Passive Solar Design Strategies: Guidelines for

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With SuN)(Jrt From: U.S. Department of Energy Passive Solar Design Strategies: Guidelines for HOlDe Building

. Boise, Idaho

Passive Solar Industrtes Council National Renewable Energy Laboratory Charles Eley Associates This document was prepared under the sponsorship of the National Renewable Energy Laboratory and produced with funds made available by the United States Department of Energy. Neither the United States Department of Energy. the National Renewable Energy Laboratory. the Passive Solar Industries Council nor any of its member organizations. nor any of their employees. nor any of their contractors. subcontractors. or their employees. makes any warranty. expressed 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. The views and opinions do not necessarily state or reflect those of the United States government. the National Renewable Energy Laboratory. or any agency thereof. This document was prepared with the assistance and participation of representatives from many organizations. but the views and opinions expressed represent general consensus and available information. Unanimous approval by all organizations is not implied. PASSIVE SOLAR DESIGN STRATEGIES CONTENTS

Guidelines

Part One. Introduction ...... 1 l. The Passive Solar Design Strategies Package ...... 2 2. Passive Solar PertoTlllance Potential ...... 5

Part Two. Basics of Passive Solar ...... 7 l. Why Passive Solar? More than a Question of Energy ...... 8 2. Key Concepts: Energy Conservation, Suntempering, Passive Solar ...... 9 3. Improving Conservation PertoTlllance ...... 10 4. Mechanical Systems ...... 13 5. South-Facing Glass ...... 14 6. TheTlllal Mass ...... 15 7. Orientation ...... 16 8. Site Planning for Solar Access ...... 17 9. Interior Space Planning ...... 18 10. Putting it Together: The as a System ... : ...... 18

Part Thr~e. Strategies for Improving Energy Performance in Boise, Idaho ...... 21 1. The Example Tables ...... 22 2. Suntempertng ...... 23 3. Direct Gain ...... 24 4. Sunspaces ...... 27 5. TheTlllal Storage ...... 30 6. Combined Systems ...... 32 7. Natural Cooling Guidelines ...... 32

Worksheets

Blank Worksheets, Data Tables, and Worksheet Instructions ...... 39

Worked Example

Description of the Example Building ...... 47 Completed Worksheets ...... 51 Annotated Worksheet Tables ...... 56 IAnytOWIl", USA ...... 59

Appendix

Glossary of TeTllls ...... 81 Summary Tables ...... 82 Technical Basis for the Builder Guidelines ...... 84

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES

Acknowledgements J. Douglas Balcomb, NREL and contributed far beyond the call LANL , whose work is the basis of duty. Stephen Szoke, Passive Solar Design Strategies: of the GUidelines; Robert Director of National Accounts, Guidelines for Home Builders McFarland, LANL, for National Concrete Masonry represents over three years of developing and programming Association, Chairman of PSIC's effort by a unique group of the calculation procedures; Alex Board of Directors during the organizations and individuals. Lekov, NREL, for assistance in development of these guidelines; The challenge of creating an the analysis; Subrato Chandra James Tann, Brick Institute of effective design tool that could and Philip W. Fairey, FSEC, America, Region 4, Chairman of be customized for the specific whose research has guided the PSIC's Technical Committee needs of builders in cities and natural cooling sections of the during the development of these towns all over the U.S. called for guidelines; the members of the guidelines; and Bion Howard, the talents and experience of NAHB Standing Committee on Chairman of PSIC's Technical speCialists in many different Energy, especially Barbara B. Committee during the areas of expertise. Harwood, Donald L. Carr, development of these guidelines, Passive Solar Design James W. Leach and Craig the Alliance to Save Energy all Strategies is based on research Eymann, for the benefit of their gave unstintlngly of their time, sponsored by the United States long experience in building their expertise, and their Department of Energy (DOE) energy-efficient ; at U.S. enthusiasm. Solar Program, and DOE, Frederick H. Morse, carried out primarily by the Los Former Director of the Office of Alamos National Laboratory Solar Heat Technologies and (LANL), the National Renewable Mary-Margaret Jenior, Program Energy Laboratory (NREL) , Manager; Nancy Carlisle and formerly Solar Energy Research Paul Notari at NREL; Helen· Institute (SERI), and the Florida English, Executive Director of Solar Energy Center (FSEC). PSIC; Michael Bell, former The National Association of Chairman of PSIC, and Layne Home Builders (NAHB) Standing Evans and Elena Marcheso­ Committee on Energy has Moreno, former Executive provided invaluable advice and Directors of PSIC; Arthur W. assistance during the Johnson, for technical development of the Guidelines. assistance in the development of Valuable information was the Guidelines and worksheets; drawn from the 14-country Michael Nicklas, who worked International Energy Agency on the Guidelines from their (lEA), Solar Heating and Cooling early stages and was program, Task VIII on Passive instrumental in the success of and Hybrid Solar Low Energy the first pilot in North Buildings (see next page for Carolina; Charles Eley, for his more about the international help in every aspect of the context of Passive Solar Design production of the Guidelines Strategies) . package. PSIC expresses particular Although all the members of gratitude to the following PSIC, especially the Technical individuals: Committee, contributed to the financial and technical support of the Guidelines, several

Boise, Idaho Passive Solar Design Strategies GUIDELINES

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department of Energy PASSIVE SOLAR DESIGN STRATEGIES 1

Part One: Introduction

1. The Passive Solar Design Strategies Package

2. Passive Solar Performance Potential

Boise, Idaho 2 GUIDELINES PART ONE: INTRODUCTION

1. The Passive Solar Passive Solar Design BuilderGuide Strategies is a package in four A special builder-friendly Design Strategies basic parts: computer program caller Package • The GuideHnes contain BuilderGuide has been information about passive solar developed to automate the The concepts of passive solar techniques and how they work. calculations involved in filling are simple. but applying it Specific examples of systems out the four worksheets. The effectively requires specific which will save various program operates like a information and attention to the percentages of energy are spreadsheet; the user fills in details of design and provided. values for the building. and the construction. Some passive • The Worksheets offer a computer completes the solar techniques are modest and simple. fill-in-the-blank method calculations. including all table low-cost. and require only small to pre-evaluate the peIiormance lookups. and prints out the changes in a builder's standard of a specific design. answers. The automated practice. At the other end of the • The Worked Example method of using the Worksheets spectrum. some passive solar demonstrates how to complete allows the user to vary input systems can almost eliminate a the worksheets for a typical values. BuilderGuide helps the house's need for purchased residence in BOise. user quickly evaluate a wide energy - but probably at a • The section titled Any Town. range of design strategies. relatively high first cost. USA is a step by step In between are a broad range explanation of the passive solar BuilderGuide is available from of energy-conserving passive worksheets for a generic the Passive Solar Industries solar techniques. Whether or example house. Council. Computer data files not they are cost-effective. containing climate data and practical and attractive enough data on component peIiormance to offer a market advantage to for 228 locations within the any individual builder depends United States. The user can on very specific factors such as then adjust for local conditions local costs. climate and market so peIiormance can be evaluated characteristics. virtually anywhere. Passive Solar Design Strategies: Guidelines for Home Builders is written to help give builders the information they need to make these decisions.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 3

The Guidelines Part Three gives more The Base Case House is a Some principles of passive solar specific advice about techniques reasonably energy-efficient design remain the same in every for suntempering, direct gain house based on a 1987 National climate. An important aspect of systems, thermal storage mass Association of Home Builders good passive solar design is that and sunspaces, and for of housing characteristics. it takes advantage of the natural cooling strategies to for seven different regions. The opportunities at the specifiC site. help offset air-conditioning Base Case used for Boise, Idaho So, many fundamental aspects needs. is from the 5,000-6,000 heating of passive solar design will The Example Tables in Part degree days region. The house is depend on the conditions in a Three are also related to assumed to be built over an small local area, and even on Worksheet numbers, so that you unheated , because the features of the building site. can compare them to the this is typical in Idaho. Many of the suggestions in this designs you are evaluating. For The examples show how to section apply specifically to example, the Passive Solar achieve 20%,40% and 60% Boise, Idaho, but there is also Sunspace Example Case which energy-use reductions using information which will be useful uses 40% less energy than the three basic strategies: in any climate. Base Case House (page 29) has: • Added Insulation: Part One introduces Passive • A ConseIVation Performance Increasing thermal resistance Solar Design Strategies, and Level of apprOximately 37,729 insulation levels without adding presents the performance Btu/yr-sf, solar features. potential of several different • An Auxiliary Heat • Suntempering: Increasing passive solar systems in the Performance Level of south-facing glazing to a Boise climate. Although in apprOximately 24,958 Btu/yr-sf, maximum of 7% of the house's practice many factors will affect and total area, without adding actual energy performance, this • A Summer Cooling thermal mass (energy storage) information gives a general idea Performance Level of 3,638 beyond what is already in the of how various systems might Btu/yr-sf. framing, standard floor perform in Boise. In this example, the energy coverings and gypsum wall­ Part Two discusses the basic savings are achieved by board and surfaces. concepts of passive solar design increasing insulation about 17% Suntempering is combined with and construction: what the over the Base Case House, increased levels of thermal advantages of passive solar are, adding a sunspace with south resistance insulation. how passive solar rel~tes to glazing area equal to 9% of the other kinds of energy house's floor area, and using a conseIVation measures, how the ceiling fan to cut some of the air primary passive solar systems conditioning load. work, and what the builder's A Base Case House is most important considerations compared with a series of should be when evaluating and example cases to illustrate using different passive solar exactly how these increased strategies. levels of energy-efficiency might be achieved.

Boise, Idaho 4 GUIDELINES PART ON£: INTRODUCTION

• Solar : Using you build now, then fill out per year (Btu/sf-yr) - the lower three different design Worksheets for that house with the heat loss, the better. approaches: Direct Gain, a variety of energy performance • Worksheet IT: Auxiliary Sunspace, and Thermal Storage strategies such as increased Heat Performance Level: Wall, with increased levels of insulation, suntempering and Determines how much heat has thermal resistance insulation. specific passive solar to be supplied (that is, provided For all strategies, the energy components. by the heating system) after savings indicated are based on The Worksheets provide a taking into account the heat the assumption that the energy­ way to calculate quickly and contributed by passive solar. efficient design and construction with reasonable accuracy how This worksheet arrives at a gUidelines have been followed, well a design is likely to perform number estimating the amount so the are properly sited in four key ways: how well it will of heating energy the house's and tightly built with high­ conserve heat energy; how much non-solar heating system has to quality and . the solar features will contribute provide in Btu/yr-sf. Again. the The Guidelines section has to its total heating energy needs; lower the value, the better. been kept as brief and how comfortable the house will • Worksheet m: Thermal straightforward as possible, but be; and how much the annual Mass/Comfort: Determines more detailed information is cooling load (need for air whether the house has adequate aVailable if needed. References conditioning) will be. thermal mass to assure comfort are indicated in the text. Also The Worksheets are and good thermal performance. included at the end of this book supported by "look-up" tables Worksheet III calculates the are a brief glossary; a summary containing pre-calculated number of degrees the of the Example Tables for Boise, numbers for the local area. temperature inside the house is Idaho, and the Technical Basis Some of the blanks in the likely to vary, or "swing", during for the Builder Guidelines which Worksheets call for information a sunny winter day without the explains the background and about the house - for example, heating system op

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 5

• Worksheet IV: Summer 2. Passive Solar system has 145 sf.The energy savings presented in this Cooling Performance Level: Performance Indicates how much air example assume that all the conditioning the house will need Potential systems are designed and built in the summer (It is not. according to the suggestions in however. intended for use in The energy performance of these Guidelines. It's also sizing equipment. but as an passive solar strategies varies important to remember that the indication of the reductions in significantly. depending on figures below are for annual net annual cooling load made climate. the specific design of heating benefits. The natural possible by the use of natural the system. and the way it is cooling section in Part Three cooling). The natural cooling built and operated. Of course. gives advice about shading and gUidelines should make the energy performance is not the other techniques which would house's total cooling load - the only consideration. A system make sure the winter heating bottom line of this Worksheet. in which will give excellent energy benefits are not at the expense Btu/yr-sf - smaller than in a performance may not be as of higher summer cooling loads. "conventional" house. The lower marketable in your area or as Please note that throughout the cooling performance level. easily adaptable to your designs the Guidelines and Worksheets the better the design. as a system which saves less the glazing areas given are for So. the Worksheets provide energy but fits other needs. the actual net area of the glass four key numbers indicating the In the following table. itself. A common rule of thumb projected performance of the several different passive solar is that the net glass area is 80 various designs you are systems are presented along percent of the rough frame evaluating. with two numbers which opening. For example. if a • The Worked Example: To indicate their performance. The south glass area of 100 sf is assist in understanding how the Percent Solar Savings is a desired. the required area of the design strategies outlined in the measure of how much the rough frame opening would be Guidelines affect the overall passive solar system is reducing about 125 sf. performance of a house. a the need for purchased energy. worked example is included. For example. the Percent Solar The example house is assumed Savings for the Base Case House to be constructed of materials is 7.1 %. because even in a non­ and design elements typical of solar house. the south-facing the area. Various design windows are contributing some features. such as direct gain heat energy. spaces. sunspaces. increased The Yield is the annual net levels of insulation and thermal heating energy benefit of adding mass. are included to illustrate the passive solar system. the effects combined systems measured in Btu saved per year have on the performance of a per square foot of additional house. Also. many features are south glazing. covered to demonstrate how The figures given are for a various conditions and 1.500 sf. Single-story house with situations are addressed in the a basement. The Base Case worksheets. A deSCription of the House has 45 sf of south-facing design features. along with the glazing. For the purposes of this house plans. elevations and example. the Suntempered sections. is included for house has 100 sf of south-faCing additional support information. glass. and each passive solar

Boise, Idaho 6 GUIDELINES PART ON£: INTRODUCTION

Performance Potential of Passive Solar Strategies in Boise, Idaho 1,500 sf, Single Story House Yield Btu Saved per Percent Solar Square Foot of Case Savings South Glass

Base Case 7.1 not applicable (45 sf of south-facing double glass) Suntempered 13.4 63,526 (100 sf of south-facing double glass)

Direct Gain (145 sf of so lith glass) Double Glass 17.7 59,027 Triple or low-e glass 19.8 76,375 Double glass with R-4 night 22.5 95,365 insulation l Double glass with R-9 night 23.6 102,542 insulation 1

Sunspace (145 sf of south glass) Attached with opaque end walls2 18.1 68,085 Attached with glazed end walls2 17.4 63,020 Semi-enclosed with vertical glazing3 18.4 66,018 Semi-enclosed with 50° sloped 22.8 96,880 glazing3

Thermal Storage Wall - Masonry/Concrete (145 sf of south glass) Black surface, double glazing 17.1 59,710 Selective surface, single glazing 22.5 96,023 Selective surface, double glazing 22.0 93,344

Thermal Storage Wall - Water Wall (145 sf of south glass) Selective surface, single glazing 25.7 115,790

1. Night insulation is assumed to cover the south glass each night and removed when sun is available. Experience has shown that many homeowners find this inconvenient and so the potential energy savings are often not achieved. Using low-e or other energy-efficient glazing is more reliable. 2. The attached sunspace is assumed to have, in addition to glazed walls, glazing at a slope of 30 degrees from the horizontal, or a 7:12 pitch. (See diagram SSB1 in the Worksheets.) 3. The semi-enclosed sunspace has only the south wall exposed to the out­ of-doors. The glazing has a slope of 50° from the horizontal, or a 14:12 pitch. The side walls are adjacent to conditioned space in the house. (See diagram SSD1 in the Worksheets.)

Boise. Idaho PASSIVE SOLAR DESIGN STRATEGIES 7

Part Two: Basics of Passive Solar

1. Why Passive Solar? More than a Question of Energy

2. Key Concepts: Energy Conservation, Suntempering,

3. Improving Conservation Performance

4. Mechanical Systems

5. South-Facing Glass

6. Thermal Mass

7. Orientation

8. Site Planning for Solar Access

9. Interior Space Planning

10. Putting it Together: The House as a System

Boise, Idaho 8 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

1. Why Passive Solar? improve energy-efficiency - but as the state of the art in energy­ added insulation is invisible to efficiency and style. and they More than a Question the prospective home buyer. A use passive solar as a part of the of Energy sunny. open living area lit by package. south-facing windows. on the The U.S. Department of Houses today are more energy­ other hand. may be a key selling Energy and the National Renew­ efficient than ever before. point. Windows in general are able Energy Laboratory (NREL) However. the vast majority of popular with homebuyers. and conducted extensive national new houses still ignore a lot of passive solar can make windows surveys of passive solar homes. energy saving opportunities - energy producers instead of home owners and potential opportunities available in the energy liabilities. buyers. Some key findings: sunlight falling on the house. in Another example: high­ • Passive solar homes work - the landscaping. breezes and efficiency heating equipment they generally require an other natural elements of the can account for significant average of about 30% less site. and opportunities in the energy savings - but it won't be energy for heating than structure and materials of the as much fun on a winter "conventional" houses. with house itself. which. with morning as breakfast in a some houses saving much more. thoughtful design. could be bright. attractive sunspace. • Occupants of passive- solar used to collect and use free The point is not that a homes are pleased with the energy. Passive solar (the name builder should choo::;e passive performance of their homes distinguishes it from "active" or solar instead of other energy­ (over 90% "very satisfied"). but mechanical solar technologies) conserving measures. The they rank the comfort and is simply a way to take important thing is that passive pleasant living environment as maximum advantage of these solar strategies can add not only just as important (in some opportunities. energy-efficiency. but also very regions. more important) to their Home buyers are also saleable amenities - style. satisfaction. and in their increasingly sophisticated about comfort. attractive interiors. decision to buy the house. as energy issues. although the curb appeal and resale value. energy considerations. average home buyer is probably In fact. in some local • Passive solar home owners much more familiar with markets. builders report that and lenders perceive the insulation than with passive they don't even make specific resale value of passive solar . solar. The "energy crisis" may reference to "passive solar". houses as high. come and go. but very few They just present their houses people perceive their own Advantages of Passive Solar household energy bills as • Energy performance: Lower energy bills all year-round getting smaller - quite the opposite. So a house with • Attractive living environment: large windows and views, sunny significantly lower monthly interiors, open floor plans energy costs year-round will • Comfort: quiet (no operating noise), solid construction, warmer in have a strong market advantage winter, cooler in summer (even during a power failure) over a comparable house down the street. no matter what • Value: high owner satisfacti~n, high resale value international oil prices may be. • Low Maintenance: durable, reduced operation and repairs There are many different ways to reduce energy bills. and • Investment: independence from future rises in fuel costs, will continue some are more marketable than to save money long after any initial costs have been recovered others. For instance. adding • Environmental Concerns: clean, renewable energy to combat growing insulation can markedly concerns over global warming, acid rain and ozone depletion

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 9

2. Key Concepts: Many of the measures that Although the concept is simple. are often considered part of in practice the relationship Energy Conservation, suntempering or passive solar - between the amounts of glazing Suntempering, such as orienting to take and mass is complicated by Passive Solar advantage of summer breezes. or many factors. and has been a landscaping for natural cooling. subject of considerable study or facing a long wall of the and experiment. From a comfort The strategies for enhancing house south - can help a house and energy standpoint. it would energy performance which are conserve energy even if no be difficult to add too much presented here fall into four "solar" features are planned. mass. Thermal mass will hold general categories: The essential elements in a warmth longer in winter and • Energy Conservation: passive solar house are south­ keep houses cooler in summer. insulation levels. control of air facing glass and thermal mass. The following sections of the infiltration. glazing type and In the simplest terms. a Guidelines discuss the size and location. mechanical equipment passive solar system collects location of glass and mass. as and energy efficient appliances. solar energy through south­ well as other considerations • Suntempering: a limited use facing glass and stores solar which are basic to both of solar techniques; modestly energy in thermal mass - suntempered and passive solar increasing south-facing materials with a high capacity houses: improving conservation area. usually by relocating for storing heat (e.g:. brick, . performance; mechanical windows from other sides of the concrete masonry. concrete systems; orientation; site house. but without adding slab. tile. water). The more planning for solar access; thermal mass. south-facing glass is used in the interior space planning; and • Solar Architecture: going house. the more thermal mass approaching to the house as a beyond conservation and must be provided. or the house totally integrated system. suntempering to a complete will overheat and the solar system of collection. storage and system will not perform as use of solar energy: using more expected. south glass. adding appropriate Improperly done. passive thermal mass. and taking steps solar may continue to heat the to control and distribute heat house in the summer. causing energy throughout the house. discomfort or high air­ • Natural Cooling: using conditioning bills. or overheat design and the environment to the house in the winter and cool the house and increase require additional ventilation. comfort. by increasing air movement and employing shading strategies. What is immediately clear is that these categories overlap. A good passive solar design must include an appropriate thermal envelope. energy efficient mechaniccil systems. energy efficient appliances and proper solar architecture. specifically the appropriate amounts and locations of mass and glass.

Boise, Idaho 10 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

3. Improving The thermal resistance of Slab edge insulation should ceiling/roof assemblies, walls be at least two feet deep. Conservation and is affected not only extending from the surface of Performance by the R-value of the insulation the floor or above. Materials for itself. but also the resistance of slab edge insulation should be The techniques described in this other elements in the selected for underground section relate to Worksheet I: construction assembly - framing durability. One material with a Conservation Performance effects. exterior sheathing. and proven track record is extruded Level. which measures the finishes and interior finishes. polystyrene. Exposed insulation house's heat loss. The energy The Worksheets include tables should be protected from conservation measures that that show Equivalent physical damage by attaching a reduce heat loss also tend to Construction R-Values which protection board. for instance. reduce the house's need for air account for these and other or by covering the insulation conditioning. effects. For instance. ventilated with a protective surface. The The most important crawlspaces and unheated use of termite shields may be measures for improving the provide a buffering required. house's basic ability to conserve effect which is accounted for in Heated basement walls the heat generated either by the the Worksheet tables. should be fully insulated to at sun or by the house's ,With ~. framing effects least four feet below grade. but conventional heating system are are minimized if the insulation the portion of the wall below in the following areas: covers the ceilingjoists. either that depth only needs to be • Insulation by using blown-in insulation or insulated to about half the R­ • Air infiltration by running an additional layer value of the upper portion. • Non-solar glazing of batts in the opposite direction Insulation can be placed on the of the ceiling jOists. Ridge outside surface of the wall, or on Insulation and/ or eave vents are needed for the inside surface of the wall. or Adding insulation to walls. ventilation. in the cores of the masonry floors. . roof and units. improves their If the basement walls are thennal resistance (R-value) - insulated on the outside. the their resistance to heat flowing materials should be durable out of the house. underground. and exposed A quality job of installing the insulation should be protected insulation can have almost as from damage. Exterior much effect on energy insulation strategies only performance as the R-value. so Insulation in an Attic require the use of a termite Insulation should extend over the top ceiling shield. In the case of a finished careful construction supervision joists and ventilation should be provided at the is important. An inspection just eaves. basement or walk-out basement. before the drywall is hung may placing insulation on the identify improvements which are In cathedral ceilings. an interior or within the cores of easy at that time but might insulating sheathing over the architectural masonry units make a big difference in the top decking will increase the R­ may be less costly than energy use of the home for the value. insulating the exterior life of the building. foundation.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 11

Air Infiltration Checklist for Minimizing Air Leakage Sealing the house carefully to ./ Tighten seals around windows and doors, and weatherstripping around reduce air infiltration - air all openings to the outside or to unconditioned ; leakage - is as necessary to ./ Caulk around all windows and doors before drywall is hung; seal all energy conservation as adding penetrations (, electrical, etc.); insulation. The tightness of houses is ./ Insulate behind wall outlets and/or plumbing lines in exterior walls; generally measured in the ./ Caulk under headers and sills; number of air changes per hour ./ Chink spaces between rough openings and millwork with insulation, or (ACH). A good, comfortable, for a better seal, fill with foam; energy-efficient house, built along the gUidelines in the table ./ Seal larger openings such as ducts into or crawlspaces with taped polyethylene covered with insulation; on this page, will have apprOximately 0.35 to 0.50 air ./ Locate continuous vapor retardants located on the warm side of the changes per hour under normal inSUlation (building wrap, continuous interior polyethylene, etc.); winter conditions. ./ Install dampers and/or glass doors on ; combined with outside Increasing the tightness of combustion air intake; tlie house beyond that may ./ Install backdraft dampers on all exhaust fan openings; improve the energy performance, ./ Caulk and seal the joint between floor slabs and walls; but it may also create problems with indoor air quality, moisture ./ Remove wood grade stakes from slabs and seal; build-up, and inadequately ./ Cover and seal sump cracks; vented fireplaces and furnaces. Some kind of additional ./ Close core voids in top of concrete masonry foundation walls; mechanical ventilation - for ./ Control concrete and masonry cracking; example, small fans, heat pump heat exchangers, integrated ./ Use of air tight drywall methods are also acceptable; ventilation systems or air-to-air ./ Employ appropriate radon mitigation techniques. heat exchangers - will probably ./ Seal seams in exterior sheathing. be necessary to avoid such problems in houses with less than 0.35 ACH (calculated or measured). Tighter houses may perform effectively with appropriate mechanical ventilation systems. The use of house sealing subcontractors to do the tightening and check it with a blower can often save the builder time and problems, especially when trying to achieve particularly high levels of infiltration control.

Boise, Idaho 12 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

Non-80lar Glazing R-values that result from be balanced against the South-faCing windows are procedures account for the benefits. considered solar glazing. The glass. the frame. the air gap and As many windows as south windows in any house are any special (low-e) coatings. possible should be kept operable contributing some solar heat North windows should be for easy natural ventilation in energy to the house's heating used with care. Sometimes summer. (See also Orientation. needs - whether it's a views or the diffuse northern page 16. Recommended Non­ significant. usable amount or light are deSirable. but in South Glass GUidelines. page hardly worth measuring will general north-faCing windows 34, and Shading. page 35) depend on design. location and should not be large. Very large other factors which are dealt north-facing windows should Low-e Glass with later under the discussions have high insulation value. or The principle mechanism of heat of suntempering and passive R-value. Since north windows transfer in multi-layer glazing is solar systems. receive relatively little direct sun thermal radiation from a warm North windows in almost in summer. they do not present pane of glass to a cooler pane. every climate lose Significant much of a shading problem. So Coating a glass surface with a heat energy and gain very little if the chOice were between an low-emissivity (low-e) metallic useful sunlight in the winter. average-sized north-facing oxide material and facing that East and west windows are window and an east or west­ coating into the gap between the likely to increase air facing window. north would glass layers significantly conditioning needs unless heat actually be a better chOice. reduces the amount of heat gain is minimized with careful considering both summer and transfer. The improvement in attention to shading. winter performance. insulating value due to the But most of the reasons East windows catch the low-e coating is roughly people want windows have very morning sun. Not enough to equivalent to adding another little to do with energy. so the provide significant energy. but. layer of glass to the multi-pane best design will probably be a unfortunately. usually enough glass unit. Two panes of glass. good compromise between to cause potential overheating one with a low-e coating. will energy efficiency and other problems in summer. If the have about the same insulating benefits. such as bright living views or other elements in the value as three clear panes. Add spaces and views. house's design dictate east argon gas to this two pane low-e Triple-glazing or double­ windows. shading should be unit and the system will be glazing with a low-e coating is done with particular care. nearly as effective as four layers advisable. Low-e glazing on all West windows may be the of clear glass. The net effect to non-solar windows may be an most problematic. and there are the building occupant is an especially useful solution few shading systems that will be improvement in comfort in both because some low-e coatings effective enough to offset the winter and summer. can insulate in winter and potential for overheating froin a In the market today. there shield against unwanted heat large west-facing window. Glass are three basic types of low-e gain in summer. with a low shading coefficient coatings: (1) high transmission A chart is provided with the may be one effective approach - low-e. (2) selective transmission worksheets that gives typical for example. tinted glass or low-e. and: (3) tinted low-e or window R-values for generic some types of low-e glass which tinted glass with low-e. window types. When possible. provide some shading while These categories are related however. manufacturer's data allowing almost clear views. The to the windows' transmission of based on National Fenestration cost of properly shading both sunlight. or Solar Heat Gain Rating Council (NFRC) east and west windows should (SHG) coeffiCient. The SHG procedures should be used. The coeffiCient will soon be made

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 13 available to builders and 4. Mechanical • Ducts: One area often consumers from uniform ratings neglected but of key importance made by the NFRC. Systems to the house's energy High transmission products performance is the design and are best suited to passive solar The passive solar features in the location of the ducts. Both the buildings designs located in house and the mechanical supply and return ducts should heating dominated climates heating, ventilating and air be located within insulated where high solar gains can 'be conditioning systems (HVAC) areas, or be well insulated if utilized by thermal mass and will interact all year round, so they run in cold areas of the where overhangs are the most effective approach will house. All segments of ducts incorporated to prevent be to design the system as an should be sealed at the jOints. unwanted summer heat gains. integrated whole. HVAC design The joints where the ducts turn Selective transmission is, of course, a complex SUbject, up into exterior walls or products are ideal for those but four areas are particularly penetrate the ceiling should be buildings that have both winter worth noting in energy-efficient particularly tight and sealed. heating and summer cooling houses: • System Efficiency: Heating requirements. The low • System Sizing: Mechanical system efficiency is rated by the emittance characteristics of this systems are often oversized for annual fuel utilization efficiency glass ensure winter performance the relatively low heating loads (AFUE). Cooling system by a reduction in heat loss. In in well-insulated passive solar . efficiency is rated by the summer, the selective properties houses. Oversized systems will seasonal efficiency is rating allow natural daylighting, but cost more in the first place, and (SEER). The higher the number, block a large fraction of solar will cycle on and off more often, the better the performance. infrared energy, reducing the wasting energy. The back-up In the National Association cooling load. systems in passive solar houses of Home Builders' Energy­ Putting a low-e coating on should be sized to provide 100% EffiCient House Project, all the tinted glass, or coloring the of the heating or cooling load on rooms were fed with low, central coating itself, creates a product the design day, but no larger. air supplies, as opposed to the with the U-value, or insulating Comparing estimates on system usual placement of registers capability, of both the products sizes from more than one under windows at the end of above. However, this glass also contractor is probably a good long runs. This resulted in good provides glare control along with idea. comfort and energy a high level of solar heat • Night Setback: Clock performance. rejection, helping control solar thermostats for automatic The performance of even the gains in cooling dominated setback are usually very most beautifully designed areas. effective - but in passive solar passive solar house can easily With this range of products systems with large amounts of be undermined by details like available in the market, nearly thermal mass (and thus a large uninsulated ducts, or by all buildings can benefit from capacity for storing energy and overlooking other basic energy the application of low-e glass. releasing it during the night), conservation measures. Home owners will enjoy setback of the thermostat may increased comfort and livability not save very much energy in interior spaces, reduced unless set properly to account operating costs, and possibly for the time lag effects resulting first cost savings from reduced from the thermal mass. HVAC equipment sizing.

Boise, Idaho 14 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

5. South-Facing Glass The third limit on south­ When the solar glazing is facing glass is the total of all tilted, its winter effectiveness as South-facing solar glass is a key passive solar systems combined, a solar collector usually component of any passive solar which should not exceed 20% of increases. However, tilted system. The system must total floor area. Using more glazing can cause serious include enough solar glazing for south glass than this limit could overheating in the summer if it good performance in winter, but lead to overheating even in is not properly shaded. not so much that cooling winter. Ordinary vertical glazing is For example, a passive solar easier to shade. less likely to performance in summer will be overheat, less susceptible to compromised. The amount of system for a 1,500 sf house damage and leaking, and so is solar glazing must also be might combine 150 sf of direct almost always a better year­ carefully related to the amount gain glazing with 120 sf of round solution. Even in the of thermal mass. Suntempered sunspace glazing for a total of winter, with the sun low in the houses use no additional 270 sf of solar glazing, or 18% of sky and reflecting off snow thermal mass beyond that the total floor area, well within the direct gain limit of 12% and cover, vertical glazing can often already in the wallboard, offer energy performance just as framing and furnishings of a the overall limit of 20%. For a design like this, thermal mass effective as tilted. typical house. Houses with solar architecture must have would be required both in the additional thermal mass. house and within the sunspace. There are three types of The Natural Cooling limits on the amount of south­ guidelines in Part Three include facing glass that can be used recommendations on the effectively in a house. The first window area that should be operable to allow for natural is a limit on the amount of glazing for suntempered houses, ventilation. 7% of the house's total floor area. Above this 7% limit, mass must be added. For direct gain systems in passive solar houses, the maximum amount of south­ facing glazing is 12% of total floor area, regardless of how much additional thermal mass is provided. This limit will reduce the problems associated with visual glare or fabric fading. Further details about the most effective sizing of south glass and thermal mass for direct gain systems are provided in Part Three.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 15

6. Thermal Mass The thermal storage The design issues related to capabilities of a given material thermal mass depend on the passive system type. For Some heat storage capacity. or depend on the material's conductivity. specific heat and sunspaces and thermal storage thermal mass. is present in all density. Most of the concrete wall systems. the required mass houses. in the framing. gypsum and masonry materials typically of the system is included in the wallboard. typical furnishings used in passive solar have design itself. For direct gain. and floor coverings. In similar specific heats. the added mass must be within suntempered houses. this Conductivity tends to increase the rooms receiving the modest amount of mass is with increasing denSity. So the sunlight. The sections on Direct sufficient for the modest amount major factor affecting Gain Systems. Sunspaces and of south-facing glass. But more performance is density. Thermal Storage Walls contain thermal mass is required in Generally. the higher the more information on techniques passive solar houses. and the density the better. for sizing and locating thermal question is not only how much. mass in those systems. but what kind and where it should be located. The thermal mass in a passive solar system is usually a conventional construction Heat Storage Properties of Materials material such as brick, poured Material Specific Density Heat concrete. concrete masonry. or Heat (Ib/ft3) Capacity tile. and is usually placed in the (BtU/lb OF) (BtU/in-sf-OF) floor or interior walls. Other materials can also be used for Poured Concrete 0.16-0.20 120 - 150 2.0 - 2.5 thermal mass. such as water or "phase change" materials. Clay Masonry 0.19-0.21 Phase change materials store Molded Brick 120 - 130 2.0 - 2.2 and release heat through a Extruded Brick 125 - 135 2.1 - 2.3 chemical reactions. Water Pavers 130 - 135 2.2 - 2.3 actually has a higher unit thermal storage capacity than Concrete Masonry 0.19-0.22 concrete or masonry. Water Concrete Masonry Units 80 - 140 1.3 - 2.3 tubes and units called "water Brick 115 - 140 1.9 - 2.3 walls" are commerCially Pavers 130 - 150 2.2 - 2.5 available (general recommendations for these Gypsum Wallboard 0.26 50 1.1 systems are included in the section on Thermal Storage Wall Water 62.4 5.2 systems).

Boise, Idaho 16 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

7. Orientation When glazing is oriented In the ideal situation. the more than 15 degrees off true house should be oriented east­ The ideal orientation for solar south. not only is winter solar west and so have its longest wall glazing is within 5 degrees of performance reduced. but facing south. But as a practical true south. This orientation will summer air conditioning loads matter. if the house's short side provide maximum performance. also significantly increase. has good southern exposure it Glazing oriented to within 15 especially as the orientation will usually accommodate sufficient glazing for an effective degrees of true south will goes west. The warmer the passive solar system. provided perform almost as well. and climate, the more east- and west-facing glass will tend to the heat can be transferred to orientations up to 30 degrees off the northern zones of the house. - although less effective - will cause overheating problems. In still provide a substantial level general. southeast orientations present less of a problem than of solar contribution. In Boise. magnetic north as southwest. Magnetic indicated on the compass is North actually 21 degrees East of true north. and this should be corrected for when planning for orientation of south glazing.

Magnetic Deviation Magnetic Diviation is the angle between true north and magnetic north.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 17

8. Site Planning for situation for providing unshaded southern exposure Solar Access during the winter. See also the figure on page 35 showing The basic objective of site landscaping for summer shade. planning for maximum energy peIiormance is to allow the south side as much unshaded exposure as possible during the winter months. Solar Subdivision Layouts As discussed above, a good Solar access may be provided to the rear solar orientation is possible yard, the side yard or the of solar homes. within a relatively large ~ 2 Story Buildings Allowed southern arc, so the flexibility Ideal Solar Access exists to achieve a workable Buildings, trees or other obstructions should balance between energy not be located so as to shade the south wall of solar buildings. At this latitude, A = 18 ft., B = peIiormance and other 31 ft., and C = 71 ft. important factors such as the slope of the site, the individual Of course, not all lots are large , the direction of enough to accommodate this prevailing breezes for summer kind of optimum solar access, so cooling, the views, the street lay­ it's important to carefully assess out, and so on. shading patterns on smaller lots But planning for solar to make the best compromise. access does place some Protecting solar access is restrictions even on an easiest in subdivisions with ~ Solar Subdivision Layouts individual site, and presents streets that run within 25 Short east-west cul-de-sacs tied into north­ even more challenges when degrees of east-west, because all south collectors is a good street pattern for solar access. planning a complete lots will either face or back up to subdivision. Over the years, south. Where the streets run Two excellent references for developers and builders of many north- south, creation of east­ idea~ about subdivision lay-out different kinds of projects all west cul-de-sacs will help to protect solar access are over the country have come up ensure solar access. Builder's Guide to Passive Solar with flexible ways to provide Home Design and Land adequate solar access. Development and Site Planning Once again, there is an ideal jar Solar Access. 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 guaranteed if the glazing is unshaded within an arc of 45 degrees. The figure on this page shows the optimum

Boise, Idaho 18 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR

9. Interior Space Another general principle is 10. Putting it that an open floor plan will Planning allow the collected solar heat to Together: The House circulate freely through natural as a System Planning lay-out by convection. considering how the rooms will Other ideas from effective Many different factors will affect be used in different seasons. passive solar houses: a house's overall performance. and at different times of day. • Orienting internal mass and these factors all interact: can save energy and increase walls as north-south partitions the mechanical system. the comfort. In houses with passive that can be "charged" on both insulation. the house's solar features. the lay-out of sides. tightness. the effects of the rooms - and interior zones • Using an east-west partition passive solar features. the which may include more than wall for thermal mass. appliances. and. very one room - is particularly • Avoid dividing the house importantly. the actions of the important. between north and south zones. people who live in the house. In In general. living areas and • Using thermal storage walls each of these areas. changes are other high-activity rooms should (see page 30): the walls store possible which would improve be located on the south side to energy all day and slowly release the house's energy performance. benefit from the solar heat. The it at night. and can be a good Some energy savings are . storage areas. alternative to ensure privacy relatively easy to get. Others and other less-used rooms can and to buffer noise when the can be more expensive and more act as buffers along the north south side faces the street: difficult to achieve. but may side. but entry-ways should be • Collecting the solar energy provide benefits over and above located away from the wind. in one zone of the house and good energy performance. Clustering baths. and transporting it to another by A sensible energy-efficient laundry-rooms near the water fans or natural convection house uses a combination of heater will save the heat that through an open floor plan. techniques. would be lost from ~onger water • Providing south-facing In fact. probably the most lines. clerestOries to "charge" north important thing to remember zones. about designing for energy performance in a way that will also enhance the comfort and value of the house is to take an integrated approach. keeping in mind the house as a total system. On the the following ~ page is a basic checklist for Interior Space Planning energy-efficient design. These Uving and high activity spaces should be techniques are dealt with in located on the south. more detail. including their impact in your location. in Part Three.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 19

Checklist for Good Design ./ 1. Building Orientation: A number of innovative techniques can be used for obtaining good solar access. No matter what the house's design, and no matter 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-efficiency can be achieved with more economical increases in insulation. On the other hand, if very high energy performance is a priority - for example, in areas where the cost of fuel is high - the most cost-effective 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 makes the house more comfortable. Indoor air quality is an important issue, and too complex for a complete discussion here, but in general, the suntempered and passive solar houses built according to the Guidelines provide an alternative approach to achieving improved energy efficiency without requiring air quality controls such as air to air heat exchangers, which would be needed if the house were made extremely airtight. ./ 4. Proper window sizing and location: Even if the total amount of glazing is not changed, rearranging 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 "'"7 but it's a fact of human nature 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 commonplace 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 performance. Using different types of glazing for windows with different orientations is worth considering 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. Addition of thermal mass: Adding thermal mass - tiled or paved concrete slab, masonry walls, brick fireplaces, tile floors, etc. - 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. ./ 8. 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 passive solar 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 which is highly marketable in most areas. Planning the rooms with attention to use pattems 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 . ./ 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. Mechanical equipment should have at least a 0.80 Annual Fuel Utilization Efficiency (AFUE). Well-insulated passive solar homes will have much lower energy loads than conventional homes, and should be sized accordingly. Oversized systems will cost more and reduce performance.

Boise, Idaho 20 GUIDELINES PART TWO: BASIS OF PASSIVE SOLAR·

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 21

Part Three: Strategies for Improving Energy Performance in Boise, Idaho 1. The Example Tables

2. Suntempering

3. Direct Gain

4. Sunspaces

5. Thermal Storage Wall

6. Combined Systems

7. Natural Cooling Guidelines

Boise, Idaho 22 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

1. The Example • Three numbers The R-values indicated in corresponding to those on the the Example tables are, of Tables Worksheets: Conservation. course. apprOximate and are Auxillary Heat, and Cooling intended to show how In the following sections of the Performance incremental improvements can Guidelines. the primary passive The Example tables then show be achieved. All R-values in the solar energy systems - how the house design could be Examples and Worksheets are Suntempering. Direct Gain. changed to reduce winter equivalent R-values for the Thermal Storage Walls and heating energy by 20, 40 and entire construction assembly, Sunspaces - are described in 60%, compared to this Base not just for the cavity insulation more detail. Case House. itself, and take into account As part of the explanation of There are, of course. other framing and buffering effects. each system. an Example table ways to achieve energy savings Other assumptions are is provided. The Examples than those shown in the noted for each Example. present the following Examples. The Examples are However. one more general information about a Base Case designed to show an effective assumption is important to note House. based on a National integration of strategies, and a here. When the Examples were Association of Home Builders useful approach to the design of calculated, it was assumed that study of a typical construction: the house as a total system.. natural cooling strategies such • Insulation levels (ceilings. Using any of these combinations as those described in these walls. floors); would result in excellent Guidelines were used. • Insulation added to the performance in your area. particularly in the very high­ perimeter of the basement walls; However. they are general performance systems. The • Tightness (measured in air indicati0I?-s only, and using the greater the percentage reduction changes per hour. ACH); Worksheets will give you more in heating energy needs using • The amount of glass area on information about your specific passive solar design. the more each side (measured as a deSign. shading and natural cooling percentage of floor area; the The Example assumes a were assumed. actual square footage for a 1.500 1,500 sf house. but the The Examples show passive sf house is also given as a percentages apply to a house of solar strategies. but an Added reference pOint); any size or configuration. Insulation Example table • The "percent solar saVings" (achieving energy savings only (the part of a house's heating by increasing insulation levels. energy saved by the solar without specific solar features) features); and is provided in the Summary beginning on page 82.

Boise, Idaho PASSIVE BOLAR DESIGN STRATEGIES 23

2. Suntempering Examples of Heat Energy Savings Suntempered Both suntempered and passive 1,500 sf Single Story House (in a specific location) solar houses: • begin with good basic Base energy-conservation, Case 20% 40% 60% • take maximum advantage of R-Values the building site through the Ceiling/Roof 29 32 39 55 Walls 17 19 23 35 right orientation for year-round Basement Wall 5 6 7 14 energy savings, and Glass 1.8 1.8 1.8 2.7 • have increased south-facing glass to collect solar energy. Air Changes/Hour 0.50 0.44 0.36 0.36 Suntempertng refers to Glass Area (percent of total floor area) modest increases in windows on West 3.0% 2.0% 2.0% 2.0% the south side. North 3.0% 4.0% 4.0% 4.0% No additional thermal mass East 3.0% 4.0% 4.0% 4.0% South 3.0% 6.7% 6.7% 6.7% is used, only the "free mass" in the house - the framing, Solar System Size (square feet) gypsum wall-:-board and South Glass 45 100 100 100 furnishings. Percent Solar Savings In a "conventional" house, 7% 17% 20% 26% about 25% of the windows face south, which amounts to about Performance (Btu/yr-sf) Conservation 43,637 40,004 31,580 22,931 3% of the house's total floor Auxiliary Heat 40,523 33,158 25,029 16,902 area. In a suntempered house, Cooling 9,580 1,437 676 0 the percentage is increased to a maximum of about 7% of the Summary: Insulation values and tightness of the house (as measured in ACH) have been increased. The window area has been slightly floor area. decreased on the west, increased slightly on the east and north, and The energy savings are more increased significantly on the south. modest with this system, but suntempering is a very low-cost Note: These examples should not be construed as recommendations - the numbers represent the effect of changes in design required to achieve the strategy. exact savings in annual auxiliary heat. In practice, the designer has great Of course, even though the latitude in selecting values to use. necessity for precise sizing of glazing and thermal mass does not apply to suntempering (as long as the total south-facing glass does not exceed 7% of the total house floor area), all other recommendations about energy­ efficient design such as the basic energy conservation measures, room lay-out, siting, glazing type and so on are still important for performance and comfort in suntempered homes.

Boise, Idaho 24 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

3. Direct Gain used in the design. as discussed Effective materials for floors below. include painted. colored or The most common passive solar vinyl- covered concrete. brick strategy system is called direct Glazing (face brick or pavers have even gain: sunlight through south­ Double glazing is recommended higher density than ordinary facing glazing falls directly into for direct gain glazing in BOise. building brick). quany tile. and the space to be heated. and is The Performance Potential table dark-colored ceramic tile lead stored in thermal mass on page 6 shows the relative directly on the slab. incorporated into the floor or performance of different types of For houses built with interior walls. The south direct gain glazing. You will crawlspaces or basements. the window area is increased above note from this table that yield incorporation of significant the 7% limit of a suntempered increases by 29% between amounts of heavy thermal mass house. and additional thermal double and triple or low-e is a little more difficult. Thermal mass is added to store the glazing. Night insulation also mass floor coverings over additional solar gains and thus improves energy performance basements. crawlspaces and prevent overheating. dramatically. In fact. as the lower stories would generally be Performance Potential table limited to thin set tile or other shows. covering the windows at thin mass floors. night or on cloudy days with the When more mass is required. equivalent ofR-4 shades or the next best option is for other material will save almost interior walls interior finishes or as much energy as with R-9 exterior walls or interior material. But studies have masonry fireplaces. When shown that only relatively few evaluating costs. 'the dual homeowners will be diligent function of mass walls should Glazing enough about operating their be remembered. They often ~ night insulation to achieve those serve as structural elements or Direct Gain savings. Energy-effiCient for fire protection as well as for Direct gain is the most common passive solar glazing. on the other hand. thermal storage. Another option system in residential applications needs no operation. and is to switch to another passive therefore is a more convenient Sizing Limit solar system type such as and reliable option. attached slab-on-grade Total direct gain glass area sunspaces or thermal storage should not exceed about 12% of Thennal Mass walls built directly on exterior the house's floor area. Beyond Thermal mass can be foundation walls. that. problems with glare or incorporated easily into houses Sunlit thermal mass floors fading of fabrics are more likely with slab-on-grade floors by should be relatively dark in to occur. and it becomes more exposing the mass. The mass is color. to absorb and store energy difficult to provide enough much more effective if sunlight more effectively. However. mass thermal mass for year-round falls directly on it. Covering the walls and ceilings should be comfort. mass with any insulation light in color to help distribute So the total south-facing material. such as carpet, greatly both heat and light more evenly. glass area in a direct gain reduces its effectiveness. A good system should be between 7% strategy is to expose a narrow (the maximum for suntempered strip about 8 ft. wide along the houses) and 12%. depending on south wall next to the windows how much thermal mass will be where the winter sun will fall directly on it.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 25

Ratio of Mass to Glass. The added for each 8.3 sf of thermal Mter that, the effectiveness simplest rule of thumb states: mass placed in the wall or doesn't increase as Significantly. For each added ft2 of direct-gain ceiling of the room. Mass in the A two-inch mass floor will be glass (above the 7% wall or ceiling does not have to about two-thirds as effective in a suntempering limit), 6 ft2 of be located directly in the direct gain system as a four­ exposed mass surface should be sunlight, as long as it is in the inch mass floor. But a six-inch added within the direct-gain same room, with no other walls mass floor will only perform space. The following procedure between the mass and the area about eight percent better than can be used to determine a where the sunlight is falling. a four-inch floor. somewhat more accurate (The 8.3 value is typical, but the The effectiveness of thermal estimate. This procedure gives true value does depend on mass m~ss is relative to the density the maximum amount of direct­ density and thickness. Refer to and thickness. The vertical axis gain glazing for a given amount the mass thickness graph for shows how many square feet of of thermal mass. If the amount more specific values to use.) mass area are needed for each of direct-gain glazing to be used More south-facing glazing added square foot of direct gain. is already known, thermal mass than the maximum as As you can see, performance can be added until this determined here would tend to increases start leveling off after procedure produces the deSired overheat the room, and to a few inches of thermal mass. proportions: reduce energy performance as 40 0 • Start with a direct gain glass well. ~ 50#/cf ..... a: area equal to 7% of the house's / ,.---...... / ...... m 30 total floor area. As noted above, / ...... / ......

Boise, Idaho 26 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

Examples of Heat Energy Savings Passive Solar-Direct Gain 1,500 sf Single Story House

Base Case 20% 40% 60% R-values Ceiling/Roof 29 32 39 50 Walls 17 19 24 31 Basement Wall 5 6 9 12 Glass 1.8 1.8 1.8 2.7

Air Changes/Hour 0.50 0.47 0.37 0.36

Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South 3.0% 7.4% 9.3% 12.0%

Added Thermal Mass Percent of Floor Area 0.0% 2.7% 13.6% 30.0%

Solar System Size (square feet) South Glass . 45 111 139 180 Added Thermal Mass 0 40 204 450

Percent Solar Savings 7% 18% 25% 36%

Performance (Btu/yr-sf) Conservation 43,637 40,671 33,593 26,494 Auxiliary Heat 40,523 33,156 25,019 16,861 Cooling 9,580 1,401 538 0

Summary: Insulation and tightness have been increased. South-facing glazing has been substantially increased. For these examples, added mass area is assumed to be six times the excess south glass area.

Boise. Idaho PASSIVE SOLAR DESIGN STRATEGIES 27

4.Sunspaces The sunspace should not be The sunspace floor is a good on the same heating system as location for thennal mass. The The sunspace is a very popular the rest of the house. A well mass floors should be dark in passive solar feature. adding an designed sunspace will probably color. No more than 15-25% of attractive living space as well as need no mechanical heating the floor slab should be covered energy perfonnance. There are system. but if necessary. a small with rugs or plants. The lower many variations on the basic fan or heater may be used to edge of the south-facing protect plants on extremely cold windows should be no more theme of the sunspace. and the winter nights. than six inches from the floor to possibilities for sunspace design The sunspace should be just make sure the mass in the floor are extraordinarily diverse. As used in this guide. a sunspace as tightly constructed and receives suffiCient direct is a separate direct-gain room insulated as the rest of the sunlight. If the windows sills on the south side of the house. house. are higher than that. additional mass may have to be located in The wall that separates the house from the sunspace is the walls. called a common wall. The Another good location for common wall should include thennal mass is the common wall (the wall separating the operable windows and doo~s that may be closed so that when sunspace from the rest of the the sunspace is not providing house). Options for the heat to the house it is not common wall are discussed in draining heat from the house. more detail later. The sunspace concept used Water in various types of in these Guidelines can be used containers is another fonn of energy storage often used in year-round. will provide most or Sunspaces all of its own energy needs. and Sunspaces provide useful passive solar . sunspaces. heating and also provide a valuable amemty to will contribute to the energy homes. needs of the rest of the house as G:lazing Clear. double-glazing is well. Thermal Mass recommended for sunspaces. Sunspaces are referred to as A sunsp~ce has extensive Adding the second pane makes "is~lated gain" passive solar south-facing glass. so sufficient a large improvement in energy systems. because the sunlight-is thennal mass is very important. savings. Triple-glazing or low-e collected in an area which can Without it. the sunspace is coatings. on the other hand. will be closed off from the rest of the liable to be uncomfortably hot further improve comfort. but will house. During the day. the during the day. and too cold for have little effect on energy doors or windows between the plants or people at night. savings. sunspace and the house can be However. the temperature in Windows on the east and opened to circulate collected the sunspace can vary more west walls should be small (no heat. and then closed at night. than in the house itself. so more than 10% of the total and the temperature in the about three square feet of four sunspace floor area) but they sunspace allowed to drop. It inch thick thermal mass for are useful for cross-ventilation. should be noted that the each square foot of sunspace common wall is often mass. and glazing should be adequate. not necessarily sufficient for the With this glass-to-mass ratio. on sunspace to be considered truly a clear winter day a temperature thennally isolated. swing of about 30°F should be expected.

Boise, Idaho 28 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

Summer Overheating Common Wall Some solar energy may be Probably the single biggest There are a number of options transferred from the sunspace to problem encountered in for the sunspace common wall. the rest of the house by sunspaces is summer The common wall may be a conduction through the overheating. Largely, this stems masonry wall, it can also be common wall if it is made of directly from poor design used for thermal mass, in which thermal mass. But energy is practice and can be avoided. case it should be solid masonry mainly transferred by natural The problem can usually be apprOximately 4 to 8 inches convection through openings in traced directly to poor glazing thick. Another option is a frame the common wall- doors, orientations - too much non­ wall with masonry veneer. windows and/ or vents. south glazing. Glass on the roof In mild climates, and when • Doors are the most common or on the west walls can create the sunspace is very tightly opening in the common wall. If major overheating. constructed, an uninsulated only doorways are used, the Like tilted or sloped glazing, frame wall is probably adequate. open area should be at least glazed roofs can increase solar However, insulating the 15% of the sunspace south­ gain, but they can also present common wall to about R-lO is a glass area. big overheating problems and good idea, espeCially in cold • Windows or sliding glass become counter-productive. If climates. An insulated common doors will provide light and either glazed roofs or tilted wall will help guard against heat views. The window area in the glazing are used in the loss during prolonged cold, common wall should be no sunspace, special care should cloudy periods, or if the thermal larger than about 40% of the be taken to make sure they can storage in the sunspace is entire common wall area. Per be effectively shaded during the insufficient. unit area, window and slider summer and, if necessary, on Probably the most important openings are about one-half as sunny days the rest of the year, factor in controlling the effective for natural convection too. The manufacturers of temperature in the sunspace, as are door openings. sunspaces and glazing are and thus keeping it as developing products with better comfortable and effi<;ient as ability to control both heat loss possible, is to make sure the and heat gain (for example, roof exterior walls are tightly glazing with low shading constructed and well-insulated. coefficients, ~hading treatments and devices, etc.). You'll note that in the Performance Potential chart on page 6, sunspaces with glazed roofs or sloped glazing perform very well. This analysis assumes effective shading in the summer. If such shading is not economical or marketable in your area, you should consider using only vertical glazing, and accepting somewhat less energy performance in winter.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 29

Summer ventilation The sunspace must be vented to Examples of Heat Energy Savings Passive Solar-Sunspace the outside to avoid overheating in the summer or on warm days 1,500 sf Single Story House in spring and fall. A properly vented and shaded sunspace Base Case 20% 40% 60% can function much like a R-Values screened-in in late spring. Ceiling/Roof 29 28 34 43 summer. and early fall. Walls 17 16 20 26 Operable windows and/ or Basement Wall 5 4 6 9 Glass 1.8 1.8 1.8 2.7 vent openings should be located for effective cross-ventilation. Air ChangeslHour 0.50 0.45 0.35 0.38 and to take advantage of the prevailing summer wind. Low Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% inlets and high outlets can be North 3.0% 4.0% 4.0% 4.0% used in a "stack effect". since East 3.0% 4.0% 4.0% 4.0% warm air will rise. These South (windows) 3.0% 3.0% 3.0% 3.0% 0.0% 6.7% 9.2% 13.0% ventilation areas should be at Sunspace least 15% of the total sunspace Solar System Size (square feet) south glass areas. South Glass 45 45 45 45 Where natural ventilation is Sunspace Glass 0 100 137 195 Sunspace Thermal Mass 0 300 413 586 insufficient, or access to natural breezes is blocked. a small. Percent Solar Savings thermostat-controlled fan set at 7% 26% 33% 44% about 76°F will probably be a Performance (Btu/yr-sf) useful addition. Conservation 43,637 44,807 37,729 30,262 Auxiliary Heat 40,523 33,107 24,958 16,781 Cooling 9,580 3,821 3,638 2,635

Summary: Insulation (for the 40 and 60% savings) and tightness have been increased. North and east-facing glazing have been increased slightly. The sunspace assumed here is semi-enclosed (surrounded on three sides by conditioned rooms of the house, as in Figure SSC1 of the worksheets), with vertical south glazing. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double.

Boise, Idaho 30 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

5. Thermal Storage Selective Surfaces A selective surface is a special Wall adhesive foil applied to the exterior side of the mass of The Thermal Storage Wall- also Thermal Storage Walls. referred to as a Trombe wall or Selective surfaces absorb a large an indirect gain system - is a percentage of solar radiation but south-facing glazed wall. usually radiate very little heat back to built of masonry. but sometimes the out-of-doors (low emittance}. using water containers or phase Thermal Storage Wall To be effective. selective change materials. The masonry A thermal storage wall is an effective passive surfaces must be applied is separated from the glazing solar system, especially to provide nighttime heating. carefully for 100% adhesion to only by a air space. Sunlight is the mass surface. absorbed directly into the wall A masonry Thermal Storage Wall In Boise. Idaho. a selective instead of into the living space. should be solid. and there surface will improve Thermal The energy is then released into should be no openings or vents Storage Wall performance by the living space over a relatively either to the outside or to the about 61%. long period. The time lag varies living space. Although vents to with different materials. the living space were once Mass Material and thicknesses and other factors. commonly built into Thermal Thickness but typically. energy stored in a Storage Walls. experience has In general. the effectiveness Thermal Storage Wall during the demonstrated that they are of the Thermal Storage Wall will day is released during the ineffective. Vents between the increase as the density of the evening and nighttime hours. Thermal Storage Wall and the material increases. The outside surface of a house tend to reduce the The optimum thickness of thermal storage wall should be a system's nighttime heating the wall depends on the density very dark color - an absorptance capability. and to increase the of the material chosen. but greater than 0.92 is temperature fluctuation in the performance is not very recommended. house. Vents to the outside are sensitive to thickness. The The summer heat gain from similarly ineffective. and do little following chart indicates the a Thermal Storage Wall is much to reduce summer heat gains. recomniended thickness of less - roughly 76% less - than Thermal Storage Walls made of from a comparable area of direct Glazing various materials. As thickness gain glazing. Double glazing is recommended is increased. the time delay of for Thermal Storage Walls heat flow through the wall is unless a selective surface is increased. and the temperature used. In this case. single variation on the inside surface is glazing performs about the same decreased. as double glazing. The space between the glazing and the thermal mass shoulq be one to three inches.

Boise. Idaho PASSIVE SOLAR DESIGN STRATEGIES 31

Mass Wall Thickness Examples of Heat Energy Savings Passive Solar-Thermal Storage Wall (inches) Density Thick- 1,500 sf Single Story House ness Material (Ib/cf) (inches) Base Case 20% 40% 60% R-Values Concrete 140 8-24 Ceiling/Roof 29 29 34 42 Concrete Masonry 130 7-18 Walls 17 17 20 26 Clay Brick 120 7-16 Basement Wall 5 5 6 10 Glass 1.8 1.8 1.8 1.8 Ltwt. Concrete 110 6-12 Masonry Air Changes/Hour 0.50 0.48 0.38 0.37 Adobe 100 6-12 Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% Water Walls North 3.0% 4.0% 4.0% 4.0% Water provides about twice the East 3.0% 4.0% 4.0% 4.0% heat storage per unit volume as South 3.0% 3.0% 3.0% 3.0% masonry, so a smaller volume of Thermal Storage Wall 0.0% 6.6% 10.9% 17.0% mass can be used. In "water Solar System Size (square feet) walls" the water is in light, rigid South Glass 45 45 45 45 containers. The containers are Thermal Storage Wall 0 98 163 255 shipped empty and easily Percent Solar Savings installed. Manufacturers can 7% 23% 35% 49% provide information about durability, installation, Performance (Btu/yr-sf) protection against leakage and Conservation 43,637 43,491 38,515 33,162 Auxiliary Heat 40,523 33,145 24,986 16,790 other characteristics. At least Cooling 9,580 1,893 1,057 0 30 pounds (3.5 gallons) of water should be provided for each Summary: In the case of a Thermal Storage Wall, south-facing glazing and thermal mass are incorporated together. The estimates here assume square foot of glazing. This is a 12-inch thick concrete Thermal Storage Wall with a selective surface equivalent to a water container and single glazing. about six inches thick, having the same area as the glazing.

Boise, Idaho 32 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

6. Combined Systems 7. Natural Cooling Fortunately. many of the features that help maintain Guidelines Although the previous sections comfort and reduce energy have presented separate needs in winter also work well in The term "natural cooling" is summer. For instance. discussions of four different used here to describe systems. it isn't necessary to additional thermal mass techniques which help a house performs well year-round. choose one and only one stay cool in summer but which Masonry matertals are equally system. In fact. passive solar require little or no energy. effective in staying cool and features work well in Natural cooling techniques work storing heat. If mass surfaces combination. to help reduce air-conditioning. can be exposed to cool night­ For example. direct gain not replace it. time temperatures - a technique works very well in conjunction These techniques are useful referred to as "night ventilation" with a sunspace or thermal not only in passive solar houses. - they will help the house stay storage wall. Since thermal but in "conventional" houses as cooler the next day. A California storage walls release energy well. The strategies outlined utility found during studies of more slowly than direct gain below - attention to the location. small test buildings that on hot systems. they are useful for size and shading of glazing. summer days the workmen at supplying heat in the evening using the opportunities on the the facility always ate l~nch in and at night. whereas the direct site for shading and natural the masonry test building gain system works best during ventilation. and using fans - can because it stayed much cooler the day. Although using a reduce air conditioning needs than any of the others. sunspace. thermal storage wall and increase comfort even if the The additional insulation and direct gain system in the house has no passive solar that increases winter same house may result in heating features. perf~rmance will also work to excellent performance. such But shading is particularly improve summer performance combinations do require a large important in passive solar by conserving the conditioned south-facing area. and careful houses. because the same air inside the house. And some design to make sure the systems features that collect sunlight so low-e windows and other glazing are well-integrated with each effectively in winter will go right with high R-value can help other and with the house's on collecting it in summer - shield against unwanted heat mechanical system. resulting in uncomfortably hot gain in summer. rooms and big air conditioning bills - unless they are shaded and the house is designed to help cool itself.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 33

The potential of some Cooling Potential natural and low-energy cooling Basecase 9,580 Btu/yr-sf strategies is shown in the following table for Boise. Energy. Savings Percent Worksheet IV: CooHng Strategy (Btu/yr-sf) Savings Performance Level indicates the total annual cooling load. No Night Ventilation 1 and so can give an idea of how without ceiling fans 0 0% with ceiling fans 2,640 28% the passive solar features increase the cooling load and Night Ventilation1 how much reduction is possible without ceiling fans 2,140 22% 4,220 when natural cooling techniques with ceiling fans 44% are used. High Mass2 It should be noted that the without ceiling fans 680 7% Cooling Performance numbers with ceiling fans 500 5% presented in the Examples for 1 With night ventilation, the house is ventilated at night when each passive solar strategy temperature and humidity conditions are favorable. assume that the design also includes the recommended 2 A "high mass" building is one with a thermal mass area at least equal to the house floor area. . natural cooling techniques. This is especially true of the higher percentage reductions; these assume better heating performance. but also better shading and other natural cooling strategies.

Boise, Idaho 34 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

Glazing and so they may interfere with As mentioned earlier, poorly Added Window Cooling Load desirable views. It is important placed windows can increase air to note, however, that some conditioning loads dramatically. Added Annual types of low-e windows block It is generally best in terms of Cooling solar transmission but also Orientation Load(Btu/yr-sf) energy performance to carefully allow clear views. These size non-solar glazing as treatments are not North 21,720 indicated in the following table. recommended for south East 50,510 windows. South 39,250 Recommended Non-south Glass As the table shows, skylights West 53,850 Guidelines present a high potential for Skylights 65,570 Percent of Total overheating, and are usually difficult to shade properly. But Orientation Floor Area These values are based on double skylights are very popular glass with a shading coefficient of features, and they save East 4% 0.88. When glazing with a different electricity by providing good North 4% shading coefficient is used the West 2% values may be scaled natural daylight to the house. In some parts of the country proportionally. almost every new house has at West-facing windows present least one skylight. A good These numbers can be reduced particularly difficult shading working compromise can by shading as described in the problems. If glazing is added usually be achieved if skylight next section. above the levels indicated, the area is limited, and if careful Using special glazing or need for shading will become attention is paid to shading, window films that block solar even more critical. either by trees or by devices transmission (low shading Cooling loads increase as such as roller shades or blinds. coeffiCient) is an option often window area increases. This The manufacturer can usually used in particularly hot relationship for Boise is shown give guidance on shading climates, but the more effective in the following table for each of options for a particular skylight they are at blocking sunlight. the cardinal window design. the less clear they are, as a rule, orientations. For instance when a square foot of west area is added or subtracted, the annual cooling load increases or decreases by 53,850 Btu/yr-sf.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 35

Shading Roof Overhangs. Fixed Shading strategies generally fall overhangs are an inexpensive into three categories: feature. and require no landscaping. roof overhangs and operation by the home owner. exterior or interior shading They must be carefully devices. designed. however. OtheIWise. an that blocks Landscaping. The ideal site for Landscaping for Summer Shade summer sun may also block sun summer shading has deciduous Trees and other landscaping features may be in the spring. when solar effectively used to shade east and west trees to shade the east and west windows from summer solar gains. heating is deSired. and. by the windows. Even small trees such same token. an overhang sized as fruit trees can help block sun Other landscaping ideas for for maximum solar gain in hitting the first story of a house. summer shade: winter will allow solar gain in Trees on the south side can • Trellises on east and west the fall on hot days. The present a difficult choice. Even covered with vines. following figure may be used to deciduous trees will shadow the • Shrubbery or other plantings determine the optimum solar glazing during the winter to shade paved areas. overhang size. and interfere with solar gain. In • Use of ground cover to In Boise. an ideal overhang fact. trees on the south side can prevent glare and heat proj ection for a four foot high all but eliminate passive solar absorption. window would be 29 inches and performance. unless they are • Trees. fences. shrubbery or the bottom of the overhang very close to the house and the other plantings to "channel" would be 15 inches above the low branches can be removed. summer breezes into the house. top of the window. allowing the winter sun to • Deciduous trees on the east penetrate under the tree canopy. and west sides of the house. as However. in many cases the shown above. to balance solar trees around the house are gains in all seasons. bigger selling points than the energy efficiency and the builder must make a choice. If a careful study of the shading patterns is done before construction. it should be possible to accomodate the south-facing glazing while South Overhang Sizing leaving in as many trees as In Boise, an ideally sized south overhang should allow full exposure of the window when possible (see page 17. Site the sun has a noon altitude of 27 degrees Planning for Solar Access). (angle A) and fully shade the window when the sun has a noon altitude of 64 degrees (angle B).

Boise, Idaho 36 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

A combination of carefully sized Ceiling Fans overhangs on the south Ceiling fans will probably save Ceiling Fan Sizes windows and shading devices on more energy than any other Largest Room Minimum Fan the other windows will probably Single cooling strategy. Studies Dimension Diameter be an effective solution. show that air movement can (inches) Adjustable overhangs that can make people feel comfortable at be seasonally regulated are higher temperatures. As a 12 feet or less 36 another option. general rule. the thermostat can 12 - 16 feet 48 be set 4 degrees higher without 16 - 17.5 feet 52 Shading Devices. External affecting comfort if the air is 17.5 - 18.5 feet 56 shades are the most effective moving at 100-150 feet per 18.5 or more feet 2 fans because they stop solar gain minute. This is enough air before the sun hits the building. movement to greatly improve A ceiling fan should have a A wide range of products are comfort but not enough to minimum clearance of ten aVailable. from canvas awnings disturb loose papers. inches between ceiling and fan to solar screens to roll-down to provide adequate ventilation blinds to shutters to vertical in a standard room with eight­ louvers. They are adjustable foot ceilings. In rooms with and perform very well. but their higher ceilings. fans should be limitation is that they require mounted 7.5 to 8.0 feet above the home owner's cooperation. the floor. Usually external screens that can be put up and taken down once a year like storm windows are more acceptable to home owners 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. add pleasant spaces to houses and are excellent for providing shade to windows. located on the east or west are another option.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 37

Ventilation The best possible When possible. the house performance of a whole-house should be positioned on the site fan results when a timer. a to take advantage of prevailing thermostat and a "humidistat" winds. The prevailing wind are used. so that the fan would direction is from the north west only operate when there is less during the cooling season. than 60% relative hUmidity and Windows. stailWells. transoms a temperature of less than 76°F. and other elements should be Natural ventilation and located for maximum cross­ Ventilation for Summer Cooling whole-house fans are effective at Natural ventilation is often impaired by ventilation in each room. The vegetation and topography. Ventilation fans removing heat. but not at free vent area (unobstructed do not depend on surroundings to be effective. moving air. Ceiling fans. on the openings like open windows) other hand. can often create should be between 6-7.5% of In cooling climates. a whole­ enough of a breeze to maintain total floor area. half located on house fan is a good idea for comfort at higher temperatures. the leeward and half on the assisting ventilation. especially and still use less power than windward side of the building. in houses with sites or designs required by air conditioning. By Insect screens can reduce the that make natural ventilation using natural cooling strategies effective free vent area by as difficult. On the other hand. and low-energy fans. the days much as 50%. Casement or when the temperature is higher when air-conditioning is needed awning windows have a 90% than about 76°F. a whole-house can be reduced substantially. open area; double hung fan will not be very effective. windows have only 50%. Research indicates that a Casement windows extend whole-house fan should pull outward from the house. approximately 10 ACH. A rule tending to channel breezes of thumb: for rooms with eight through the opening if properly foot ceilings. total floor area placed. Improperly placed multiplied by 1.34 will equal the casements might deflect breezes. necessary CFM of the fan. For Double-hung windows do not 10 foot ceilings. multiply floor have this advantage. area by 1.67. 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.

Boise. Idaho 38 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

Boise, Idaho Passive Solar Design Strategies WORKSHEETS

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department of Energy PASSIVE SOLAR DESIGN STRATEGIES 39

NOTE: Please make copies of the blank worksheets and tables before entering • numbers so that the worksheets may be used to evaluate several design options .

•

Boise, Worksheets Idaho

• 40 PASSIVE SOLAR DESIGN STRA TEGIES General Pro· ect Information

project Name Floor Area ~------~------Desjgner • Worksheet I: Conservation Performance Level

A. Envelope Heat Loss

Construction R-value Heat Description Area [Table A] Loss

Q!2i1i09~L[!;lQf~

~

lo~ul~d EIQQ[~

t:jQO-SQI5l.[ !:alaziOg + QQw. .. Btu/'F-h Total B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss

SI5l.b~-QO-!:a[5l.d!2 X t:l!2~d a5l.~!2m!2ot~ X UOb!25l.t!2d a5l.~!2m!201~ X P!2[im!21!2[ lo~ul~d Q[5l.WISI25l.I

C. Infiltration Heat Loss X X .018 Btu/OF-h Building Air Changes Volume per Hour

D. Total Heat Loss per Square Foot 24 X Btu/DD-sf Total Heat Loss Floor Area (A+B+C)

E. Conservation Performance Level

X X Btu/yr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C] Day Multiplier Square Foot [Table C]

F. Comparison Conservation Performance (From Previous Calculation or from Table D) Btu/yr-sf

Com are Line E to Line F •

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 41 Worksheet II: Auxili Heat Performance Level A. Projected Area of Passive Solar Glazing

Solar System Rough Frame Net Area Adjustment Projected Reference Code Area Factor Factor [fable E] Area X 0.80 X • X 0.80 X X 0.80 X X 0.80 X X 0.80 X X 0.80 X X 0.80 X sf Total Area Total Projected Area

Total Floor Total Projected Projected Area Area per Area Square Foot

B. Load Collector Ratio 24 X Total Total Heat Loss Projected [Worksheet I] Area

C. Solar Savings Fraction

System Solar Savings Solar System Projected Fraction Reference Code Area [fable F] X • X X X X X X

Total Total Solar Projected Savings Area Fraction

D. Auxiliary Heat Performance Level

[1 - lx Btulyr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E]

E. Comparative Auxiliary Heat Performance (From Previous Calculation or from Table G) Btulyr-sf • Compare Line D to Line E

Boise, Idaho 42 PASSIVE SOLAR DESIGN STRATEGIES Worksheet III: Thermal Mass/Comfort A. Heat Capacity of Sheetrock and Interior Fmnishings Unit Total Heat Heat Floor Area Capacity Capacity

RQQIIlS with Di[ect Giilin X 4.7 Spaces CQnnecwd tQ Di[ect Giilin SPiilces ______X 4.5 •

Total B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces

Unit Heat Mass Description Capacity Total Heat (include thickness) Area rrable H] Capacity IrolIlbe Wiill!s X 8.8 Wiilte[ Wiill!s ______X 10.4 EXPQsed Slab in Syn ______X 13.4 EXPQsed Sliilb NQt in Sun X 1.8 X X X Btu/oF Total

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces

Unit Heat Mass Description Capacity Total Heat (include thickness) Area rrable H] Capacity

I[QlIlbe WiillI~ X 3.8 Wiilte[WiillI~ X 4.2 X X X Btu/OF • Total

D. Total Heat Capacity Btu/oF (A+B+C)

E. Total Heat Capacity per Square Foot Btu/OF-sf Total Heat Conditioned Capacity Floor Area

F. Clear Winter Day Temperature Swing

Total Comfort Projected Area Factor [Worksheet II] rrable I] Direct Giilin X SynsPiilces Q[ X Vented ImlIlbe Wiill!s Total Total Heat Capacity G. Recommended Maximum Temperature Swing 'F Compare Line F to Line G • ~------

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 43 Worksheet IV: Summer Coolin Performance Level A. Opaque Surfaces Radiant Barrier Absorp- Heat Gain Heat Loss Factor tance Factor Description [Worksheet I] [Table J] [Table K] [Table L] Load

Ceilings/roofs X X X • X X X X X X Wsill.s. X na X X na X QQru. X na X kBtu/yr Total B. Non-solar Glazing Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load

North Glass X 0.80 X X X 0.80 X X East Glass X 0.80 X X X 0.80 X X Wi~l !:aliil~~ X 0.80 X X X D.80 X X ~lsllligtJl~ X 0.80 X X X 0.80 X X kBtu/yr Total C. Solar Glazing

Solar System Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load

i:li[iQl !:aiilio X 0.80 X X X 0.80 X X • ~lQ[iil9i Wiilll~ X 0.80 X X X 0.80 X X ~!J[l~PiilQi X 0.80 X X X 0.80 X X kBtu/yr Total D. Internal Gain +( X ) kBtu/yr Constant Variable Number of Component Component [Table N] [Table N] E. Cooling Load per Square Foot 1,000 X + Btu/yr-sf (A+B+C+D) Floor Area F. Adjustment for Thermal Mass and Ventilation Btu/yr-sf [Table 0] G. Cooling Performance Level Btu/yr-sf (E -F) H. Comparison Cooling Performance (From Previous Calculation or from Table P) Btu/yr-sf • Compare Line G to Line H

Boise. Idaho 44 PASSIVE SOLAR DESIGN STRATEGIES

Table A-continued __ Table A-Equivalent Thermal Performance of Assemblies Table D-Base Case R-values (hr-F-sf/Btu) Conservation Performance (Btu/yr­ AS-Doors sf) Solid wood with 2.2 Base Case 43,637 Weatherstripping A1-Ceilings/Roofs Metal with rigid 5.9 Attic Insulation R-value foam core Table E-Projected Area Construction R-30 R-38 R-49 R-60 Adjustment Factors • 27.9 35.9 46.9 57.9 Degrees off Solar System Type Framed Insulation R-value Table B-Perimeter Heat Loss True DG, TW, SSA SSB, Construction R-19 R-22 R-30 R-38 Factors for Slabs-on-Grade and South WW. SSC SSD SSE Unheated Basements (Btu/h-F-ft) o 1.00 0.77 0.75 2x6 at 16"oc 14.7 15.8 16.3 5 1.00 0.76 0.75 2x6 at 24'oc 15.3 16.5 17.1 Heated Unheated Insulated 10 0.98 0.75 0.74 2x8 at 16'oc 17.0 18.9 20.6 21.1 Perimeter Siabs-on- Base- Base- Crawl- 15 0.97 0.74 0.73 2x8 at 24'oc 17.6 19.6 21.6 22.2 Insulation Grade ments ments spaces 20 0.94 0.72 0.70 2xl0 at 16'oc 18.1 20.1 24.5 25.7 None 0.8 1.3 1.1 1.1 25 0.91 0.69 0.68 2xl0 at 24"oc 18.4 20.7 25.5 26.8 R-5 0.4 0.8 0.7 0.6 30 0.87 0.66 0.65 2x12 at 16'oc 18.8 21.0 25.5 30.1 R-7 0.3 0.7 0.6 0.5 2x12 at 24 'oc 19.0 21.4 27.3 31.4 R-ll 0.3 0.6 0.5 0.4 R-19 0.2 0.4 0.5 0.3 Table F-Solar System Saving R-30 0.1 0.3 0.4 0.2 Fractions A2-Framed Walls Single F1-Direct Gain Wall Insulation R-value Table C-Heating Degree Days Framing R-ll R-13 R-19 R-25 (F-day) Load DGC1 DGC2 DGC3 2x4 at 16'oc 12.0 13.6 Collector Double Low-e R-9 Night 2x4 at 24'oc 12.7 13.9 Ratio Giazing Glazing Insulation 2x6 at 16"oc 14.1 15.4 17.7 19.2 C1-Heating Degree Days (Base 65°F) 400 0.05 0.05 0.06 2x6 at 24"oc 14.3 15.6 18.2 19.8 300 0.06 0.07 0.08 Boise 5,802 200 0.09 0.10 0.12 Double Caldwell 5,594 150 0.11 0.12 0.15 Wall Total Thickness (inches) Emmett 5,655 100 0.15 0.17 0.21 Framing 8 10 12 14 80 0.18 0.21 0.26 Grand View 5,519 25.0 31.3 37.5 43.8 60 0.22 0.26 0.32 Mountain Home 5,980 50 0.24 0.30 0.37 NYSSA 6,000 45 0.26 0.32 0.40 The R-value of insulating sheathing should be added to Ola 6,577 40 0.28 0.35 0.43 the values in this table. 35 0.31 0.38 0.47 30 0.33 0.42 0.52 25 0.37 0.47 0.58 C2-Heating Degree Day MuHiplier A3-lnsulated Floors 20 0.41 0.53 0.65 Passive Solar 15 0.45 0.60 0.74 Insulation R-value Heat Loss Glazing Area per Framing R-11 R-19 R-30 R-38 per Square per Square Foot • 2x6s at 16'oc 18.2 23.8 29.9 Foot .00 .05 .10 .15 .20 F2-Trombe Walls 2x6s at 24"oc 18.4 24.5 31.5 12.00 1.09 1.10 1.10 1.10 1.11 TWF3 TWA3 TWJ2 TWI4 2x8s at 16'oc 18.8 24.9 31.7 36.0 11.50 1.09 1.09 1.10 1.10 1.10 Load Unvented Vented Unvented Unvented 2x8s at 24 'oc 18.9 25.4 33.1 37.9 11.00 1.08 1.08 1.09 1.09 1.10 Collector Non- Non- Selec- Night 2xl0 at 16'oc 19.3 25.8 33.4 38.1 10.50 1.07 1.08 1.08 1.09 1.09 Ratio selective selective tive Insulation 2xl0 at 24'oc 19.3 26.1 34.4 39.8 10.00 1.06 1.07 1.08 1.08 1.09 400 0.03 0.06 0.03 0.01 2x12 at 16'oc 19.7 26.5 34.7 39.8 9.50 1.05 1.06 1.07 1.07 1.08 300 0.04 0.07 0.06 0.03 2x12 at 24'oc 19.6 26.7 35.5 41.2 9.00 1.05 1.05 1.06 1.06 1.07 200 0.07 0.10 0.11 0.07 8.50 1.03 1.04 1.05 1.06 1.06 150 0.09 0.12 0.15 0.11 These R-values include the buffering effect of a 8.00 1.02 1.03 1.04 1.05 1.05 ventilated crawlspace or unconditioned basement. 100 0.13 0.17 0.23 0.18 7.50 1.01 1.02 1.03 1.04 1.04 80 0.16 0.19 0.28 0.22 7.00 0.99 1.00 1.02 1.02 1.03 60 0.20 0.24 0.35 0.29 6.50 0.98 0.99 1.00 1.01 1.02 50 0.23 0.27 0.40 0.33 A4-Windows 6.00 0.96 0.97 0.98 1.00 1.01 45 0.25 0.29 0.43 0.36 5.50 0.93 0.95 0.96 0.98 0.99 40 0.27 0.31 0.46 0.39 Air Gap 5.00 0.90 0.92 0.94 0.96 0.97 35 0.30 0.34 0.50 0.43 4.50 0.86 0.89 0.91 0.94 0.95 30 0.33 0.37 0.55 0.48 1/4 in. 1/2 in. 1/2 in. argon 4.00 0.82 0.85 0.88 0.91 0.93 25 0.37 0.41 0.60 0.53 Standard Metal Frame 3.50 0.77 0.81 0.84 0.87 0.90 20 0.42 0.46 0.67 0.60 Single .9 3.00 0.70 0.75 0.79 0.83 0.86 15 Q~ Q~ Q~ Q~ Double 1.1 1.2 1.2 2.50 0.61 0.67 0.73 0.77 0.81 Low-e (e<=0.40) 1.2 1.3 1.3 2.00 0.48 0.57 0.65 0.71 0.76 Metal frame wtth thermal break Double 1.5 1.6 1.7 Low-e (e<=0.40) 1.6 1.8 1.8 Low-e (e<=0.20) 1.7 1.9 2.0 Wood frame with vinyl cladding Double 2.0 2.1 2.2 Low-e (e<=0.40) 2.1 2.4 2.5 Low-e (e<=0.20) 2.2 2.6 2.7 Low-e (e<=O.1 0) 2.3 2.6 2.9 These R-values are based on a 3 mph wind speed and are typical for the entire rough framed opening. Manufacture's data, based on National Fenestration Rating Council procedures, should be used when available. One half the R-value of movable insulation should be added, when appropriate. •

Boise. Idaho PASSIVE SOLAR DESIGN STRATEGIES 45

F3-Water Walls Table H-Unit Heat Capacities Table L-Heat Gain Factors (Btu/F-st) Ceilinglroofs 45.0 Load WWA3 WWB4 WWC2 Walls and Doors 24.6 Collector No Night Night Selective North Glass 21.7 Ratio Insulation Insulation Surface H1-Mass Surfaces Enclosing Direct Gain Spaces East Glass 50.5 400 0.05 0.01 0.02 West Glass 53.8 300 0.07 0.04 0.05 Skylights 65.6 200 0.10 0.09 0.10 Thickness (inches) Direct Gain Glazing 39.2 • Material 1 2 3 4 6 8 12 150 0.13 0.14 0.14 Trombe Walls and 9.5 100 0.18 0.22 0.22 Poured Conc. 1.8 4.3 6.7 8.8 11.3 11.5 10.3 Water Walls 80 0.21 0.27 0.27 Conc. Masonry 1.8 4.2 6.5 8.4 10.2 10.0 9.0 Sunspaces 60 0.26 0.35 0.34 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSA1 26.7 50 0.29 0.40 0.39 Flag Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSB1 26.7 45 0.32 0.43 0.42 Builder Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSC1 9.5 40 0.34 0.47 0.46 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSDI 26.7 35 0.37 0.51 0.50 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 SSE1 26.7 30 0.40 0.56 0.55 Water 5.2 10.4 15.6 20.8 31.2 41.6 62.4 25 0.45 0.62 0.60 20 0.50 0.69 0.67 15 0.57 0.77 0.75 H2-Rooms with no Direct Solar Gain Table M-Sbading Factors F4-Sunspaces Projection Thickness (inches) Factor South East Nortr, West Load Material 1 2 3 4 6 8 12 0.00 1.00 1.00 1.00 1.00 Collector Sunspace Type Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 0.20 0.77 0.94 0.91 0.93 Ratio SSAI SSB1 SSCI SSDI SSEI Conc. Masonry 1.6 2.9 3.5 3.6 3.6 3.4 3.2 0.40 0.22 0.77 0.82 0.75 400 0.10 0.08 0.05 0.10 0.08 Face Brick 1.8 3.1 3.6 3.7 3.5 3.4 3.2 0.60 0.59 0.72 0.55 300 0.12 0.10 0.06 0.12 0.09 Flag Stone 1.9 3.1 3.4 3.4 3.2 3.1 3.0 0.80 0.40 0.62 0.34 200 0.15 0.12 0.09 0.16 0.13 Builder Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 1.00 0.26 0.52 0.18 150 0.17 0.14 0.11 0.19 0.16 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 1.20 0.11 0.42 0.02 100 0.22 0.18 0.16 0.25 0.20 Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.1 80 0.25 0.21 0.18 0.28 0.24 Multiply by 0.8 for low-e glass, 0.7 for tinted glass and 60 0.29 0.25 0.23 0.33 0.28 0.6 for low-e tinted glass. 50 0.32 0.27 0.26 0.37 0.31 45 0.34 0.29 0.28 0.39 0.33 Table I-Comfort Factors 40 0.36 0.31 0.30 0.41 0.35 (Btu/st) Table N-Intemal Gain Factors 35 0.38 0.33 0.32 0.44 0.38 30 0.41 0.36 0.35 0.47 0.41 Direct Gain 790 25 0.45 0.39 0.39 0.51 0.44 Constant Component 690 20 0.49 0.44 0.44 0.56 0.49 Suns paces and 260 kBtulyr 15 0.55 0.50 0.51 0.62 0.55 Vented Trombe Walls Variable Component 290 kBtu/yr-BR

Table J-Radiant Barrier Factors Table O-Thermal Mass and • Ventilation Adjustment (Btu/yr-st) Radiant Barrier 0.75 Total Heat Night Night No Night No Night No Radiant Barrier 1.00 Capacity Vent wi Vent wi No Vent wi Vent wi No per SF Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan 0.0 1,090 -1,320 -490 -3,470 1.0 1,670 -540 090 -2,690 Table K-Solar Absorptances 2.0 2,060 -020 480 -2.160 3.0 2,320 330 740 -1,810 Color Absorptance 4.0 2,500 570 920 -1,580 5.0 2,620 730 1.030 -1,420 Gloss WMe 0.25 6.0 2,700 840 1.110 -1,310 Semi-gloss Wh~e 0.30 7.0 2,750 910 1.160 -1.240 Light Green 0.47 8.0 2,780 950 1,200 -1,190 Kelly Green 0.51 9.0 2,810 990 1.220 -1,160 Medium Blue 0.51 10.0 2,820 1,010 1,240 -1,140 Medium Yellow 0.57 Medium Orange 0.58 Total heat capacity per square foot is calculated on Medium Green 0.59 Worksheet III, Step E. Light Buff Brick 0.60 Bare Concrete 0.65 Red Brick 0.70 Medium Red 0.80 Medium Brown 0.84 Table P-Base Case Cooling Performance (Btu/ sf-yr) Table G-Base Case Auxiliary Dark Blue-Grey 0.88 Dark Brown 0.88 Heat Performance (Btu/yr-st) Base Case 9.580

Base Case 40,523 •

Boise, Idaho 46 PASSIVE SOLAR DESIGN STRATEGIES

General additional building insulation or slab area that i~ assumed to be in the The Worksheets provide a reducing non-south glass area. sun should not exceed 1.5 times the calculation procedure to estimate the adjacent south glass area. performance level of passive solar Worksheet II-Auxiliary Heat In Step F. the projected area of solar • building designs. It is recommended Performance Level glazing calculated on Worksheet II is that the results be compared to This is an estimate of the amotmt of used to calculate the comfort Worksheet calculations for the builder's heat that must be provided each year performance level. The projected area of typical house. Performance levels for the from the auxiliary heating system. It water walls and unvented Trombe walls NAHB Base Case House used in the accounts for savings due to solar energy. is excluded in this step. Guidelines are also prOVided for In Step A .the user may enter the A high temperature swing indicates comparison. A separate worksheet is rough frame area of solar glazing, since inadequate thermal mass or too much provided for the four separate it is generally easier to measure the direct gain solar glazing. If the comfort performance levels and associated base rough frame area than it is the net performance level is greater than desired cases. glazing area. The worksheet includes a (13°F recommended). additional thermal The worksheets are supported by a net area factor of 0.80 to account for mass should be added to the building or number of data tables. The tables are window frames and mullions. If the direct gain glazing should be reduced. given a letter designation and are designer enters the net glass area, then referenced next to each worksheet entry. the net area factor is 1.00. Worksheet IV-Summer Cooling when applicable. The projected area of the solar Performance Level The floor area used in the energy systems may be calculated using This is an estimate of the annual cooling calculations should not include the adjustment factors in Table E or by load of the building-the heat that needs suns paces, garages or other making a scaled elevation drawing of the to be removed from the building by aI, unconditioned spaces. building facing exactly south and air conditioner in order to maintain measuring the glazing area from the comfort during the summer. Worksheet I-Conservation scaled drawing. In Step A. only the envelope Performance Level The projected area per square foot is surfaces that are exposed to sunlight are This is an estimate of the amount of calculated as the last part of Step A. to be included. For instance. floors over heat energy needed by the building each This is used to determine the heating crawlspaces and walls or doors adjacent year from both the solar system and the degree days adjustment used on to garages are excluded. auxiliary heating system. Worksheet 1. Step E. Steps B and C of the worksheet For Step A. it is necessary to The load collector ratio is calculated account for solar gains. They use the measure the net area of surfaces that in Step B. This is used to determine the rough frame area since this is easier to enclose conditioned space. For walls, solar savings fractions in Step C. measure. The worksheets include a net the net surface area is the gross wall The solar energy systems used in area factor of 0.80 to account for window area less the window and door area. Step C should be identical to those used frames and mullions. If the net window Rough frame dimensions are in Step A. The first and last of area is used. the net area factor is 1.00. generally used to measure window area. Step A are simply carried down. Table M gives the shade factor for The R-values in Table A4 are for the The solar savings fraction is windows with overhangs based on a • rough frame window area. determined separately for each type of projection factor. The projection factor Heat loss from passive solar passive solar system by looking up is the ratio between the horizontal systems is excluded. The surface area of values in Tables F1 through F4. The projection of the overhang from the direct gain glazing, Trombe walls, water sunspace system types are shown surface of window and the distance from walls and the walls that separate beneath Table F4. the bottom of the window to the bottom sunspaces from the house are ignored. If the auxiliary heat performance of the overhang. When windows have Step A includes consideration of level calculated in Step D is larger than sunscreens, tints or films, the shade insulated floors over crawlspaces, desired, the designer should consider factors in Table M should not be used. unheated basements or garages. increasing the size of the solar energy Instead. a shading coefficient should be R-values are provided in Table A3 that systems or adding additional solar determined from manufacturers' account for the buffering effect of these energy systems, i.e. thermal storage literature. unconditioned spaces. When insulation walls. is not installed in the floor assembly, but rather around the perimeter of a Worksheet III-Comfort crawlspace or unheated basement, Step Performance Level B should be used. This is the temperature swing expected The perimeter method of Step B is on a clear winter day with the auxiliary used for slabs-on-grade, the below-grade heating system not operating. portion of heated basements, unheated This worksheet requires that two basements (when the floor is not sub-areas be defined within the building: insulated), and perimeter insulated those areas that receive direct solar crawlspaces (when the floor is not gains and those areas that are insulated). Heated basement walls that connected to rooms that receive direct If the cooling performance level is are above grade should be considered in solar gains. Rooms that are separated greater than desired. the designer Step A. from direct gain spaces by more than should consider reducing non-south Slab edge perimeter, unheated one door should not be included in glass. providing additional shading or basements or perimeter insulated either category. increasing thermal mass. crawlspaces adjacent to sunspaces Thermal mass elements located in should not be included. unconditioned spaces such as sunspaces The conservation performance level are not included. is calculated as the product of the heat An exposed slab is one finished with loss per degree day per square foot [Step vinyl tile, ceramic tile or other highly DJ and the heating degree days, adjusted conductive materials. Carpeted slabs for the heat loss and solar glazing per should not be considered exposed. The square foot. The adjustment is taken exposed slab area should be further from Table C. based on data calculated reduced by about 50 percent to account on Worksheet I, Step D and Worksheet II, for throw rugs and furnishings. Step A. As a rule-of-thumb, exposed slab • Should the estimated conservation area should be considered to be in the performance level be greater than sun only when it is located directly desired, the designer should consider behind south glazing. The maximum Boise, Idaho Passive Solar Design Strategies EXAMPLE

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department of Energy PASSIVE SOLAR DESIGN STRATEGIES 47

Boise, The Worked Idaho ExalDple 48 WORKED EXAMPLE The Worked Example The house has a semi­ The house is equipped with enclosed sunspace with vertical a ceiling fan to help reduce the Description of glazing. The sunspace floor has air-conditioning load. North Example Building a four-inch thick slab-on-grade windows have an overhang with with quany tile set in a mortar a projection factor of 0.30. East A 1,504 square foot passive bed. The sunspace is separated and west windows are small and solar. single-family home with from the conditioned portion of have no effective overhang an 8.3 ft. average ceiling height the house by sliding glass doors because of the gable roof. South is used to illustrate how to fill in and a masonry wall. windows. including the the worksheets. See sketches Sunspace ventilation is provided sunspace windows. have an for the building layout. A to the outside by awning overhang with a projection variety of design features have windows located at the top and factor of 0.20. been incorporated into the bottom of the south wall. Take-offs from the house are house to help illustrate how to South facing windows given in the worksheets. Refer handle different situations in provide direct gain solar heating to the Circled values in the the worksheets. to the dining area. and worksheet tables to locate where The building selected has master . The south the various values which show good insulation as described on glazing in the kitchen and up in the worksheets come from. Worksheet I. dining area provides heat to an Performance is found to be The east portion of the exposed slab-on-grade finished satisfactory on all four house is slab on grade. The with ceramic tile to provide worksheets. and master bedroom direct gain heat storage. are constructed over a The house faces 10 degrees basement. to the east of true south.

l\:r-----=2=O'--'-----7)K;.t;;j ___-=22=' ___ ~)<.<:; ...... ?~: ...... >

Garage

3040 ~;:;:C==;;::::===~e;-, ...... i'!( ...... ~: 4040 ...... y. .. Bedroom Bedroom

Great Room

Master

~l Bedroom ~i Sunspace ~"""""':";';';';;';;':';'====>""""",:~=::!J ...... St...... ~ ...... ~ ...... L::::==~4O-S-0c::: .::: :::tf:J:tJ:J:-h 8020 5030 ! : 8088 8068 8088 : ! ! 14'! 28' : 24' ! i(·····························X························:·····································x··············...... )1<; ..i ° 2 4 8 12 FLOOR PLAN ......

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 49

SOUTH ELEVATION

o 2 4 8 12 NORTH ELEVATION ......

::::::::::::::::::1 !':~, .. Sunsp .~.1

ABOVE GRADE SECTION o...... 2 4 8 12

Boise, Idaho 50 WORKED EXAMPLE

I'I-+'~f-- Insulation

Insulation -¥"""'~ Insulation,--i;::;Z:;l-+I{:=::"j

.'

) • lo,' ••,. ~~ ::~ r~-'r -I . i. -C~~ == 1111 ~ 1111 ~ 1111 ~ 1111 ~ II . , .... ~: .~ .... ··~IIII~III1~1111 .. "'I~III1~1I " Ii • " 0 • "11 ~ 1111 [:... ~~~:.::..L::.L:.L:'-

TYPES OF FOUNDATIONS

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 51

NOTE: These worksheets are completed for the example house descrtbed on the previous pages. Also the reference tables are marked up showing how the numbers are selected.

Boise, Worked Exalllple Idaho

Boise, Idaho 52 WORKED EXAMPLE WORKSHEETS

General Project Information

Floor Area ~------

Worksheet I: Conservation Performance Level

B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss

Slabs-on-Grade ______9~..LL . OJ!______x zl Heated Basements ______~..:::...-L._.!....- "/1 _____ X if? Unheated Basements ______X Perimeter Insulated Crawls paces ______X 91 Total

C. Infiltration Heat Loss "'7"0° 2 '-0 / VT, '/ X 0.;..) X .018 = 1/2- Building Air Changes Volume per Hour

D. Total Heat Loss per Square Foot iuO~ 24 X JolP ..,... I~ot - Q C Btu/DD-sf Total Heat Loss Floor Area (A+B+C)

E. Conservation Performance Level

$BOz, (),9( :thCf .r- 'l~$7 X X - I Btu/yr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C] Day Multiplier Square Foot [Table C]

F. Comparison Conservation Performance (From Previous Calculation or from Table D) Btu/yr-sf Com are Line E to Line F

Boise. Idaho PASSIVE SOLAR DESIGN STRATEGIES 53 Worksheet II: Auxili Heat Performance Level

A. Projected Area of Passive Solar Glazing

Solar System Rough Frame Net Area Adjustment Projected Reference Code Area Factor Factor [Table E] Area !)&GZ- §!~ X 0.80 X 2/, L~ -(£c,1 ~ X 0.80 X 19~ 1~ 7b36' X 0.80 X X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = 2-"'tb ~2 sf Total Area Total Projected Area O./J,...- J.?>~ + 1501 Total Floor Total Projected Projected Area Area per Area Square Foot

B. Load Collector Ratio sec. 24 X + :2.3).. = 32, Total Total Heat Loss Projected [Worksheet I] Area

C. Solar Savings Fraction

System Solar Savings Solar System Projected Fraction Reference Code Area [Table F] ,Y'-JC'l- X 5<;c.l •L~~ X =g#t = iJief X = X X = X = X

5.2, f)). + 232- 0.3.6 Total Total Solar Projected Savings Area Fraction

D. Auxiliary Heat Performance Level

[1- tJ.3b X :i.bltl/ /9).2.6 Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E]

E. Comparative Auxiliary Heat Performance (From Previous Calculation or from Table G) t.fvf'v Btu/yr-sf Com are -Line D to Line E Boise, Idaho 54 WORKED EXAMPLE WoAKSHEETS Worksheet III: Thermal Mass Comfort

A. Heat Capacity of Sheetrock and Interior Furnishings

Unit Total Heat Heat Floor Area Capacity Capacity X 4.7 = Z1b7 SpacesJ

B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces

Unit Heat Mass Description Capacity Total Heat (include thickness) Area [Table H] Capacity TrornbeWalls X 8.8 Water Walls ______X 10.4 = ExPosed Slab in Syn ______Lo'3 X 13.4 &go Exposed Slab Not in Syn 13# X 1.8 z''i::f X = X X "Zb2.~ Btu/oF Total

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces

Unit Heat Mass Description Capacity Total Heat (include thickness) Area [Table H] Capacity Trornbe Walls X 3.8 Water Walls ----...... "r-::.-==-o'""""---,-,...~~--- X 4.2 = fAa 1IltCi g ~t! /11 X 51 = ¥// X X ZIti Btu/OF Total

D. Total Heat Capacity grJD Btu/OF (A+B+C)

E. Total Heat Capacity per Square Foot ~f{'jo isOl + = &.b Btu/OF-sf Total Heat Conditioned Capacity Floor Area

F. Clear Winter Day Temperature Swing Total Comfort Projected Area Factor [Worksheet II] [Table I] SCIS7CJ Oi[!i!!

(J. Q~iliDgllll:QQtll 77 X lev X '/1 X trJ".o = '1gb X /.t:f(> X t). X y-r 0 ::ssg. )Ih if.? X X X = ~ '10 X nfa tJ~l° X ~L{. b 6.~c;l.. X nfa X = ~ '3 X nfa O.~o X L.iJ....h = U L,~s..lr kBtulyr Total B. Non-solar Glazing Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load

NQrth Glalls ,-/0 X 0.80 X I)~ £/1 X J../, .., l.f.29 X 0.80 X X = Eallt Glalill b X 0.80 X 0.: ;SO X .$Ci-~ = /jr! X 0.80 X X . WelitGlalili b X 0.80 X o..~C X ~A~r 2(;11 X 0.80 X X ~Isllligbt~ X 0.80 X X = X 0.80 X X = ~D kBtulyr Total C. Solar Glazing

Solar System Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load

Qi[~Qt ~liliD :0S X 0.80 X ab.z.. X ~r..i- = I~/I X 0.80 X X StQ[;ag~ Wlillill X 0.80 X X = X 0.80 X X = ,~ X tQtO).. SYDlIRlilQe 2bE 0.80 X X 2-7 = X 0.80 X X = "26U kBtulyr Total D. Internal Gain b7() +( 2'10 X s ) = lS""bD kBtulyr Constant Variable Number of Component Component Bedrooms [Table N] [Table N] E. Cooling Load per Square Foot 1,000 X tkblv + I~¥ r~2. Btufyr-sf (A+B+C+D) Floor Area F. Adjustment ~or ThermjMass and Ventilation {'l)vo cSJD Btulyr-sf /lIo Nr'rtrl ('uV I VLS U / Pr;N [Table 0] G. Cooling Performance Level 7 S;?ysl' Btufyr-sf (E -F) H. Comparison Cooling Performance (From Previous Calculation or from Table P) ?rfo Btulyr-sf Com are Line G to Line H

Boise, Idaho 56 WORKED EXAMPLE TABLES

Table A-continued __ Table A-Equivalent Thennal Table D-Base Case Conservation Perfonnance of Assemblies A5-0oors Perfonnance (Btu/yr-sf) R-values (hr-F-sf/Btu) Solid wood with 2.2 Base Case 43,637 Weatherstripping A1-<:eillngs/Roofs Metat with rigid 5.9 foam core Attic Insulation R-value Table E-Projected Area Adjustment Construction R-30 R-38 R-49 R-60 Factors 27.9 35.9 46.9 57.9 Table B-Perimeter Heat Loss Degrees off Solar System Type Factors for Slabs-on-Grade and True DG, TW, SSA SSB, Framed Insulation R-value Unheated Basements (Btu/h-F-ft) South WW, SSC SSD SSE Construction R-19 R-22 R-30 R-38 o 1.00 0.77 0.75 Heated Unheated Insulated 5 2x6 at 16'oc 14.7 15.8 16.3 Perimeter Siabs-on- 1.00 0.76 0.75 Base- Base- Crawl- 10 0.98 0.75 0.74 2x6 at 24'oc 15.3 16.5 17.1 Insulation Grade ments ments spaces 2x8 at 16'oc 17.0 18.9 20.6 21.1 15 0.97 0.74 0.73 2x8 at 24"oc 17.6 19.6 21.6 22.2 None 0.8 1.3 1.1 1.1 20 0.94 0.72 0.70 2xl0 at 16'oc 18.1 20.1 24.5 25.7 R-5 0.4 0.8 0.7 0.6 25 0.91 0.69 0.68 2xl0 at 24 'oc 18.4 20.7 25.5 26.8 R-7 0.3 0.7 0.6 0.5 30 0.87 0.66 0.65 2x12 at 16'oc 18.8 21.0 25.5 30.1 R-ll 0.3 0.6 0.5 0.4 2x12 at 24 'oc 19.0 21.4 27.3 31.4 R-19 0.2 0.4 0.5 0.3 R-30 0.1 0.3 0.4 0.2 Table F-Solar System Saving Fractions A2-Framed Walls Single Table C-Heating Degree Days Wall Insulation R-value (F-day) F1-Direct Gain Framing R-ll R-13 R-19 R-25 Load DGCl DGC2 DGC3 2x4 at 16'oc 12.0 13.6 Collector Double Low-e R-9 Night 2x4 at 24'oc 12.7 13.9 C1-Heatlng Degree Days (Base 65°F) Ratio Glazing Glazing Insulation 2x6 at 16'oc 14.1 15.4 17.7 19.2 400 0.05 0.05 0.06 2x6 at 24"oc 14.3 15.6 18.2 19.8 Boise 5,802 300 0.06 0.07 0.08 Double Caldwell 5,594 200 0.09 0.10 0.12 Wall Total Thickness (inches) Emmett 5,655 150 0.11 0.12 0.15 Framing 8 10 12 14 Grand View 5,519 100 0.15 0.17 0.21 80 0.18 0.21 0.26 25.0 31.3 37.5 43.8 Mountain Home 5,980 60 0.22 0.26 0.32 NYSSA 6,000 50 0.24 0.30 0.37 The R-value of insulating sheathing should be added to Ola 6,577 45 0.26 0.32 0.40 the values in this table. 40 0.28 0.35 0.43 35 0.31 0.38 0.47 C2-Heating Degree Day Multiplier 30 0.33 0.42 0.52 25 0.37 0.47 0.58 A3-lnsulated Floors Passive Solar 20 0.41 0.53 0.65 Heat Loss Glazing Area per 15 0.45 0.60 0.74 Insulation R-value per Square per Square Foot Framing R-ll R-19 R-30 R-38 Foot .00 .05 .10 .15 .20 2x6s at 16'oc 18.2 23.8 29.9 12.00 1.09 1.1 0 1.1 0 1.1 0 1.11 F2-Trombe Walls 2x6s at 24"oc 18.4 24.5 31.5 11.50 1.09 1.09 1.1 0 1.1 0 1.10 2x8s at 16"oc 18.8 31.7 36.0 11.00 1.08 1.08 1.09 1.09 1.10 TWF3 TWA3 TWJ2 TWI4 24.9 Load Unvented Vented Unvented Unvented 2x8s at 24"oc 18.9 25.4 33.1 37.9 10.50 1.07 1.08 1.08 1.09 1.09 2xl0 at 16'oc 10.00 1.06 1.07 1.08 1.08 1.09 _ Collector Non- Non- Selec- Night 19.3 25.8 33.4 38.1 Ratio selective selective tive Insulation 2xl0 at 24 'oc 19.3 26.1 34.4 39.8 9.50 1.05 1.06 1.07 1.07 1.08 9.00 1.05 1.05 1.06 1.06 1.07 400 0.03 0.06 0.03 0.01 2x12 at 16"oc 19.7 26.5 34.7 39.8 300 0.04 0.07 0.06 0.03 2x12 at 24 'oc 19.6 26.7 35.5 41.2 8.50 1.03 1.04 1.05 1.06 1.06 8.00 1.02 1.03 1.04 1.05 1.05 200 0.07 0.10 0.11 0.07 These R-values include the buffering effect of a 7.50 1.01 1.02 1.03 1.04 1.04 150 0.09 0.12 0.15 0.11 ventilated crawlspace or unconditioned basement. 7.00 0.99 1.00 1.02 1.02 1.03 100 0.13 0.17 0.23 0.18 6.50 0.98 0.99 1.00 1.01 1.02 80 0.16 0.19 0.28 0.22 6.00 0.96 0.97 0.98 1.00 1.01 60 0.20 0.24 0.35 0.29 50 0.23 0.27 0.40 0.33 A4-Windows 5.50 0.93 0.95 0.96 0.98 0.99 5.00 0.90 0.92 0.94 0.96 0.97 45 0.25 0.29 0.43 0.36 Air Gap 4.50 0.86 0.89 0.91 0.94 0.95 40 0.27 0.31 0.46 0.39 4.00 0.82 0.85 0.88 0.91 0.93 35 0.30 0.34 0.50 0.43 1/4 in. 1/2 in. 1/2 in. argon 3.50 0.77 0.81 0.84 0.87 0.90 30 0.33 0.37 0.55 0.48 25 0.37 0.41 0.60 0.53 Standard Metal Frame 3.00 0.70 0.75 0.79 0.83 0.86 0.67 0.73 0.77 0.81 20 0.42 0.46 0.67 0.60 Single .9 2.50 0.61 15 0.49 0.53 0.75 0.69 Double 1.1 1.2 1.2 2.00 0.48 0.57 0.65 0.71 0.76 Low-e (e<=O.40) 1.2 1.3 1.3 Metal frame with thermal break Double 1.5 1.6 1.7 Low-e (e<=0.40) 1.6 1.8 1.8 Low-e (e<=0.20) 1.7. 1.9 2.0 Wood frame with vinyl cladding Double 2.0 2.1 2.2 Low-e (e<=0.40) 2.1 2.4 2.5 Low-e (e<=0.20) 2.2 2.6 2.7 Low-e (e<=O.l 0) 2.3 2.6 2.9 These R-values are based on a 3 mph wind speed and are typical for the entire rough framed opening. Manufacture's data, based on National Fenestration Rating Council procedures, should be used when available. One half the R-value of movable insulation should be added, when appropriate. Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 57

F3-Water Walls Table H-Unit Heat Capacities Table L-Heat Gain Factors Load WWA3 WWB4 WWC2 (BtufF-sf) Ceiling/roofs 45.0 Collector No Night Night Selective Walls and Doors 24.6 Ratio Insulation Insulation Surtace North Glass 21.7 400 0.05 0.01 0.02 H1-Mass Surfaces Enclosing Direct Gain East Glass 50.5 300 0.07 0.04 0.05 Spaces West Glass 53.8 200 0.10 0.09 0.10 Skylights 65.6 150 0.13 0.14 0.14 Thickness (inches) Material 2 3 4 6 8 12 Direct Gain Glazing 39.2 100 0.18 0.22 0.22 Trombe Walls and 9.5 80 0.21 0.27 0.27 Poured Conc. 1.8 4.3 6.7 8.8 11.311.510.3 Water Walls 60 0.26 0.35 0.34 Conc. Masonry 1.8 4.2 6.5 8.4 10.2 10.0 9.0 Sunspaces 50 0.29 0.40 0.39 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSA1 26.7 45 0.32 0.43 0.42 Flag Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSBI 26.7 40 0.34 0.47 0.46 Builder Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSCI 9.5 35 0.37 0.51 0.50 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSDI 26.7 30 0.40 0.56 0.55 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 SSEI 26.7 25 0.45 0.62 0.60 Water 5.2 10.4 15.620.831.2 41.6 62.4 20 0.50 0.69 0.67 15 0.57 0.77 0.75 H2-Rooms with no Direct Solar Gain Table M-Shading Factors F4-Sunspaces Thickness (inches) Projection Load Material 2 3 4 6 8 12 Factor South East North West Collector Sunspace Type Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 0.00 1.00 1.00 1.00 1.00 Ratio SSAI SSBI SSC1 SSDI SSEI Conc. Masonry 1.6 2.9 3.5 3.6 3.6 3.4 3.2 0.20 0.77 0.94 0.91 0.93 400 0.10 0.08 0.05 0.10 0.08 Face Brick 1.8 3.1 3.6 3.7 3.5 3.4 3.2 0.40 0.22 0.77 0.82 0.75 300 0.12 0.10 0.06 0.12 0.09 Flag Stone 1.9 3.1 3.4 3.4 3.2 3.1 3.0 0.60 0.59 0.72 0.55 200 0.15 0.12 0.09 0.16 0.13 Builder Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 0.80 0.40 0.62 0.34 150 0.17 0.14 0.11 0.19 0.16 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 1.00 0.26 0.52 0.18 100 0.22 0.18 0.16 0.25 0.20 Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.1 1.20 0.11 0.42 0.02 80 0.25 0.21 0.18 0.28 0.24 60 0.29 0.25 0.23 0.33 0.28 Multiply by 0.8 for low-e glass, 0.7 for tinted glass and 50 0.32 0.27 0.26 0.37 0.31 0.6 for low-e tinted glass. 45 0.34 0.29 0.28 0.39 0.33 40 0.36 0.31 0.30 0.41 0.35 Table I-Comfort Factors (Btu/ sf) 35 0.38 0.33 0.32 0.44 0.38 Direct Gain 790 30 0.41 0.36 0.35 0.47 0.41 25 0.45 0.39 0.39 0.51 0.44 Suns paces and 260 Table N-IntemaI Gain Factors 20 0.49 0.44 0.44 0.56 0.49 Vented Trombe Walls Constant Component 690 kBtulyr 15 0.55 0.50 0.51 0.62 0.55 Variable Component 290 kBtu/yr-BR

Table J-Radiant Barrier Factors Radiant Barrier 0.75 Table O-Thermal Mass and No Radiant Barrier 1.00 Ventilation Adjustment (Btu/yr-sf) Total Heat Night Night No Night No Night Capacity Vent wi Vent wi No Vent wi Vent wi No per SF Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan 0.0 1,090 -1,320 -490 -3,470 Table K-Solar Absorptances 1.0 1,670 -540 090 -2,690 Color Absorptance 2.0 . 2,060 -020 480 -2,160 3.0 2,320 330 740 -1,810 Gloss White 0.25 4.0 2,500 570 920 -1,580 Semi-gloss White 0.30 5.0 2,620 730 1,030 -1,420 Light Green 0.47 6.0 2,700 840 1,110 -1,310 Kelly Green 0.51 7.0 2,750 910 1,160 -1,240 Medium Blue 0.51 8.0 2,780 950 1,200 -1,190 Medium Yellow 0.57 9.0 2,810 990 1,220 -1,160 Medium Orange 0.58 10.0 2,820 1,010 1,240 -1,140 Medium Green 0.59 Light Buff Brick 0.60 Total heat capacity per square foot is calculated on Bare Concrete 0.65 Worksheet III, Step E. Red Brick 0.70 Medium Red 0.80 Medium Brown 0.84 Dark Blue-Grey 0.88 Dark Brown 0.88 Table P-Base Case CooUng Table G-Base Case AWl:i1iary Heat Performance (Btu/sf-yr) Performance (Btu/yr-sf) Base Case 9,580 Base Case 40,523

Boise, Idaho 58 WORKED EXAMPLE TABLES

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 59

Note: This is a generic example to explain how to fill out the worksheets. For an example specific to this book, refer to the worked example on the prior pages. The actual house design used for both examples is the same, but specific numerical values will be different.

Anytown , USA

Anytown, USA 60 INTRODUCTION Introduction A separate worksheet is The estimates from provided for each of four Worksheets I and II are based on Purpose separate performance levels a heating thermostat setting of perfo~ance level and 70°F. The .estimates from The purpose of the Any Town, associated target. These are Worksheet IV are based on a USA section is to explain how to deSCribed below: cooling thermostat setting of use the passive solar Worksheet I: Conservation 78°F with no ceiling fans and worksheets in the Passive Solar Performance Level: the 82°F with ceiling fans. Design Strategies: Guidelines for estimated heat energy needed by The worksheets are Home BUilding. Separate the building each year from both supported by a number of data Worksheets booklets are the solar and auxiliary heating tables. The data tables are given available for specific locations systems. The units are a letter deSignation and are throughout the continental Btu/yr-sf. referenced when applicable next USA. Each booklet contains Worksheet II: Auxiliary Heat to each worksheet entry. detailed technical data for a Performance Level: the A description and drawings specific location. Although the estimated heat that must be of the example building are example presented in this provided each year by the provided below, followed by booklet is for a moderate mid­ auxiliary heating system. This completed worksheets. Data Atlantic climate, the procedure worksheet accounts for the solar tables have also been included is presented in a general savings. The units are when appropriate. manner and is intended to be . Btu/yr-sf. Each step of the worksheets used for all locations. Worksheet III: Thermal is then explained in detail. Mass / Comfort: the temperature General Description swing expected on aclear winter day with the auxiliary heating of Worksheets system not operating. The units \ are OF. The Worksheets booklet for each location provides an easy-to-use Worksheet N: Summer Cooling calculation procedure, allowing Performance Level: the the designer to estimate the estimated annual cooling load of performance level of a particular the building. The units are building design and compare it Btu/yr-sf. against a base-case performance level or against the performance of the builder's more conventional house.

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 61

Description of The building has an South facing windows attached sunspace. The provide direct gain solar heating Example Building ( sunspace floor has a four-inch to the dining area. kitchen and ) thick slab-on-grade with quarry master bedroom. The south A 1.504 square foot passive tile set in a mortar bed. The glazing in the kitchen and solar. single-family home with sunspace is separated from the dining area provides heat to an an 8.3 ft. average ceiling height conditioned portion of the house exposed slab-on-grade. is used to illustrate how to use by sliding glass doors and a The east portion of the the worksheets. A floor plan. masonry fireplace wall. Awning house is slab-on-grade building elevations. building windows located at the top and construction. The great room sections and details are shown bottom of the south wall provide and master bedroom suite are below. outside ventilation for the raised floor construction. The sunspace. slab-on-grade floor in the kitchen and dining area is finished with ceramic tile so that the floor may function as thermal mass. The exterior doors are metal with a foam core center.

~r--~2~O~' --.....;*~i~ __ ..!:2=2-'--~r· ...... ·.... ·...... g4.'...... :...... \

Garage

4040

Bedroom

Great Room

Master Bedroom ;...,... Suns pace

8088 8088 14' o 2 4 8 12 FLOOR PLAN ----

AnytOWD, USA 62 INTRODUCTION

SOUTH ELEVATION

024 B 12 NORTH ELEVATION

'...... ---- ...... ::::::::::::::J

"r ABOVE GRADE SECTION ) 02...... 4 B 12

Insulation,.---i''ti"*t:=;::::::l I . ., ...... ' : .r'''<:'.:l.-m~'-'-:! """"!1rf"'_'11IT'nl-.LA .' .' • § 1111 § III I;, : .....: . ini~),i~, §1I11 § 1111 ., ..•• ". 1I11§1Il1t=' •.• ' :." .•• 1I11§1II" .• : .' ~'. 1111" ", ....• "II .~. ", . ....111' . .'" .•.... . " . ",'.' . . . -... '. -. .' ... ", .. ' ... " . ,' . • ' II' .' II'

SLAB-ON-GRADE CRAWLSPACE FULL BASEMENT

\ TYPES OF FOUNDATIONS /

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 63

General pro~ect Information

~:Area 1504 sf

Worksheet I: Conservation Performance Level

A. Envelope Heat Loss Construction R-value Heat Description Area [Table A] Loss

Q!!iliog~L[QQt~ B-;36 io 8!liQ ]Q64 + ;3f2!:! = ;3Q B-;3Q io Qrull!!Qml Q!!iliog 42Q + 24f2 = ]I ..,... WiillI~ B-l!:!± B-Z SIl!!iillIliog io BigiQ IO~!JliiI!iQO !:!!:!2 24Z = 4Q B-1!:! io ~iilmg!! 14Q + lZZ 6 IO~!JliiI!!!Q EIQQ[~ B-1!:! io EIQQ[ Qll!![ ~!!ois!Q Q[5nIl1~I2ii1Q!! Z64 + 2f26 = ;3Q + = ~Qo-~QliiI[ ~Iiili:iog OQ!Jbl!! !:aliilZ!!Q WQQQ E[iillD!! liZ' iili[ giill2 f22 + 16 2!:! - L.QY:l-i; (!!:;;- 4Q) + OQQ[~ M!!!iilllI:li!1l EQiillD QQ[!! 4Q + f2!:! = Z + = 1121 Btu/OF-h Total B. Foundation Perimeter Heat.Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss

Sliilb~-QO-!:a[iilQ!! B-Z 62 X Q;3Q 2f2 ~ H!!iilis!Q BiilS!!ID!!O!S X = I Uoll!!ru!!Q Eliil~!!ID!!O!~ X = E!![iID!!t!![ IO~!Jliilt!!Q Qmll:ll~I2ii1Q!!~ X = 2f2 Btu/oF-h Total

C. Infiltration Heat Loss 1246;3 X Qf2Q X .018 112 Btu/OF-h Building Air Changes Volume per Hour

D. Total Heat Loss per Square Foot

24 X 2~6 + lf2Q4 = 4Z!2 Btu/DD-sf Total Heat Loss Floor Area (A+B+C)

E. Conservation Performance Level

H!2 X nQ;3 X Qn = lZQn Btu/yr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C] Day Multiplier Square Foot [Table C]

F. Comparison Conservation Performance (From Previous Calculation or from Table O) 2f2 ;3!2Q Btu/yr-sf Com are Line E to Line F

Anytown, USA 64 CONSERVATION PERFORMANCE LEVEL

Worksheet I: Step A. Envelope Heat Loss Ceilings/Roofs Conservation The first step is to calculate the There are two types of Performance Level heat loss through the building ceiling/roof construction in the) Worksheet I is essentially a heat envelope. The building envelope example building. R-38 mineral \ loss calculation, similar to the consists of all walls, roofs, insulation is located in an attic type of calculation made to size floors, non-solar windows and space, and R-30 insulation is heating and cooling equipment. doors that enclose the located in the framed cathedral The major difference is that the conditioned space of the house. ceiling. The total R-value is calculation does not consider Heat loss for each envelope selected from Table Al for each heat loss through any of the component is calculated by ceiling/ roof component. The passive solar systems. The dividing the surface area of the values in Table Al account for following building corriponents component by the total R-value. the buffering effect of the attic in the example building are not The total envelope heat loss is (when applicable), the ceiling considered in the calculation: the sum of the heat loss for all material (sheetrock) and the • Heat loss through direct gain of the envelope components. effect of framing. solar glazing. Table A in the Worksheets • Heat loss through walls and booklet contains R-values that A 1-Ceilings/Roofs Attic Insulation R-value windows that separate the may be used in the calculation. Construction R-30 I!1J R-49 R-60 house from the sunspace. There are actually five separate 27.9 35 46.9 57.9 Framed Insulation R-value If the example building had tables labeled AI, A2, A3, A4 Construction R-19 R-22 R-30 R-38 2x6 at 16"oc 14.7 15.8 16.3 - Trombe walls or water walls, and A5. A separate table is 2x6 at 24'oc 15.3 16.5 17.1 - heat loss through these passive provided fQr ceilings/roofs, 2x8 at 16"oc 17.0 18.9 20.6 21.1 2x8 at 24"oc 17.6 19.6~ 22.2 solar systems would also be walls, floors, windows and 2x10 at 16"oc 18.1 20.1 24. 25.7 2x10 at 24"oc 18.4 20.7 . 26.8 excluded from the calculation. doors. The R-values' in these 2x12 at 16"oc 18.8 21.0 25.5 30.1 Heat loss from the passive tables include the thermal 2x12 at 24 'oc 19.0 21.4 27.3 31.4 solar energy systems is excluded resistance of both the insulation The area and R-value of the ) since the solar savings fractions and other materials that two different types of in Worksheet II take these losses typically make up the construction are entered on two into account. construction assembly such as lines of the table under exterior sheathing and "ceilings/roofs" and the heat sheetrock. They also account loss is calculated by dividing the for framing members that surface area by the total . penetrate the insulation and R-value. Note that the ceiling reduce the effectiveness. over the sunspace is not included in this calculation.

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 65

Walls The R-value of each wall The total R-value is selected There are two types of wall type is detennined from Table from Table A3, which considers '\ construction in the example A2 in the Worksheets booklet. the buffering effect of the ) building. The typical exterior The R-value of both wall types is crawlspace as well as framing wall is of 2x6 wood frame 17.7 from the table, but since and the floor materials. The construction with R-19 mineral the first wall type has R-7 area and R-value is entered on insulation in the cavity. An insulating sheathing, this is one line of the table and the insulating sheathing with an R- added to the value from the heat loss is calculated by . 7 rating is attached to the table so that 24.7 is used in the dividing the area by the R-value. exterior surface of the framing. calculations. These R-values The wall is finished with 1/2 along with the associated areas A3-lnsulated Floors Insulation R·value inch sheetrock on the inside are entered on two lines of the Framing R-11 R-19 R-30 R-38 2x6s at 16"oc 18.2 23.8 29.9 and a brick veneer on the table and the heat loss is 2x6s at 24"oc 18.4 24.5 31.5 outside. calculated by dividing each 2x8s at 16"oc 18.8 24.9 31.7 36.0 2x8s at 24"oc 18.9 33.1 37.9 The second type of wall surface area by the 2x10 at 16"oc 19.3 4W25.8 33.4 38.1 2x10 at 24"oc 19.3 .1 34.4 39.8 construction separates the corresponding R-value. 2x12 at 16"oc 19.7 26.5 34.7 39.8 house from the garage. This 2x12 at 24"oc 19.6 26.7 35.5 41.2 These R·values include the buffering effect of a wall is also of 2x6 wood frame A2-Framed Walls ventilated crawlspace or unconditioned basement. Single Wall Insulation R·value construction With R-19 in the Framing R-11 R-13 R-19 R-25 Had there been different cavity, but it does not have the 2x4 at 16"oc 12.0 13.6 insulation conditions for the 2x4 at 24"oc 12.7 13.9 ~ - insulating sheathing or the 2x6 at 16"oc 14.1 15.4 17. 19.2 raised floor, an additional line of 2x6 at 24"oc 14.3 15.6 . 19.8 brick veneer. Note that the Double the table would be completed for Wall Total Thickness (inches) walls that separate the house Framing 8 10 12 14 each condition. from the sunspace are not 25.0 31.3 37.5 43.8 If the example building had included...... The R·value of insulating. sheathing should be insulated floors over a garage or \ added to the values in this table. / It is necessary to measure unheated basement, these the surface area of each type of components would also be wall construction. The surface Floors included in this step. area may be determined by Only the raised floor is As an alternative to multiplying the length of wall by considered in this step of the insulating between the floor the average height and heat loss calculation; heat loss joists, the perimeter walls of the subtracting the area of doors from the slab-on-grade floor is crawlspace could have b~en and windows. conSidered in Step B. There is insulated and floor insulation one type of raised floor eliminated. When this construction in the example technique is used, the perimeter building. R-19 mineral heat loss method in Step B insulation is placed between should be used. Step A only 2xlO floor joists at 16 inches on includes floors when insulation center; the crawlspace beneath is placed in the floor assembly. is ventilated.

Anytown, USA 66 CONSERVATION PERFORMANCE LEVEL

Non-solar Glazing Windows in the example These values are entered in Next, heat loss from the non­ building are all double-pane the table and the heat loss is solar glazing is calculated. Note wood windows with a 1/2 inch calculated by dividing the door that the passive solar direct gain air space between the panes. areas by the R-value. If the glazing is not included. Also the The R-value for this window example building had more than windows that separate the type is 2.1, selected from Table one door type (different house from the sunspace are A4. R-values), then additional lines not included. The non-solar window area of the table would be completed. The rough frame opening of is taken from the building plans. each window is generally used These values are entered in the Total for the window area. This is table and the heat loss is The heat loss of all components because the R-values presented calculated by dividing the of the building envelope is in Table A4 and most heat loss window area by the window summed at the bottom of the data presented by window R-value. If the example building table and this completes Step A manufacturers is for the rough had more than one window type of the worksheet. frame opening. Using the rough (different R-values), then frame opening also makes it additional lines of the table easier to estimate window areas would be completed. since windows are usually specified on the plans in terms Doors of the rough frame dimensions. The doors are the last component of the envelope to A4-Windows Air Gap consider. The example building 1/4 in. 1/2 in. 1/2 in. argon has two exterior doors: the main Slandar'd Metal Frame Single .9 entrance and an additional door Double 1.1 1.2 1.2 Low-e (e<=0:40) 1.2 1.3 1.3 to the garage. These have a Metal frame with thermal break total surface area of 40 square Double 1.5 1.7 Low-e le<=0.40} 1.6 '. I.S feet and an R-value is selected Low-e e<=0.20} 1.7 2.0 Wood frame with vinyl cladding from Table A5. Note that the Double 2.0 2.1 2.2 Low-e (e<=0.40l 2.1 2.4 2.5 door that separates the garage Low-e le<=0.20 2.2 2.6 2.7 Low-e e<=0.10 2.3 2.6 2.9 from the exterior is not included since the garage is These R-values are based on a 3 mph wind speed and are typical for the entire rough framed opening. unconditioned. Manufacture's data, based on National Fenestration Rating Council procedures, should be used when available. One half the R-value of AS-Doors movable insulation should be added, when Solid wood with 2.2 appropriate. Weatherstripping Metal with rigid C1i) foam core

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 67

Table B-Perimeter Heat Loss Factors Step B. Foundation for Slabs·on·Grade and Unheated The building volume is Perimeter Heat Loss . Basements (Btuth·F·ft) calculated by multiplying the Heated Unheated Insulated ) Foundation heat loss from Perimeter Siabs-on- Base· Base- Crawl· average ceiling height by the slabs-on-grade. basements and Insulation Grade ments ments spaces conditioned floor area. In this None 0.8 1.3 1.1 1.1 insulated crawispaces is R 5 ~ 0.8 0.7 0.6 example the average ceiling R:7 0.3 0.7 0.6 0.5 estimated by multiplying the R·11 . 0.6 0.5 0.4 height is 8.3 ft. The conditioned R-19 0.2· 0.4 0.5 0.3 length of perimeter times an R-30 0.1 0.3 0.4 0.2 floor area is 1,504 sf which does appropriate heat loss factor When a raised floor assembly is not include the garage or the taken from Table B. not insulated, for instance, over sunspace. The resulting The dining area, kitchen and crawlspaces insulated at the building volume is 12,483 cubic secondary bedrooms in the perimeter or basements, heat feet. example house have slab-on­ loss occurs primarily at the The units of infiltration heat grade construction. R-7 perimeter. loss are Btu;oF-h, the same as insulation is installed around The example house does not for the building envelope and the perimeter. have a basement or a heated the foundation perimeter. The heat loss factor for the crawlspace, but if it did, the Step D. Total Heat Loss per slab edge is 0.3, selected from foundation heat loss would be Square Foot Table B. The heat loss factor is calculated by multip1ying the The total building heat loss is multiplied by the perimeter to perimeter of these elements by a the sum of the heat loss for the calculate the heat loss. The heat loss factor selected from building envelope (Step A), the units of heat loss, using the Table B. foundation perimeter (Step B) perimeter method, are the same When houses have heated and infiltration (Step C). For as for the building envelope basements, heat loss from , residences this value will range calculated in the previous step. basement walls located above between 200 and 500. It Note that sunspace slab is not grade would be included in represents the Btu of heat loss included in this calculation. Step A. The slab edge perimeter from the building envelope over adjacent to the crawlspace and Step C. Infiltration Heat Loss the period of an hour when it is the sunspace is also excluded. The heat loss from infiltration or one OF colder outside than air leakage is estimated by inside. This total heat loss, of multiplying the building volume course, does not include heat times the air changes per hour loss from the solar systems, times a heat loss factor of 0.018. including direct gain glazing. The example building is The result of Step D, estimated to have an infiltration however, is the annual heat loss rate of 0.50 based on local per degree day per square foot. building experience. This value is calculated by mUltiplying the total heat loss by 24 hours/ day and dividing by the conditioned floor area.

Anytown, USA 68 CONSERVATION PERFORMANCE LEVEL

Step E. Conservation The heating degree days are Step F. Comparison Performance Level selected from Table C 1 and Conservation Performance Once the total heat loss per based on specific locations. The The conservation performance square foot is calculated, the heating degree day multiplier is level for the proposed design conservation perfonnance level selected from Table C2 and is may be compared to the base may be calculated by based on the total heat loss per case perfonnance level for the multiplying the total heat loss square foot (Step D) and the area, given in Table D. per square foot (Step D) by the passive solar glazing area per Table D-Base Case Conservation heating degree days times the square foot of floor area Performance (Btu/v. • heating degree day multiplier. (Worksheet II, Step A). Base Case 25,38 Alternatively, the C1-Heating Degree Days ~ 65°F) C2-Heating Degree Day Multiplier conservation perfonnance level Raleigh·Durham ~ Passive Solar Heat Loss Glazing Area per may be compared to other This value is from TMY weather tapes and per Square per Square Foot should be used for Worksheet Calculations. Foot .00 .05 .10 .15 .20 building designs considered by It will vary from long term averages. 8.00 1.03 1.05 1.07 1.09 1.11 7.50 1.01 1.04 1.06 1.07 1.10 the builder to be typical of the 7.00 0.99 1.02 1.04 1.06 1.08 6.50 0.97 1.00 1.02 1.04 1.06 area. In this case, the 6.00 0.94 0.97 1.00 1.03 1.05 worksheets would first be 0.90 0.94 0.98~. 1.03 .00 0.86 0.91 0.95 . 1.01 completed for the typical design ~5 Q~ Q~ Q~ Q9 Q~ ~. 0 0.77 0.83 0.88 . 2 0.96 and the results of these 3.50 0.72 0.78 0.83 0.88 0.93 calculations would be entered in The conservation Step F. perfonnance level for the If the conservation example building is compared to per.(onnance level of the the base case conservation proposed building (Step E) is perfonnance level in the next greater than the base case or ) step. typical-design conservation perfonnance level. the designer should conSider additional building insulation or reduced non-solar glass area.

Anytown; USA PASSIVE SOLAR DESIGN STRATEGIES 69

Worksheet II: Auxili Heat Performance Level / A. Projected Area of Passive Solar Glazing I. ) Solar System Rough Frame Net Area Adjustment Projected Reference Code Area Factor Factor [Table E] Area

Q~QI ee X 0.80 X ~e fl~ SSQI 2Qe X 0.80 X ~e jfl~ X 0.80 X X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = 2~fl 2~2 sf Total Area Total Projected Area

2~2 -;- jf!Q4 = jf! Total Floor Total Projected Projected Area Area per Area Square Foot

B. Load Collector Ratio

24 X 2~a + 2~2 = ~Q e~ Total Total Heat Loss Projected [Worksheet I] Area

C. Solar Savings Fraction ) System / Solar Savings Solar System Projected Fraction Reference Code Area [Table F]

Q~Qj fl~ X 44 ~Q ~fl SSQl jfl~ X 4f! = Z~~f! X = X = X = X = X =

jQ~ Zj + 2~2 Q4f! Total Total Solar Projected Savings Area Fraction D. Auxiliary Heat Performance Level

[1 - Q4f! jx 1ZQ~Z = ~Q4~ Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E]

E. Comparative Auxiliary Heat Performance (From Previous Calculation or from Table G) 23 Q99 Btu/yr-sf Com are Line D to Line E ,

Anytown, USA 70 AUXILIARY HEA T PERFORMANCE LEVEL

Worksheet II: The reference codes are shown Auxiliary Heat on Tables FI through F4 for Performance Level various types of solar systems. Worksheet II is used to estimate More information about the the savings from passive solar system types is provided in the systems and to estimate the discussion under Step C of this auxiliary heat performance level.. worksheet. The reference code This is the amount of heat that for the direct gain system is must be provided to the building "DGC 1" because night each year after the solar savings insulation is not proposed. The have been accounted for. reference code for the sunspace The example building has is "ssc 1" since all the sunspace two solar systems: direct gain glazing is vertical. south glazing and a sunspace. The south wall of the

South example building actually faces Step A. Projected Area of Projection 10° east of south because of site Passive Solar Glazing Projected Area of Passive Solar Glazing conditions. The adjustment The solar savings fraction is based on the The first step is to calculate the projected area of solar glazing. factor is therefore 0.98 for both projected area of the solar The worksheet allows the solar systems as selected from glazing. The proj ected area of user to enter the rough frame Table E. Each solar system area passive solar glazing is the area area of solar glazing. since it is is multiplied by the net area projected on a plane facing true generally easier to measure this. factor and the appropriate south (the actual glazing may be The rough frame area is adj ustment factor to calculate oriented slightly east or west of multiplied by a net area factor of the projected area. Both the true south). The projected solar 0.80 to account for window total projected area and the total . glazing also accounts for sloped framing and mullions. If the net area are summed at the bottom glazing in certain types of glass area is entered. the net of the table. sunspaces. area factor is 1.00. For most solar systems the Table E-ProJected Area The example building has Adjustment Factors projected area may be calculated two separate passive solar Degrees off ~solar System Type True D SSA SSB, by multiplying the actual glazing systems: direct gain and a South ,S SSD SSE area times an adjustment factor sunspace. This means that two o 1.00 0.77 0.75 5 c$? 0.76 0.75 taken from Table E. lines of the table must be 10 0.98 0.75 0.74 15 . 0.74 0.73 Alternatively. the projected completed. If the example 20 0.94 0.72 0.70 25 0.91 0.69 0.68 area may be determined by building had other types of solar 30 0.87 0.66 0.65 making a scaled elevation systems. for instance Trombe The last part of Step A is to drawing of the building. looking walls or water walls. additional divide the total projected area by exactly north. Surface areas lines in the table would be the conditioned floor area. giving may then be measured from the completed. the total projected area per scaled elevation drawing. This In the first . the square foot. This value is used concept is illustrated in the reference code for each type of in Worksheet I. Step E to figure below. solar system is entered along determine the heating degree with a description of the system. day multiplier.

, ./

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 71

Step B. Load Collector Ratio A reference code, for The solar savings fraction for The load collector ratio is instance "DGC 1", is also each system is multiplied by the calculated by taking the total provided for each solar system projected area and totaled at the heat loss from Worksheet I, Step variation. These references are bottom of the table. This total is D and multiplying this value entered on the worksheet "Solar then divided by the total times 24 (hours/ day) and System Reference Code". They projected area from Step A to dividing by the total projected are also a key to additional calculate the weighted average area of the solar glazing information about each solar solar savings fraction for the calculated in the previous step. system as provided in Passive whole building. Solar Heating Analysis and The solar savings fractions Step C. Solar Savings Fraction other reference manuals. are based on reference designs. The next step is to calculate the The assumptions made about solar savings fraction for the F1-Direct Gain these reference designs are Load DGCI DGC2 DGC3 building. This is calculated as a Collector Double Low-e R-9 Night summarized below. weighted average of the solar Ratio Glazing Glazing Insulation 200 0.10 0.11 0.13 savings fraction for the separate 155 0.13 0.14 0.17 Direct Gain 100 0.18 0.20 0.24 passive solar systems. The 80 0.22 0.25 0.30 The direct gain reference 60 0.28 0.31 0.38 weightings are based on 50 0.32 0.36 0.44 designs are all assumed to have projected area. 45 0.34 0.39 0.47 40 0.37 0.43 0.51 double-pane glass and sufficient The solar systems used in 0.47 0.56 heat storage to limit the clear 0.52 0.62 this step should be identical to ar ~. 9 0.58 0.69 day temperature swing to 13°F. 20 0.55 0.65 0.77 those used above in Step A. The 15 0.62 0.74 0.85 For the case with night first two columns are simply insulation, the thermal carried down from the first and F4-Sunspaces resistance is assumed to be R-9. Load last columns in· Step A. Collector sunsEace Type ) The solar savings fraction for Ratio SSAI SSBI SCI SSDI SSEI Trombe Walls 200 '0.17 0.14 0.11 0.19 0.15 e9-ch individual system is taken 155 0.20 0.17 0.14 0.23 0.19 The Trombe wall reference 100 0.26 0.22 0.19 0.30 0.26 from Tables F1 through F4 80 0.30 0.25 0.23 0.35 0.30 designs are all assumed to have based on the load collector ratio 60 0.35 0.30 0.28 0.42 0.36 50 0.39 0.34 0.32 0.46 0.40 double-pane glass. The mass calculated in Step B and the 45 0.42 0.36 0.35 0.49 0.43 wall is assumed to be 12 inches 40 0.44 0.39 0.38 0.52 0.46 type of solar system. Table F1 is 0.48 0.42 0.56 0.49 thick and constructed of for direct gain systems, Table F2 0.52 0.46 0.60 0.54 ~ 0.56 0.50 ~.0 0.65 0.59 masonry or concrete. for thermal storage walls, Table 20 0.62 0.56 0.57 0.72 0.65 15 0.70 0.64 0.65 0.79 0.73 F3 for water walls and Table F4 Water Walls for sunspaces. There are The water wall reference designs multiple columns in each table are all assumed to have double­ that account for system design pane glass. The water tank is features such as night assumed to be nine inches insulation or selective surfaces. thick, extending continuously in front of the glazing surface. The space between the water tank and the glazing is assumed to be sealed.

Anytownl USA 72 AUXILIARY HEA T PERFORMANCE LEVEL

Sunspaces Step D. Auxiliary Heat Data is provided for five Performance Level sunspace reference designs as The auxiliary heat performance illustrated on the following level is calculated by multiplying figure. Double glazing is the conservation performance assumed for all reference level from Worksheet I, Step E, designs. Reference designs times one minus the solar SSAl, SSB 1 and SSD 1 are savings fraction, calculated in assumed to have opaque end the previous step. This value walls. All are assumed to have a represents the amount of heat concrete or masonry floor about that must be provided to the six inches thick and a masonry building by the auxiliary heating or concrete common wall system(s). separating the sunspace from the living areas of the house. Step E. Comparative Auxiliary The glazing for designs SSAI Heat Performance and SSD 1 is assumed to be The calculated auxiliary heat sloped at an angle of 50° from performance level may be the horizon. The sloped glazing compared to the performance in designs B and E is assumed level for a typical basecase to be at an angle of 30°. building in the area. This may be taken from Table G and is 23,099 Btu/yr-sf.

\ ) I Alternatively, the performance level may be compared to a previous worksheet calculation made for a typical builder house. If the auxiliary heat performance level calculated in Step D were larger than the base case auxiliary heat performance, the designer should conSider increasing the size of the solar

Sunspace Reference Designs systems, adding additional solar Data is provided for five types of sunspaces. systems or increasing insulation levels.

\ /

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 73

Worksheet III: Thermal Mass/Comfort ( \ A. Heat Capacity of Sheetrock and Interior Furnishings '\ ) Unit Total Heat Heat Floor Area Capacity Capacity

BQQIDl! lIlli!b Qi[~Q! !:aiilie 424 X 4.7 2H~1 QRiilQ~l! QQee~Q!~g !Q Qi~Q! !:aiilie QRiilQ~l! ~4~ X 4.5 = 42Z1 2452 Btu/OF Total B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description capaci~ Total Heat (include thickness) Area [Table ] Capacity

nQIDb~ WslIIl! X 8.8 , wm~[Wiillll! X 10.4 = E~RQl!~g Qliilb ie Que lQa X 13.4 = laaQ E~RQl!~g Qliilb IlIQ! ie Que laZ X 1.8 = 24Z X = X = X = 122Z Btu/OF Total

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description Capacity Total Heat (include thickness) Area [Table H] Capacity I[QIDb~ WslIIl! . X 3.8 W~[WiillIl! X 4.2 = ) EiilQ~ 6[iQis 4" III X 3,Z = 4ll X = X = 4ll Btu/OF Total

D. Total Heat Capacity a4~Q Btu/OF (A+B+C)

E. Total Heat Capacity per Square Foot

a4~Q + 15Q4 = 52 Btu/OF-sf Total Heat Conditioned Capacity Floor Area

F. Clear Winter Day Temperature Swing Total Comfort Projected Area Factor [Worksheet II] [Table I]

Qi~Q! !:aiilie 2~ X a22 = 5~Z54 Quel!RiilQ~l! Q[ 12a X 2~~ = 4a zaz ~e!~g nQIDb~ WslIIl! lQa 4~1 + a4~Q = 12 a OF Total Total Heat Capacity G. Recommended Maximum Temperature Swing 13 OF ) Com are Line F to Line G

Anytown, USA 74 COMFORT PERFORMANCE LEVEL

Worksheet III: Step A. Heat Capacity of In the example building, the Thermal Sheetrock and Interior master bedroom, dining area Mass/Comfort Furnishings and kitchen are all direct gain This worksheet is used to The first step is to estimate the space.s. The secondary calculate the thermal effective heat capacity bedrooms, and mass/comfort performance level, associated with low-mass master bedroom are which is the temperature swing construction and interior directly connected to the direct expected on a clear winter day furnishings. To complete this gain spaces. The with the auxiliary heating step it is necessary that two and entry foyer are not system not operating. A high sub-areas be identified within conSidered in this calculation temperature swing would the building: those areas that since they are not connected to indicate that inadequate thermal receive direct solar gains and a direct gain space. These areas mass is provided in the building those areas that are connected are illustrated for the example design, which not only creates to rooms that receive direct solar building. discomfort but decreases solar gains. This is because the mass The direct gain space is heating performance. of sheetrock and furnishings multiplied by 4.7 and the spaces The general procedure of the located in direct gain rooms is connected to direct gain spaces worksheet is to calculate the more effective. Rooms that are are multiplied by 4.5. These effective heat capacity of mass separated from direct gain products are summed and elements located within the spaces by more than one door represent the effective heat conditioned space of the should not be included in either capacity associated with the building. The total effective heat category. sheetrock and interior capacity is then combined with furnishings. the direct gain projected area to estimate the clear winter day temperature swing. Note that ) thermal mass elements located within unconditioned spaces such as the sunspace are not included in this calculation.

1i)))1 Direct Gain Spaces Unconditioned Garage I,l@ililm Spaces Connected to Direct Gain Spaces moo Spaces Not Connected to Direct Gain Spaces

Suns pace

Building Sub-areas for Calculating Effective Heat Capacity Worksheet 11/ requires that the building be divided into sub-areas.

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 75

Step B. Heat Capacity of Mass Exposed slabs-on-grade Step C. Heat Capacity of Mass Surfaces Enclosing include those with a surface of Surfaces Enclosing Spaces () Direct Gain Spaces vinyl tile. ceramic tile or other Connected to Direct Gain The heat capacity of thermal materials that are highly Spaces mass elements (other than conductive. Slabs that are The same type of calculation is sheetrock and furnishings) that covered with carpet should not performed for mass surfaces enclose the direct gain spaces is be considered to be exposed. that enclose spaces connected conSidered in this step. The The exposed slab area should be to direct gain spaces. The surface area of each element is further reduced. when primary difference is the unit measured from the building appropriate. to account for heat capacity figures taken from plans and multiplied by the unit throw rugs and furnishings. Table H2 instead of Table H 1. heat capacity. The unit heat The exposed slab area is In the example building. the capacity is printed directly in then subdivided into two areas: fireplace wall and are the table for Trombe walls. water that which is expected to be in considered in this category. walls. and exposed slabs-on­ the sun and that which is not. This area and the unit heat grade. The unit heat capacity As a rule-of-thumb. slab area capacity is entered in the table for other mass elements is should be considered in the sun and multiplied by each other. selected from Table H 1. Note only when it is located directly This represents the total that thermal mass located in the behind south glazing. In any effective heat capacity of mass sunspace is not included in this event. the slab area assumed to elements that enclose the calculation. be in the sun should not exceed spaces connected to direct gain 1.5 times the south glass area. spaces. H1-Mass Surfaces Enclosing Direct Gain Spaces . In the example building. the Thickness (inches) slabs-on-grade located in the H2-Rooms with no Direct Solar Gain Material 1 2 3' 4 6 8 12 Thickness (inches) Poured Conc. 1.8 4.3 6.7 8.8 11.311.5 10.3 kitchen and are Material 1 2 ~ 4 6 8 12 ) Conc. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 located within direct gain Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 Face Brick 2.0 4.7 7.1 9.0 10.49.9 9.0 Conc. Masonry 1.6 2.9 3.5 ~.6 3.4 3.2 Flag Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 spaces. Some of this area is Face Brick 1.8 3.1 3.6 3.7 .5 3.4 3.2 Builder Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 Fla~Stone 1.9 3.1 3.4 . 3.2 3.1 3.0 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 considered to De in the sun and Builder Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 Water 5.2 10.415.6 20.8 31.241.6 62.4 the remainder not. These Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.1 surface areas are entered in the table and multiplied by the appropriate unit heat capacity. The products are then summed at the bottom of the table.

Anytown, USA 76 COMFORT PERFORMANCE LEVEL

Step D. Total Heat Capacity Step F. Clear Winter Day Step G. Recommended The total heat capacity is the Temperature Swing Maximum Temperature Swing sum of the heat capacity from The clear winter day The comfort performance target '\ Steps A, B and C. This temperature swing is calculated for all locations is 13°F. If the ) represents the effective heat in Step F. The projected area of comfort performance level capacity of all thermal mass all direct gain glazing is entered calculated in Step F had been within the building. in the first row. This includes greater than 13°F, additional all direct gain systems either thermal mass should be added Step E. Total Heat Capacity with or without night insulation. to the building or direct gain per Square Foot In the second row, the projected glazing should be reduced. The total heat capacity area of sunspace glazing and calculated in Step D is divided Trombe walls vented to the by the total floor area of the indoors is entered. Unvented building to get the total heat Trombe walls and water walls capacity per square foot. The are not included in this floor area used in this calculation since solar gain from calculation should not include these systems does not the sunspace or other contribute to the temperature unconditioned spaces. This swing of the conditioned space. value is calculated here for The appropriate comfort convenience, but it is not used factor is entered in the second until Worksheet IV is completed. column, selected from Table I. ,(he projected areas are multiplied by the appropriate comfort factors and summed. '\ This sum is then divided by the ! total heat capacity from Step D to yield the clear winter day temperature Swing.

Table I-Comfort Fact~rBtu/sf) Direct Gain Suns paces and 99 Vented Trombe Walls

)

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 77

Worksheet IV: Summer Coolin Performance Level A. Opaque Surfaces '\ Radiant Barrier Absorp- Heat Gain j Heat Loss Factor tance Factor Description [Worksheet I] [Table J] [Table K] [table L] Load

Q!2i1iDg:!lrQQf:! ~Q X j QQ X Q!lZ X !lZQ = !2!2~ lZ X j QQ X Q!I:Z X !lZQ = ~Z!2 X X X = W§II:! !lQ X na QZQ X 2!2~ = Z~!2 X na X = OQQ[:! ~fi X na Q~Q X 2!2~ = 2a jaQ~ kBtu/yr Total B. Non-solar Glazing Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load

t!/Q[tb !:al~:!:! !lQ X 0.80 X Q!2Z X ~ZQ = ~~fi X 0.80 X X = ESI:!t !:a lSi:!:! !2 X 0.80 X QaQ X !2a ~ = ~~j X 0.80 X X = W!2:!t!:aI~:!:! !2 X 0.80 X QaQ X Z~2 = ~fij X 0.80 X X = Slsllligbt:! X 0.80 X X = X 0.80 X X = j!2ZZ kBtu/yr Total C. Solar Glazing Solar System Rough Frame Net Area Shade Factor Heat Gain \ Description Area Factor [Table M] Factor [Table L] Load ) Oi[!2Qt !:a~iD aa X 0.80 X Qa~ X fifiQ = ~2g X 0.80 X X = StQ[~g!2 llll~lI~ X 0.80 X X X 0.80 X X = S!.ID:!J2~Q!2 2Qa X 0.80 X Qa~ X j22 = j!2afi X 0.80 X X = !la~~ kBtu/yr Total D. Internal Gain

22fiQ +( ~!lQ X ~ = fiQZQ kBtu/yr Constant Variable Number of Component Component Bedrooms [Table N] [Table N] E. Cooling Load per Square Foot

1,000 X j~ !I!I~ + jfiQ!I a~!l2 Btu/yr-sf (A+B+C+D) Floor Area F. Adjustment for Thermal Mass and Ventilation No night vent with no ceiling fan Z~!2 Btu/yr-sf [Table 0] G. Cooling Performance Level a2Q!2 Btu/yr-sf (E -F) H. Comparison Cooling Performance (From Previous Calculation or from Table P) 9Z!2!2 Btu/yr-sf Com are Line G to Line H

Anytown, USA 78 SUMMER COOLING PERFORMANCE LEVEL

Worksheet IV: Table J-Radiant Barrier Factors The heat loss from each of Radiant Barrier Summer Cooling No Radiant Barrier .0 these elements is carried over Performance Level from Worksheet I. Note that the Worksheet IV is used to Table K-Solar Absorptances door heat loss is reduced by half . Color Absorptance calculate the summer cooling Gloss White since one of the two doors does performance level. This is the Semi-gloss White not receive sunlight. The Light Green heat that would need to be Kelly Green I proposed building does not have Medium Blue 0.51 removed from the bUilding by an Medium Yellow 0.57 a radiant barrier in the attic, so Medium Orange 0.5B air conditioner in order to Medium Green 0.59 the radiant barrier factor is 1.00. maintain comfort during the Light Buff Brick 0.60 Absorptances are selected based Bare Concrete summer. Red Brick on the exterior building colors Medium Red ~ The worksheet accounts for Medium Brown 0.B4 and the heat gain factors are Dark Blue-Grey O.BB four sources of cooling load: Dark Brown O.BB from Table L. opaque surfaces exposed to the sun, non-solar windows, passive Step B. Non-solar Glazing solar systems, and internal gain. Ceiling/roofs Cooling load associated with the Walls and Doors These loads are then adjusted to North Glass windows that do not face south, East Glass account for ventilation and West Glass i.e. those that are not part of one Skylights of the solar systems, is thermal mass .. Direct Gain Glazing Trombe Walls and calculated by multiplying the Water Walls Step A. Opaque Surfaces Sunspaces surface area in each orientation SSAl 39.3 Not all opaque surfaces SSBl times the net area factor, a contribute to the cooling load of SSCl .~ shade factor (from Table M) and SSDl the building: only those surfaces SSEl 39.3 a heat gain factor (from Table L). exposed to sunlight In the example building, four This calculation gives the (ceilings/roofs and walls) are lines of the table are completed, annual cooling load for each ) included in the calculation. For two for the ceiling/roof types, non-solar glazed surface. The each ceiling and wall surface one for the exterior walls with total for the building is the sum listed on Worksheet I and brick veneer and one for the of the cooling load for each exposed to the sun, the heat entrance door. The wall that surface. loss should be carried over to separates the house from the Table M-Shading Factors this worksheet along with a garage and the door in this wall Projection consistent description. This are not included, since they are Factor South st North 21 0.00 ~ . 1.00 . heat loss is then multiplied by a not exposed to sunlight. 0.20 . .93 ~ .93 . 4I1o,~ 0.40 . 3 ~0.B1 O.Bl • 1 9' c;1JC7 radiant barrier factor when 0.60 0.49 0.71 0.7 '67 0.6B O.BO 0.35 0.60 0.6f 0.56 appropriate (from Table J), the 1.00 0.30 0.50 0.54 0.45 absorptance (from Table K) and 1.20 0.24 0.40 0.46 0.3B a heat gain factor (from Table L). -... Multiply by O.B for low-e glass, 0.7 for tinted glass and 0.6 for low-e tinted Qlass. The end product of this The rough frame area is calculation is an estimate of the generally entered in the table annual cooling load that is and adjusted by the net area associated with each suIface in factor. If the net glazing area is thousands of Btu per year entered instead, then the net (kBtu/yr). area factor is 1.00.

Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 79

Table M gives the shade If the example building had Step C. Solar Glazing factor for overhangs. The tinted glazing. glazing films or The solar systems addressed on overhang shade factor depends external shading devices. the Worksheet II reduce heating on the orientation of the window shade factors from Table M energy. but they also can and the projection factor. The should not be used. Sunscreen increase cooling energy. The proj ection factor is the overhang and glass manufacturers cooling energy impact of the projection divided by the usually rate the shading effect of solar systems is calculated in distance from the bottom of the their devices by publishing a this step. Each solar system window to the bottom of the shading coefficient. The listed on Worksheet II should be overhang. as illustrated below. shading coefficient is a number carried over to this worksheet. between zero and one that The cooling energy for each A indicates how much solar heat system is calculated by makes it through the window multiplying the total surface compared to an unshaded 1/8 area (not the projected area) inch clear pane. This shading times the net area factor. the coefficient may be used in the appropriate shade factor (as calculation instead of the value discussed above) and a heat from Table M. gain factor (from Table L). This The overhang on the east calculation gives the annual and west is at the eave. well cooling load for each passive above the window. and does not solar system. Overhang Projection Factor provide any useful shading. For A shade factor of 0.83 is The projection factor is the overhang projection divided by the distance between the these windows. the shade factor used because of south bottom of the window and the bottom of the is 1.00. overhangs. This is based on a overhang. Each glazing area is projection factor of about 0.2 as \ The north windows have a multiplied by the net area factor discussed above. height of four feet and the and the appropriate shade The annual cooling load bottom of the overhang is about factor. The products are associated with all the passive six inches above the window summed at the bottom of the solar systems is summed at the head. The overhang projection table. bottom of the table. is 1.5 feet. The projection factor is calculated by dividing the overhang projection by the distance from the bottom of the window to the bottom of the overhang. This is about 0.33. A shade factor of 0.84 is used in the calculations. which is interpolated between the values for a projection factor of 0.2 and 0.4

Anytown, USA 80 SUMMER COOLING PERFORMANCE LEVEL

Step D. Internal Gains Step F. Adjustment for Step G. Cooling The last component of cooling Thermal Mass and Ventilation Performance Level load is from internal gain. The total cooling load calculated The summer cooling \ Internal gain is heat given off by in Step E is adjusted in this step performance level is calculated' ) lights, appliances and people. to account for the effects of by subtracting the adjustment Some of the cooling load thermal mass and ventilation. in Step F from the cooling load associated with internal gain is The adjustment depends on per square foot calculated in considered to be constant for all the total heat capacity per Step E. This is an estimate of houses regardless of the number square foot calculated on the amount of heat that must be of bedrooms or size. This is Worksheet III, Step E, but also removed from the building each because all houses have a depends on whether or not the year by the air conditioner. refrigerator and at least one building has night ventilation or occupant. Another component ceiling fans. The adjustment is Step H. Comparison Cooling of cooling load from internal entered in the blank in Step F. Performance gain is considered to be variable The cooling performance level Table 0-Thermal Mass and Ventilation for the proposed design may be and depends on the number of Adjustment (Btu/yr-sf) bedrooms. These components Total Heat Night Night No Night No Night compared to the base case Capacity Vent wI Vent wI No Vent wI Vent wI N are accounted for separately in per SF Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan cooling performance level for the 0.0 4,250 400 2,320 -1,600 the calculation. 1.0 5,550 1,480 3,620 -520 area, given in Table P. 2.0 6,240 2,080 4,310 080 Both the constant 3.0 6,610 2,420 4,680 410 component and the variable 6,800 2,600 4,8 600 . 6,910 2,700 ,0 700 component are taken from Table 6.0 6,960 2,760 5,0 760 dP. 6,990 2,790 , 60 790 N. The variable component is 8.0 7,010 2,810 5,080 810 Alternatively, the cooling 9.0 7,010 2,820 5,080 820 multiplied by the number of 10.0 7,020 2,820 5,090 820 performance level may be compared to other building bedrooms in the house and Total heat capacity per square foot is calculated on added to the constant Worksheet III Ste E. designs conSidered by the ) component to yield the total The example building has a builder to be typical of the area. cooling load from internal gain. total heat capacity per square In this case, the worksheets foot of 5.6. It has neither night would first be completed for the ventilation nor ceiling fans. typical design and the results of Constant Component Variable Component Night ventilation is a these calculations would be building operation strategy entered in Step H. Step E. Cooling Load per where windows are opened at If the cooling performance Square Foot night when the air is cooler. level of the proposed building This step sums the cooling load The cool night air allows heat to (Step G) is greater than the base associated with opaque escape from the thermal mass case or typical-design surfaces, non-solar glazing, elements in the building. The conservation performance level, passive solar systems and cooler thermal mass elements the designer should conSider internal gain (Steps A, B, C and help keep the building measures to reduce the cooling D). The sum is then divided by comfortable the following day performance leveL Such the floor area of the building when air temperatures rise. measures might include and multiplied by 1,000 to reducing non-solar glass, convert the cooling energy into providing additional shading or terms consistent with the base increasing thermal mass. case cooling performance.

Anytown, USA Passive Solar Design Strategies APPENDIX

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department of Energy PASSIVE SOLAR DESIGN STRATEGIES 81

Passive Solar: a whole building design Suntempering: an increase of south­ Glossary and construction techniques which help facing glass to about 7 percent of a total a building make use of solar energy by floor area. without additional thennal non-mechanical means. as opposed to mass beyond the "free" mass already in a active solar techniques which use typical house -- gypsum wall board. Auxiliary Heating System: a tenn for equipment such as roof-top collectors. framing. conventional furnishings and the system (gas. electric. oil. etc.) which floor coverings. provides the non-solar portion of the house's heating energy needs. referred to Phase-Change Materials: materials such as the "auxiliuy heat." as salts or waxes which store and release Temperature SWing: a measure of the energy by changing "phase". Most store number of degrees the temperature in a energy when they turn liqUid at a certain space will vary during the course of a British Thermal Unit (Btu): a unit used temperature and release energy when sunny winter day without the furnace to measure heat. One Btu is about equal they turn solid at a certain temperature: operating; an indicator of the amount of to the heat released from burning one some remain solid but undergo chemical thermal mass in the passive solar kitchen match. changes which store and release energy. system. Phase change materials can be used as Conservation: in addition to energy thennal mass. but few products are Thermal Mass: material that stores conservation in the general sense. the commercially available at this time .. energy. although mass will also retain tenn is used to refer to the non-solar. coolness. The thennal storage capacity energy-saving measures in a house Purchased Energy: although the tenns of a material is a measure of the which are primarily involved with are often used interchangably. a house's material's ability to absorb and store improving the building envelope to guard "purchased energy" is generally greater heat. Thennal mass in passive solar against heat loss -- the insulation. and than its "auxiliuy heat" because heating buildings is usually dense material such air infiltration reduction measures. systems are seldom 1 00% efficient. and as brick or concrete masonry, but can more energy is purchased than is also be tile, water. phase change Direct Gain: a passive solar energy actually delivered to the house. materials. etc. system in which the sunlight falls directly into the space where it is stored R-Value: a unit that measures the Thermal Storage Wall: a passive llolar and used. resistance to heat flow through a given energy system also sometimes called material. The higher the R-value. the Trombe Wall or indirect gain system; a Glazing: often used interchangeably with better insulating capability the material south-facing glazed wall. usually made of window or glass. the tenn actually refers has. The R-value is the reciprocal of the masonry but can also be made of to specifically just to the clear material U-factor. containers of water. which admits sunlight. and so can also be plastic. Double and triple glazing Radiant Barrier: reflective material used Trombe Wall: a thennal storage wall. refer to two or three panes. in hot climates to block radiant heat. referred to by the name of its inventor, particularly in a house's roof. Dr. Felix Trombe. Indirect Gain: a passive solar system in which the sunlight falls onto thennal Shading Coefficient: a measure of how U-Factor: a unit representing the heat mass which is positioned between the much solar heat will be transmitted by a loss per square foot of surface area per glazing and the space to be heated. i.e. a glazing material. as compared to a single degree OF of temperature difference (see Thennal Storage Wall or Trombe Wall. pane of clear uncoated glass. which has R-value above). a shading coefficient (SC) of 1. For LoW-Emissivity: the tenn refers to a example. clear double-pane glass might surface's ability to absorb and re-radiate have an SC in the range of .88. heat. A material with a low emissivity Reflective glass might have SC's of .03- absorbs and re-radiates relatively small .06. In general. lower shading amounts of heat. Low-emissivity or "low­ coefficients are desirable when heat gain e" glass sandwiches a thin layer of is a problem. metallic film or coating between two panes of glass. The low-e glass blocks Sunspace: passive solar energy system radiant heat. so it will tend to keep heat sometimes also referred to as an isolated energy inside the house during the gain system. where sunlight is collected winter. and keep heat energy outside the and stored in a space separate from the house during the summer. living space. and must be transferred there either by natural convection or by fans.

Boise, Idaho 82 SUMMARY FOR BOIS£, IDAHO Example Tables

Examples of Heat Energy Savings Examples of Heat Energy Savings Added Insulation Passive Solar-Direct Gain 1 ,500 sf Single Story House 1,500 sf Single Story House Base Base Case 20% 40% 60% Case 20% 40% 60% R-values R-values 35 63 Ceiling/Roof 29 44 Ceiling/Roof 29 32 39 50 40 Walls 17 21 27 Walls 17 19 24 31 18 Basement Wall 5 7 10 Basement Wall 5 6 9 12 1.8 3.3 Glass 1.8 2.7 Glass 1.8 1.8 1.8 2.7 0.40 0.40 0.36 ·Air ChangesJHour 0.50 Air ChangesJHour 0.50 0.47 0.37 0.36

Glass Area (percent of total floor area) Glass Area (percent of total floor area) 3.0% 2.0% 2.0% 2.0% West West 3.0% 2.0% 2.0% 2.0% 4.0% 4.0% 4.0% North 3.0% North 3.0% 4.0% 4.0% 4.0% 4.0% 4.0% East 3.0% 4.0% East 3.0% 4.0% 4.0% 4.0% 3.0% 3.0% South 3.0% 3.0% South 3.0% 7.4% 9.3% 12.0%

Percent Solar Savings Added Thermal Mass 9% 15% 7% 11% Percent of Floor Area 0.0% 2.7% 13.6% 30.0%

Performance (Btu/yr-sf) Solar System Size (square feet) Conservation 43,637 36,660 28,408 20,040 South Glass 45 111 139 180 Auxiliary Heat 40,523 33,178 25,062 16,940 Added Thermal Mass 0 40 204 450 Coolinq 9580 1737 1097 0 Percent Solar Savings 7% 18% 25% 36%

Performance (Btu/yr-sf) Conservation 43,637 40,671 33,593 26,494 Auxiliary Heat 40,523 33,156 25,019 16,861 Examples of Heat Energy Savings Cooling 9,580 1,401 538 0 Suntempered 1,500 sf Single Story House Summary: Insulation and tightness have been increased. South­ facing glazing has been substantially increased. For these Base examples, added mass area is assumed to be six times the added Case 20% 40% 60% south glass area. R-Values Ceiling/Roof 29 32 39 55 Walls 17 19 23 35 Basement Wall 5 6 7 14 Glass 1.8 1.8 1.8 2.7

Air ChangesIHour 0.50 0.44 0.36 0.36

Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South 3.0% 6.7% 6.7% 6.7%

Solar System Size (square feet) South Glass 45 100 100 100

Percent Solar Savings 7% 17% 20% 26%

Performance (Btu/Yr-sf) Conservation 43,637 40,004 31,580 22,931 Auxiliary Heat 40,523 33,158 25,029 16,902 Cooling 9,580 1,437 676 0

Summary: Insulation values and tightness of the house (as measured in ACH) have been increased. The window area has been slightly decreased on the west, increased slightly o~ the east and north, and increased significantly on the south.

Boise, Idaho 84 TECHNICAL BASIS Annual Heat Loss Central Ave. Unit B-l, Boulder, CO Technical Basis for 80301. (Worksheet 1) the Builder 2. J. Douglas Balcomb. Robert W. Jones, The heat-loss calculation is based on a Robert D. McFarland, and William O. Guidelines straightforward summation of the Wray, Passive Solar Heating Analysis, traditional elements that make up the American Society of Heating. building heat-loss coefficient (excluding Refrigerating, and Air-Conditioning the solar components). The worksheet Engineers, 1984. Available from How the Builder procedure estimates the annual heat loss ASHRAE, 1719 Tullie Circle, NE, Atlanta, Guidelines Were by multiplying the heat-loss coefficient GA 30329. Produced by annual degree days (times 24 to convert from days to hours). Degree days 3. J. Douglas Balcomb and William O. for each month were determined using Wray, Passive Solar Heating Analysis. The text of the Builder Guidelines book is an appropriate base temperature that Supplement One. Thermal Mass Effects generated by merging two computer files. accounts for an assumed thermostat and Additional SLR Correlations, The first is a word-processor file setting of 70 degrees, an assumed American Society of Heating, containing the text; it does not change internal heat generation of 36 Btu/ day Refrigerating. and Air-Conditioning from location to location. The second per sq ft of floor area. and the total Engineers, 1987. See ASHRAE address contains numbers and text and is building loss coefficient. This forms the above. location dependent. This second file is basis of the table of heating degree day produced by running a computer multipliers. The result of the worksheet program that calculates performance is an estimate of the annual heat Temperature Swing numbers based on long-term monthly required to maintain comfort. excluding III) weather and solar data compiled by the both positive and negative effects (Worksheet National Oceanic and AtmospheriC resulting from the solar components. In Administration for a particular location. this estimate. no solar heating credit is The temperature,swing estimate on The merge operation slots the numbers given to east. west, and north windows. worksheet III is based on the diurnal and text in the second file into their because it is assumed that these will be heat capacity (dhc) method (reference 3). correct locations in the first file. This is protected by vegetation or other shading The method is an analytic procedure in then laser printed to produce the in accordance with the Builder Guideline which the total heat stored in the camera-ready manuscript. recommendations. This is a conservative building during one day is estimated by assumption because there will always be summing the effective heat storage some solar gain through these windows. potential of the all the various materials More than a Decade of in the building for a 24-hour periodic Experience cycle of solar input. Rooms with direct Annual Auxiliary Heat gain are assumed to have radiative (Worksheet II) coupling of the solar heat to the mass. The concentrated effort of research, Rooms connected to rooms with direct design, construction, monitoring, and gain are assumed to have convective The tables of passive solar savings evaluation of actual buildings that coupling. which is rather less effective, started at the First Passive Solar fractions are calculated using the solar especially for massive elements. The dhc Conference in Albuquerque in 1976 has load ratio (SLR) method (references 1 and of the sheetrock, framing, and, continued up to the present. It is 2). Monthly solar savings fraction (SSF) estimated that more than 200,000 values are determined using correlation is approximated as 4.5 or 4.7 Btu/OF per passive solar homes have been built in fits to the results of hourly computer sq ft of floor area. Worksheet Tables HI the United States during this time. This simulation calculations for a variety of and H2 list the increased value of diurnal wealth of experience has been reviewed climates. These 12 values are converted heat capacity for various conventional by NREL. the Technical Committee of into an annual value and entered into materials that are often used to provide PSIC. and by the Standing Committee on worksheet Tables Fl-F4. The SLR method extra heat storage, assuming these Energy of the National Association of gives answers that agree within about materials replace sheetrock. Home Builders and is distilled into these 5% of the hourly computer simulations Guidelines. and within 11 % of the measured passive solar performance of 55 buildings monitored under the Solar Buildings Analysis Procedures Program. The SSF estimates account properly for both solar gains and heat The analysis procedures used throughout losses through the solar aperture and. the Guidelines were developed using thus. correct for omitting the solar simple, well-established methods for components from the calculation of estimating the performance of passive annual heat loss. solar heating and natural cooling strategies. These procedures (described 1. J. Douglas Balcomb. Robert W. Jones. below) were developed at the Los Alamos Robert D. McFarland, and William O. National Laboratory with funding from Wray. "Expanding the SLR Method". the U.S. Department of Energy Solar Passive Solar Journal. Vol. 1. No.2. Buildings Program. See the references for 1982. pp. 67-90. Available from the more information. American Solar Energy Society. 2400

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 83

Examples of Heat Energy Savings Examples of Heat Energy Savings Passive Solar-Sunspace Passive Solar-Thermal Storage Wall 1,500 sf Single Story House 1,500 sf Single Story House

Base Base Case 20% 40% 60% Case 20% 40% 60% R-Values R-Values Ceiling/Roof 29 28 34 43 Ceiling/Roof 29 29 34 42 Walls 17 16 20 26 Walls 17 17 20 26 Basement Wall 5 4 6 9 Basement Wall 5 5 6 10 Glass 1.8 1.8 1.8 2.7 Glass 1.8 1.8 1.8 1.8

Air Changes/Hour 0.50 0.45 0.35 0.38 Air Changes/Hour 0.50 0.48 0.38 0.37

Glass Area (percent of total floor area) Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South (windows) 3.0% 3.0% 3.0% 3.0% South 3.0% 3.0% 3.0% 3.0% Sunspace 0.0% 6.7% 9.2% 13.0% Thermal Storage Wall 0.0% 6.6% 10.9% 17.0%

Solar System Size (square feet) Solar System Size (square feet) South Glass 45 45 45 45 South Glass 45 45 45 45 Sunspace Glass 0 100 137 195 Thermal Storage Wall 0 98 163 255 Sunspace Thermal Mass 0 300 413 586 Percent Solar Savings Percent Solar Savings 7% 23% 35% 49% 7% 26% 33% 44% Performance (Btu/yr-sf) Performance (Btu/yr-sf) Conservation 43,637 43,491 38,515 33,162 Conservation 43,637 44,807 37,729 30,262 Auxiliary Heat 40,523 33,145 24,986 16,790 Auxiliary Heat 40,523 33,107 24,958 16,781 Cooling 9,580 1,893 1,057 0 Cooling 9,580 3,821 3,638 2,635 Summary: In the case of a Thermal Storage Wall, south-facing Summary: Insulation (for the 40 and 60% savings) and tightness glazing and thermal mass are incorporated together. The estimates have been increased. North and east-facing glazing have been here assume a 12-inch thick concrete Thermal Storage Wall with a increased slightly. The sunspace assumed here is semi-enclosed selective surface and single glazing. (surrounded on three sides by conditioned rooms of the house, as in Figure SSCl of the worksheets), with vertical south glazing. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double.

Cooling Potential

Basecase 9,580 Btu/yr-sf

Energy Savings Percent Strategy (Btu/yr-sf) Savings

No Night Ventilation 1 without ceiling fans 0 0% with ceiling fans 2,640 28

Night Ventilation 1 without ceiling fans 2,140 22 with ceiling fans 4,220 44

High Mass2 without ceiling fans 680 7 with ceiling fans 500 5

1 With night ventilation, the house is ventilated at night when temperature and humidity conditions are favorable.

2A "high mass" buildingls one with a thermal mass area at least eaual to the house floor area.

Boise, Idaho PASSIVE SOLAR DESIGN STRATEGIES 85 The only numbers in worksheet III temperature is less than 62 OF. This Getting Data that are location dependent are the restriction avoids ventilation when high comfort factors. taken from Table I. The hUmidity might cause discomfort Heating and cooling degree-day data can direct-gain comfort factor is 61 % of the be obtained from the National Climatic solar gain transmitted through vertical. 4. Robert D. McFarland and Gloria Center. Asheville. NC. Refer to south-facing double glazing on a clear Lazarus. Monthly Auxiliary Cooling Climatography of the United States No. January day. The driving effect of Estimation for Residential Buildings. 81 which lists monthly normals for the sunspaces and vented Trombe walls is lA-11394-MS. Los Alamos National period 1951-1980 on a state-by-state assumed to result in one-third this value. Laboratory. NM 87545. 1989. basis. More than 2400 locations are based on data from monitored buildings. listed in this data base. The origin of the 61 % factor is described in the references. Notfor Sizing Equipment

Annual Auxiliary Cooling All heating and cooling values given in the Builder Guidelines Tables and (Worksheet IV) numbers calculated using the worksheets are for annual heat delivered or removed The purpose of including the summer by the mechanical heating or cooling cooling estimates in the Builder system. You cannot directly use these Guidelines is to (1) determine if design numbers for sizing the capacity of this elements added to promote passive solar equipment. The methods developed by heating will cause excessive summer the American Society of Heating. cooling loads and (2) provide a rough Refrigerating. and Air Conditioning estimate of the effectiveness of solar Engineers for sizing equipment are well­ shading and natural cooling strategies. established and are recommended. The The analysis method is based on a purpose of the guidance provided in modified monthly degree-day procedure these booklets is to minimize the in which the day is divided into day and operating time and resources consumed night periods (reference 4). All estimates by this equipment. are derived from correlations based on hourly computer simulations. Solar. conduction. and internal gains are Using the Worksheets in estimated for each half-day period in Nearby Locations each month. Delay factors are used to account for heat carryover from day to The applicability of worksheets I and II night and night to day. The results are can be extended somewhat by using the estimates of annual sensible cooling base-65 OF degree-day value for a site delivered by the air conditioner and do which is close to the location for which not include latent loads. the worksheet tables were generated. We Because the the original Los Alamos recommend limiting such applications to monthly procedure is too complex to be sites where the annual heating degree­ implemented in a worksheet. a Simplified days are within plus or minus 10% of the procedure is adopted on worksheet N. parent location and where it is Heat Gain Factors and Internal Gain reasonable to assume that the solar Factors in Tables L and N are the radiation is about the same as in the calculated annual incremental cooling parent location. The procedure is simple: loads resulting from a one-unit incremental change in the respective Use the measured base-65 OF degree-day heat input parameter (that is. a one-unit value in worksheet I. line F. instead of change in UA, glazing area. or number of the degree-day value for the parent bedrooms). The combined heat load location. resulting from all inputs is summed and Worksheet III depends only slightly then adjusted for thermal mass and on location. The only variables are the ventilation. This correction includes a Comfort Factors in Table I. which only constant required to match the change with latitude. Thus. this calculated cooling load of the base-case worksheet can be used anywhere within bUilding. This linearized procedure gives 4 degrees oflatitude of the parent accurate estimates for cooling loads that location. are less than about 150% of the base­ The cooling estimate obtained from case building: however. it underestimates worksheet N is specific to the location. very large cooling loads in poorly Within the same vicinity and within plus designed buildings. or minus 20%. the result could be The adjustment factors for adjusted. based on a ratio of cooling ventilation properly account for degree days. However. this adjustment is maintaining comfort in hot and humid not done automatically within the climates. Ventilation is restricted to worksheet. times when the outside dew-point

Boise, Idaho