space. On the left is 

the existing configuration; the right image shows the new configuration. 

Figure 29. Pressure boundary being moved up to the bottom of the scissor trusses to allow ducts 

to remain within the building envelope 

(Image courtesy of Building Media, Inc.)

Session attendees commissioned the HVAC system at Sierra Hills. The external static pressure 

drop of the HVAC system without the supply registers was 0.11 in. w.c. The double deflection 

supply registers were not available during the training session, but Mr. Chitwood anticipated that 

the external static pressure would be no greater than 0.24 in. w.c. 

The total duct leakage was measured to be 17 cfm at 25 Pascals. This equates to 1.7% leakage 

based on system airflow. The duct leakage to outside was measured to be negligible. 
31 

The individual supplies were balanced using the manual dampers at each supply branch takeoff. 

Table 13 shows that overall balancing of each supply register was within ±3% of the design flow 

rates. The return air pathways for the central return system were also confirmed to be acceptable 

by measuring the pressure difference between both bedrooms with closed doors and the main 

living space (see Table 14).

Table 13. Air Balancing Results at the Sierra Hills Home

Room Design 

(cfm)

Final 

(cfm)

Deviation

(%)

Living/Kitchen 699 681 –2.6

Master Bedroom 228 230 0.9

Bedroom 2 213 212 –0.5

Total 1,140 1,123

Table 14. Verification of Suitable Return Air Pathways at the Sierra Hills Home

Room Pressure Differential 

(Pascals)

Master Bedroom 1.1

Bedroom 2 2.0
32 

5 Final Performance Modeling

Based on CARB’s final performance testing, the Carmen home and Sierra Hills home achieved

predicted source energy savings targets of 51% and 34%, respectively. The Carmen home 

slightly underperformed compared to the initial BA model, but still exceeded the 50% source 

energy savings goal. This was because the atmospheric natural gas water heater was used as the 

backup heating source for the solar thermal system, rather than switching to a natural gas 

tankless water heater. The Sierra Hills home outperformed the initial BA model. This was 

because of the changes in the building specifications (see Table 7) and because the tested 

building infiltration rate was lower than the goal of 4.0 ACH50. 

Table 15 provides the Home Energy Rating System (HERS) Index for the pre-retrofit and 

finalized homes. The reference home for the HERS Index is based on the 2006 International 

Energy Conservation Code. An average code compliant new home has a HERS Index of 100; 

according to RESNET, the typical resale home scores 130 on the HERS Index. 

 

Table 15. Pre- and Post-Retrofit HERS Indexes for the Vegas Retrofits

Home HERS Index

Pre-Retrofit Post-Retrofit

Carmen 126 66

Sierra Hills 98 61

5.1 Carmen

A summary of the specifications for the four primary cases discussed in this report for the 

Carmen home are provided in Table 16. 
33 

Table 16. Summary of Specifications at the Carmen Home

Building Component Existing NSP BA Proposed Final

Above-Grade Walls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III)

Attic Vented attic, R-24 fiberglass batts at ceiling plane Unvented attic, R-30 closed cell spray 

polyurethane foam at roof deck

Windows Aluminum double pane, clear (assumed U-0.76, 

SHGC-0.67)

Vinyl double pane, low-e retrofit windows 

(U-0.26, SHGC-0.23)

Cooling/Heating

Packaged furnace/AC, 

60 kBtu/h heating input, 

natural gas, 76% AFUE, 

40.5 kBtu/h cooling 

capacity, R-22 

refrigerant, SEER 8.5

Packaged furnace/AC, 

60 kBtu/h heating input, 

natural gas, 78% AFUE, 

40.5 kBtu/h cooling 

capacity, R-410A 

refrigerant, SEER 14

Split ASHP (SEER 18.5/9.2 HSPF), 25.6 kBtu/h

cooling capacity, 24.2 kBtu/h heating capacity, 

R-410A refrigerant with TXV valve 

Ductwork R-2 ductwork in vented 

attic (poor condition)

R-6 ductwork in vented 

attic

Compact distribution design, R-6 ductwork in 

unvented attic, sealed with mastic

Local Ventilation Kitchen exhausted to exterior and bathroom 

exhaust fans

Efficient exhaust fans with delay off timers in 

bathrooms

Whole-House 

Ventilation – Spot ERV

Hot Water 

50-gal atmospheric 

water heater, natural 

gas, 0.55 EF 

50-gal atmospheric 

water heater, natural 

gas, 0.59 EF 

Solar thermal system 

(40 ft2 of collectors 

facing south) with 80-

gal preheat tank and 

tankless water heater 

backup (0.84 EF)

Solar thermal system 

(40 ft2 of collectors 

facing west) with 80-

gal preheat tank and 

existing water heater 

backup (0.55 EF)

Lighting Mostly incandescent except fluorescents in kitchen All CFLs or LEDs

Appliances Old appliances ENERGY STAR appliances

Infiltration 9.8 ACH50 9.2 ACH50 4.0 ACH50 3.2 ACH50
34 

The finalized BEopt model in Figure 30 confirms that the Carmen home was a very successful 

retrofit showcasing how typical homes in the region can be improved to reduce source energy 

consumption by 50% or more while maintaining annualized costs roughly the same over a 15-

year period (after which the retrofit is cash positive). The difference between the final BA home 

and the minimum cost option was the use of solar thermal with the existing water heater versus a 

gas tankless water heater.

Figure 30. Final energy savings prediction for the Carmen home

To achieve the 50% level of energy savings without significantly disturbing the interior gypsum 

board and finishes, the team thought a solar thermal hot water system would be required. 

CARB’s proposed specifications were for a solar thermal system and using a tankless water 

heater as the auxiliary water heater. The project team was interested in showcasing the solar 

thermal technology, but the first cost of the solar thermal system was, so it elected to leave the 

atmospheric tank water heater. 

In hindsight, as a result of the tighter building infiltration results than anticipated, the home could 

have achieved similar performance at a lower first cost by switching the domestic water heating 

to a tankless water heater rather than a solar thermal system. Though the available solar resource 

is excellent in this climate region, the system was sized to only about 60% of domestic hot water 

design load and was installed on the west roof slope. Being nearly 90 degrees from true south 

may result in a 10%–20% reduction in solar thermal output. The hot water use pattern will 
35 

determine the performance of the solar system, which is configured for afternoon and evening 

hot water use. 

Figure 31 provides a look at the component end use for the various specification packages of the 

Carmen home. Based on the energy modeling, the predicted annual utility bill savings for the 

Carmen home is $1,138 ($2,543 pre and $1,405 post = $1,138) based on current utility rates (NV 

Energy $0.11751/kWh and Southwest Gas $0.76659/therm). This is a 45% savings in annual 

utility costs. 

Figure 31. Cumulative contribution to total energy savings, by measure and end use, 

for the Carmen home

Lighting, appliances, and miscellaneous electric loads (LAMELs) are often grouped together as 

the remaining contributors to the total home electricity demand after space heating, space 

cooling, domestic hot water, and ventilation. In the existing home, the LAMELs accounted for 

only 31% of the overall energy consumption. In the retrofitted home, the LAMELs now account 

for 55% of the remaining energy consumption. These are all top of the line units (ENERGY 

STAR labeled, if available), so little currently can be done from a technology standpoint to 

reduce this use. The same is true of the fixed lights, which are all CFLs) or LEDs. Essentially, 

the occupants would need to alter their behavior to see a significant reduction in their LAMELs 

consumption. 

5.2 Sierra Hills

Table 17 provides a summary of the specifications for the four primary cases discussed in this 

report for the Sierra Hills home.
36 

Table 17. Summary of Specifications at the Sierra Hills Home

Building Component Existing NSP BA Proposed Final

Above-Grade Walls 2 × 4 wood framing @ 16 in. w/R-11 fiberglass batts (grade III) + 1 in. EPS foam

Attic Vented attic, R-24 fiberglass batts at ceiling plane Vented attic, R-49 fiberglass batts at ceiling plane

Windows Aluminum double pane, clear 

(assumed U-0.76, SHGC-0.67) 

Apply low-e film to 

existing windows 

(SHGC-0.43) 

Vinyl double pane, 

low-e retrofit windows 

(U-0.26, SHGC-0.23) 

Cooling/Heating

Packaged furnace/AC, 

60 kBtu/h heating input, 

natural gas, 79.6% 

AFUE, 35 kBtu/h

cooling capacity, R-22 

refrigerant, SEER 13 

Packaged furnace/AC, 

60 kBtu/h heating input, 

natural gas, 78% AFUE, 

35 kBtu/h cooling 

capacity, R-410A 

refrigerant, SEER 15 

Mini-split heat pumps 

(SEER 16/8.5 HSPF), 

35.4 kBtu/h cooling 

capacity, 36.0 kBtu/h

heating capacity, 

R-410A refrigerant 

Split ASHP (SEER 

18.5/9.2 HSPF), 25.6 

kBtu/h cooling 

capacity, 24.2 kBtu/h

heating capacity, R410A refrigerant with 

TXV valve

Ductwork R-4 ductwork in vented 

attic

R-6 ductwork in vented 

attic – 

Compact distribution 

design, R-6 ductwork 

in conditioned space

Local Ventilation Kitchen exhausted to exterior and bathroom 

exhaust fans

Efficient exhaust fans with delay off timers in 

bathrooms

Whole-House 

Ventilation – Spot ERV

Hot Water 

50-gal atmospheric 

water heater, natural 

gas, 0.56 EF 

50-gal atmospheric 

water heater, natural 

gas, 0.59 EF 

50-gal premium water heater, natural gas, 

0.67 EF 

Lighting Mostly incandescent light except fluorescent 

lighting in kitchen All CFLs or LEDs 

Appliances Old appliances ENERGY STAR appliances

Infiltration 6.1 ACH50 6.0 ACH50 4.0 ACH50 3.2 ACH50
37 

The finalized BEopt model in Figure 32 confirms that the Sierra Hills home exceeded the source

energy consumption goal of 30%. The final home performance is not even on the optimization 

curve, because the level of airtightness achieved—though minimally invasive—exceeded what 

was thought to be feasible during the initial analysis. Unfortunately, as the Sierra Hills home 

already had equipment replaced over the past decade, any energy efficiency measures would 

result in higher annualized costs over the 15-year financing period (after which the retrofit would 

be cash positive). 

In this case, the final retrofit resulted in a 28.2% efficiency improvement over the NSP-proposed 

specifications and reduced the annualized costs by $305/year. So if the decision has already been 

made to make improvements, the efficiency measures recommended by CARB can lead to lower 

annualized costs with improved comfort. 

Figure 32. Final energy savings prediction for the Sierra Hills home

Figure 33 provides a look at the component end use for the various specification packages of the 

Sierra Hills home. Based on the energy modeling, the predicted annual utility bill savings for the 

Sierra Hills Home is $480 ($1,672 pre and $1,192 post = $480). This is a 28.7% savings in 

annual utility costs. 
38 

Figure 33. Cumulative contribution to total energy savings, by measure and end use, for the Sierra 

Hills home

In the existing home, the LAMELs accounted for 44% of the overall energy consumption. In the 

retrofitted home, the LAMELs now account for 59% of the remaining energy consumption. This 

makes achieving higher levels of energy savings difficult for this housing type/class without 

significantly higher annualized energy related costs. 
39 

6 Cost Analysis

When we are trying to determine whether energy efficiency measures are cost effective, the real issue

is whether we have developed a compelling home for the marketplace. According to Kerry Landley, 

Director of Sustainable & High Performance Lending at the Real Estate Mortgage Network, 

homebuyers in this region can use two strategies to purchase an existing home. 

• Common Strategy 

o Purchase a traditionally built home (based on market price). 

o Obtain market-based mortgage financing. 

o Pay market-based monthly utilities. 

o Pay market-based home ownership expenses (maintenance and repairs). 

• Efficiency Strategy

o Purchase a traditionally built home (based on distressed property pricing). 

o Add renovation and energy retrofit cost (based on energy saving goals). 

o Obtain optimized mortgage financing. 

o Pay discounted monthly utilities (from energy-related improvements). 

o Pay discounted home ownership expenses (maintenance and repairs). 

Based on the purchaser’s timeframe, the cost benefit of the efficiency strategy will also vary. The 

15- and 30-year mortgages are the most common. Table 18 compares the annualized energyrelated cost estimates from BEopt for the two retrofit homes based on length of a mortgage and 

timeframe over which the cost analysis is evaluated. This cost analysis only accounts for 

estimated first costs, utility bills, and potential equipment replacement costs over the analysis 

period. It does not take into account the potential for improved comfort, durability, and indoor air 

quality. 

Table 18. Comparison of Annualized Energy-Related Costs Based on 

Length of Mortgage and Analysis Period

House 

(Mortgage Term/Analysis Period) Existing NSP Proposed

BA 

Final

Annualized 

Savings 

Over 

Existing

Annualized 

Savings 

Over NSP 

Proposed

Carmen (15 years/15 years) $2,543 $2,754 $3,103 –$560 –$349

Carmen (15 years/30 years) $2,392 $2,629 $1,565 $827 $1,064

Carmen (30 years/30 years) $2,392 $2,614 $1,547 $845 $1,067

Sierra Hills (15 years/15 years) $1,525 $2,202 $2,349 –$824 –$147

Sierra Hills (15 years/30 years) $1,525 $2,011 $1,222 $303 $789

Sierra Hills (30 years/30 years) $1,525 $1,996 $1,204 $321 $792

For a 15-year mortgage and analysis period, the implemented efficiency measures were not cost 

neutral over the existing home. For a 30-year mortgage and analysis period, the efficiency measures 
40 

were cost beneficial over the existing home. Because of the age and condition of the home and 

equipment, many of these improvements, though maybe to a lesser efficiency level, would have 

needed to be made. The NSP proposed specifications are a good reference for the minimal 

needed to be done to make these homes market ready. This comparison nets the same overall 

results as the existing home, but the savings are higher (or additional expenses are lower) across 

all cases. To be cost neutral across all instances in Table 18, the solar thermal system would need 

to be removed from the Carmen specifications and, rather than replacing the windows at the 

Sierra Hills home, a low-e film should be considered. 

The general contractor provided the following project specific cost information in Table 19 and 

Table 20 for the Carmen and Sierra Hills retrofits, respectively. In these homes, labor was 

provided by the training session attendees, so the labor costs in these tables are estimates. The 

window costs were quite similar to the BEopt estimates, but BEopt underestimated the cost of 

the high efficiency heat pump and solar thermal hot water system by nearly half. Whether this 

cost discrepancy is based on regional price variations or something else is unclear. 
41 

Table 19. First Costs of Efficiency Measures at the Carmen Residence

Quantity Units Unit Price Cost Cost/ft2

Materials 120 LF $ 6.25 $ 750.00 $ 0.49 /sq ft

Grills, Fittings, etc 60 EA $ 6.25 $ 375.00 $ 0.25 /sq ft

Labor 20 HRS $ 35.00 $ 700.00 $ 0.46 /sq ft

$ 1,825.00 $ 1.20 /sq ft

Air Handler Unit 1 EA $ 3,062.50 $ 3,062.50 $ 2.01 /sq ft

Heat Pump Unit 1 EA $ 6,062.50 $ 6,062.50 $ 3.99 /sq ft

Thermostat 1 EA $ 156.25 $ 156.25 $ 0.10 /sq ft

Labor 31 HRS $ 35.00 $ 1,085.00 $ 0.71 /sq ft

10,366.25$ $ 6.82 /sq ft

Shingles 30 SF $ 8.00 $ 240.00 $ 0.16 /sq ft

Plywood 30 SF $ 1.00 $ 30.00 $ 0.02 /sq ft

Materials 1 LS $ 50.00 $ 50.00 $ 0.03 /sq ft

Labor 6 HRS $ 35.00 $ 210.00 $ 0.14 /sq ft

$ 530.00 $ 0.35 /sq ft

12,721.25$ $ 8.36 /sq ft

Simonton Windows 190 SF $ 37.00 $ 7,030.00 $ 4.62 /sq ft

Foam 13 EA $ 2.50 $ 32.50 $ 0.02 /sq ft

Labor 32 HRS $ 25.00 $ 800.00 $ 0.53 /sq ft

$ 7,862.50 $ 5.17 /sq ft

$ 7,862.50 $ 5.17 /sq ft

Closed Cell Polyurethane (Material & Labor) 1,825 SF $ 5.75 10,494.90$ $ 6.90 /sq ft

10,494.90$ $ 6.90 /sq ft

10,494.90$ $ 6.90 /sq ft

ENERGY STAR Refrigerator 1 EA $ 1,375.00 $ 1,375.00 $ 0.90 /sq ft

ENERGY STAR Dishwasher 1 EA $ 487.50 $ 487.50 $ 0.32 /sq ft

ENERGY STAR Clothes Washer 1 EA $ 879.00 $ 879.00 $ 0.58 /sq ft

ENERGY STAR Clothes Dryer 1 EA $ 817.00 $ 817.00 $ 0.54 /sq ft

Labor 6 HRS $ 25.00 $ 150.00 $ 0.10 /sq ft

$ 3,708.50 $ 2.44 /sq ft

$ 3,708.50 $ 2.44 /sq ft

Solar Hot Water 1 Ea $ 6,930.00 $ 6,930.00 $ 4.56 /sq ft

Labor 12 HRS $ 25.00 $ 300.00 $ 0.20 /sq ft

$ 7,230.00 $ 4.75 /sq ft

$ 7,230.00 $ 4.75 /sq ft

$ 42,017 $ 27.62 /sq ft

Installing High Efficiency HVAC Equipment

Installing New HVAC Distribution System

Repairing Roof After HVAC Removal

Insulation Total

Converting to Unvented Attic

Subtotal

Appliances Total

Providing ENERGY STAR Appliances

Subtotal

Adding a Solar Hot Water System

Subtotal

Water Heating Total

Total Costs of Energy Efficiency Measures

Subtotal

Subtotal

Subtotal

Subtotal

HVAC Total

Windows Total

Installing New Windows
42 

Table 20. First Cost of Efficiency Measures at the Sierra Hills Residence

The costs for all the other alternatives run in BEopt to generate the least cost optimization curve 

are unknown, so CARB did not adjust the costs of various measures within this software. This 

would unfairly weight those alternative strategies with lower cost estimates, and translating the 

actual costs into BEopt would be difficult. For example, the cost for converting to an unvented 

attic is specified as a single cost for spray foam insulation at the roof deck, but in BEopt, this 

cost would have to be judiciously divided among insulation, infiltration, and ducts (bringing 

ducts within conditioned space). 

The project team was able to obtain the cost estimate report from the City of Las Vegas Housing 

Rehabilitation Program for the Sierra Hills home (a scope of work had been developed for the 

Carmen home, but a cost estimate report had not been completed). The cost increase for the 

Quantity Units Unit Price Cost Cost/ft2

Materials 120 LF $ 6.25 $ 750.00 $ 0.66 /sq ft

Grills, Fittings, etc 60 EA $ 6.25 $ 375.00 $ 0.33 /sq ft

Labor 20 HRS $ 35.00 $ 700.00 $ 0.62 /sq ft

$ 1,825.00 $ 1.61 /sq ft

Air Handler Unit 1 EA $ 4,312.50 $ 4,312.50 $ 3.81 /sq ft

Heat Pump Unit 1 EA $ 6,562.50 $ 6,562.50 $ 5.80 /sq ft

Thermostat 1 EA $ 156.25 $ 156.25 $ 0.14 /sq ft

Labor 31 HRS $ 35.00 $ 1,085.00 $ 0.96 /sq ft

12,116.25$ $ 10.71 /sq ft

13,941.25$ $ 12.33 /sq ft

Simonton Windows 180 SF $ 37.00 $ 6,660.00 $ 5.89 /sq ft

Foam 13 EA $ 2.50 $ 32.50 $ 0.03 /sq ft

Labor 32 HRS $ 25.00 $ 800.00 $ 0.71 /sq ft

$ 7,492.50 $ 6.62 /sq ft

Blown Fiberglass 1,131 SF $ 0.70 $ 791.70 $ 0.70 /sq ft

Labor 32 HRS $ 25.00 $ 800.00 $ 0.71 /sq ft

$ 1,591.70 $ 1.41 /sq ft

$ 1,591.70 $ 1.41 /sq ft

ENERGY STAR Refrigerator 1 EA $ 1,375.00 $ 1,375.00 $ 1.22 /sq ft

ENERGY STAR Dishwasher 1 EA $ 487.50 $ 487.50 $ 0.43 /sq ft

ENERGY STAR Clothes Washer 1 EA $ 879.00 $ 879.00 $ 0.78 /sq ft

ENERGY STAR Clothes Dryer 1 EA $ 817.00 $ 817.00 $ 0.72 /sq ft

Labor 6 HRS $ 25.00 $ 150.00 $ 0.13 /sq ft

$ 3,708.50 $ 3.28 /sq ft

High Efficiency DHW System 1 Ea $ 1,188.75 $ 1,188.75 $ 1.05 /sq ft

Labor 6 HRS $ 25.00 $ 150.00 $ 0.13 /sq ft

$ 1,338.75 $ 1.18 /sq ft

$ 28,073 $ 24.82 /sq ft

Providing ENERGY STAR Appliances

Installing New Windows

Windows Total

HVAC Total

Total Costs of Energy Efficiency Measures

Replacing Hot Water System

Appliances Total

Subtotal

Insulation Total

Insulating Vented Attic

Water Heating Total

Installing New HVAC Distribution System

Subtotal

Installing High Efficiency HVAC Equipment

Subtotal
43 

higher efficiency measures at the Sierra Hills home was about $11,000 more than what was 

originally intended under the NSP. However, several of the big ticket items of the NSP cost 

estimates seem optimistic, based on feedback from the general contractor of these retrofits. For 

example, it is unlikely that a completely new HVAC system, including new ductwork, can be 

designed, installed (unit located on roof), and commissioned per the NSP proposed scope of 

work for $4,500. The distribution system alone cost $1,825, so the cost of the packaged 

furnace/AC and the installation of that unit would need to be less than $2,675, which is unlikely. 

The percent differential in costs from BEopt was used to estimate a more appropriate first cost 

for the NSP specifications. For the Carmen and Sierra Hills homes, the cost differential was 58% 

and 13%, respectively. For the Carmen home, an estimate of the NSP proposed specifications 

based on the BEopt cost differential would be $24,300. For the Sierra Hills home, this would 

mean that a potentially more reasonable estimate would be about $7,500 more than the NSP cost 

estimate report indicated or a difference of about $3,500 between the NSP specifications and the 

BA specifications cost. 

As the NSP specifications would need to be done for the most part to make these homes 

marketable again, a simple payback (SPB) between the NSP specifications and BA specifications 

is provided based on the adjusted annualized energy-related cost savings potential (based on first 

cost differential percentages) of these homes with a 30-year mortgage and analysis period. The 

simple payback would be about 16.6 years for the Carmen home and about 6.4 years for the 

Sierra Hills home. If the solar thermal system were replaced with a tankless natural gas water 

heater, the SPB would be reduced to about 12.9 years. For the Carmen home, this SPB is higher 

than the 5- to 10-year timeframe that is typically used when making investment decisions, but the 

SPB metric excludes the value of improved comfort, durability, and indoor air quality of the 

retrofitted home. 
44 

7 Conclusions

These two test homes proved to be valuable resources in demonstrating the effort (design and 

implementation) and cost required to retrofit existing homes in the Southwest climate region to 

various BA energy saving targets. In addition to validating and vetting BA solution packages, 

these homes were used as training centers for local contractors and have been opened to the local

community for tours. These tours focus on how energy efficiency can be effectively incorporated 

into other existing homes in the region. A Nevada ENERGY STAR® Partners website has been 

set up for this project. The site provides information on tour availability, links to video segments 

filmed during the project, and brief story lines of the retrofits. 

The overarching research question was, “How do we determine what solution package(s) can be 

readily implemented in hot, dry climate homes to achieve a 30% plus and a 50% plus energy 

savings home compared to the pre-retrofit home (as defined by the BA B10 Benchmark)? CARB 

has provided two robust solution packages for retrofitting homes built in this region from the 

1980s to the early 1990s without substantially inconveniencing the occupants. These BA 

solutions focused on air sealing the building envelope where accessible to reduce the overall 

space conditioning loads. Windows were replaced with double-pane low-e retrofit windows. The 

replacement windows reduced solar heat gain entering the homes and allowed for these rough 

openings to be better air sealed. Another essential strategy was to simplify the design and 

distribution of the high efficiency HVAC systems. This included bringing the ductwork within 

the conditioned building envelope. High efficiency technology is beneficial only if it is designed 

and installed appropriately. For more details about these solution packages, refer to Table 16 and 

Table 17. Whether energy savings of 30% or greater or 50% or greater are achieved depends 

primarily on the pre-retrofit state of the home and whether mechanical equipment updates have 

been performed since initial construction. The final estimated performance of these homes is 

summarized in Table 21. 

Table 21. Final Estimated Performance of the Two Test Homes

Home

Source 

Energy 

Savings

Annual 

Utility 

Savingsa

Annualized 

Energy Related 

Cost Savingsb

HERS Index

Pre-Retrofit Post-Retrofit

Carmen 51% $1,138 $845 126 66

Sierra Hills 34% $480 $321 98 61 a $0.1175/kWh +$10 monthly charge, $0.7666/therm + $9 monthly charge

b 30-year mortgage, 4.0% loan interest rate, 1.6% inflation rate, 3.0% discount rate (real), 0% fuel escalation 

rate

The determination of whether the selected solution package for each home is commercially 

viable comes down to marketability and adoption. Assessors are just starting to incorporate 

efficiency measures into the assessments of home values (though usually at a significant discount 

compared to aesthetic features, such as granite countertops). The City of Las Vegas 

Neighborhood Services Department is encouraged by the results of these two test homes and is 

working to incorporate these solution packages into its scopes of work for future NSP-funded 

homes. Work is also being done to incorporate these solution packages into the new EnergyFit 

Nevada program. 
45 

Even though there has been tremendous positive feedback from tour visitors of the Carmen 

home, success is based on retrofit implementation and not just interest. A homeowner’s focus is 

most often on first cost, but when incorporating improvements in a mortgage, the key is the 

annualized energy-related costs. The question is whether it is better to pay a larger mortgage and 

pay less on utility bills annually. The answer depends on the timeframe of the investment. The 

longer a homeowner intends to live in a home, the more cost beneficial the energy efficiency 

measures are. Over a 30-year analysis period, whether a 15- or 30-year mortgage, these solution 

packages are cost effective. 

To make these solution packages even more cost effective and achieve the BA energy savings 

targets, CARB determined that the solar thermal system could be removed from the Carmen 

specifications (replaced with a natural gas tankless water heater) and rather than replacing the 

windows at the Sierra Hills home, a low-e film should be considered. CARB also looked at an 

alternative solution at the Sierra Hills home that included using ductless mini-split heat pumps as 

the space conditioning strategy and found comparable performance and cost. Also, to enable 

large-scale implementation of these solution packages across this region, contractor training on 

air sealing and simplified, compact HVAC design needs to continue. 

With more than 11% of the existing housing stock of Las Vegas in foreclosure (more than 8,100 

homes), the potential for energy retrofit savings in this region is substantial. If even 10% of those 

homes implement these solution packages (5% at the 50% energy savings target and 5% at the 

30% energy savings target), an energy reduction of more than 71,000 MMBtu or roughly 

$655,000 in annual utility bill cost for residents could be achieved. 
46 

References 

Arena, L. (2011). “Evaluation of the Performance of a Spot Energy Recovery Ventilator in a 

Retrofit Application.” Consortium for Advanced Residential Buildings, March 2011. Accessed 

August 20, 2012. 

www.carb-swa.com/articles/homepage/ERV%20Update_022811_CARBwebsite.pdf

Gunshinan, J. (2007). “Energy Star Changes Approach to Programmable Thermostats.” Home 

Energy Magazine, March/April 2007. Accessed August 10, 2012. 

www.waptac.org/data/files/website_docs/technical_tools/energy_star/energy_star_changes_appr

oach_to_programmable_thermostats.pdf 
DOE/GO-102013-3898 ▪ April 2013

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 10% post-consumer waste.