The DOE-HUD Initiative on Energy Efficiency in Housing 

This Design Guide is a product of the DOE-HUD Initiative on Energy Efficiency 

in Housing. The Initiative was created in 1990 as a collaborative framework to 

harness the technical skills of the Department of Energy's (DOE's) laboratories 

and programs for making energy efficiency improvements in Federally-aided 

housing. This multi-year Initiative supports both the Department of Energy's 

National Energy Strategy and the Department of Housing and Urban 

Development's (HUD's) mission to make low- and moderate-income housing 

more affordable. 

Funding for the Initiative is provided by the Department of Energy through its 

existing conservation research and technical assistance programs. Technical 

support for projects is supplied by staff from DOE, including its Support 

Offices, the Department of Housing and Urban Development with its Field 

Offices, DOE's National Laboratories, and private contractors. Aid in 

incorporating project experience into ongoing HUD housing activities, through 

publication, guidance, technical assistance and regulations is also provided by 

the groups mentioned. 

This Design Guide was prepared by the National Renewable Energy Laboratory 

(NREL) under contract to DOE. It is based on research sponsored by DOE and 

carried out primarily by the Los Alamos National Laboratory (LANL), NREL 

(formerly the Solar Energy Research Institute), and the Florida Solar Energy 

Center (FSEC). The Guide incorporates, by permission, major portions of the 

Passive Solar Design Strategies: Guidelines for Home Builders, published by the 

Passive Solar Industries Council (PSIC), and developed jointly by PSIC, NREL, 

and Charles Eley Associates, with funding support from DOE. 

Dr. J. Douglas Balcomb, the Design Guide's author, wishes to acknowledge the 

American Indian Council of Architects and Engineers (AICAE) for the 

opportunity to become acquainted with the issues of Indian housing by 

participating in the Council's workshops. The AICAE wrote the companion 

document, Our Home: Giving Form to Traditional Values, Design Principles for 

Indian Housing, published at the same time and under the same auspices as 

this Guide. This book discusses the cultural issues of Indian housing. Dr. 

Balcomb also thanks the AICAE for permission to use two designs that came 

out of the workshops as examples in this Guide. He is particularly grateful to 

Louis Weller, Burke Wyatt, David Sloan, Gilbert Honanie, Charles 

Archamboult, Edmund Gongales, and Veronica Tiller of the AICAE and also 

Richard Hill for their guidance and help. 

Nancy Carlisle, Terry Penney, and Ren Anderson of NREL all made important 

contributions to this project. Norm Weaver and Sara Farrar of Environmental 

Research Groups International performed many of the calculations using the 

ARES and BuilderGuide programs. 
Preface 

Energy Efficiency Guides and Software Today 

Today, as Native American cultures seek to return to culturally relevant 

building design, electronics-based software programs can become extremely 

valuable aids. Designers will soon have access to software systems that readily 

combine all the features that high energy efficiency, environmental quality, 

safety, soundness, and culturally related building design will require. This 

Design Guide offers a useful starting point for energy efficiency. It can be used 

by itself or with the BuilderGude software that is available to accompany it. 

Those considering using this Guide's software are probably aware that there 

are increasing numbers of such systems to consider using in the design and 

specification of buildings and for housing in particular. It is a field of rapid 

evolution. BuilderGuide is most useful for, but not limited to, design of passive 

solar systems. Other software systems also exist for passive solar. One new 

system now on the market provides designers with a program for preliminary 

design that includes energy efficiency and greatly simplifies the process of 

exploring the options and their building design consequences. Still others are 

available for defining such details as the times of annual peak use for cooling 

or heating (useful in designing for utility rebates), for evaluation and sizing of 

domestic heating plants, hot water appliances and other such details and for 

other technical purposes. It is presumed that the designer will make the best 

choice amongst all such alternatives in proceeding with a specific project's 

resolution. 

Neither the United States Government nor any agency thereof, 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. The views and opinions of authors expressed herein do not necessarily state or 

reflect those of the United States Government or any agency thereof. 
Table of Contents 

Section I: GUIDELINES FOR DESIGN 

Part One: Introduction 

1. The Energy-Efficiency Design Guide 1 

2. How Energy Efficiency Relates to Cultural Issues in Indian 

Housing 4 

3. Energy-Efficiency Savings Potential 8 

Part Two: Basics of Energy Efficiency 

1. Why Energy-Efficient? 11 

2. Key Concepts: Energy Conservation, 

Suntempering, Passive Solar 12 

3. Improving Conservation Performance 13 

4. Mechanical Systems 22 

5. South-Facing Glass 23 

6. Thermal Mass 26 

7. Orientation 27 

8. Site Planning for Solar Access 27 

9. Interior Space Planning 29 

10. Putting it Together: The House as a System 30 

Part Three: Passive Solar Strategies 

1. Suntempering 

2. Direct Gain 

3. Sunspaces 

4. Thermal Storage Wall 

5. Combined Systems 

Part Four: Natural Cooling Guidelines 

1. Glazing 

2. Shading 

3. Ceiling Fans 

4. Ventilation 

SECTION 11. BuiZderGuide 

Part One: Description of BuilderGuide 

Part Two: The Basecase House 

Part Three: Worked Examples: The Method in Practice 

Section 111. ENERGY-EFFICIENCY PERFORMANCE GOALS 

Glossary of Terms 

Technical Basis for the Guidelines and BuilderGuide 

References 
Direct-gain passive solar house on the Pojoaque Indian Reservation northwest of 

Santa Fe. New Mexico. Photo credit: D. Balcomb. 

Mimbres Quail 
Passive solar house on the Nambe Indian Reservation in New Mexico. This house 

features Trombe walls on the south for delayed solar heat and clerestory windows for 

direct gain to the northern rooms. In the cold but sunny climate of the upper Rio 

Grande valley, good insulation and passive solar combine to produce good comfort and 

low heating bills. Photo credit: D. Balcomb. 

The Zuni sun symbol is the State Emblem of New Mexico. 
Opinion gathering: Louis Weller and Veronica Tiller at the American Indian 

Council of Architects and Engineers (AICAE) workshop in Seattle, Washington, 

April 10, 1991. Indians from the region were asked to comment on their 

housing needs and preferences. The AICAE report, Our Home: Giving Form to 

Traditional Values, Design Principles for Indian Housing, describes their 

findings. Participants were genuinely concerned with high heating costs and 

inadequate comfort. 

Design concepts in the making: Burke Wyatt working with participants at the 

AICAE workshop in Albuquerque, New Mexico, February 28, 199 1. Indians from 

the region related their housing needs by sketching them. Two out of the 

dozens of design concepts that emanated from these workshops are included as 

examples in Section I1 starting on page 55. Photo credits: D. Balcomb. 
SECTION I: GUIDELINES FOR DESIGN 

Part One: Introduction 

1. The Energy-Efficiency Design Guide 

The ideas behind energy-efficient housing are simple, but applying them 

effectively does require information and attention to the details of design 

and construction. In this design guide, energy efficiency includes the 

concepts of conservation, passive solar heating, and natural cooling. 

Some of these techniques are modest and very low cost, and require only 

small changes in a designer's standard practice. At the other end of the 

spectrum, an integration of several energy-efficient systems can almost 

eliminate a house's need for purchased energy--but perhaps at a 

somewhat higher first cost. 

In between is a broad range of energy-efficient techniques. Whether or 

not they are cost effective, practical, and attractive enough to offer an 

advantage to any individual designer depends on very specific factors 

such as local costs and climate. 

The Energy-Effkiency Design Guide is written to help give designers the 

information they need to make these decisions. 

The Design Guide is a package in three basic sections: 

rn Section I contains information about energy-efficient techniques and 

how they work, and gives some specific design advice. 

rn Section 11 introduces the reader to the personal computer program 

BuilderGuide, which provides a sim le, fill-in-the-blanks format you 

can use to quickly evaluate the pe 2 ormance of your specific design. 

It includes two worked examples for proposed Indian houses. 

Section I11 gives designers and Indian Housing Authorities a realistic 

set of goals for energy-efficient design in different climates. 

It is intended that these guidelines be used in conjunction with the 

BuilderGuide computer program. Nonetheless, it is entirely possible to 

use the guidelines without this program and get good results. The value 

of BuilderGuide is to add confidence by giving you a quantitative fix on 

the performance of the house you are planning to build. You will need 

BuilderGuide to ascertain whether your design conforms to the energyefficiency performance goals. 
Paae 2 ENERGY-EFFICIENCY DESIGN GUIDE 

Overview of SECTION I: Guidelines for Design 

Some principles of energy-efficient design remain the same in every 

climate. But the important thing about energy efficiency is that it makes 

better use of the opportunities in a house's surroundings. So, many 

fundamental aspects of the energy-efficient house's design will depend on 

the conditions in a small local area, and even on the features of the 

building site itself. 

Part One introduces the Energy-Efficiency Design Guide and presents a 

quick overview of the performance potential of energy-efficient systems. 

Althou h in practice many factors will affect actual energy performance, 

this in f omation will give you a general idea of what to expect in your 

area. The relation of energy efficiency to Indian cultural issues is also 

discussed. 

Part Two discusses the basic concepts of energy-efficient design and 

construction: what the advantages are of energy-efficient construction; 

how improved insulation, tight construction, passive solar heatin 

natural cooling relate to each other; how the primary energy-e ficient P and

systems work; and what the designer's most important considerations 

should be when evaluating and using different strategies. Guidelines for 

insulation levels, window types, and solar glazing areas are given for 

43 U.S. locations. 

Part Three gives more specific advice about the passive solar techniques 

of suntempering, direct gain, sunspaces, and thermal storage mass 

walls. 

Part Four gives more specific advice about the use of natural cooling to 

increase summer comfort. 

These are the terms that will be used in this Design Guide: 

Added Insulation: increasing insulation levels without adding solar 

features. 

Tight Construction: decreasing air infiltration and the heat needed 

to warxn this air. 

Suntempering: increasing south-facing glazing to a maximum of 

7% of the house's total floor area, but without adding thermal mass 

(energy storage) beyond what is already in the framing, standard 

floor coverings and gypsum wall-board, and ceiling surfaces. 

Insulation levels are also increased. 

Passive Solar: using three different design approaches: Direct Gain, 

Sunspace, and Thermal Storage Wall. Passive solar includes all 

types of solar heating systems in which heat flow is by natural 

means--radiation, conduction, and natural convection. No pumps or 

fans are required for the system to operate. These systems are well 
FOR INDIAN HOUSING Paae 3 

integrated into the architecture of the house using norrnal materials 

of construction. 

The Guide has been kept as brief and straightforward as possible, but 

more detailed information is available if needed. Some references are 

indicated in the text, and a list of other information sources can be found 

in the References. Also included at the end of the Guide are a brief 

Glossary and two pages explaining some of the background and 

assumptions behind the Guidelines and BuilderGuide called Technical 

Basis for the Design Guidelines. 

Overview of SECTION 11: The BuilderOuide PC Program 

Few designers can confidently achieve good energy-efficient designs 

without "doing the numbers". In the past, this has been an onerous 

undertaking that involved extensive calculations. Most designers never 

did any calculations to support their design decisions because it took too 

long or required the assistance of an engineer who was knowledgeable in 

the complexities of the analysis. BuilderGuide changes all that. 

BuilderGuide is a PC program that is easy to use, "builder friendly", as 

they say. Calculations that you will make with this program are a very 

important part of the energy-efficient design process because they allow 

you to quickly assess different energy-efficient strategies or combinations 

of strategies and the effect that changes will have on the overall 

performance of the house in your climate. 

BuilderGuide provides a simple way to quickly calculate how well a 

design is likely to perfom in four key ways: how well the house will 

conserve heat; how much the solar features will contribute to the total 

heating energy needs; how comfortable the house will be; and how much 

air conditioning will be needed to maintain summer comfort. You can 

compare your results with the appropriate performance goal to see how 

well you are doing. You can also do tradeoffs quickly, for example, to see 

the benefit of adding insulation or extra mass. 

So, BuilderGuide provides you with four key numbers indicating the 

projected performance of the various designs you are evaluating. 

Two Examples are included in Section I1 that demonstrate the use of 

BuilderGuide in evaluating the performance of two houses designed by 

Indians. 

Note that the BuildetGuide computer program itself is not included 

with the Energy-Effkiency Design Guide. However, the computer disks 

and manual can be readily obtained from the Passive Solar Industries 

Council, together with data files for any of 205 locations in the United 

States. 
Pa~e 4 ENERGY-EFFICIENCY DESIGN GUIDE 

Overview of SECTION 111: Energy-Efficiency Performance Goals 

This section contains recommendations for the overall performance of the 

house, presented in terms of the maximum amount of auxiliary heat and 

auxiliary cooling the house should use, as computed by BuiZderGuide. 

These are voluntary goals. Results are presented as tables of maximum 

allowable Btu/ft2 for 43 U .S. locations. 

For guidance on how to reach your conservation performance goal, refer 

to the insulation guidelines on pages 20 and 21. These tables give 

suggestions for components, such as R-values for walls, ceiling, and 

perimeter, window type, and equipment efficiencies. If these component 

recommendations are followed, then the house will likely meet the 

conservation performance goal. For guidance on how to reach your 

auxiliary heating performance goal, refer to the guidelines for passive 

solar glazing area on page 25. 

The performance goals are presented in the spirit of voluntary 

compliance. They have no force in law or regulation. However, they have 

been developed based on the principle of economic optimization. This 

means that it is cost effective to install enerm-efficient features as 

required to meet the performance goals, based orthe payback in energy 

savings that will accrue over the life of the house. Different goals are 

given for houses heated by gas and those heated'by electricity. 

Index to the Tables 

Tables for 43 cities are scattered throughout this guide. These tables and 

their page locations are as follows: 

Table Page 

Savings of houses that meet the performance goals 

Insulation guidelines, houses heated with gas 

Insulation guidelines, houses heated with electricity 

Passive solar guidelines 

NAHB 1980 housing characteristics 

BuilderGuide results for NAHB basecase 

Conservation performance goals 

Auxiliary heating performance goals 

Summer cooling performance goals 

Heating and cooling degree days 
FOR INDIAN HOUSING Paae 5 

2. How Energy Efficiency Relates to Cultural Issues in 

Indian Housing 

Energy efficiency is not only completely compatible with culturally 

relevant Indian housing, but it should be part of it. 

Indian cultures have always stressed living in harmony with their 

environment. That which is taken is replaced. The natural order is left 

intact. Modem American culture, by contrast, seems more inclined to 

exploit nature and to disrupt the natural order. 

Original Indian cultures in America and early cultures in Europe did 

little to heat their houses. The home provided shelter from the wind, 

snow, and rain. Wood-burning stoves aid fireplaces were used to keep a 

small area, a room or two, somewhat warmer than the outside, at least 

part of the time. People were tough, inured to the cold, and used to 

dressing warmly, even when inside. 

We read of Indian homes in New England that were as "warm as the best 

English houses" and of tipis that were "warm in the winter and cool in 

the summer". These statements must be understood in the context of 

their time. Comfort can be relative. English houses of that time were 

really uncomfortable. Certainly conditions inside the Indian house on a 

harsh winter night would have been much better than outside. Enough 

people crowded around the tipi fire would maintain reasonable comfort 

for awhile. The natural ventilation of the tipi would be very effective in 

the plains but would hardly cope with the humidity of a Florida summer. 

These are traditions that have been lost. Most people, Indian or not, do 

not yearn for a return to these conditions. It is now expected that houses 

will be kept comfortable. The loss of this lifestyle is no more mourned 

than the demise of the outdoor toilet. Comfort standards for Indians are 

no different than those for any other people. Indians expect and deserve 

comfortable places to live and work. The cost of this comfort is now 

accepted as a necessity, not a luxury. 

The Cost of Comfort 

But what should it cost to maintain modem standards of comfort? We 

have developed a culture of poorly insulated houses maintained 

comfortable only by the use of prodigious amounts of energy. If the 

energy equivalent of the 20 barrels of oil required to heat the house for 

one winter were to be stacked inside, it would fill the living room. We are 

not so aware of this because it usually amves in the form of natural gas 

delivered quietly though a pipe. Awareness arrives with the utility bill. 

The United States uses 13% of its energy just to heat and cool its homes 

and hot water. The energy equivalent is that of some 1690 million barrels 

of oil at a cost of $55 billion each year. That is $613 per household each 

year. The irony is that most of this energy is not really needed. We now 

know how to build houses that can be kept comfortable on no more than 

30% of this energy, and they do not cost much more to build (perhaps 
Paae 6, ENERGY-EFFICIENCY DESIGN GUIDE 

5% added on to the total construction cost). The purpose of this Design 

Guide is to begin changing this situation--at least with new houses for 

Indians and Alaskan Natives. 

The cost of supplying comfort goes beyond dollars. The cost to our 

environment is staggering--a cost measured in tons of particulates in the 

air, in dead ocean birds, in lost national and personal security, in trees 

killed by acid rain. Indians once lived in balance with their environment-- 

a sustainable lifestyle--but no longer. Our present course is not 

sustainable. 

It is a far better thing to use a cubic foot of natural gas in the 

manufacture of fiberglass insulation than in the heating of a house. The 

fiberglass will save dozens of cubic feet of gas that would otherwise be 

burned during the lifetime of the house. 

A house that meets the auxiliary heating performance goals suggested in 

these guidelines is unlikely to ever freeze, even without backup heat. 

The Symbolism of Light 

The sunlight that enters a thoughtfully designed passive solar home will 

reinforce Indian cultural traditions. Most Indian cultures look to the 

morning sun. The door of a Navajo hogan opens to the east. This same 

light that nourishes the soul will warn the house on a winter morning. 

The Indian sense of place is usually identified with the four directions, 

the cardinal points of the compass. Passive solar design principles also 

teach us to treat each of the four building facades differently--in 

response to the very different impact that sun and wind have on the 

house. The south side is the primary passive solar receiver. Most of the 

windows are placed on the south--to accept the winter sun and shut out 

the summer sun--a natural consequence of the changing sun path 

between winter and summer. Moderate use of east windows provides 

early morning wakeup, both visually and thermally. West windows are 

kept to a minimum to prevent summer overheating. Moderate use of 

north windows provides a high quality of daylight on the north side; 

summer heating is minimal and winter heat losses can be controlled with 

the use of modem low-loss windows. Summer breezes, usually from the 

west or south, ventilate the house through well-placed window openings, 

refreshing and cooling the house. The designer of the house must create 

a sensitive blend of these characteristics with the symbolism of the tribal 

perception of the four directions, embodying the appropriate use of light, 

texture, and color. No universal formula can be prescribed because the 

symbolism varies from one Indian culture to another. 

Passive solar apertures are also often placed in the roof, as clerestories or 

roof monitors with the glass vertical and facing south. This same feature 

opens the possibility of visually opening the roof to the sky, symbolizing 

the duality of light above and dark below (which is also good passive 

solar design practice). The sun, perhaps the most important celestial 
FOR INDIAN HOUSING Paae 7 

symbol, is brought into the life of the house, blessing it with light and 

warmth. 

The Symbolism of Space 

As a general principle, a large and open central space is critical to Indian 

tradition. The space serves a communal function. The space is often 

circular, representing a "philosophy of the cycles of nature and the 

continuity of life". The circle also "symbolizes equality and the concept of 

sharing". 

Openness of space also serves well in passive solar design. Solar heat is 

collected primarily on the south side of the house and must be 

distributed, primarily by natural convection, to the north side. A open 

floor plan facilitates this transfer. A large central area, with rooms 

radiating from it to the east, north, and west, is an ideal passive solar 

plan. 

The Symbolism of Materials 

Indians traditionally lived in constant contact with the materials of their 

natural environment and came to regard these materials as important 

symbols. Such materials can also serve important thermal and 

luminance functions within a house. 

Massive natural materials, such as adobe and rock, are very effective for 

storing solar heat admitted into the house during the day. Their 

effectiveness in this role depends on their location and color, as 

discussed in Parts 'Ibo and Three of Section I. A massive floor, always a 

feature of traditional Indian houses, is very effective heat storage but 

only where the sun shines directly on it. Other mass in walls or roof is 

effective even without direct solar radiation. Generally, floors should be 

dark in color and other surfaces light in color for the greatest 

effectiveness. This may or may not be completely consistent with cultural 

tradition. These are factors that the designer must weigh. 

Wood is another primary material used in traditional Indian houses. 

Unfortunately, wood is not particularly effective for energy efficiency. 

Although wood has a low thermal conductivity, it cannot compete with 

fiberglass for wall or roof insulation. Although it has a high heat 

capacity, the low conductivity prevents it from being very effective for 

thermal storage. The wonderful texture, color, and character of wood are 

justification enough for using it inside the house, but it should not be 

considered as a particularly effective insulating or heat-storage material. 

Harmony with Nature 

More than anything else, energy-efficient passive solar houses are 

designed to exist in harmony with nature. The natural environmental 

influences of sun, wind, heat, and cold are taken into account in the 

desi n. The pleasure of living in a house that naturally maintains 

com f ort most of the time, both winter and summer, must be experienced 
Paae 8 ENERGY-EFFICIENCY DESIGN GUIDE 

to be appreciated. It is a marvel that will reinforce culturally relevant 

Indian housing. 

Indigenous materials, southerly orientation, and building form were used to 

enhance the comfort of pueblo structures such as Taos Pueblo. With modem 

insulation and windows, much greater thermal performance and comfort can 

be obtained while retaining traditional architectural texture and feel. 

Energy-Efficient y Savings Potential 

The energy performance of ener -efficient strategies varies significantly, 

depending on climate, the speci P ic design of the system, and the way it is 

built and operated. Of course, energy performance is not the only 

consideration, but it is an important one. 

As a starting point, we choose a 1500-ft2 basecase single-story house 

insulated in accordance with a 1980 survey done by the National 

Association of Home Builders. These conservation levels are given on 

page 53 in Section 11. To this we then add consenration, passive solar, 

and natural cooling measures to achieve the performance goals 

recommended in Section 111. The total savings are listed for 43 U.S. 

locations in the table on page 10. For electrically heated homes, the 

overall annual energy savings vary from 18% in Brownsville, Texas, to 

66% in Cheyenne, Wyoming. The savings are smaller for houses heated 

with gas but are still quite substantial. 

Another figure of interest shown in the table is the solar savings fraction, 

SSF, assuming that you follow both the conservation and the passive 

solar guidelines. This number indicates the percentage of the heat 

required by the nonsolar elements of the house (all heat loss except the 

south glass) that is saved by solar heat trapped by the south glass. It is 
FOR INDIAN HOUSING Paae 9 

the net benefit of the solar elements accounting for both solar gains and 

heat losses. For electrically heated homes, these SSFs vary from 10% in 

Buffalo, New York, to 6 1% in Reno, Nevada. 

Images from the plains 
Paae 10 ENERGY-EFFICIENCY DESIGN GUIDE 

Energy Savings, percent of the annual energy requirements of the 

basecase house. 

This table gives the percent savings for a house that follows the 

uidelines compared with the NAHB basecase house. The solar savings 

Extion of the house is also included. 

House Heating: Gas 

Heating Cooling 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 

Total 

29 

24 

24 

40 

42 

46 

11 

39 

38 

24 

49 

39 

34 

51 

36 

24 

34 

41 

23 

22 

30 

24 

19 

22 

32 

33 

37 

37 

40 

38 

18 

39 

40 

16 

36 

43 

21 

10 

41 

43 

13 

39 

28 

Electricity 

SSF Heating Cooling Total SSF 
FOR INDIAN HOUSING Paae 11 

Part Two: Basics of Energy Efficiency 

1. Why Energy-Efficient? More than a Question of Energy 

Houses today are more energy efficient than ever before. However, the 

vast majority of new houses still ignore a lot of energy-saving 

opportunities--opportunities available in the sunlight falling on the 

house, in the landscaping, breezes, and other natural elements of the 

site, and opportunities in the structure and materials of the house itself, 

which, with thoughtful design, could be used to collect and use free 

energy. Passive solar (the name distinguishes it from "active" or 

mechanical solar technologies) is simply a way to take maximum 

advantage of these opportunities. 

In addition to economic and environmental advantages, energy-efficient 

homes are inherently more comfortable and adaptable to cultural and 

individual requirements. Other related advantages are simplicity, ease of 

maintenance, and reliability. A house that appropriately combines the 

three key ingredients emphasized in this guide--mass, glass and 

insulation--and meets the suggested performance goals for electrically 

heated homes--is very stable. It responds very slowly to weather changes 

and is unlikely to freeze during a power outage. 

The public has become increasingly sophisticated about energy issues, 

although the average person is probably much more familiar with 

insulation than with passive solar. The "energy crisis" may have ups and 

downs, but very few people perceive their own household energy bills to 

be getting lower, in fact, quite the opposite. Everyone knows that energy 

efficiency is an investment in the future. 

But there are many different ways to reduce energy bills, and some are 

more evident than others. For instance, adding insulation can markedly 

improve energy efficiency, but added insulation is invisible. A sunny, 

open living area lit by south-facing windows or a bright, attractive 

sunspace, on the other hand, not only reduces energy costs but 

enhances the quality of life of those living in the house. Windows, in 

general, are popular, and passive solar can make windows energy 

producers instead of energy liabilities. 

Passive solar is a very important option to consider. The point is not that 

a designer should choose passive solar instead of other energyconserving measures. The important thing is that passive solar can add 

not only energy efficiency, but also very attractive amenities--style, 

comfort, and attractive interiors--and help associate the house with 

cultural traditions of the tribe. 
Page 12 ENERGY-EFFICIENCY DESIGN GUIDE 

Advantages of Energy Efficiency 

Energy performance: lower energy bills year-round 

Attractive living environment: large windows and views, sunny interiors, open floor plans 

Comfort: quiet (no operating noise), solid construction, warmer in 

winter, cooler in summer (even during a power failure) 

Value: high occupant satisfaction 

Low maintenance: durable, reduced operation and repairs 

Investment: independence from future rises in fuel costs will continue 

to save money long after any initial costs have been recovered 

Environmental concerns: clean, renewable energy to combat growing 

concerns over global warming, acid rain, and ozone depletion 

2. Key Concepts: Energy Conservation. Suntempering, Passive Solar 

The strategies for enhancing energy performance that are presented here 

fall into four general categories: 

w Energy Conservation: insulation levels, control of air infiltration, 

glazing type and location, and mechanical equipment. 

Suntempering: a limited use of passive solar techniques; modestly 

increasing south-facing window area, usually by relocating windows 

from other sides of the house, but without adding thermal mass. 

Passive Solar: going beyond conservation and suntempering to a 

complete system of collection, storage, and use of solar energy: 

using more south-facing glass, adding significant thermal mass, and 

taking steps to control and distribute heat energy throughout the 

house. 

Natural Cooling: Using design and the environment to both cool the 

house and reduce summer heating by the sun. 

What is immediately clear is that these categories overlap. For instance, 

a good energy conservation package is the necessary starting point of all 

well-designed suntempered and passive solar houses. There's no use 

collecting solar energy if it is immediately lost through leaky windows or 

poorly insulated walls. Overdone or improperly done, passive solar will 

continue to heat the house in the summer, causing discomfort or high air-conditioning bills. 

In the same way, many of the measures that are often considered part of 

suntempering or passive solar--such as orienting to take advantage of 
FOR INDIAN HOUSING Paae 13 

summer breezes, landscaping for natural cooling, or facing a long wall of 

the house south--can help a house conserve energy even if no "solar" 

features are planned. 

The essential elements in a passive solar house are south-facing glass 

and thermal mass. 

In the simplest terms, a passive solar system collects solar energy 

through south-facing glass and stores solar energy in thermal mass-- 

materials with a high capacity for storing heat (for example, adobe, brick, 

concrete masonry, concrete slab, and tile). The more south-facing glass 

is used in the house, the more thermal mass must be provided, or the 

house will overheat, and the solar system will not perform as expected. 

With too much glass and/or insufficient mass, solar energy can work too 

well, and the house can be uncomfortably hot even on a winter day. 

Although the concept is simple, in practice, the relationship between the 

amount of glazing and the amount of mass is complicated by many 

factors, and has been a subject of considerable study and experiment. 

From a comfort and energy standpoint, it would be difficult to add too 

much mass. Thermal mass will hold warmth longer in winter and keep 

houses cooler in summer. But thermal mass has a cost, and so adding 

too much mass for just thermal storage purposes can be unnecessarily 

expensive. 

The following sections of the Design Guide discuss the size and location 

of glass and mass, as well as other considerations that are basic to both 

suntempered and full passive solar houses: improving conservation 

performance; mechanical systems; orientation; site planning for solar 

access; interior space planning; and taking an integrated approach to the 

house as a total system. 

3. Improving Conservation Performance 

The most important measures for improving the house's basic ability to 

consenre the heat generated either by the sun or by the house's 

conventional heating system are in the following areas: 

Insulation 

Air infiltration 

Nonsolar glazing 

Guidelines for insulation levels and window types are given for 43 U.S. 

locations. 

Insulation 

Adding insulation to walls, floors, ceilings, the roof, and the foundation 

improves their thermal resistance (R-value)--their resistance to heat 

flowing out of the house. 
Paqe 14 ENERGY-EFFICIENCY DESIGN GUIDE 

A quality job of installing the insulation can have almost as much effect 

on energy performance as does the R-value, so careful construction 

supervision is important. An inspection just before the drywall is hung 

identifies improvements that are easy to complete at that time but will 

make a big difference in the energy use of the home for years to come. 

The thermal resistance of ceiling/roof assemblies, walls, and floors is 

affected not only by the R-value of the insulation itself, but also by the 

resistance of other elements in the construction assembly--framing 

effects, sheathing, interior drywall, and so on. The help text in 

BuilderGuide includes tables that show Equivalent Construction R-values 

for walls, ceilings, and house perimeters, that account for these and 

other effects. For instance, ventilated crawlspaces and unheated 

basements provide a buffering effect. One of these BuilderGuide tables is 

reproduced below. 

Single 

Wall Insulation R-value 

Framing R-11 R-13 R-19 R-25 

2x4 at 16'oc 12.0 13.6 - - 

2x4 at 24'0~ 12.7 13.9 - - 2x6 at 16'oc 14.1 15.4 17.7 19.2 

2x6 at 24%~ 14.3 15.6 18.2 19.8 

Double 

Wall Total Thickness (inches) 

Framing 8 10 12 14 

The R-value of insulating sheathing should be added to 

the values in this table. 

Source : BuilderGuide help text 

R-values for Particular Wall 

Constructions 

These numbers are overall 

effectiue R-values including 

allowance forfrarning, 

sheathing, and inside and 

outside film coeff~cients. To 

account for insulating 

sheathing added to the 

exterior, simply add the 

R-ualue of the sheathing to 

these values. 

With attics, framing effects are minimized if the insulation covers the 

ceiling trusses, either by using blown-in insulation or by running an 

additional layer of batts in the opposite direction of the ceiling joists. 

Ridge and/or eave vents are needed for ventilation. 
FOR INDIAN HOUSING Paae 15 

Insulation in an Attic 

Insulation should extend over 

the top ceiling joists, and 

ventilation should be provided 

at the eaves. 

In framed ceiling/roof assemblies, an insulating sheathing over the top 

decking will increase the R-value. 

Slab edge insulation should extend at least 2-ft deep, measured from the 

surface of the floor. Materials for slab edge insulation should be selected 

for underground durability. One material with a proven track record is 

extruded polystyrene. Exposed insulation should be protected from 

physical damage by attaching a protection board, for instance, or by 

covering the insulation with a protective surface. 

In colder climates, basement walls should be fully insulated to at least 

4-ft below grade, but the portion of the wall below that depth only needs 

to be insulated to about half the R-value of the upper portion. Insulation 

can be placed on the outside surface of the wall, on the inside surface of 

the wall, or in the cores of the masonry units. 

If the basement walls are insulated on the outside, the materials should 

be durable underground, and exposed insulation should be protected 

from damage. In the case of a finished basement or walk-out basement, 

placing insulation on the interior may be less costly than insulating the 

exterior foundation. 

Air Infiltration 

Sealing the house carefully to reduce air infiltration--air leakage--is as 

necessary to energy conservation as adding insulation. Air will flow 

rapidly through cracks and crevices in the wall, in the same way water 

flows through the drain in a bathtub, so even a small opening can allow 

heat to bypass the insulation and lead to big energy losses. 

The tightness of houses is generally measured in the number of air 

changes per hour (ACH). A good, comfortable, energy-efficient house that 

follows the checklist on the next page will have approximately 0.35 to 

0.50 air changes per hour under normal winter conditions. 

Increasing the tightness of the house beyond that can improve the energy 

performance, but it can also create problems with indoor air quality, 

moisture buildup, and inadequately vented fireplaces and furnaces. 
Paae 16 ENERGY-EFFICIENCY DESIGN GUIDE 

Some kind of additional mechanical ventilation--for example, small fans, 

heat pump heat exchangers, integrated ventilation systems, or air-to-air 

heat exchangers--will probably be necessary to avoid such problems in 

houses with less than 0.35 ACH. 

In cold climates (above about 6000 heating degree days), the combination 

of a super-tight house and an air-to-air heat exchanger will be quite cost 

effective. However, because this is a mechanical system, it is subject to 

failure. The builder should ensure that the occupants of the house are 

properly aware of the system, of the necessity of its continued operation 

through the years, and that repairs and replacement parts will be 

available. 

The use of a house-sealing subcontractor to do the tightening and check 

it with a blower door can often save the designer time and problems, 

especially when trying to achieve particularly high levels of infiltration 

control. This may be warranted in cold climates. 

Kwakuitl raven 
FOR INDIAN HOUSING Paae 17 

Checklist for Minimizing Air Leakage 

Tighten seals around windows and doors, and weatherstripping around all 

openings to the outside or to unconditioned rooms 

Caulk around all windows and doors before drywall is hung: seal all penetrations 

(plumbing, electrical, etc.) 

Insulate behind wail outlets and/or plumbing lines in exterior walls 

Caulk under headers and sills 

Chink spaces between rough openings and millwork with insulation, or for a 

better seal, fill with foam 

Seal larger openings such as ducts into attics or crawlspaces with tapec 

polyethylene covered with insulation 

Locate continuous vapor retardants located on the warm side of the insulatior 

(building wrap, continuous interior polyethylene, etc.) 

Install dampers and/or glass doors on fireplaces, combined with outsidt 

combustion air intake 

Install backdraft dampers on all exhaust fan openings 

Caulk and seal the joint between the basement slab (or the slab on grade) and 

the basement wall 

Remove wood grade stakes from slabs and seal 

Cover and seal sump cracks 

Close core voids in top of block foundation walls 

Control concrete and masonry cracking 

Using air tight drywall methods is also acceptable (see Reference 11) 

Employ appropriate radon mitigation techniques (see References 1 3 and 14). 

South-facing windows are considered solar glazing. The south windows 

in any house are contributing some solar heat energy to the house's 

heating needs--whether it's a significant, usable amount or hardly worth 

measuring will depend on design, location, and other factors that are 

dealt with later under the discussions of suntempering and passive solar 

systems. 

North windows in almost every climate lose significant heat energy and 

gain very little useful sunlight in the winter. East and west windows are 

likely to increase air conditioning needs unless heat gain is minimized 

with careful attention to shading. 
Paae 18 ENERGY-EFFICIENCY DESIGN GUIDE 

But most of the reasons people want windows have very little to do with 

energy, so the best design will probably be a good working compromise 

between efficiency and other benefits, such as bright living spaces and 

views. 

Double glazing of all glazing is advisable. Storm windows over double 

glazing or double glazing with a low-e coating is advisable in cold 

climates. Low-e glazing on all windows may be an especially useful 

solution because some low-e coatings can insulate in winter and shield 

against unwanted heat gain in summer. 

Manufacturers will provide actual R-values for their windows (the 

thermal performance of glazing can be expressed either as an R-value or 

its reciprocal, the U-value; here all thermal performance values are given 

in tem-s of R-value). The chart shows app6oximate window R-values for 

various types. (The Overall Effective R-value pertains to the entire 

rough-frame window opening.) 

Double 

1 /4' space 

1/2" space 

Lowe 

Triple 

114' space 

1i2"pace 

Metal 

Standard Frame w/ 

Wood Metal Thermal 

Frame Frame Break 

Overall Effective R-values 

for Windows 

This table accounts for the 

frame and is based on the 

rough frame opening area. 

These R-values are for the entire rough frame window 

opening. When storm sash is added, an additional 1.1 

may be added. One half the R-value of moveable 

insulation may also be added, when appropriate. 

Source: BuilderGuide help text 

North windows should be used with care. Sometimes views or diffuse 

northern light are desirable, but in general, north-facing windows should 

not be large. Because north windows receive relatively little direct sun in 

summer, they do not present much of a shading problem. So if the 

choice were between an average-sized north-facing window and an east 

or west-facing window, north would actually be a better choice, 

considering both summer and winter performance. 

East windows catch the morning sun. This can be particularly 

important in Indian housing because openin s to the east have a special 

symbolism in most Indian cultures. Be care f ul, however, not to oversize, 

because the net energy benefit may be small, and, unfortunately, an east 

orientation can cause potential overheating problems in summer. 

Shading may be advised. 

West windows may be the most problematic, and there are few shading 

systems that will be effective enough to offset the potential for 
FOR INDIAN HOUSING Paae 19 

overheating from a large west-facing window. Glass with a low shading 

coefficient may be one effective approach--for example, tinted glass or 

some types of low-e glass that provide some shading while allowing 

almost clear views. The cost of properly shading both east and west 

windows should be balanced against the benefits. 

As many windows as possible should be kept operable for easy natural 

ventilation in summer. (See also Orientation, page 27, Recommended 

Non-South Glass Guidelines, page 45, and Shading, page 45). 

Conservation Guidelines 

The two tables on pages 20 and 2 1 can be used for uidance in selecting 

insulation levels and window type. The first table is f or houses heated by 

gas and the second is for houses heated by electricity. If you use these 

numbers in your design, you should come close to the conservation 

performance goal given in Section 111. You can deviate up or down from 

these values, depending on your favorite construction technique, but the 

overall building heat loss should still be below the goal. 

The tables provide minimum values for the following quantities: 

Rc 

Rw 

Floor 

Rf 

RP 

Windows 

AF'UE 

SEER 

ceiling insulation R-value 

wall insulation R-value 

prevalent floor type 

floor insulation R-value, crawl space 

perimeter insulation R-value, slab or basement 

windows and frame (TB is thermal break) 

windows with low-e should also have a thermal break 

heating annual fuel utilization efficiency, percent 

ER refers to electric-resistance heat 

cooling seasonal energy efficiency rating, Btu/kWh 

The tables have been developed using the Automated Residential Energy 

Standards (ARES) computer program developed at the Pacific Northwest 

Laboratory. This means that they are the economic-optimum values for 

the climate. See page 80 in Section I11 for a discussion of the basis for 

these guidelines. 
Paae 20 ENERGY-EFFICIENCY DESIGN GUIDE 

Conservation Guidelines, Houses Heated with Gas 

City 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville , FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York. NY 

Rc Rw Floor Rf Rp Windows AFUE SEER 

Slab 

Slab 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Slab 

Slab 

Bsmnt 

Slab 

Slab 

Slab 

Slab 

0 Double w/o TB 85 10 

0 Double w/o TB 85 10 

0 Double w/o TB 78 10 

10 to 4 ft Double Low-E 95 10 

5 to 4 ft Double Low-E 78 10 

10 to 4 ft Double Low-E 80 10 

0 Double w/o TB 78 11 

5 to 4 ft Double Low-E 90 10 

5 to 4 ft Double Low-E 95 10 

0 Double w/o TB 78 10 

5 to 4 ft Double Low-E 85 10 

10 to 4 ft Double Low-E 90 10 

5 to 4 ft Double Low-E 78 10 

5 to 4 ft Double Low-E 78 10 

0 Double Low-E 78 10 

0 Double w/o TB 78 10 

5 to 2 ft Double w/o TB 78 10 

5 to 4 ft Double Low-E 95 10 

0 Double w/o TI3 78 10 

0 Double w/o TB 78 10 

0 Double Low-E 78 10 

0 Double w/o TB 78 10 

30 23 Crawl 30 Double wjo TB 85 10 

30 23 Slab 0 Doublew/oTB 85 10 

30 23 Bsmnt 5 to 4 ft Double Low-E 95 10 

30 23 Slab 5 to 2 ft Double w/o TB 85 10 

30 23 Bsmnt 5 to 4 ft Double Low-E 78 10 

~klahoma City, OK30 13 Slab 

Omaha, NE 30 23 Bsmnt 

Philadelphia, PA 30 23 Bsmnt 

Phoenix, AZ 30 23 Slab 

Pittsburgh, PA 30 23 Bsmnt 

Portland, ME 30 23 Bsmnt 

Portland, OR 30 23 Crawl 30 

Reno, NV 30 23 Crawl 30 

Salt Lake City, UT 30 23 Bsmnt 

San Antonio, TX 30 13 Slab 

San Diego, CA 19 13 Slab 

San Francisco, CA 30 13 Slab 

Seattle, WA 30 23 Bsmnt 

Tampa, FL 19 11 Slab 

Topeka, KS 30 23 Bsmnt 

Washington, DC 30 23 Bsmnt 

0 Double Low-E 80 10 

10 to 4 ft Double Low-E 85 10 

5 to 4 ft Double Low-E 78 10 

0 Double w/o TB 78 11 

5 to 4 ft Double Low-E 78 10 

5 to 4 ft Double Low-E 90 10 

Double w/o TB 85 10 

Double TB 78 10 

5 to 4 ft Double Low-E 78 10 

0 Double w/o TB 78 10 

0 Single w/oTB 80 10 

5 to 2 ft Double w/o TB 78 10 

5 to 4 ft Double Low-E 78 10 

0 Double w/o TB 78 10 

10 to 4 ft Double Low-E 85 10 

5to4ft Doublew/oTB 85 10 

See page 19 to identify terms. 
FOR INDIAN HOUSING Paae 21 

Conservation Guidelines, Houses Heated with Electricity 

City 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville , TX 

Buffalo, NY 

Burlington, W 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville , FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeies, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York. NY 

Rc Rw Floor Rf Rp Windows AFUE SEER 

Slab 

Slab 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Slab 

Slab 

Bsmnt 

Slab 

Slab 

Slab 

Slab 

5 to 2 ft Dou 

5 to 2 ft Dou 

10 to 2ft Dou 

10 to 8 ft Trip 

10 to 4ft Trip 

10 to 4ft Trip 

0 Dou 

10 to 4 ft Trip 

10 to 8 ft Dou 

5 to 2 ft Dou 

10 to 4 ft Trip 

10 to4ft Trip 

10 to 4 ft Trip 

10 to 4 ft Trip 

5 to 2 ft Dou 

5 to 2 ft Dou 

5 to 2 ft Dou 

10 to 8 ft Trip 

5 to 2 ft Dou 

5 to 2 ft Dou 

5 to 2 ft Dou 

5 to 2 ft Dou 

3le Low-E 

Ae Low-E 

sle Low-E 

e Low-E 

e Low-E 

e Low-E 

sle w/o TI3 

e Low-E 

Ae Low-E 

de Low-E 

e Low-E 

e Low-E 

e Low-E 

e Low-E 

Ae TB 

sle Low-E 

Ae Low-E 

e Low-E 

sle TB 

sle w/o TB 

de Low-E 

3le TB 

60 26 Crawl 30 Double Low-E ER 10 

38 23 Slab 5 to 2 ft Double Low-E ER 10 

60 26 Bsmnt 10 to 8 ft Triple Low-E ER 12 

38 23 Slab 5 to 2 ft Double Low-E ER 10 

49 26 

~klahoma City, OK38 23 

Omaha, NE 60 26 

Philadelphia, PA 60 26 

Phoenix, AZ 30 23 

Pittsburgh, PA 49 26 

Portland, ME 60 26 

Portland, OR 38 23 

Reno, NV 60 26 

Salt Lake City, UT 60 26 

San Antonio, TX 30 13 

San Diego, CA 30 19 

San Francisco, CA 30 23 

Seattle, WA 60 26 

Tampa, FL 30 19 

Topeka, KS 60 26 

Washington, DC 38 26 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Crawl 30 

Crawl 30 

Bsmnt 

Slab 

Slab 

Slab 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

10 to 4 ft Triple Low-E ER 10 

5 to 2 ft Double Low-E ER 10 

10 to 4 ft Triple Low-E ER 10 

10 to 4 ft Triple Low-E ER 10 

0 Double w/o TB ER 1 1 

10 to 4 ft Triple Low-E ER 10 

10 to 4 ft Double Low-E ER 10 

Double Low-E ER 10 

Triple Low-E ER 12 

10 to 4 ft Triple Low-E ER 1 1 

5 to 2 ft Double Low-E ER 10 

5 to 2 ft Double w/o TB ER 10 

5 to 2 ft Double TI3 ER 10 

10 to 4 ft Double Low-E ER 10 

0 Double w/o TB ER 11 

10 to 4 ft Triple Low-E ER 10 

10 to 4 ft Double Low-E ER 10 

See page 19 to identify terms. 
Paae 22 ENERGY-EFFICIENCY DESIGN GUIDE 

4. Mechanical Systems 

The energy-efficient features in the house and the mechanical heating, 

ventilating, and air-conditioning systems (HVAC) will interact all year 

round, so the most effective approach will be to design the system as an 

integrated whole. HVAC design is, of course, a complex subject, . - but the 

four areas below are particularly worth noting in energy-efficient houses: 

System Sizing. Mechanical systems are often oversized for the 

relatively low heating loads in well-insulated energy-efficient houses. 

Oversized systems will cost more in the first place, and will cycle on 

and off more often, which wastes energy. The backup systems in 

energy-efficient houses should be sized to provide 100% of the 

heating or cooling load on the design day, but should be no larger. 

Comparing estimates on system sizes from more than one 

contractor is probably a good idea. 

Night Setback. Clock thermostats for automatic night setback are 

usually ve effective--but in energy-efficient systems with large 

amounts o '7 thermal mass (and thus a large capacity for storing 

energy and releasing it during the night), night setback of the 

thermostat may not save very much energy. 

Ducts. One area often neglected but of key importance to the 

house's energy performance is the design and location of the ducts. 

Both the supply and return ducts should be located within 

insulated areas (or the ducts should be well insulated where they 

run through cold areas of the house) and well sealed at the joints. 

The joints where the ducts turn up into exterior walls or penetrate 

the ceiling should be particularly tight and caulked. 

System Efficiency. Heating system efficiency is rated by the annual 

fuel utilization efficiency, AFUE. Cooling system efficiency is rated 

by the seasonal energy efficiency rating, SEER. Recommended 

minimum values for these ratings are given in the conservation 

guideline tables on pages 20 and 2 1. 

In the National Association of Home Builders' Energy-Efficient House 

Project, all the rooms were fed with low, central air supplies, as op osed 

to the usual placement of registers under windows at the end or) long 

runs. This resulted in good comfort and energy performance. 

The performance of even the most carefully designed energy-efficient 

house can easily be undermined by details like uninsulated ducts or by 

overlooking other basic energy conservation measures. 
FOR INDIAN HOUSING Paae 23 

5. South-Facing Glass 

South-facing solar glass is a key component of any passive solar system. 

The system must include enough solar glazing for good performance in 

winter, but not so much that cooling performance in summer will be 

compromised. The amount of solar glazing must also be carefully related 

to the amount of thermal mass. Suntempered houses require no 

additional thennal mass beyond that already in the wallboard, framing, 

and furnishings of a typical house. Passive solar houses must have 

additional thermal mass. 

There are three types of limits on the amount of south-facing glass that 

can be used effectively in a house. The first is a limit on the amount of 

glazing for suntempered houses. This limit (without adding thermal 

mass) is 7% of the house's total floor area. Above the 7% limit, mass must 

be added. 

For direct-gain systems in passive solar houses, the maximum amount of 

south-facing glazing is 12% of the total floor area, regardless of how 

much additional thermal mass is provided. Further details about the 

most effective sizing of south-facing glass and thermal mass for directgain systems are provided in Part Three. 

The third limit on south-facing glass is the total of all passive solar 

systems combined, which should not exceed 20% of the total floor area. 

Using more south-facing glass than this limit could lead to overheating 

even in winter. 

The Natural Cooling Guidelines in Part Four include recommendations 

on the window area that should be operable to allow for natural 

ventilation. 

When the solar glazing is tilted, its winter effectiveness as a solar 

collector usually increases. However, tilted glazing can cause serious 

overheating in the summer, and it is very difficult to effectively shade 

tilted glazing. Ordinary vertical glazing is easier to shade, less likely to 

overheat, and less susceptible to damage and leaking, so it is almost 

always a better year-round solution. Even in the winter, with the sun low 

in the sky and reflecting off snow cover, vertical glazing can often offer 

energy performance just as effective as can tilted glazing. 

Guidelines for the total area of passive solar glazing are listed in the table 

on page 25 for 43 U.S. locations. The guidelines are given in two ways: 

(1) total south glazing area as a fraction of house floor area, GF, and 

(2) recommended load-collector ratio, LCR*. Initially, the designer should 

use the GF guideline, which is easiest to use early in the design process. 

* LCR is a an intermediate parameter that is used in the BuilderGuide computer 

program: it is the ratio of net loss coefficient to projected area and has units of 

Btu/"Fdayft2. LCR is displayed on Line B of Worksheet 11. 
Paae 24 ENERGY-EFFICIENCY DESIGN GUIDE 

Later, after the design has progressed and design analysis has started, 

the LCR guideline can be used as a way to adjust the window area. 

For those cases with a recommended glazing fraction of 7%, it is 

recommended that the house be suntempered. Added mass associated 

with higher levels of direct gain will not be economical. However, if mass 

is to be present anyway, then the designer could economically justify 

increasing the solar glazing area. 

Solar savings fractions are also listed in the table. These give a general 

indication of the solar savings that you should expect to achieve with the 

LCR values listed; however, this will vary somewhat with the passive 

system type you are using. 

Gable-end roof openings were sometimes used to bring light into the plank 

houses of the Indians of the Pacific Northwest, but at a sacrifice of comfort. With 

modern glazing materials, even more light can be admitted while comfort is 

enhanced. 
FOR INDIAN HOUSING Page 25 

Passive Solar Guideline, Total Area of South-Facing Glass of All Passive 

Systems Combined 

GF glazing fraction, south net glass area/floor area, percent 

LCR load-collector ratio (see BuilderGuide program), Btu/ OF-day-ft2 

SSF solar savings fraction, percent 

House heating: 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville , FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 

Gas 

LCR 

62 

118 

118 

82 

89 

83 

132 

90 

91 

119 

40 

83 

98 

47 

107 

118 

104 

88 

122 

122 

lo6 

130 

94 

119 

90 

98 

100 

lo6 

83 

100 

118 

90 

91 

95 

49 

88 

121 

149 

107 

91 

132 

83 

111 

Electricitv 

LCR 
Paae 26 ENERGY-EFFICIENCY DESIGN GUIDE 

6. Thermal Mass 

Some heat storage capacity, or thermal mass, is present in all houses, in 

the framing, gypsum wall and ceiling board, typical furnishings and floor 

coverings. In suntempered houses, this modest amount of mass is 

sufficient for the modest amount of south-facing glass. But more 

thermal mass is required in passive solar houses, and the question is not 

only how much, but what kind and where it should be located. 

The thermal mass in a passive solar system is usually a conventional 

construction material such as brick, adobe, rock, cast concrete, concrete 

masonry, concrete slabs, or tile, and is usually placed in the floor or 

interior walls. Water actually has a higher unit thermal storage capacity 

than concrete or masonry. Water tubes and units called "water walls" 

are commercially available (general recommendations for these systems 

are included in the section on Thermal Storage Wall systems). 

The thermal storage capabilities of a given material depend on the 

material's conductivity, specific heat, and density. Most of the concrete 

and masonry materials typically used in passive solar have similar 

specific heats. Conductivity tends to increase with increasing density. 

So the major factor affecting performance is density. Generally, the 

higher the density, the better. 

Heat Storage Properties of Materials 

Material 

Poured Concrete 

Clay Masonry 

Adobe 

Molded Brick 

Extruded Brick 

Pavers 

Concrete Masonry 

Block 

Brick 

Pavers 

Gypsum Wallboard 

Water 

Density Heat Capacity 

(lb/ft3) (Btu/in. -ft2-OF) 
FOR INDIAN HOUSING Page 27 

The possibility of using natural materials that have a cultural 

significance arises in discussions of Indian housing. Adobe, rock, and 

wood are the materials that are most often mentioned. Of these, adobe 

and rock will certainly be effective; however, wood is not very effective 

beyond a thickness of 2 in. because of its relatively low thermal 

conductivity, which inhibits heat transfer in and out of the material. 

The design issues related to thermal mass depend on the passive system 

type. For sunspaces and thermal storage wall systems, the required 

mass of the system is included in the design itself. For direct gain, the 

added mass must be within the rooms receiving the sunlight. The 

sections on Direct Gain Systems, Sunspaces, and Thermal Storage Walls 

contain more information on techniques for sizing and locating thermal 

mass in those systems. 

7. Orientation 

The ideal orientation for solar glazing is within 5 degrees of true south. 

This orientation will provide maximum performance. Glazing oriented to 

within 15 degrees of true south will perform almost as well, and 

orientations up to 30 degrees off--although less effective--will still provide 

a substantial level of solar contribution. 

Magnetic north as indicated on the compass is actually different than 

true north, and this correction should be made when planning for 

orientation of south glazing. 

When glazing is oriented more than 15 degrees off true south, not only is 

winter solar performance reduced, but summer air-conditioning loads 

also significantly increase, especially as the orientation goes west. The 

warmer the climate, the more east- and west-facing glass will tend to 

cause overheating problems. In general, southeast orientations present 

less of a problem than southwest orientations. 

In the ideal situation, the house should be oriented east-west and so 

have its longest wall facing south. But as a practical matter, if the 

house's short side has good southern exposure, it will usually 

accommodate sufficient glazing for an effective passive solar system, 

provided the heat can be transferred to the northern zones of the house. 

8. Site Planning for Solar Access 

The basic objective of site planning for maximum energy performance is 

to allow the south side unshaded exposure from 9 am to 3 pm during the 

winter months. 

As discussed above, a good solar orientation is possible within a 

relatively large southern arc, so the flexibility exists to achieve a 

workable balance between energy performance and other important 

factors such as the slope of the site, the individual house plan, the 
Page 28 ENERGY-EFFICIENCY DESIGN GUIDE 

direction of prevailing breezes for summer cooling, the views, the street 

layout, and so on. 

But planning for solar access does place some restrictions even on an 

individual site. and resents even more challenges when ~lanning a 

complete subdi~ision.~ Over the years, developers kd buildek of many 

different kinds of projects all over the country have come up with flexible 

ways to provide adequate solar access. 

Once again, there is an ideal situation and then some degree of flexibility 

to address practical concerns. Ideally, the glazing on the house should 

be exposed to sunlight with no obstructions within an arc of 60 degrees 

on either side of true south, but reasonably good solar access will still be 

f uaranteed if the glazing is unshaded within an arc of 45 degrees. The 

igure shows the optimum situation for providing unshaded southern 

exposure. See also the figure on page 46 showing landscaping for 

summer shade. The winter and summer requirements are compatible but A 

do require careful planning. 

Ideal Solar Access 

Buildings, trees, or other 

obstructions should not be 

located so as to shade the 

south wall of solar buildings. 

The following setbacks ift) are 

recommended. 

Latitude A B C 

Of course, not all lots are large enough to accommodate this kind of 

optimum solar access, so it's important to carefully assess shading 

patterns on smaller lots to make the best compromise. 

Protecting solar access is easiest in subdivisions with streets that run 

within 15 degrees of east-west, because all lots will either face or back up 

to the south. Where the streets run north-south, creation of east-west 

cul-de-sacs will help ensure solar access. 
FOR INDIAN HOUSING Paae 29 

Solar Subdivision Layouts 

Solar access may be provided 

to the rear yard, the side yard 

or thefront yard of solar 

homes. 

Solar Subdivision Layouts 

A good street pattern for solar 

access is short east-west culde-sacs tied into north-south 

collectors, 

Two excellent references for ideas about subdivision layout to protect 

solar access are the Designer's Guide to Passive Solar Home Design and 

Land Development and Site Planning for Solar Access. (See References 17 

and 18.) 

9. Interior Space Planning 

Planning room layout by considering how the rooms will be used in 

different seasons and at different times of day can save energy and 

increase comfort. In houses with energy-efficient features, the layout of 

rooms--and interior zones that may include more than one room--is 

particularly important. 

In general, living areas and other high-activity rooms should be located 

on the south side to benefit from the solar heat. The closets, storage 

areas, garage, and other less-used rooms can act as buffers along the 

north side, but entryways should be located away from the wind. 

Clustering baths, kitchens, and laundry rooms near the water heater will 

save the heat that would be lost from longer water lines. 
Paae 30 ENERGY-EFFICIENCY DESIGN GUIDE 

Interior Space Planning 

Living and high activity spaces 

should be located on the south. 

Another general principle is that an open floor plan will allow the 

collected solar heat to circulate freely through natural convection. 

Other ideas from effective energy-efficient houses: 

Orienting internal mass walls as north-south partitions that can be 

"charged" on both sides, thus making maximum use of the mass. 

Using an east-west partition wall for thermal mass, but making sure 

the interior space isn't divided into a south zone that may get too 

warm and a north zone that may get too cold. 

Using thermal storage walls (see page 40); the walls store energy all 

day and slowly release it at night and can be a good alternative to 

ensure privacy and to buffer noise when the south side faces the 

street; 

Collecting the solar energy in one zone of the house and 

transporting it to another by fans or natural convection through an 

open floor plan. 

Providing south-facing clerestories to "charge" north zones. 

10. Putting it Together: The House as a System 

Many different factors will affect a house's overall performance. and these 

factors all interact: the mechanical system, the insulation, the house's 

tightness, the effects of the energy-efficient features, the appliances, and, 

very importantly, the actions of the people who live in the house. In each 

of these areas, changes are possible that would improve the house's 

energy performance. Some energy savings are relatively easy to get. 

Others can be more expensive and more difficult to achieve, but may 

provide benefits over and above good energy performance. 

A sensible energy-eficient house uses a combination of techniques. 

In fact, probably the most important thing to remember about designing 

for energy performance in a way that will also enhance the comfort and 
fOR INDIAN HOUSING Paae 31 

value of the house is to take an integrated approach, keeping in mind the 

house as a total system. On the following page is a basic checklist for 

energy-efficient design. 

Checklist for Good Design 

/ 1. Building orientation: A number of innovative techniques can be used to obtain good solar 

xcess on less-than-ideal sites (see References 17 and 18). No matter what the house's design, and no 

natter what the site, some options for orientation will be more energy-efficient than others, and even a 

very simple review of the site will probably help you choose the best option available. 

/ 2. Upgraded levels of insulation: It is possible, of course, to achieve very high energy-efficiency 

with a "superinsulated" design. But in many cases, one advantage of passive solar design is that energy 

:fficiency can be achieved with more modest increases in insulation. On the other hand, if very high 

mergy performance is a priority--for example, in areas where the cost of fuel is high--the most cost- 

:ffective way to achieve it is generally through a combination of high levels of insulation and passive 

solar features. 

/ 3. Reduced air infiltration: Air tightness is not only critical to energy performance, but it also 

nakes the house more comfortable. Indoor air quality is an important issue, and too complex for a 

:omplete discussion here, but in general, the suntempered and passive solar houses built according to the 

yidelines provide an alternative approach to achieving improved energy efficiency without requiring air 

pality controls such as air-to-air heat exchangers, which would be needed if the house were made 

:xtremely airtight. 

/ 4. Proper window sizing and location: Even if the total amount of glazing is not changed, 

*earranging the location alone can often lead to significant energy savings at little or no added cost. 

Some energy-conserving designs minimize window area on all sides of the house--but it's a fact of human 

Iature that people like windows, and windows can be energy producers if located correctly. 

/ 5. Selection of glazing: Low-emissivity (low-e) glazing types went from revolutionary to 

:ommonplace in a very short time, and they can be highly energy-efficient choices. But the range of 

glazing possibilities is broader than that, and the choice will have a significant impact on energy 

3erformance. Using different types of glazing for windows with different orientations is worth 

:onsidering for maximum energy performance; for example, using heat-rejecting glazing on west 

windows, high R-value glazing for north and east windows, and clear double glazing on solar glazing. 

/ 6. Proper shading of windows: If windows are not properly shaded in summer--either with 

shading devices or by high-performance glazing with a low shading coefficient--the air conditioner will 

have to work overtime, and the energy savings of the winter may be canceled out. Even more important, 

unwanted solar gain is uncomfortable. 

/ 7. Interior design for easy air distribution: If the rooms in the house are planned carefully, the 

flow of heat in the winter will make the energy-efficient features more effective, and the air movement 

will also enhance ventilation and comfort during the summer. Often this means the kind of open floor 

plan that is highly marketable in most areas. Planning the rooms with attention to use patterns and 

energy needs can save energy in other ways, too--for instance, using less-lived-in areas like storage 

rooms as buffers on the north side. 

/ 8. Addition of thermal mass: Adding effective thermal mass--for example, tiled or paved 

concrete slab, masonry walls, brick fireplaces, and tile floors--can greatly improve the comfort in the 

house, holding heat better in winter and keeping rooms cooler in summer. In a passive solar system, of 

course, properly sized and located thermal mass is essential. 

/ 9. Selection and proper sizing of mechanical systems, and selection of energy-efficient 

appliances: High-performance heating, cooling, and hot water systems are extremely energy efficient, 

and almost always a good investment. Well-insulated energy-efficient homes will have much lower 

energy loads than conventional homes, and should be sized accordingly. Oversized systems will cost 

more and reduce the house's performance. For guides to the selection of energy-efficient appliances, see 

References 13 and 14. 
Paae 32 ENERGY-EFFICIENCY DESIGN GUIDE 

Part Three: Passive Solar Strategies 

1. Suntempering 

Both suntempered and passive solar houses: 

rn Begin with good basic energy conservation 

H Take maximum advantage of the building site through the right 

orientation for year-round energy savings 

H Have increased south-facing glass to collect solar energy. 

Suntempering is the simplest passive solar system and refers to modest 

increases in windows on the south side. 

No additional thermal mass is necessary. only the "free mass" in the 

house-- the framing, gypsum wall-board, and furnishings. 

In a "conventional" house, about 25% of the windows face south, which 

amounts to about 3% of the house's total floor area. In a suntempered 

house, the percentage is increased to a maximum of about 7% of the 

houses' total floor area. 

The energy savings are more modest with this system, but suntempering 

is a very low-cost strategy. 

Of course, even though the necessity for precise sizing of glazing and 

thermal mass does not apply to suntempering (as lon as the total southfacing glass does not exceed 7% of the total house Ti oor area), all other 

recommendations about energy-efficient design, such as the basic energy 

conservation measures, room layout, siting, and glazing type, are still 

important for performance and comfort in suntempered homes. 

2. Direct Gain 

The most common passive solar system is called direct gain: sunlight 

through south-facing glazing penetrates directly into the space to be 

heated and is stored in thermal mass incorporated into the floor or 

interior walls. The south window area is increased above the 7% limit of 

a suntempered house, and additional thermal mass is added to store the 

additional solar gains and thus prevent overheating. 

Direct Gain 

Direct gain is the most common 

passive system. 
Savings from direct gain 

These are the net annual Btus 

of heat saved perff2 of directgain glazing, assuming the use 

of clear double glazing. 

sizing Limit 

Total direct-gain glass area should not exceed about 12% of the house's 

floor area. Beyond that, problems with lare or fading of fabrics are more 

mass for year-round comfort. 

likely to occur, and it becomes more d' & icult to provide enough thermal 

So the total south-facing glass area in a direct-gain system should be 

between 7% (the maximum for suntempered houses) and 12%, 

depending on how much thermal mass will be used in the design, as 

discussed below. 

Glazing 

Double glazing with a low-e coating is recommended for direct-gain glazing in cold climates or regular double glazing in moderate climates. 

Generally follow the guidelines on pages 20 and 21 for g1;lazing and 

window frames. Theoretically, night insulation will improve energy 

performance dramatically; however, studies have shown that only a 

relatively few homeowners will be diligent enough about operating their 

night insulation to achieve those savin s. Low-e glazing, on the other 

reliable option. 

hand, needs no operation, and there f ore is a more convenient and 

Thermal Mass 

Thermal mass can be incorporated easily into houses with slab-on-grade 

floors by exposing the mass. The floor is much more effective if sunlight 

falls directly on it. Covering the floor with any insulation material, such 

as carpet, greatly reduces its effectiveness. A good strategy is to expose a 

narrow strip about 8-ft wide along the south wall next to the windows 

where the winter sun will fall directly on it. 

Effective materials for floors include painted, colored, or vinyl-covered concrete, brick (face brick or pavers have even higher density than 
Paae 34 ENERGY-EFFICIENCY DESIGN GUIDE 

ordinary building brick), quarry tile, and dark-colored ceramic tile laid 

directly on the slab. 

For houses built with crawlspaces or basements, the incorporation of 

significant amounts of heavy thermal mass is a little more difficult. 

Thermal mass floor coverings over basements and crawlspaces would 

generally be limited to thin-set tile or other thin-mass floors. 

When more mass is required, the next best option is interior walls or 

interior masonry fireplaces. Unlike floor mass, wall or ceiling mass does 

not have to be in the direct sun to be effective. Any mass that encloses a 

direct-gain space will be effective as long as there is a line-of-sight 

connection between the mass and the sunlit area. 

When evaluating costs, the dual function of mass walls should be 

remembered. They often serve as structural elements, serve as fire 

protection, or provide a cultural connection, as well as providing thermal 

storage. hother option is to switch to another passive solar system type 

such as sunspaces or thermal storage walls that have built-in thermal 

mass. 

Sunlit thermal mass floors should be relatively dark in color, to absorb 

and store energy low in the space. However, mass walls and ceilings 

should be light in color to help distribute both heat and light more 

evenly. 

Guideline: Ratio of Mass to Glass. The simplest rule of thumb states: 

For each added ft2 of direct-gain glass (above the 7% 

suntempering limit), 6 ft2 of exposed mass surface should be 

added within the direct-gain space. 

The following procedure can be used to determine a somewhat more 

accurate estimate. This procedure gives the maximum amount of directgain glazing for a given amount of thermal mass. (If the amount of 

direct-gain glazing to be used is already known, thermal mass can be 

added until this procedure produces the desired proportions.) 

Start with a direct-gain glass area equal to 7% of the house's total 

floor area. As noted above, the "free mass" in the house will be able 

to accommodate this much solar energy. 

An additional 1.0 ft2 of direct-gain glazing may be added for every 5.5 ft2 of uncovered, sunlit mass floor. Carpet or area rugs will 

seriously reduce the effectiveness of the mass. The maximum floor 

mass that can be considered as "sunlit" may be estimated as about 

1.5 times the south window area. 

An additional 1.0 ft2 of direct gain glazing may be added for every 

40 ft2 of thermal mass in the floor of the room, but not in the sun. 
FOR INDIAN HOUSING Paae 35 

An additional 1.0 ft2 of direct-gain glazing may be added for each 8.3 

ft2 of thermal mass placed in the wall or ceiling of the room. Mass 

in the wall or ceiling does not have to be located directly in the 

sunlight, as long as it is in the same room, with no obstructions 

between the mass and the surface where the sunlight is falling. (The 

8.3 value is typical, but the true value does depend on mass density 

and thickness. Refer to the mass thickness graph for more specific 

values to use.) 

More south-facing glazing than the maximum as determined here would 

tend to overheat the room and to reduce energy performance as well. 

Mass Location and 

Effectiveness 

Additional mass must be 

provided for southfacing glass 

over 7% ofthe floor area. The 

ratio of mass area to 

additional glass area depends 

on its location within the 

direct-gain space. 

155 fa Wit Floor 1- for 

(should no1 exceed 1:40 for Floor Walls & 

1.5 times wndow area) not in Sm Ceiknqs 

Thickness. For most materials, the effectiveness of the thermal mass in 

the floor or interior wall increases proportionally with thickness up to 

about 4 in. After that, the effectiveness doesn't increase as significantly. 

A 2-in. mass floor will be about two-thirds as effective in a direct-gain 

system as a 4-in. mass floor. But a 6-in. mass floor will only perform 

about 8% better than a 4-in. floor. 

The following figure shows the effectiveness of thermal mass in relation 

to density and thickness. The vertical axis shows how many ft2 of mass 

area are needed for each added ft2 of direct gain. As you can see, 

performance increases start leveling off after a few inches of thermal 

mass. 
Paae 36 ENERGY-EFFICIENCY DESIGN GUIDE 

Mass Thickness 

0 : 1 I k 

0 5 10 15 

Thickness Cinches) 

The eflectiveness of thermal 

mass depends on the density 

of the material and thickness. 

This graph is for wall or ceiling 

mass in the direct-gain space, 

not forjZoors. The ratio of 8.3 

was used earlier as a 

representative value. More 

accurate values can be read 

from this graph and used in 

the fourth step of the 

procedure. 

In cases in which you are still uncertain if thermal mass is adequate, you 

can go to BuilderGuide, which includes a more comprehensive procedure. 

3. Sunspaces 

The sunspace is a very popular passive solar feature, adding an 

attractive living space as well as energy performance. There are many 

variations on the basic theme of the sunspace, and the possibilities for 

sunspace design are extraordinarily diverse (References 19 through 22 

include specific design ideas). 

Sunspaces 

Sunspaces provide useful 

passive solar heating and also 

provide a valuable amenity to 

homes. 
FOR INDIAN HOUSING Paae 37 

Savings from a Sunspace 

These are the net annual Btus 

of heat saved perft2 of 

sunspace south glazing, 

assuming the glass is sloped 

(type SSDIJ. 

As used in this guide, a sunspace is a separate direct-gain room on the 

south side of the house that can be thermally isolated from the rest of 

the house by closing doors between the house and the sunspace. The 

sunspace provides solar heat to the house but does not drain heat from 

the house or require additional heat itself. The wall that separates the 

house from the sunspace is called a common wall. 

The sunspace concept, as defined above, adds a room to the house that 

can be used year-round, that will provide most or all of its own energy 

needs, and that will contribute to the energy needs of the rest of the 

house as well. 

Sunspaces are sometimes referred to as "isolated gain" passive solar 

systems, because the solar heat is collected in an area that can be closed 

off from the rest of the house. During the day, the doors or windows 

between the sunspace and the house can be opened to circulate collected 

heat, and then dosed at night, and the temperature in the sunspace 

allowed to drop. 

The sunspace should not be on the same heating system as the rest of 

the house. A well-designed sunspace will robably need no mechanical 

heating system, but if necessary, a small P an or heater may be used to 

protect plants on extremely cold winter nights. 

Probably the most important factor in controlling the temperature in the 

sunspace, and thus keeping it as comfortable and efficient as possible, is 

to make sure the exterior walls are tightly constructed and well 

insulated. To function properly, the sunspace exterior walls and roof 

should be just as tightly constructed and insulated as the rest of the 

house. 
Paae 38 ENERGY-EFFICIENCY DESIGN GUIDE 

Sunspace geometries that 

can be evaluated in 

BuilderGuide 

There are many sunspace 

confgurations. 

Thermal Mass 

A sunspace has extensive south-facing glass, so designing in adequate 

thermal mass is very important. Without it, the sunspace is liable to be 

uncomfortably hot during the day and too cold for plants or people at 

night. 

However, the temperature in the sunspace can vary more than in the 

house itself, so about 3 ft2 of 4-in. thick thermal mass for each square 

foot of sunspace glazing should be adequate. With this glass-to-mass 

ratio, on a clear winter day, a temperature swing of about 30°F should be 

expected. 

The sunspace floor is a good location for thermal mass. The mass floors 

should be dark in color. No more than 15%-25% of the floor slab should 

be covered with rugs or plants. The lower ed e of the south-facing 

windows should be no more than 6 in. from the a oor or the planter bed 

to make sure the mass in the floor receives sufficient direct sunlight. If 

the window sills are higher than that, additional mass will have to be 

located in the wall. 

Another good location for thermal mass is the common wall (the wall 

separating the sunspace from the rest of the house). Options for the 

common wall are discussed in more detail below. 

Water in various types of containers is another forrn of energy storage 

sometimes used in sunspaces. 

Glazing 

Clear, double glazing is recommended for sunspaces. Adding the second 

pane makes a large improvement in energy savings. Triple glazing or 

low-e coatin s, on the other hand, will further improve comfort, but will 

have little ef f ect on energy savings. 
FOR INDIAN HOUSING Paae 39 

Windows on the east and west walls should be small (no more than 10% 

of the total sunspace floor area), but they are very effective for summer 

cross-ventilation. 

Summer Overheating 

Probably the single biggest problem encountered in sunspaces is 

summer overheating. Largely, this stems directly from poor design 

practice and can be avoided. The problem can usually be traced directly 

to poor glazing orientations--too much non-south glazing. Glass on the 

roof or on the west walls can create major overheating. 

Like any tilted or sloped glazing, a glazed sunspace roof can increase 

winter solar gain, but it can also present big summer overheating 

problems. If either glazed roofs or tilted glazing are used in the sunspace, 

special care should be taken to make sure they can be effectively shaded 

during the summer. The manufacturers of sunspaces and glazing are 

developing products with a better ability to control both heat loss and 

heat gain (for example, roof glazing with low shading coefficients, shading 

treatments, and shading devices). 

Sunspaces with glazed roofs or sloped glazing perform very well. 

However, if you are not prepared to provide effective shading for the 

summer months, you should consider using only vertical glazing and 

accepting somewhat less energy performance in winter. 

Common Wall 

There are a number of options for the sunspace common wall--the wall 

that separates the sunspace from the house. In mild climates, and when 

the sunspace is very tightly constructed, an uninsulated frame wall is 

probably adequate. However, insulating the common wall to about R- 10 

is a good idea, especially in cold climates. An insulated common wall will 

help guard against house heat loss to the sunspace during prolonged 

cold, cloudy periods. 

The preferred design practice is to make the common wall of masonry so 

that it also serves for thermal mass. The wall should be solid masonry 

approximately 4-in. to 8-in. thick and does not need to be insulated. 

Another option is a frame wall with masonry veneer. 

Some solar energy may be transferred from the sunspace to the rest of 

the house by conduction through the common wall if it is made of 

thermal mass. But energy is mainly transferred by natural convection 

through openings in the common wall--doors, windows, and/or vents. 

rn Doors are the most common opening in the common wall. If only 

doorways are used, the open area should be at least 15% of the 

sunspace south-facing glass area. 
Paae 40 ENERGY-EFFICIENCY DESIGN GUIDE 

rn Windows in the common wall will provide light and views from the 

house, and will augment natural convection. The window area 

should be no larger than about 40% of the entire common wall area. 

Per unit area, window openings are about one-half as effective for 

natural convection as are door openings. 

Summer Ventilation 

The sunspace must be vented to the outside to avoid overheating in the 

summer or on warm days in the spring and the fall. A properly vented 

and shaded sunspace can function much like a screened-in porch. 

Operable windows and/or vent openings should be located for effective 

cross-ventilation, and to take advantage of the prevailing summer wind. 

Low inlets and high outlets can be used in a "stack effect", because warm 

air will rise. These ventilation areas should be at least 15% of the total 

sunspace south-facing glass areas. 

Where natural ventilation is insufficient or access to natural breezes is 

blocked, a small, thermostat-controlled fan set at about 76°F will 

probably be a useful addition. 

4. Thermal Storage Wall 

The Thermal Storage Wall--also sometime.^ referred to as a Trombe wall 

or an indirect-gain system--is a south-facing glazed wall, usually built of 

heavy masonry, but sometimes using water containers or phase-change 

materials. The masonry is separated from the glazing only by a small air 

space. Sunlight is absorbed directly into the wall instead of into the 

living space. The energy is then released into the living space over a 

relatively long period. The time lag varies with different materials, 

thicknesses, and other factors, but typically, energy stored in a Thermal 

Storage Wall during the day is released during the evening and nighttime 

hours. 

The outside surface of a thermal storage wall should be a very dark 

color--an absorptance greater than 0.92 is highly recommended. Using a 

light color will spoil the performance of the wall. 

The summer heat gain from a Thermal Storage Wall is much less than 

that from a comparable area of direct-gain glazing. 
FOR INDIAN HOUSING Paae 41 

Thermal Storage Wall 

A thermal storage wall is an 

effective passive solar system, 

especially to provide nighttime heating. 

A masonry Thermal Storage Wall should be solid, and there should be no 

openings or vents either to the outside or to the living space. Although 

vents to the living space were once commonly built into Thennal Storage 

Walls, experience has demonstrated that they are ineffective. Vents 

between the Thermal Storage Wall and the house tend to reduce the 

system's nighttime heating capability and to increase the temperature 

fluctuation in the house. Vents to the outside are similarly ineffective 

and do little to reduce summer heat gains. 
Paae 42 ENERGY-EFFICIENCY DESlGN GUIDE 

Savings from a Trombe Wall 

These are the net annual Btus 

of heat saved perft2 Trombe 

wall south glazing. The wall is 

high-density concrete block, 

12-in. thick, and double 

glazed. It has aflat-black 

surface and is unvented. 

Additional Savings from 

Using a Selective Surface on 

a Trornbe Wall 

Btus of additional heat saved 

perftz Trombe wall south 

glazing. Add these values to 

the values shown on the map 

above to obtain the total Btu 

savings ofa wall with a 

selective surface. The wall has 

a single water-white glazing 

instead of conventional double 

glazing. 

Glazing 

Double glazing is recommended for Thermal Storage Walls unless a 

selective surface is used. In that case, single glazing performs about the 

same as does double glazing in all but the coldest climates. 

The space between the glazing and the thermal mass should be between 

one-half in. and 3 in. 

Selective Surfaces 

A selective surface is a special adhesive foil applied to the exterior side of 

the mass of Thermal Storage Walls. Selective surfaces absorb a large 
FOR INDIAN HOUSING Paae 43 

percentage of solar radiation but radiate very little heat back to the outof-doors (low emittance). 

To be effective, selective surfaces must be applied carefully for 100% 

adhesion to the mass surface. 

Mass Material and Thickness 

In general, the effectiveness of the Thermal Storage Wall will increase as 

the density of the material increases. Low-density materials are not 

recommended. Block filled with sand, for example, will perform poorly. 

The optimum thickness of the wall depends on the density of the 

material chosen, but performance is not very sensitive to thickness. The 

following chart indicates the recommended thicknesses of Thermal 

Storage Walls made of various materials. As thickness is increased, the 

time delav of heat flow through the wall is increased, and the 

ternperatu?e variation on the insid; surface is decreased. 

Mass Wall Thickness 

Density Thickness 

Material (lb / ft3) (in .) 

Concrete 140 8-24 

Concrete Block 130 7-18 

Clay Brick 120 7-16 

Ltwt. Concrete 110 6-12 

Block 

Adobe 100 6-12 

Water Walls 

Water provides about twice the heat storage per unit volume as masonry, 

so a smaller volume of mass can be used. In "water walls", the water is 

in light, rigid containers. The containers are shipped empty and are 

easily installed. Manufacturers can provide information about durability, 

installation, protection against leakage, and other characteristics. At 

least 30 lb (3.5 gal.) of water should be provided for each ft2 of glazing. 

This is equivalent to a water container about 6-in. thick, having the same 

area as the glazing. 
Paae 44 ENERGY-EFFICIENCY DESIGN GUIDE 

5. Combined Systems 

Although the previous sections have presented separate discussions of 

four different systems, it isn't necessary to choose one and only one 

system. In fact, passive solar features work best in combination. 

For example, direct gain works very well in conjunction with a sunspace 

or thermal storage wall. Because thermal storage walls release energy 

more slowly than direct-gain systems, they are useful for supplying heat 

in the evening and at night, whereas the direct-gain system works best 

during the day. Although using a sunspace, a thermal storage wall, and 

a direct-gain system in the same house may result in excellent 

performance, such combinations do require a large south-facing area 

and careful design to make sure the systems are well integrated with 

each other and with the house's mechanical system. 

Part Four: Natural Cooling Guidelines 

The term "natural cooling" is used here to describe techniques that help 

a house stay cool in summer but require little or no energy. Natural 

cooling techniques work to help reduce air conditioning, not to replace it. 

These techniques are useful not only in passive solar houses, but in 

"conventional" houses as well. The strategies outlined below--attention 

to the location, size, and shading of glazing; using the opportunities on 

the site for shading and natural ventilation; and using fans--can reduce 

air-conditioning needs and increase comfort even if the house has no 

passive solar heating features. 

But shading is particularly important in passive solar houses, because 

the same features that collect sunlight so effectively in winter will go 

right on collecting it in summer--resulting in uncomfortably hot rooms 

and big air-conditioning bills--unless those features are properly shaded 

and the house is designed to help cool itself. 

Fortunately, many of the features that help maintain comfort and reduce 

energy needs in winter also work well in summer. For instance, 

additional thermal mass performs well year-round. Masonry materials 

are equally effective in staying cool and storing heat. If mass surfaces 

can be exposed to cool nighttime temperatures--a technique referred to 

as "night ventilationw--they will help the house stay cooler the next day. 

A California utility found during studies of small test buildings that on 

hot summer days, the workmen at the facility always ate lunch in the 

masonry test building because it stayed much cooler than any of the 

others. (See Reference 9.) 

The additional insulation that increases winter performance will also 

work to improve summer performance by conserving the conditioned air 

inside the house. And some low-e windows and other glazing with high 

R-values can help shield against unwanted heat gain in summer. 
FOR INDIAN HOUSING Paae 45 

1. Glazing 

As mentioned earlier, poorly placed windows can increase airconditioning; loads dramatically. It is generally best in terrns of energy 

perforrnanc~ to carefully size nonsolar glazing as indicated in the 

following table. 

Recommended Non-South Net 

Glass Area 

Percent 

of Total 

Orientation Floor Area 

East 

North 

West 

As mentioned earlier, west-facing windows present particularly difficult 

shading problems. If glazing is added above the recommended 2% of the 

floor area, the need for shading will become even more critical. 

Using special glazing or window films that block solar transmission (low 

shading coefficient) is an option often used in particularly hot climates, 

but the more effective they are at blocking sunlight, the less clear they 

are, as a rule, and so they may interfere with desirable views. It is 

important to note, however, that some types of low-e windows block solar 

transmission but also allow clear views, These treatments are not 

recommended for south windows because the winter solar gain is so 

desirable. 

Skylights present a high potential for overheating because the summer 

sun passes nearly overhead, and because they are especially difficult to 

shade properly. But skylights are a very popular feature, and they save 

electricity by providing good natural daylight to the house. In some parts 

of the country, almost every new house has at least one skylight. A good 

working compromise can usually be achieved if the skylight area is 

limited, and if careful attention is paid to shading, either by using a low 

shading coefficient glass or by devices such as roller shades or blinds. 

The manufacturer can usually give guidance on shading options for a 

particular skylight design. 

2. Shading 

Shading strategies generally fall into three categories: landscaping, roof 

overhangs, and exterior or interior shading devices. 

Landscaping. The ideal site for summer shading has deciduous trees to 

shade the east and west windows. Even small trees such as fruit trees 

can help block sun hitting the first story of a house. 
Paae 46 ENERGY-EFFICIENCY DESIGN GUIDE 

Trees on the south side can present a difficult choice. Even deciduous 

trees will shadow the solar glazing during the winter and interfere with 

solar gain. In fact, trees on the south side can all but eliminate passive 

solar performance, unless they are very close to the house and the low 

branches can be removed, allowing the winter sun to penetrate under the 

tree canopy. However, in many cases, the trees around the house are 

bigger selling points than the energy efficiency, and the designer must 

make a choice. 

If a careful study of the shading patterns is done before construction, it 

should be possible to accommodate the south-facing glazing while 

leaving in as many trees as possible (see page 27, Site Planning for Solar 

Access). 

Landscaping for Summer 

Shade 

Trees and other landscaping 

features may be effectively 

used to shade east and west 

windows from summer solar 

gains. 

Other landscaping ideas for summer shade: 

a Trellises covered with vines on the east and west and west sides of 

the house 

Shrubbery or other plantings to shade paved areas 

w Ground cover to prevent glare and heat absorption 

Trees, fences, shrubbery or other plantings to "channel" summer 

breezes into the house 

w Deciduous trees on the east and west sides of the house, as shown 

above, to balance solar gains in all seasons. 

Roof Overhangs. Fixed overhangs are an inexpensive feature and require 

no operation by the homeowner. They must be carefully designed, 

however. Otherwise, an overhang that blocks summer sun may also 

block sun in the spring, when solar heating is desired, and, by the same 

token, an overhang sized for maximum solar gain in winter will allow 

solar gain in the fall on hot days. The following figure may be used to 

determine the optimum overhang size. 
FOR INDIAN HOUSING Paae 47 

South Overhang Sizing 

An ideally sized south 

overhang should allow full 

exposure of the window when 

the sun has a noon altitude 

angle A and fully shade the 

window when the sun has a 

noon altitude angle B. 

Latitude A B 

A combination of carefully sized overhangs on the south windows and 

shading devices on the other windows will probably be an effective 

solution. Adjustable overhangs that can be seasonally regulated are 

another option. 

Shading Devices. External shades are the most effective because they 

stop solar gain before the sun hits the building. A wide range of 

products is available, from canvas awnings to solar screens to roll-down 

blinds to shutters to vertical louvers. They are adjustable and perform 

very well, but their limitation is that they require the homeowner's 

cooperation. Usually external screens that can be put up and taken 

down once a year like storm windows are more acceptable to 

homeowners than those requiring more frequent operation. 

Interior shades must be operated, too, and have the further disadvantage 

of permitting the sun to enter the house and be trapped between the 

window and the shading device. But highly reflective interior blinds and 

curtains are relatively low cost and easy to operate. 

Another shading "device" well worth considering is a porch. Especially 

on the east and west sides, porches add pleasant spaces to houses and 

are excellent for providing shade to windows. Carports located on the 

east or west are another option. 

3. Ceiling Fans 

Ceiling fans will probably save more energy than any other single cooling 

strategy. Studies show that air movement can make people feel 

comfortable at higher temperatures. As a general rule, the thermostat 

can be set 4 degrees higher without affecting comfort if the air is moving 

at 100-150 ft per minute. This is enough air movement to greatly 

improve comfort but not enough to disturb loose papers. 
Paae 48 ENERGY-EFFICIENCY DESIGN GUIDE 

Ceiling Fan Sizes 

Minimum Fan 

Largest Room Diameter 

Dimension (in .) 

12 ft or less 36 

12-16 ft 48 

16-17.5 ft 52 

17.5-18.5 ft 56 

18.5 or more ft 2 fans 

A ceiling fan should have a minimum clearance of 10 in. between ceiling 

and fan to ~rovide adeauate ventilation in a standard room with 8-ft 

ceilings. IA rooms with higher ceilings, fans should be mounted 

7.5 to 8 ft above the floor. 

4. Ventilation 

When possible, the house should be positioned on the site to take 

advantage of prevailing winds. Windows, stairwells, transoms, and other 

elements should be located for maximum cross-ventilation in each room. 

The free vent area (unobstructed openings like open windows) should be 

between 6% and 7.5% of total floor area, half located on the leeward side 

and half located on the windward side of the building. Insect screens 

can reduce the effective free vent area by as much as 50%. Casement or 

awning windows have a 90% open area: double hung windows have only 

50%. Casement windows extend outward from the house, tending to 

channel breezes through the opening; double-hung windows do not have 

this advantage. 

Natural ventilation can help keep houses cool and comfortable at the 

beginning and end of the cooling season and thus shorten the time when 

air conditioning is required. But natural ventilation can seldom do the 

entire cooling job, especially for less than ideal sites with little natural air 

movement . 
FOR INDIAN HOUSING Paae 49 

twal Ventilation 

Ventilation for Summer 

Cooling 

Natural ventilation is often 

impaired by vegetation and 

topography. Ventilation fans 

do not depend on surroundings 

to be effective. 

In cooling climates, a whole-house fan is a good idea for assisting 

ventilation, especially in houses with sites or designs that make natural 

ventilation difficult. On the other hand, when the temperature is higher 

than about 76°F. a whole-house fan will not be very effective. 

Research indicates that a whole-house fan should pull approximately 

10 ACH. A rule of thumb: for rooms with 8-ft ceilings, the total floor area 

multiplied by 1.34 will equal the necessary CFM of the fan. For 10-ft 

ceilings, multiply the floor area by 1.67. 

Natural ventilation and whole-house fans are effective at removing heat, 

but not at moving air. Ceiling fans, on the other hand, can often create 

enough of a breeze to maintain comfort at higher temperatures and still 

use less power than required by air conditioning. The days when air 

conditioning is needed can be reduced substantially by using natural 

cooling strategies and low-energy fans. 
Paae 50 ENERGY-EFFICIENCY DESIGN GUIDE 

SECTION 11. BuilderGuide 

Part One: Description of BuilderGuide 

BuilderGui.de is a PC program that is easy to use. Calculations that you 

will make with this program are a very important part of the energyefficient design process because they allow you to quickly evaluate 

different energy-efficient strategies or combinations of strategies, and the 

effect that design changes will have on the overall perforrnance of the 

house. 

The results that you get from BuilderGuide can be compared with values 

that you expect from conventional nonsolar construction. This way you 

can see how your house will perform in comparison with other houses in 

the area. You will be surprised at how much energy you will save if you 

follow the recommendations in this guide. 

BuilderGuide results can also be compared with performance goal values 

that are listed in Section III. If your numbers meet or beat these 

perforrnance goals, then you can be confident that your design is okay. 

TWO sets of goals are given, one for houses heated with gas and one for 

houses heated with electricity. The goals for electrically heated houses 

are much more stringent because of the higher assumed cost of 

electricity. 

BuilderGuide is supported by "look-up" tables containing precalculated 

factors and numbers for the local area. These files are available for 208 

locations in the United States. Some of the blanks in BuilderGuide call 

for information about the house--for example, floor area, projected area 

of passive solar glazing, and so forth. These are taken from the house 

plans. The look-up tables are automatic in the program operation. 

BuilderGuide contains four worksheets to calculate four key performance 

indicators, as follows: 

a Worksheet I: Conservation Performance Level--determines how 

well the house's basic energy conservation measures (insulation, 

sealing, caulking, etc.) are working to prevent unwanted heat loss in 

the winter. The bottom line of this Worksheet is a number 

measuring heat loss in British thermal units per square foot per 

year (Btu/ft2-yr) --the lower the heat loss, the better. 

Worksheet 11: Auxiliary Heat Performance Level--determines how 

much heat has to be supplied (that is, provided by the heating 

system) after taking into account the heat contributed by passive 

solar. This worksheet arrives at a number estimating the amount 

of heating energy the house's nonsolar heating system has to 

provide in Btu/ft2-yr. Again, the lower, the better. 

a Worksheet 111: Thermal Mass/Comfort--determines whether the 

house has adequate thermal mass to assure comfort and good 
FOR INDIAN HOUSING Paae 51 

thermal performance. Worksheet I11 calculates the number of 

degrees the temperature inside the house is likely to vary, or 

"swing", during a sunny winter day without the heating system 

operating. A well-designed house should have a temperature swing 

of no more than 13 degrees, and the less the better. The 

temperature swing not only measures potential discomfort, it serves 

as an indicator of adequate thermal mass in the house. If the 

temperature swing exceeds 13"F, there is too little thermal mass. 

The smaller the temperature swing, the better. 

Worksheet IV: Summer Cooling Performance Level--indicates how 

much air conditioning the house will need in the summer (it is not, 

however, intended for use in sizing equipment, but as an indication 

of the reductions in annual cooling load made possible by the use of 

natural cooling). The natural cooling guidelines should make the 

house's total cooling load--the bottom line of this Worksheet, in 

Btu/ft2-yr--smaller than in a conventional house. 

Availability of BuilderCuide 

BuilderGuide and city files for 208 U.S. locations are available at a very 

reasonable price from the Passive Solar Industries Council (PSIC). The 

program is essential if you are to make full use of these guidelines and 

wish to compare the performance of your design with the performance 

goals in Section 111. The PSIC address is: 

Passive Solar Industries Council 

15 1 1 K St. W, Suite 600 

Washington, DC 20005 

Part TWO: The Basecase House 

Even before you start to design, we strongly recommend that you set up 

a basecase house using BuilderGuide. This basecase serves as a 

reference point--it gives you numbers that you can compare with the 

numbers for your energy-efficient design. It also gives you a quick feeling 

for the magnitudes of the heating and cooling loads. 

To set up a basecase house, you have three choices: (1) You can use the 

automatic basecase generation feature in BuilderGuide, (2) you can enter 

a house design of your choosing, or (3) you can use suggested values in 

this guide. The three options are described in the following paragraphs. 

(1) Automatic basecase generation. You specify the house floor area, the 

number of stories, and the floor type. These should be the same as those 

for the house that you plan to design. BuilderGuide then calculates all 

the input data, including house takeoffs and insulation levels, evaluates 

this house design, and saves the results for later comparison with 

numbers corresponding to your design. The insulation levels that are 

assigned may be somewhat better than standard practice. 
Paae 52 ENERGY-EFFICIENCY DESIGN GUIDE 

(2) Custom basecase. You fill out the worksheets, using any values you 

think are representative. These might correspond to your last house 

design, to efiergy regulations in force in youf area, or" to conventional 

practice. You can start with blank worksheets or, better yet, start with 

the worksheets filled out by the automatic basecase generation feature. 

You can then change only those values that you feel are inappropriate. 

(3) Sw. The National Association of Home Builders (NAHB) 

conducted a national survey in 1980 to determine conservation levels 

that were being used in conventional houses. These results are listed on 

page 53 for 43 cities in the United States. We entered these values into 

BuilderGuide and used the program to calculate the bottom-line 

conservation, heating, and cooling numbers for the same 43 cities. The 

house takeoffs used are for a one-story, 1500-ft2 house, as calculated by 

BuilderGuide. The results are given on page 54. These numbers should 

be reasonable choices for a basecase. 
FOR INDIAN HOUSING Page 53 

NAHB 1980 Housing Construction Practice (Basecase House) 

City 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville , FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Rc Rw Floor Rf Rp Windows 

Slab 

Slab 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Slab 

Bsmnt 

Bsmnt 

Bsmnt 

Bsmnt 

Slab 

Slab 

Slab 

Bsmnt 

Slab 

Slab 

Slab 

Slab 

30 11 Crawl 19 

19 11 Slab 0 

30 13 Bsmnt 0 

19 11 Slab 0 

19 11 Bsmnt 0 

Oklahoma City, OK 19 1 1 

Omaha, NE 30 13 

Philadelphia,PA 19 11 

Phoenix, AZ 30 13 

Pittsburgh, PA 19 11 

Portland, ME 19 11 

Portland, OR 30 11 

Reno, NV 30 11 

Salt Lake City, UT 19 1 1 

San Antonio, TX 19 11 

San Diego, CA 19 11 

San Francisco, CA 19 1 1 

Seattle, WA 19 11 

Tampa, FL 19 13 

Topeka, KS 30 13 

Washington, DC 19 1 1 

Slab 0 

Bsmnt 0 

Bsmnt 0 

Slab 0 

Bsmnt 0 

Bsmnt 0 

Crawl 19 

Crawl 19 

Bsmnt 0 

Slab 0 

Slab 0 

Slab 0 

Bsmnt 0 

Slab 0 

Bsmnt 0 

Bsmnt 0 

Single/Al/Reg 

Single/Al/Reg 

Double/Al/Reg 

Double/Wood/Reg 

Double/Al/Reg 

Double/Wood/Reg 

Single/Al/Reg 

Double/Wood/Reg 

Double/Wood/Reg 

Single /Al/Reg 

Double/Al/Reg 

Double/Wood/Reg 

Double/Wood/Reg 

Double/Al/Reg 

Single /Al/Reg 

Single/Al/Reg 

Single /Al/Reg 

Double/Al/Reg 

Single /Al/ Reg 

Single /A/ Reg 

Single/Al/Reg 

Single/Al/Reg 

Double/Al/Reg 

Double/Al/Reg 

Double/Wood/Reg 

Double/Al/Reg 

Double/Wood/Reg 

Single/Al/Reg 

Double/Wood/Reg 

Double/Wood/Reg 

Single/Al/Reg 

Double/Wood/Reg 

Double/Wood/Reg 

Double/Al/Reg 

Double/Al/Reg 

Double/Al/Reg 

Single /Al/ Reg 

Single/Al/Reg 

Single/Al/Reg 

Double/Al/Reg 

Single/Al/Reg 

Double/Wood/Reg 

Double/Wood/Reg 

See page 19 to identify terms. 
Paae 54 ENERGY-EFFICIENCY DESIGN GUIDE 

Performance of the Basecase Houses, Btu/ft2 per year 

BuilderGuide Worksheet I, 11, and N results for a 1500-ft2 house with 

conservation values according the NAHB survey of standard housing 

construction practice. The house has 45 ft2 of windows on each side, no 

shading, no night 'ventilation, and no ceiling fan. These values are 

suitable numbers to use as a basecase comparison with your results. 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 

Conservation Heating 

37835 

3 1342 

28134 

77216 

52887 

53700 

6122 

65472 

75993 

22275 

6500 1 

55849 

46195 

533 16 

2572 1 

24564 

27394 

71497 

14441 

16786 

22610 

16539 

32959 

32343 

68877 

36596 

51259 

37786 

52927 

50617 

1 1876 

56779 

7 1743 

33222 

34948 

52404 

16121 

13251 

33372 

49584 

7175 

45 149 

4208 1 

Cooling 

13813 

14243 

13680 

7259 

10880 

7886 

1961 1 

657 1 

6004 

16699 

456 1 

10330 

8965 

6246 

17264 

17427 

19209 

5907 

17686 

17341 

19893 

9134 

8999 

14795 

7742 

13157 

9657 

15092 

12484 

11353 

18404 

7512 

5009 

498 1 

8845 

13287 

17390 

9732 

4139 

293 1 

19497 

14309 

10898 
FOR INDIAN HOUSING Paae 55 

Part Three: Worked Examples: The Method in Practice 

Two worked examples are included to help you understand how 

BuilderGuide works and to demonstrate how useful the program can be 

in meeting your energy-efficiency goals as you work through the design 

process. 

Example One--Bob's House 

The first example is a design that came out of one of four special 

workshops held by the American Indian Council of Architects and 

Engineers (AICAE). The original design was drawn by Bob Gachupin, who 

attended the workshop in Albuquerque. Bob's sketch was originally 

converted into a house plan by David Sloan, an architect working on the 

AICAE team. It was then adapted and redrawn at NREL. 

The house plan provides a communal area in a circular living room. The 

front door is on the east, facing the rising sun. A comdor runs across the 

south side of the main house. The plan was flipped and rotated so that 

main windows and the main outdoor area are on the south and east of 

the house, providing good warmth in the winter and shelter from the 

west sun in the summer. Windows along the corridor provide winter 

solar gain and the tiled-slab floor of the corridor and adobe back wall 

provide thermal mass. Although this hallway works somewhat like a 

sunspace, it is open to the house and was therefore analyzed as a direct 

gain feature. 

The following is a summary of the BuilderGuideresults: 

Basecase Design Goal 

I. Conservation Performance 42039 18049 22213 

Btu/ft2-year 

111. Temperature Swing - 8.2 ~13°F 6. OF 

N. Auxiliary Cooling 

Btu /ft2-year 

Note that the design reduces the required annual auxiliary heat by 80% 

and the required annual auxiliary cooling by 60%, compared with the 

basecase. The design is well within the performance goals. The 

temperature swing is well within the 13OF limit recommended, indicating 

that there is adequate thermal mass. The basecase numbers shown are 
Paae 56 ENERGY-EFFICIENCY DESIGN GUIDE 

from the table on page 54, and the goals are from Section 111 (multiplied 

by 0.96 to account for the 2000-ft2 floor area). 

The 57% reduction in conservation performance is a measure of the 

improvement in the therrnal tightness of the envelope. The solar savings 

fraction of 58% is a measure of the fraction of the heat required by the 

nonsolar elements of the house that is saved by the solar elements. In 

this example, you can see that both conservation and solar contribute to 

the good performance, without adversely affecting the summer cooling 

requirements. The resulting low level of cooling that remains indicates 

that the house may well get by just fine without any auxiliary air 

conditioning. A small evaporative cooler may be warranted for the 

occasional hot spell. 

Floor plan of Bob's house. 

Floor Plan 

North-south section of Bob's house through the kiva room. 

Section 
FOR INDIAN HOUSING Paae 57 

Example Two-Ernie's House 

The second example also came out of one of the workshops held by the 

AICAE. No one person originated the design, but it came from manylng 

the general plan of a passive solar house (rectangular, elongated eastwest) with the octagonal form of the Navajo hogan. The plan was 

developed by David Sloan of the AICAE and was redrawn without 

modification at NREL. We arbitrarily located the house in Window Rock, 

Arizona, which is on the Navajo Indian Reservation. This is a cold, sunny 

climate (6416 heating degree days), and summer cooling is not a major 

concern. We assumed that the house is of adobe construction, insulated 

on the exterior, providing ample thermal mass. 

The BuilderGuide printout is shown following the design drawings. 

Various area takeoffs were determined from the plans. Insulation levels 

are the guideline values given in Section I. 

The following is a summary of the results: 

Basecase Design Goal 

I. Conservation Performance 61 161 2306 1 28813 

Btu/ft2-year 

11. Auxiliary Heat 

Btu/ft2-year 

111. Temperature Swing - 12.7 ~13°F OF 

N. Auxilialy Cooling 

Btu/ft2-year 

Note that the design reduces the required annual auxiliary heat by 81% 

and the required annual auxiliary cooling by 3596, compared with the 

basecase. The design is within the heating performance goals. The 

temperature swing is well within the 13°F limit recommended, indicating 

that there is adequate thermal mass. The basecase numbers shown are 

from the table on page 54 and the goals are from Section 111. The 

basecase values and performance goals for Denver were used because 

the climates are quite similar; the numbers were adjusted by the ratio of 

heating or cooling degree days, as recommended (see page 74). 

The 62% reduction in conservation performance is a measure of the 

improvement in the thermal tightness of the envelope. The solar savings 

fraction of 53% is a measure of the fraction of the heat required by the 

nonsolar elements of the house that is saved by the solar elements. In 

this examde. vou can see that both conservation and ~assive solar heat 

contributd td ihe good performance. The cooling perf&-mance does not 

meet the target, but the number, 2399 Btu/ft2-yr, is still relatively small. 
Paae 58 ENERGY-EFFICIENCY DESIGN GUIDE 

If cooling did prove to be a problem, an inexpensive solution would be to 

apply shade screen to some of the south-facing windows during the 

summer months only. 
FOR INDIAN HOUSING Paue 59 

Schematic showing the mamage of two house footprints, a conventional 

passive-solar rectangle and a hogan octagon. 

Passive Solar 

Traditional 

Ernie's House 

Perspective view of Ernie' house from the southwest. 
Paae 60 ENERGY-EFFICIENCY DESIGN GUIDE 

Floor plan of Ernie's house. 

North-south section of Emie's house. 

Floor Plan 

Section 4 South 
FOR INDIAN HOUSING Paae 61 

Comment on the Examples 

These examples show very large savings, in the range of 70% to 80%, 

compared with the basecase. This is quite realistic. To some extent, this 

is because both examples are located in the sunny southwest, where 

good solar performance can be achieved. However, even in cloudy 

climates, very substantial savings, in the range of 30% to 50%, will result 

just from meeting the performance goals. To see this, refer again to the 

numbers in the table on page 10. In cloudy climates, the savings are 

mostly because of improved levels of conservation, although even in 

these cases, solar savings fractions of 10% to 20% are achieved. 

BuilderGuide Printouts 

The printouts from BuilderGuide are reproduced on the following pages. 

Various area takeoffs were determined from the plans. Insulation levels 

used are the guideline values for electrically heated homes in the locality, 

as given in Section I. 

The reference cases listed are computed using the automatic basecase 

generation feature of BuilderGuide. The numbers are somewhat different 

than those listed in the previous summary table. The differences are 

caused by different assumptions for typical insulation levels for the two 

localities. 
Paae 62 ENERGY-EFFICIENCY DESIGN GUIDE 

BuilderGuide Results for Bob's House 

I Site: Albuquerque, NM Date: 8/18/92 j 

+--------------------------------------------------------------------------+ 

: Conservation Perf. 18049 30000 -39.84 

I Btu/yr-sf I 

I Aux. Heat Perf. 7581 26130 -70.99 I 

I [ Btu/yr-sf I , I Temp. Swing 8.2 9.2 -10.87 

[ degrees F I 

: Cooling Perf. 5482 13236 -58.58 I I 

I [ Btu/yr-sf ] +--------------------------------------------------------------------------+ 

In BuilderGuide, the user fills in fields on the computer screen, such as 

the Area and R-value, and the program calculates other numbers, such 

as Heat Loss. The program also performs table lookups, such as Heating 

Degree-Day Multiplier. Pop-up help screens provide useful information, 

such as definitions of terms and tables of R-values for typical 

construction. There is an initial summary of results, followed by one page 

each for the four worksheets. Two numbers show at the bottom of each 

worksheet, the value for the house being designed and a comparison 

value for the basecase house. These pairs of numbers also show on the 

summary. Thus the user has a benchmark for comparison, with 

percentage improvements shown on the summary. The notations on 

these printouts are fairly self-explanatory; however, the reader should 

refer to the user manual and the help text in the program for complete 

descriptions. As with any engineering evaluation, the results depend on 

good, informed judgment being applied by the user at each step. 

The DGC2 solar system reference code shown on Worksheet I1 refers to 

direct gain with low-e glass. In Bob's house, adobe walls are shown on 

Worksheet 111. These add significantly to the heat capacity of the house 

and reduce the temperature swing to a very comfortable level. The use of 

night vent with ceiling fan and no west windows on Worksheet IV 

decreases the cooling loads markedly. The large south glazing area 

combines with Albuquerque's favorable climate to produce a very 

respectable 58% solar savings fraction. 
FOR INDIAN HOUSING Paue 63 

Bob's Worksheet I 

Worksheet I: Heat Loss (excluding solar aperture) 

+--------------------- 

:Walls 2x6 w/ R-5 sheathing 1680 

+--------------------- 

! Insulated N/A 

: Floors 

+--------------------- 

:NO~-Solar (Total Rough Frame 84.0 

: Glass Area from Worksheet IV) +--------------------- 

l Doors 2 Doors / metal-foam 40 

R-Value Heat Loss ---------A+------------------- 

/ 25.7 = 77.8 

/ = 0.0 L 

I , / = 0.0 I 

+----------------------------------------------------------------------------+ 

Subtotal 186.6 

Btu/deg F-h B. Foundation Perimeter Heat Loss 

Heat Loss Description Perimeter Factor Heat Loss +----------------------------------------------------------------------------+ 

!Slab-on-grade R-5 to 2 ft perimete 210 x 0.4 = 84.0 

:Heated 

: Basement 

, 

l Unheated 

: Basement 

!Perimeter Ins 

I Crawlspace +----------------------------------------------------------------------------+ 

Subtotal 84.0 

Btu/deg F-h C. Infiltration Heat Loss ++---------------------------------------------------------------------------+ 

D. Total Heat Loss per Square Foot +-------------------------------------------------------------------+--------+ 

24 X 366.0 / 2000 = 4.392 

Total Heat Loss Floor Area Btu/DD-sf I 

( A+B+C) P 

E. Annual Heat Loss (excluding solar aperture) *----------------------------------------------------------------------------+ 

F. Comparison Heat Loss +----------------------------------------------------------------------------+ 

: (From Previous Calculation or from Table D) 30000 Btu/yr-sf 
Paae 64 ENERGY-EFFICIENCY DESIGN GUIDE 

Bob's Worksheet I1 

Worksheet 11: Auxiliary Heat 

A. Projected Area of Passive Solar Glazing +----------------------------------------------------------------------------t 

I Solar System Rough Frame Net Area Adjustment Projected I 

: Reference Code Area (sf) Factor Factor Area (sf) l +----------------------------------------------------------------------------+ 

I DCC2 279 X 0.8 X 1.0 = 223.2 

279.0 

Total Area 

223.2 

Total Projected Area I 

I 

223.2 / 2000 = 0.112 i 

Total Floor Total : 

Projected Area Projected 1 

Area Area per I 

Square Foot; 

24 X 366.0 / 223.2 = 39 

Total Total Projected , Heat Loss 

-. 

ed solar aavings 

C. Solar Savings Fraction 

I Solar System system 

I Reference Project ' - 1 - n-.. 

I Code Area Fractlon 

8 Total 129.46. I 

/ 223.2 = 0.580 6 I 

Total Solar 

I Projected I 

Savings 

I Area Fraction I I 

2 

I (From Previous Calculation or from Table G) 3 
FOR INDIAN HOUSING Paae 65 

E3ob's Worlrsl~cd III 

Korksheet 111: Thermal Nass / Comfort 

I Spaces Connected to Direct Gain Spaces 1000 X 4.5 = 4500 

Total 7837 

Btu/deg F : 

: Exposed Slab 580t.6 3 4 8 X 13.4 = 4663 

insun 

: Exposed Slab remainder 232 X 1.8 = 418 

: not in Sun 

I Other Mass adobe walls 1184 X 4.9 = 5802 

1 Other Mass X = 0 I 

I Other Mass X = 0 

Total 10883 I Btu/deg F 

+----------------------------------------------------------+-----------------+ 

C. Heat Capacity of Mass Surfaces 

Enclosing Spaces Connected to Direct Gain Spaces +----------------------------------------------------------------------------+ 

1 Mass Description Unit Heat Total Heat I 

(include thickness) Area Capacity Capacity I +----------------------------------------------------------------------------+ 

I Trombe Walls X 3.8 = 0 

: Water Walls X 4.2 = 0 I 

I Other Mass adobe walls X 2.4 = 4898 

+----------------------------------------------------------------------------+ 

I D. Total Heat Capacjty (A + B + C) 23618 I 

Btu/deg F 

E. Total Heat Capacity per Square Foot +--------------------+-------------------------------------------------------+ 

I 

23618 / 2000 = 11.8 

I Total Heat Conditioned Btu/deg F , 

I Capacity Floor Area per sf I +-----------+----------------------------------------------------------------+ 

/ 23618 I 

= 8.2 

deg F I 

+----------------------------------------------------------------------------+ 

: C. Recommended Maximum Temperature Swing 13 deg F +----------------------------------------------------------------------------+ 

-- End of Worksheet 111 -- 
Paae 66 ENERGY-EFFICIENCY DESIGN GUIDE 

Bob's Worksheet IV 

Worksheet IV: Auxiliary Cooling 

B. Non-solar Glazing +----------------------------------------------------------------------------+ 

I Rough Net Shade Heat I Frame Area Factor Gain 

: Description Area Factor Factor Load 

I 

I West Glass 0.0 X 0.8 X 1.0 X 75.4 = 0 

) Skylights 0.0 X 0.8 X 1.0 X102.7 =O 

Total 3154 

kBtu/yr : 

C. Solar Glazing +----------------------------------------------------------------------------+ 

4 

, Rough Net Shade Heat I Frame Area Factor Gain I 

I Area Factor Factor Load t 

+----------------------------------------------------------------------------+ 

I Direct Gain 279.0 X 0.8 X 0.8 X47.1 =a410 t 

: Storage Walls 0.0 X 0.8 X 1.0 X 11 = 0 -- 

: Sunspace 0.0 X 0.8 X 1.0 X 36.7 = 0 I 

I I 

Total 8410 

kBtu/yr I +----------------------------------------------------------------------------+ 

I 

I 1000 X 18281 / 2000 = 9140 

(A+B+C+D) Floor Area Btu/yr-sf ; 

9 

+----------------------------------------------------------------------------+ 

F. Adjustment for Thermal Mass and Ventilation +---------------------------------------------------------------------------++ 

0 

I Strategy: Night Vent with Ceiling Fan 3658 I 

0 (Table 0) Btu/yr-s f 
FOR INDIAN HOUSING Paae 67 

BuilderGuide Results for Emie's House 

1 BuilderGuide, Version l.Oe, Aug 1992 , 

I Developed by the National Renewable Energy Laboratory I +-------------------------------------------------------+ 

Genera1,Project Information +------------------------------------------------------------------------+ 

! Project Name:Erniels House Floor Area:1090 

: Site: Window Rock, Arizona Date: 8/18/92 

I Designer: AICAE 

I Comment: 

Location: Ganado 4 

+--------------------------------------------------------------------------+ 

1 Current Case Reference Case % Difference I +--------------------------------------------------------------------------+ 

I Conservation Perf. 23061 41241 -44.08 I 

[ Btu/yr-sf ] 

: Aux. Heat Perf. 10793 37323 -7 1.08 I [ Btu/yr-sf 1 6 

I Temp. Swing 12.7 9.2 38.04 

[ degrees F ] 

I Cooling Perf. 2399 7271 -67.01 b 

I [ Btu/yr-sf 1 L 

+----------------------:---------------------------------------------------+ 

At 1090 ft2, Emie's house is more modest. Because it uses frame 

construction, rather than adobe, the solar glazing area has been scaled 

down to avoid excessive temperature swings. The energy solution is 

primarily to use high levels of insulation, as is appropriate in this cold 

and windswept location. The walls are built with 2x6 studs on 24-in. 

centers covered over with 11/2 inches of expanded-polystyrene-foam 

exterior sheathing (no CFCs!). Good airtightness is essential to avoid high 

infiltration losses. The plan also benefits from being quite compact, thus 

presenting a minimum exterior surface area for heat loss. 

The solar savings fraction is a respectable 53%. Worksheet I11 results 

indicate that the south window area is at the maximum permissible 

without exceeding the 1 3°F temperature-swing limit. 

Summer cooling is not a big issue at Window Rock's 6750 ft elevation; 

however, the intense sun invites one to seek shade, especially in the 

afternoon. One attractive addition to the plan would be a long covered 

porch along the east wall connecting to the small existing entry porch. 

This would be a popular place for people and dogs to hang out on 

summer afternoons. 
Paae 68 ENERGY-EFFICIENCY DESIGN GUIDE 

Ernie's Worksheet I 

Worksheet I: Heat Loss (excluding solar aperture) 

A. Envelope Heat Loss 

Construction Description Area R-Value Heat Loss 

:Ceilings/Roofs Roof, R38 in attic 1090 / 35.9 = 

I / +--------------------- 

:Walls Exterior Walls 1072 /25.2 = , / +--------------------- 

:Insulated See below 0.0 / 

: Floors I 

, / +--------------------- 

:NO~-Solar (Total Rough Frame 36.0 / 3.0 : Glass Area from Worksheet IV) +--------------------- 

1 Doors 2Doors,metal/foam 40 / 5.9 

B. Foundation Perimeter Heat Loss Heat Loss 

Description Perimeter Factor Heat Loss 

l Heated 

: Basement , 

l Unheated 

L Basement 

:Perimeter Ins. 1 Crawlspace 
FOR INDIAN HOUSING Paae 69 

Ernie's Worksheet I1 

Worksheet 11: Auxiliary Heat 

127.2 / 1090 = 0.117 

Total Floor Total 1 

Projected Area Projected : Area Area per : 

Square Foot: 

C. Solar Savings Fraction 

D. Annual Auxiliary Heat Required +----------------------------------------------------------------------------+ 

4 

[ 1 - 0.532 1 X 23061 = 10793 

Solar Conservation Btu/yr-sf 

Savings Performance 1 

Fraction Level 
Paae 70 ENERGY-EFFICIENCY DESIGN GUIDE 

Ernie's Worksheet I11 

Worksheet 111: Thermal Mass / Comfort 

A. Heat Capacity of Sheetrock and Interior Furnishings +----------------------------------------------------------------------------+ 

Unit Heat Total Heat : Floor Area Capacity Capacity : 

: Spaces Connected to Direct Gain Spaces 150 X 4.5 -675 I 

I Water Walls X 10.4 = 0 

I Exposed Slab Living Room 300 X 13.4 = 4020 b 

I in Sun 

: Exposed Slab Other connected 150 X 1.6 = 270 

I not in Sun 

I Other Mass X = 0 d 

1 Other Mass 

: Other Mass 

Total 4290 

Btu/deg F ; 

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces 

: Mass Description Unit Heat Total Heat I 

(include thickness) Area Capacity Capacity I +----------------------------------------------------------------------------+ 

I Trombe Walls X 3.8 = 0 I 

I 

: Water Walls X 4.2 = 0 

I Other Mass X = 0 I 

I 

1 Other Mass X = 0 I 

: Other Mass X = 0 , 

: Sunspaces or 0.0 X 290 = 0 

I Vented Trombe Walls 1 

1 Total 110664 I 

c / 8725 9 , 

= 12.7 

deg F I 

: G. Recommended Maxlmum Temperature Swing 13 

deg F ; 1 

+----------------------------------------------------------------------------+ 

-- End of Worksheet I11 -- 
FOR INDIAN HOUSING Paae 71 

Ernie's Worksheet N 

Worksheet It: Auxiliary Coollng 

A. Opaque Surfaces 

B. Non-solar Glazing +----------------------------------------------------------------------------+ 

Rough Net Shade Heat 

Frame Area Factor Gain 

I Description Area Factor Factor Load 

C. Solar Glazing +----------------------------------------------------------------------------+ 

# Rough Net Shade Heat I Frame Area Factor Gain Area Factor Factor Load +----------------------------------------------------------------------------+ 

I 

: Direct Gain 159.0 X 0.8 X 0.8 X23.5 ~2391 

I Storage Walls 0.0 X 0.8 X 1.0 X 3.3 = 0 , I 

r 

: Sunspace 0.0 X 0.8 X 1.0 1( 17.4 = 0 

Total 2391 

kBtu/yr ; 

D. Internal Gain +----------------------------------------------------------------------------+ 

, 300 + 130 X 3 = 690 I 1 

E. Cooling Load per Square Foot +----------------------------------------------------------------------------+ 

F. Adjustment for Thermal Mass and Ventilation +----------------------------------------------------------------------------+ 

I Strategy: Night Vent with Ceiling Fan 

(Table 01 

C. Annual Auxiliary Cooling Required +-------------------------+--------------------------------------------------+ 

-- End of Worksheet IV -- 
Paae 72 ENERGY-EFFICIENCY DESIGN GUIDE 

SECTION 111. ENERGY-EFFICIENCY PERFORMAN'CE 

GOALS 

Energy-efficiency performance goals are given in this section. These 

performance goals are presented in the spirit of goals for design. They are 

suitable as guideline values. They are moderately ambitious goals but 

represent numbers that you can expect to meet or beat just by following 

the guidance. 

The goals are performance targets and are simple to use. You 

compare the performance goals for your area with the bottom-line 

numbers from the BuilderGuide worksheets. If your numbers are 

equal to or less than the corresponding goal numbers, then you 

have succeeded in meeting your objective. 

Design guidance is given in Section I. For guidance on how to reach the 

conservation performance goals, refer to the insulation guidelines on 

pages 20 and 21. These tables give suggestions for components, such as 

R-values for walls, ceiling, and perimeter, window type, and equipment 

efficiencies. If these component recommendations are followed, then the 

house will likely meet the conservation performance goal. Annual 

auxiliary heat performance goals are less than the corresponding 

conservation performance goals to account for the passive solar heating 

contribution. For guidance on how to reach these goals, refer to the 

guidelines for passive solar glazing area on page 25. Annual cooling 

energy performance goals are based on a house without passive solar 

features; thus it will be necessary to minimize the summer heating 

consequences of the passive solar elements and to compensate in other 

ways, such as appropriate shading and ventilation. 

Because the performance goals are given as Btu/ft2 of house, larger 

houses have an inherent advantage because of a smaller surface-tovolume ratio. To remove this bias, it is recommended that the 

performance goals be adjusted, based on the size of the house. The 

following factors are suggested: 

House size, ft2 Factor 

Multiply the Btu/ft2 performance goals in the tables by the appropriate 

factor to obtain the corrected goals. The factors are based on a one-story 

house. You will find that two-story houses have an inherent advantage 

for houses larger than about 600 ft? 
FOR INDIAN HOUSING Paae 73 

The goals are voluntary guidelines. They have no force in law or 

regulation. However, they have been developed based on the principle of 

economic optimization. This means that the added cost of the energyefficient features should be economically justified, based on the payback 

in energy savings that will accrue over the life of the house. 

Step One: Conservation Performance Goals 

Your conservation performance goal is the maximum annual Btu/ft2 that 

your house should require for heating before you account for passive 

solar gains. This number is calculated on Worksheet I in BuilderGuide. 

Conservation performance goals are given on page 76 for 43 cities in the 

United States. Two values are listed for each city, one for houses that are 

heated with gas and one for houses that are heated with electricity. If the 

conservation performance level of your house design is less than the 

goal, then you are okay. The conservation performance level is calculated 

on Worksheet I of BuilderGuide. It depends on the areas of external 

surfaces and on the insulation R-values you are using. It indicates the 

heat required to maintain the house comfortable before solar gains are 

taken into account. 

If your location does not correspond to one of the cities listed in the 

table, you should adjust the performance goal for a city in the same 

region of the United States that has similar heating degree days. The 

adjustment is the ratio of heating degree days. For example, on the 

Navajo Indian Reservation near Ganado, Arizona, we could start with 

Denver, Colorado. Heating degree days are 6016 in Denver and 6416 in 

Ganado. The conservation performance goal for an electrically heated 

house would be: 

Heating degree days for the 43 cities are listed on page 79. 

Step Two: Auxiliary Heat Performance Goals 

Your auxiliary heat perfomance goal is the maximum annual Btu/ft2 

that your house should require for heating afer you account for passive 

solar gains. 

Auxiliary heat performance goals are given on page 77 for 43 cities in the 

United States. Two values are listed for each city, one for houses that are 

heated with gas, and one for houses that are heated with electricity. If 

the auxiliary heat performance level of your house design is less than the 

performance goal, then you are okay. The auxiliary heat performance 

level is calculated on Worksheet I1 of BuilderGuide. It depends on the 

conservation performance level carried over from Worksheet I and on the 

passive solar savings that you will achieve. This depends on the size and 

type of passive solar heating systems that you use. The auxiliary heat 

performance level indicates the heat required to maintain the house 

comfortable in the winter. 
Paae 74 ENERGY-EFFICIENCY DESIGN GUIDE 

These performance goals are based on the assumption that the site is not 

shaded in the winter--that solar access is not impeded. In many cases, 

this will not be a good assumption because of site constraints, 

neighboring buildings or trees, or trees on the property that the owner 

rightly does not want to cut or prune. In these cases, the auxiliary heat 

performance goals must necessarily be relaxed--perhaps up to the 

conservation performance goals (corresponding to a zero solar savings fraction). 

If your location does not correspond to one of the cities listed in the 

table, you should adjust the performance goal value of a city in the same 

region of the United States that has similar heating degree days. The 

adjustment is the ratio of heating degree days. For example, in Ganado, 

Arizona, we could start with Denver, Colorado. Heating degree days are 

6016 in Denver and 6416 in Ganado. The auxiliary heat performance 

goal for an electrically heated house would be: 

Heating degree days for the 43 cities are listed on page 79. 

Step Three: Comfort / Thermal Mass Performance Goals 

This performance goal is easy to describe: 

The temperature swing on a clear 

winter day should not exceed 1 3°F. 

The temperature swing of your design is calculated on Worksheet 111 of 

BuilderGuide. If the value exceeds 13"F, then you have too much solar 

gain for the amount of thermal mass in the house. You should either 

increase mass or decrease direct solar gain. If you have too much direct 

gain and do not want to sacrifice solar performance, you can convert 

some of the direct gain to an indirect system, such as a Trombe wall or a 

sunspace. A Trombe wall contributes nothing to temperature swing 

(assuming that it is unvented, as recommended). A sunspace contributes 

about one-third as much to temperature swing as does the same glass 

area of direct gain. 

Step Four: Summer Cooling Performance Goals 

Your summer cooling performance goal is the maximum annual Btu/ft2 

that your house should require for cooling. 

Summer cooling performance goals are given on page 78 for 43 cities in 

the United States. If the summer cooling requirement of your house 

design is less than the performance goal, then you are okay. The summer 

cooling performance level is calculated on Worksheet N of BuilderGuide. 

It depends on the insulation levels, window areas, shading, and the use 

of either night-vent cooling or ceiling fans. The summer cooling 
FOR INDIAN HOUSING Paae 75 

performance level indicates the cooling system output required to 

maintain the house comfortable in the summer. 

If your location does not correspond to one of the cities listed in the 

table, you should adjust the performance goal for a city in the same 

region of the United States that has similar cooling degree days. The 

adjustment is the ratio of cooling degree days. For example, on the 

Tohono Oo'dham Indian Reservation near Tucson, Arizona, we could 

start with Phoenix. Cooling degree days are 3746 in Phoenix and 2840 in 

Tucson. The summer cooling performance goal would be: 

Cooling degree days for the 43 cities are listed on page 79. 
Paae 76 ENERGY-EFFICIENCY DESIGN GUIDE 

Performance Goals for Conservation, Btu/ft2 per year 

BuilderGuide Worksheet I results on Line E should not exceed these 

targets. 

House heating 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresncs, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 

Gas Electricity 

23139 

1871 1 

16729 

43468 

2657 1 

27429 

6202 

32467 

40668 

13437 

3 1968 

30796 

27016 

27008 

16985 

14738 

15989 

35385 

9579 

11673 

14137 

11 134 

23501 

19571 

38776 

20936 

27885 

21171 

29582. 

27536 

12634 

28860 

38073 

24650 

22742 

26149 

10321 

9830 

21597 

25275 

7188 

25157 

25032 
FOR INDIAN HOUSING Paae 77 

Performance Goals for Auxiliary Heat, Btu/ft2 per year 

BuilderGuide Worksheet I1 results on Line D should not exceed these 

targets. 

House heating 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville , TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 

Gas 

26210 

23288 

2 1689 

46390 

30587 

28527 

4475 

40109 

4678 1 

15977 

33030 

33067 

3 1437 

26458 

15570 

17437 

15956 

41913 

10131 

12000 

14557 

11793 

2808 1 

25262 

46682 

23745 

31964 

2429 1 

30826 

3 1880 

832 1 

34289 

43957 

28599 

226 18 

29702 

11503 

1 1997 

19013 

28448 

5126 

25835 

30203 

Electricity 

14636 

14633 

12989 

39068 

21103 

24236 

3975 

3075 1 

37925 

10602 

21355 

27788 

24285 

171 16 

10696 

10864 

12476 

29760 

7077 

9312 

8974 

6950 

19701 

15642 

36016 

17950 

24982 

15754 

24409 

23793 

832 1 

26789 

34978 

22058 

13902 

19228 

7667 

6040 

' 14053 

22392 

427 1 

20024 

20374 
Paae 78 ENERGY-EFFICIENCY DESIGN GUIDE 

Performance Goals for Summer Cooling, Btu/ft2 per year 

BuilderGuide Worksheet IV results on Line G should not exceed these 

targets. 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, W 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 
FOR INDIAN HOUSING Paae 79 

Heating and Cooling Degree Days 

These are 30-year averages (1 95 1- 1980) taken from Climatography of the 

United States No.81 published by the National Oceanic and Atmospheric 

Administration. The base temperature is 65°F. 

Heating DD Cooling DD 

Albuquerque, NM 

Atlanta, GA 

Birmingham, AL 

Bismarck, ND 

Boise, ID 

Boston, MA 

Brownsville, TX 

Buffalo, NY 

Burlington, VT 

Charleston, SC 

Cheyenne, WY 

Chicago, IL 

Cincinnati, OH 

Denver, CO 

El Paso, TX 

Fort Worth, TX 

Fresno, CA 

Great Falls, MT 

Jackonsville, FL 

Lake Charles, LA 

Las Vegas, NV 

Los Angeles, CA 

Medford, OR 

Memphis, TN 

Minneapolis, MN 

Nashville, TN 

New York, NY 

Oklahoma City, OK 

Omaha, NE 

Philadelphia, PA 

Phoenix, AZ 

Pittsburgh, PA 

Portland, ME 

Portland, OR 

Reno, NV 

Salt Lake City, UT 

San Antonio, TX 

San Diego, CA 

San Francisco, CA 

Seattle, WA 

Tampa, FL 

Topeka, KS 

Washington, DC 
Paae 80 ENERGY-EFFICIENCY DESIGN GUIDE 

Basis for the Energy-Efficiency Performance Goals 

Conservation Performance Goals 

Conservation performance goals have been generated based on the 

Automated Residential Energy Standards (ARES) computer program 

developed at the Pacific Northwest Laboratory for the United States 

Department of Energy. This program was mandated by federal 

legislation. 

ARES computes a set of component values that are economically 

optimum for a set of assumed energy costs, component costs, and 

financial parameters. These costs and parameters are part of the data 

base stored within the program. Refer to the program documentation for 

these assumptions and for the associated financial algorithms. The 

energy calculations in ARES are based on regression analysis of annual 

heatzg and cooling numbers calculated using the ~08-2 computer 

program developed at the Lawrence Berkeley Laboratory. Nationalaverage economic parameters were used. 

The conservation performance goals were generated in two steps. The 

first step was to run the ARES program for each of the cities. The ARES 

output is a set of component values. These results are the guideline 

values given on pages 20 and 21 for houses heated by gas and electricity, 

respectively. In the second step, the component values were inserted into 

BuilderGuideWorksheet I. The area takeoffs that were used are for a onestory 1500-ft2 house as determined in the automatic basecase 

generation. The conservation performance level is the number calculated 

on Line E of Worksheet I. 

The table of component values could be interpreted as a set of 

prescriptive standards. We prefer not to characterize them in this way 

because it is really the net result that is important to keep under 

control--the overall building heat loss. This depends both on building 

design and on the component values. It is possible to influence the net 

result by changing any of several inputs. For example, the designer can 

compensate for a lower wall R-value by using a higher ceiling R-value or 

by designing a more compact house with a small wall-surface area. 

Component values can be usually be relaxed somewhat if the house is 

two stories because the ceiling area is reduced. 

Auxiliary Heating Performance Goals 

The goals for auxiliary heating performance level are based on work at 

the Los Alamos National Laboratory on balancing conservation and 

passive solar. The procedure is to calculate a global economic life-cycle 

optimum considering both conservation and passive solar heating. The 

results were presented as guidelines for both insulation levels, presented 

in terrns of a parameter called a conservation factor, and the loadcollector ratio (LCR), a parameter that is used in calculating the solar 

savings fraction. Rather than using the Los Alamos conservation factors, 

we used the insulation values calculated by ARES, as indicated 
FOR INDIAN HOUSING Paae 81 

previously. This will not change the passive solar optimization to any 

significant degree. 

The auxiliary heating performance goals were calculated in three steps, 

starting with the conservation values determined previously: (1) the 

passive solar glazing area was set to achieve the desired value of LCR. 

The LCR values from Table I of the Los Alamos/Arnerican Society of 

Heating, Refrigerating, and Air-conditioning Engineers publication, 

Passive Solar Heating Analysis, were multiplied by a factor of 1.3 to 

reduce the glazing area by 30%. This was done to bring the maximum 

guideline glazing fractions within current guidelines. The LCR values 

corresponding to the high fuel cost were used for electrically heated 

houses. This corresponds to $O.O7/kWh. For houses heated by gas, the 

LCR values for low-cost fuel were used, corresponding to $1 1 /million Btu 

delivered heat (one-half the high-cost value). (2) BuilderGuide was then 

run to determine the solar savings fraction achieved. (3) These SSF 

values were multiplied by a factor of 0.70 to compute the auxiliary heat 

performance goal. The 30% factor provides a margin to account for a 

less-than-ideal solar-gain situation, such as site shading or off-south 

orientation. The resulting goals still represent the use of an aggressive 

passive solar strategy in cases where this would be economically 

justified. The SSF values computed (prior to the 0.7 adjustment) assume 

that the windows are unshaded during winter hours from 9 am to 3 pm 

and that the solar glazing orientation is true south. If winter shading is 

extreme or the site or design precludes good orientation, then the 

performance goals should be relaxed as described in Step Two. 

The solar system used for the BuilderGuide calculation is either direct 

gain or a combination of direct gain and sunspace, where appropriate. 

Sunspace type SSCl was used. This is a semi-enclosed sunspace with 

vertical glazing. The total passive solar area was adjusted to match the 

Los Alamos guideline LCR value. If this area was below 155 ft2, then 

105 ft2 was used (this is 7% of the floor area, which is the suntempering 

limit). If the area was greater than 155 ft2, then a sunspace was used to 

account for all glass area exceeding 105 ft2. 

Summer Cooling Performance Goals 

The summer cooling goals are the numbers calculated by BuilderGuide 

for the same 1500-ft2 house design that was used to calculate the 

conservation performance goals. Note that this is a nonsolar house in 

that there is only 45 ft2 of window on each facade. This house has night 

ventilation but no ceiling fan. The numbers for the gas-heated house 

were used. 

The cooling values for a nonsolar house were used as performance goals 

because it was not felt that designers of solar houses should be excused 

for building houses that use more cooling energy than do nonsolar 

houses. Of course, if passive solar is added to the house, then the 

summer cooling load will be greater than that for the comparable nonsolar house. The designer can compensate by shading windows, 

decreasing west windows, adding night ventilation, adding a ceiling fan, 

or by using a combination of these. Experience has shown that this is 

quite practical and is usually done anyway by conscientious designers. 
Paae 82 ENERGY-EFFICIENCY DESIGN GUIDE 

GLOSSARY OF TERMS 

Awdliary Heating System: a term for the system (gas, electric, oil, etc.) 

that provides the nonsolar portion of the house's heating energy needs, 

referred to as the "auxiliary heat". 

British Thermal Unit (Btu): a unit used to measure heat. One Btu is 

about equal to the heat released from burning one kitchen match. 

Conservation: in addition to energy conservation in the general sense, 

the tern is used to refer to the nonsolar, energy-saving measures in a 

house that are primarily involved with improving the building envelope to 

guard against heat loss--the insulation, the air infiltration reduction 

measures, and so forth. 

Direct Gain: a passive solar system in which the sunlight falls directly 

into the space where it is stored and used. 

Glazing: often used interchangeably with window or glass, the term 

actually refers specifically to the clear material that admits sunlight, and 

so it can also be plastic. Double and triple glazing refer to two or three 

panes. 

Indirect Gain: a passive solar system in which the sunlight falls onto 

thermal mass that is positioned between the glazing and the space to be 

heated, i.e., a Thermal Storage Wall or Trombe Wall. 

Low-Emittance: the term refers to a surface's ability to absorb and reradiate heat. A material with a low emittance absorbs and re-radiates 

relatively small amounts of heat. Low-emittance or "low-et' glass has a 

thin layer of a low emittance film or coating on the glass surface. The 

low-e glass reflects radiant heat, so it will tend to keep heat energy inside 

the house during the winter and keep heat energy outside the house 

during the summer. 

Passive Solar: design and construction techniques that help a building 

make use of solar energy by nonmechanical means, as opposed to active 

solar techniques that use equipment such as roof-top collectors. 

Phase-Change Materials: materials such as salts or waxes that store 

and release &ergy by changing "phase"; most materials store energy 

when thev turn liauid at a certain temperature and release enera when 

they t~~solid at & certain temperatuie. Some phase-change maerials, 

however, remain solid but undergo chemical changes that store and 

release energy. Phase-change materials can be used as thermal mass, 

but few products are commercially available at this time. 

Purchased Energy: although the terms are often used interchangeably, 

a house's "purchased energy" is generally greater than its "auxiliary heat" 

because heating systems are seldom 100% efficient, and more energy is 

purchased than is actually delivered to the house. 
FOR INDIAN HOUSING Paae 83 

R-Value: a unit that measures the resistance to heat flow through a 

given material. The higher the R-value, the better insulating capability 

the material has. The R-value is the reciprocal of the U-value (see 

below). 

Radiant Barrier: reflective material used in hot climates to block 

radiant heat, particularly in a house's roof. 

Shading Coefficient: a measure of how much solar heat will be 

transmitted by a glazing material compared with a single pane of clear 

uncoated glass that has a shading coefficient (SC) of 1. For example, 

clear double-pane glass might have an SC in the range of 0.88. 

Reflective glass might have SCs of 0.03-0.06. In general, lower shading 

coefficients are desirable when heat gain is a problem. 

Sunspace: a passive solar system, sometimes also referred to as an 

isolated gain system, in which sunlight is collected and stored in a space 

separate from the living space, and must be transferred there either by 

natural convection or by fans. 

Suntempering: a modest form of a direct-gain passive solar system. 

Suntempered houses increase south-facing glass to about 7% of the total 

floor area but add no thermal mass beyond the "free" mass already in a 

typical house--gypsum board, framing, conventional furnishings, and 

floor coverings. 

Temperature Swing: a measure of the number of degrees the 

temperature in a space will vary during the course of a sunny winter day 

without the furnace operating; an indicator of the amount of thermal 

mass in the passive solar system. 

Thermal Mass: material that stores heat or coolness. The thermal 

storage capacity of a material is a measure of the amount of heat stored 

when the material changes temperature by 1°F. Although all materials 

will store some heat, thermal mass added to passive solar buildings is 

usually dense material such as brick or concrete masonry but can also 

be tile, water, phase-change materials, etc. 

Thennal Storage Wall: a passive solar system also sometimes called a 

Trombe Wall or an indirect-gain system; a south-facing glazed wall 

usually made of masonry but can also be made of containers of water. 

Trombe Wall: a thermal storage wall of masonry material, referred to by 

the name of its inventor, Dr. Felix Trombe. 

U-value: a unit representing the heat loss per square foot of surface 

area per degree F of temperature difference. The U-value is the 

reciprocal of the R-value (see above). 
Paae 84 ENERGY-EFFICIENCY DESIGN GUIDE 

Technical Basis for the Guidelines and BuilderGuide 

More than a Decade of Experience 

The concentrated effort of research, design, construction, monitoring, 

and evaluation of actual buildings that started at the First Passive Solar 

Conference in Albuquerque, New Mexico, in 1976 has continued up to 

the present. It is estimated that more than 200,000 passive solar homes 

have been built in the United States during this time. This wealth of 

experience has been reviewed by NREL, the Technical Committee of 

PSIC, and the Standing Committee on Energy of the NAHB and is 

distilled into these Guidelines. 

Analysis Procedures 

The analysis procedures used throughout the Guidelines and in 

BuilderGuide were developed using simple, well-established methods for 

estimating the performance of passive solar heating and natural cooling 

strategies. These procedures were developed at the Los Alamos National 

Laboratory with funding from the U.S. Department of Energy Solar 

Buildings Program. 

Annual Heat Loss (BuilderGuide Worksheet I) 

The heat-loss calculation is based on a straightforward summation of the 

traditional elements that make up the building heat-loss coefficient 

(excluding the solar components--the solar effects are accounted for in 

Worksheet 11). The worksheet procedure estimates the annual heat loss 

by multiplying the heat-loss coefficient by annual degree days (times 24 

to convert from days to hours). Degree days for each month were 

determined using an appropriate base temperature that accounts for an 

assumed thermostat setting of 70 degrees, an assumed internal heat 

generation of 36 Btu/day-ft2 of floor area, and the total building loss 

coefficient. This forms the basis of the table of heating degree-day 

multipliers. The result of the worksheet is an estimate of the annual heat 

required to maintain comfort, excluding both positive and negative effects 

resulting from the solar components. In this estimate, no solar heating 

credit is given to east, west, and north windows, because it is assumed 

that these will be protected by vegetation or other shading in accordance 

with the guideline recommendations. This is a conservative assumption, 

because there will always be some solar gain through these windows. 

Annual Auxiliary Heat (Buildeffiuide Worksheet 11) 

The tables of passive solar savings fractions are calculated using the 

solar load ratio (SLR) method (References 21 and 22). Monthly solar 

savings fraction (SSF) values are determined using correlation fits to the 

results of hourly computer simulation calculations for a variety of 

climates. These 12 values are converted into an annual value and 

entered into tables accessed by BuilderGuide. The SLR method gives 

answers that agree within about 5% of the hourly computer simulations 

and within 11% of the measured passive solar performance of 55 

buildings monitored under the Solar Buildings Program. The SSF 
FOR INDIAN HOUSING Paae 85 

estimates account properly for both solar gains and heat losses through 

the solar aperture, and thus correct for omitting the solar components 

from the calculation of annual heat loss. 

Temperature Swing (BuilderGuide Worksheet 111) 

The temperature swing estimate on Worksheet I11 is based on the diurnal 

heat capacity (DHC) method (Reference 23). The method is an analytic 

procedure in which the total heat stored in the building during one day is 

estimated by summing the effective heat storage potential of all the 

various materials in the building for a 24-hour periodic cycle of solar 

input. Rooms with direct gain are assumed to have radiative coupling of 

the solar heat to the mass. Rooms connected to rooms with direct gain 

are assumed to have convective coupling, which is rather less effective. 

especially for massive elements. The DHC of the sheetrock, framing, and 

furniture is approximated at 4.5 or 4.7 Btu/"F per ft2 of floor area. Tables 

accessed by BuilderGuide list the increased value of diumal heat capacity 

for various conventional materials that are often used to provide extra 

heat storage, assuming these materials replace sheetrock. 

The only numbers used in Worksheet I11 that are location-dependent are 

the comfort factors. The direct-gain comfort factor is 61% of the solar 

gain transmitted through vertical, south-facing double glazing on a clear 

January day. The driving effect of sunspaces and vented Trombe walls is 

assumed to result in one-third this value, based on data from monitored 

buildings. The origin of the 61% factor is to account for the 

nonsinusoidal shape of a typical daily room temperature variation. 

Annual Auxiliary Cooling (BuilderGuide Worksheet IV) 

The purpose of including the summer cooling estimates in the Builder 

Guidelines is to (1) determine if design elements added to promote 

passive solar heating will cause excessive summer cooling loads and (2) 

provide a rough estimate of the effectiveness of solar shading and natural 

cooling strategies. The analysis method is based on a modified monthly 

degree-day procedure in which the day is divided into day and night 

periods (Reference 24). All estimates are derived from correlations based 

on hourly computer simulations. Solar, conduction, and internal gains 

are estimated for each half-day period in each month. Delay factors are 

used to account for heat carryover from day to night and from night to 

day. The results are estimates of annual sensible cooling delivered by the 

air conditioner and do not include latent loads. 

Because the original Los Alamos monthly procedure is too complex to be 

implemented in a worksheet, a simplified procedure is adopted on 

Worksheet N. Heat Gain Factors and Internal Gain Factors are the 

calculated annual incremental cooling loads resulting from a one-unit 

incremental change in the respective heat input parameter (that is, a 

one-unit change in UA, glazing area, or number of bedrooms). The 

combined heat load resulting from all inputs is summed and then 

adjusted for thermal mass and ventilation. This correction includes a 

constant required to match the calculated cooling load of the basecase 

building. This linearized procedure gives accurate estimates for cooling 
Pa~e 86 ENERGY-EFFICIENCY DESIGN GUIDE 

loads that are less than about 150% of the base-case building; however, 

it underestimates very large cooling loads in poorly designed buildings. 

The adjustment factors for ventilation properly account for maintaining 

comfort in hot and humid climates. Ventilation is restricted to times 

when the outside dew-point temperature is less than 62°F. This 

restriction avoids ventilation when high humidity might cause 

discomfort. 

Getting Data 

Heating and cooling degree-day data can be obtained from the National 

Climatic Center, Asheville, North Carolina. Refer to Climatography of the 

United States No. 81, which lists monthly normals for the period 195 1 - 

1980 on a state-by-state basis. More than 2400 locations are listed in 

this data base. 
FOR INDIAN HOUSING Paqe 87 

REFERENCES 

General 

A Sunbuilder's Primer, Solar Energy Research Institute. 

Passive: It's a Natural, Solar Energy Research Institute. 

The Passive Solar Construction Handbook, Steven Winter 

Associates/Northeast Solar Energy Center/National Concrete 

Masonry Association/Portland Cement Association/Brick Institute of 

America. Available for $29.95 plus $3.00 handling, from Steven 

Winter Associates, Attn: Publications, 6100 Empire State Building, 

New York, N.Y. 1000 1. 

Suntempering in the Northeast, Steven Winter Associates. Available 

from Steven Winter Associates at the address above for $9.50. 

Passive Solar Design Handbook, Volumes I, 11, 111. Available from 

National Technical Information Service, U.S. Dept. of Commerce, 

5285 Port Royal Road, Springfield, VA, 22 16 1, $32.00 each for I and 

11, $12.00 for 111. 

Balcomb, J.D., et al. Passive Solar Heating Analysis. This volume 

supersedes and expands Volume I11 of the Passive Solar Design 

Handbook (Ref. 5). Available from ASHRAE, Publications, 179 1 Tullie 

Circle NE, Atlanta, GA, 30329, $30.00 for ASHRAE members, $60.00 

for nonmembers. 

Living With the Sun (for consumers) and Building With the Sun (for 

builders), PPG Industries. 

The Passive Solar Information Guide, PSIC. 

Passive Solar Trends. Technical briefs from PSIC. 

Infiltration in Passive Solar Construction 

The State of the Art in Passive Solar Construction 

Passive Solar in Factory-Built Housing 

Radiant Barriers: Top Performers in Hot Climates 

Glazings: The Design Considerations Aren't as Clear as Glass 

Ideas for Passive Solar Remodeling 

Passive Homes in the Marketplace (Class C Studies) 

Daylighting in Commercial Buildings 

Human Comfort and Passive Solar Design 

Passive Design for Commercial Buildings 

Passive Solar: Principles and Products 

Increasing Design Flexibilitv 

m. Utilities 5nd ~Zssive: predicting the Payoff 
Paae 88 ENERGY-EFFICIENCY DESIGN GUIDE 

Insulation 

10. NAHB Insulation Manual. National Association of Home Builders, 

National Research center. Available from NAHB Bookstore, 15th and 

M Streets, N.W., Washington, DC 20005. (202) 822-0200. 

Lischkoff, James K. The Airtight House: Using the Airtight Drywall 

Approach, Iowa State University Research Foundation. Available for 

$14.95; Attn: Sarah Terrones, EES Building, Iowa State University, 

Ames, 1A 500 1 1. 

Spears, John. Radon Reduction in New Construction, Interim Guide, 

National Association of Home Builders, Environmental Protection 

Agency OPA 87-009, August 1987. Available from the EPA or the 

NAHB Bookstore, 15th and M Streets, N.W., Washington, DC 20005. 

(202) 822-0200. Also A Citizens Guide to Radon, What It Is, August 

86, Environmental Protection Agency OPA 86-004. From Drew 

Gillett : Radon Reduction Techniques for Detached Housing, Technical 

Guide, 2nd Edition, EPA 6255-87 019. A builder would never read 

this, but it is the "Bible". Also Chuck Silver of SolarPlex wrote a 

training manual for the New York State Energy Office that contains 

much the same information but is much more readable. 

Appliances 

Saving Energy and Money with Home Appliances, Environmental 

Science Department, Massachusetts Audubon Society/Arnerican 

Council for an Energy Efficient Economy. Available for $2.00 apiece 

from ACEEE, 100 1 Connecticut Ave., N.W., Suite 535, Washington, 

DC 20036. 

The Most Energy Eff~cient Appliances, 1 988 Edition, ACEEE, $2.00 

each at address above. 

Site Planning 

15. Builder's Guide to Passive Solar Home Design and Land Development, 

National Fenestration Council. Available for $12.00 from NFC, 33 10 

Harrison, White Lakes Professional Building, Topeka, KS 666 1 1. 

16. Site Planning for Solar Access, U.S. Department of Housing and 

Urban Development/Arnerican Planning Association. Available for 

$6.50 from Superintendent of Documents, U.S. Government Printing 

Office, Washington, DC 20402. 

Sunspaces 

17. Jones, Robert W. and Robert D. McFarland. The Sunspace Primer A 

Guide for Passive Solar Heating, available for $32.50 from Van 

Nostrand Reinhold, 1 15 5th Avenue, New York, NY 10003. 

18. Greenhouses for Living, from Steven Winter Associates, Attn: 

Publications, 6 100 Empire State Building, New York, NY 1000 1, 

$6.95. 
FOR INDIAN HOUSING Paae 89 

19. Concept W, from Andersen Corporation, Bayport, MN 55003, $6.95. 

20. Passive Solar Greenhouse Design and Construction, Ohio Department 

of Energy/John Spears, 882 1 Silver Spring, MD 209 10. 

Technical 

21. J. Douglas Balcomb, Robert W. Jones, Robert D. McFarland, and 

William 0. Wray, "Expanding the SLR Method", Passiue Solar Journal, 

Vol. 1, No. 2, 1982, pp. 67-90. Available from the American Solar 

Energy Society, 2400 Central Ave., Unit G- 1, Boulder, CO 8030 1. 

22. J. Douglas Balcomb, Robert W. Jones, Robert D. McFarland, and 

William 0. Wray, Passive Solar Heating Analysis, American Society of 

Heating, Refrigerating, and Airconditioning Engineers, 1984. 

Available from ASHRAE, 17 19 Tullie Circle, NE, Atlanta, GA 30329. 

23. J. Douglas Balcomb and William 0. Wray, Passive Solar Heating 

Analysis, Supplement One, Thermal Mass Effects and Additional SLR 

Correlations, American Society of Heating, Refrigerating, and Air 

Conditioning Engineers, 1987. See ASH= address above. 

24. Robert D. McFarland and Gloria Lazarus, Monthly Awciliay Cooling 

Estimation for Residential Buildings, LA- 1 1394-MS, Los Alamos 

National Laboratory, Los Alamos, NM 87545, 1989. 

More Information 

Consenration and Renewable Energy Inquiry and Referral Service 

(CAREIRS) 

Renewable Energy Information 

Box 8900 

Silver Spring, MD 20907 

800-523-2929. 

National Association of Home Builders 

Attention: Technical Services 

15th & M Streets, N.W. 

Washington, DC 20005. 

National Concrete Masonry Association 

Attention: Energy Engineer 

2302 Horse Pen Road 

Herndon, VA 22070.