Passive Solar Design Strategies: Guidelines for Horne

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

Jackson, Mississippi

Passive Solar Industries 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. PA:;):;)/VI= :;)ULAH UI=:;)/GN :;) / HA II=WI=:;) r..;UN I cN I ::;

Guidelines

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

Part Two. Basics of Passive Solar ...... 7 .1. Why Passive Solar? More than a Question of Energy...... 8 2. Key Concepts: Energy Conservation, Suntempertng, Passive Solar ...... 9 3. Improving Conservation Perfonnance...... 10 4. Mechanical Systems...... 13 5. South-Facing Glass ...... ,14 6. Thennal 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 Three. Strategies for Improving Energy Performance in Jackson, Mississippi...... 21 l. The Example Tables...... 22 2. Suntempertng ...... 23 3. Direct Gain ...... ' ...... 24 4. Sunspaces,...... 27 5. Thennal 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 Filled in Worksheets ...... 51 Annotated Worksheet Tables...... 56 "Any'fown", USA •..•..•.....•...... 59

Appendix

Glossary of Tenns...... 81 References...... 82 Summary Tables...... 84 Technical Basis for the Builder Guidelines...... 87

JackBon, MiBBiBBippi PASSIVE SOLAR DESIGN STRATEGIES

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

Jackson, Mississippi 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

Jackson, Mississippi 2 GUIDELINES PART ONE: INTRODUCTION

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

Jackson, Mississippi 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 help for seven different regions. The opportunities at the specific site. offset air-conditioning needs. Base Case used for Jackson. So, many fundamental aspects The Example Tables in Part Mississippi is from the 1,000- of passive solar design will Three are also related to 2,500 heating degree days depend on the conditions in a Worksheet numbers. so that you region. The construction small local area, and even on the can compare them to the is assumed to be slab-on-grade, features of the building site. designs you are evaluating. For because this is typical in Many of the suggestions in this example. the Passive Solar Mississippi. section apply specifically to Sunspace Example Case which The examples show how to Jackson, Mississippi. but there uses 40% less energy than the achieve 20%, 40% and 600A> is also information which will be Base Case House (page 29) has: energy-\.lse reductions using useful in any climate. • A ConseIVation Performance three basic strategies: Part One introduces Passive Level of apprOximately 23,479 • Added Insulation: Solar Design Strategies, and Btu/yr-sf. Increasing thermal resistance presents the performance • An Auxiliary Heat insulation levels without adding potential of several different Performance Level of solar features. passive solar systems in the approximately 15,073 Btu/yr-sf, • Suntemperlng: Increasing Jackson climate. Although in and south-faCing glazing to a practice many factors will affect • A Summer Cooling maximum of 7% of the house's actual energy performance. this Performance Level of 14,439 total floor area. without adding information gives a general idea Btu/yr-sf. thermal mass (energy storage) of how various systems might In this example. the energy beyond what is already in the perform in Jackson. savings are achieved by framing, standard floor Part Two discusses the basic increasing insulation about 7% coverings and gypsum wall­ concepts of passive solar design over the Base Case House, board and surfaces. and construction: what the adding a sunspace with south Suntempertng is combined with advantages of passive solar are. glazing area equal to 11% of the increased levels of thermal how passive solar relates to house's floor area. and using a reSistance insulation. other kinds of energy ceiling fan to cut some of the air conseIVation measures. how the conditioning load. primary passive solar systems A Base Case House is work, and what the builder's compared with a series of most important considerations example cases to illustrate should be when evaluating and exactly how these increased using different passive solar levels of energy-effiCiency might strategies. be achieved.

Jackson, Mississippi 4 GUIDELINES PART ONE: INTRODUCTION

• Solar : Using The Worksheets from the Solar System Savings three different design The Worksheets are specifically Fraction table or from the Heat approaches: Direct Gain, tailored for Jackson, Mississippi, Gain Factor table. Sunspace, and Thermal Storage and are a very important part of The Worksheets allow Wall, with increased levels of this package because they allow calculation of the follOWing thermal resistance insulation. you to compare different passive performance indicators: For all strategies, the energy solar strategies or combinations • Worksheet I: Conservation savings indicated are based on of strategies, and the effect that Performance Level: Determines the assumption that the energy­ changes will have on the overall how well the house's basic efficient design and construction performance of the house. energy conservation measures gUidelines have been followed, so The most effective way to use (insulation, sealing, caulking, the are properly sited the Worksheets is to make etc.) are working to prevent and tightly built with high­ multiple copies before you fill unwanted heat loss or gains. quality and . them out the first time. You can The bottom line of this The Guidelines section has then use the Worksheets to Worksheet is a number been kept as brief and calculate several different measuring heat loss in British straightforward as possible, but designs. For instance, you could thermal units per square foot more detailed information is first calculate the performance of per year (Btu/ sf-yr) - the lower available if needed. Some the basic house you build now, the heat loss, the better. references are indicated in the then fill out Worksheets for that • Worksheet U: AuxlUary text, and a list of other house with a variety of energy Heat Performance Level: information sources can be performance strategies such as Determines how much heat has found in the References. Also increased insulation, to be supplied (that is, provided included at the end of this book suntempering and specific by the heating system) after are a brief glossary: a summary passive solar components. taking into account the heat of the Example Tables for The Worksheets provide a contributed by passive solar. Jackson, MisSissippi, and the way to calculate quickly and This worksheet arrives at a Technical Basis for the Builder with reasonable accuracy how number estimating the amount Guidelines which explains the well a design is likely to perform of heating energy the house's background and assumptions in four key ways: how well it will non-solar heating system has to behind the Guidelines and conserve heat energy: how much provide in Btu/yr-sf. Again, the Worksheets. the solar features will contribute lower the value, the better. to its total heating energy needs: • Worksheet m: Thermal how comfortable the house will Mass/Comfort: Determines be: and how much the annual whether the house has adequate cooling load (need for air thermal mass to assure comfort conditioning) will be. and good thermal performance. The Worksheets are Worksheet III calculates the supported by "look-up" tables number of degrees the containing pre-calculated temperature inside the house is numbers for the local area. likely to vary, or "swing", during Some of the blanks in the a sunny winter day without the Worksheets call for information heating system operating. A about the house - for example, well-designed house should have floor area and proJected area of a temperature swing of no more passive solar glazing. Other than 13 degrees, and the less blanks require a number from the better. one of the tables - for example,

JacksOD, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 5

• Worksheet IV: Summer 2. Passive Solar glass, and each passive solar Cooling Performance Level: Performance system has 145 sf. Indicates how much air The energy savings conditioning the house will need Potential presented in this example in the summer (It is riot, assume that all the systems are however, intended for use in The energy performance of designed and built according to sizing equipment, but as an passive solar strategies varies the suggestions in these indication of the reductions in significantly, depending on Guidelines. It's also important annual cooling load made climate, the specific design of to remember that the figures possible by the use of natural the system, and the way it is below are for annual net heating cooling). The natural cooling built and operated. Of course, benefits. The natural cooling guidelines should make the energy performance is not the section in Part Three gives house's total cooling load - the only consideration. A system advice about shading and other bottom line of this Worksheet, in which will give excellent energy techniques which would make Btu/yr-sf - smaller than in a performance may not be as sure the winter heating benefits "conventional" house. The lower marketable in your area or as are not at the expense of higher the cooling performance level, easily adaptable to your designs summer cooling loads. the better the design. as a system which saves less Please note that throughout So, the Worksheets provide energy but fits other needs. the Guidelines and Worksheets four key numbers indicating the In the following table, several the glazing areas given are for projected performance of the different passive solar systems the actual net area of the glass various designs you are are presented along with two itself. A common rule of thumb evaluating. numbers which indicate their is that the net glass area is 80 • The Worked Example: To performance. The Percent Solar percent.ofthe rough frame assist in understanding how the Savings is a measure of how opening. For example, if a south design strategies outlined in the much the passive solar system is glass area of 100 sf is desired, Guidelines affect the overall reducing the need for purchased the required area of the rough performance of a house, a energy. For example, the frame opening would be about worked example is included. Percent Solar Savings for the 125 sf. The example house is assumed Base Case House is 9.6%, to be constructed of materials because even in a non-solar and design elements typical of house, the south-facing windows the area. Various design are contributing some heat features, such as direct gain 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 slab floor. 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.

Jackson, Mississippi 6 GUIDELINES PART ONE: INTRODUCTION

Perfonnance Potential of Passive Solar Strategies In Jackson, Mississippi 1,500 sf, Single Story House Yield Percent Btu Saved per Solar Square Foot of Case Savings South Glass

Base Case 9.6 not applicable (45 sf of south-facing double glass) Suntempered 18.3 58,909 (100 sf of south-facing double glass)

Direct Gain (145 sf of south glass) Double Glass 24.2 54,531 Triple or low-e glass 25.3 60,925 Double glass with R-4 night insulation 1 27.6 70,703 Double glass with R-9 night insulation 1 28.3 73,831

Sunspace (145 sf of south glass) Attached with opaque end walls2 23.6 55,276 Attached with glazed end walls2 23.0 52,711 Semi-enclosed with vertical glazing3 24.6 57,367 Semi-enclosed with 50· sloped glazing3 29.8 79,771

Thennal Storage Wall- Masonry/Concrete (145 sf of south glass) Black surface, double glazing 22.6 50,429 Selective surface, single glazing 28.5 74,690 Selective surface, double glazing 27.6 71,354

Thennal Storage Wall - Water Wall (145 sf of south glass) Selective surface, single glazing 32.3 89,637

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.)

Jackson, Mississippi 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. Solar Architecture

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

Jackson, Mississippi 8 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR

1. Why Passive Solar? insulation is inviSible to the They just present their houses More than a Question prospective home buyer. A as the state of the art in energy­ sunny. open living area lit by effiCiency and style. and they of Energy south-faCing windows. on the use passive solar as a part of the other hand. may be a key selling package. Houses today are more energy­ point. Windows in general are The U.S. Department of efficient than ever before. popular with homebuyers. and Energy and the National Renew­ However. the vast majority of passive solar can make windows able Energy Laboratory (NREL) new houses still ignore a lot of energy producers instead of conducted extensive national energy saving opportunities - energy liabilities. surveys of passive solar homes. opportunities available in the Another example: high- home owners and potential sunlight falling on the house. in efficiency heating eqUipment can buyers. Some key findings: the landscaping. breezes and account for significant energy • passive solar homes work other natural elements of the savings - but it won't be as - they generally require an site. and opportunities in the much fun on a winter morning average of about 300Al less structure and materials of the as breakfast in a bright. energy for heating than house itself. which. with attractive sunspace. "conventional" houses. with thoughtful design. could be used The point is not that a some houses saving much more. to collect and use free energy. buUder should choose passive • occupants of passive solar Passive solar (the name solar instead of other energy- homes are pleased with the distinguishes it from "active" or conserving measures. The performance of their homes (over mechanical solar technologies) is important thing is that passive 90% "very satisfied"). but they simply a way to take maximum solar strategies can add not only rank the comfort and pleasant advantage of these energy-efficiency. but also very living environment as just as opportunities. saleable amenities - style. important (in some regions. Home buyers are also comfort. attractive interiOrs. more important) to their increasingly sophisticated about curb appeal and resale value. satisfaction. and in their energy issues. although the In fact. in some local decision to buy the house. as average home buyer is probably markets. builders report that energy considerations. much more familiar with they don·t even make specific • passive solar home owners insulation than with passive reference to "passive solar". and lenders perceive the solar. The "energy crisis" may resale value of passive solar come and go. but very few people houses as high. perceive their own household Advantages of Passive Solar energy bills as getting smaller - quite the opposite. So a house • Energy perfonnance: Lower energy bills all year-round with significantly lower monthly • Attractive living environment: large windows and views, sunny energy costs year-round will interiors, open floor plans have a strong market advantage • Comfort: quiet (no operating noise), solid construction, warmer in over a comparable house down winter, cooler in summer (even during a power failure) the street. no matter what • Value: high owner satisfaction, high resale value international oU prices may be. • Low Maintenance: durable, reduced operation and repairs There are many different • Investment: independence from future rises in fuel costs, will continue ways to reduce energy bills. and to save money long after any initial costs have been recovered some are more marketable than • Environmental Concerns: clean, renewable energy to combat others. For instance. adding growing concerns over global warming, acid rain and insulation can markedly improve ozone depletion energy-efficiency - but added

Jackson. Mississippi PASSIVE SOLAR DESIGN STRATEGIES 9

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

JacksOD, Mississippi 10 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR

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

Jackson, Mississippi PASSIVE SOLAR DESIGN STRA TEGIES 11

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

JacksoD. Mississippi 12 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR

Non-Solar Glazing account for the glass. the frame. West windows may be the South-faCing windows are the air gap and any special (low­ most problematic. and there are considered solar glazing. The e) coatings. few shading systems that will be south windows in any house are North windows should be effective enough to offset the contributing some solar heat used with care. Sometimes potential for overheating from a energy to the house's heating views or the diffuse northern large west-faCing window. Glass needs - whether it's a light are desirable. but in with a low shading coeffiCient significant. usable amount or general north-faCing windows may be one effective approach - hardly worth measuring will should not be large. Very large for example. tinted glass or some depend on design. location and north-facing windows should types oflow-e glass which other factors which are dealt have high insulation value. or provide some shading while with later under the discussions R-value. Since north windows allOwing almost clear views. The of suntempering and passive receive relatively little direct sun cost of properly shading both solar systems. in sununer. they do not present east and west windows should North windows in almost much of a shading problem. So be balanced against the benefits. every climate lose significant if the choice were between an As many windows as heat energy and gain very little average-sized north-facing possible should be kept operable useful sunlight in the winter. window and an east or west­ for easy natural ventilation in East and west windows are likely facing window. north would summer. (See also Orientation. to increase air conditioning actually be a better chOice. page 16. Reconunended Non­ needs unless heat gain is considering both sununer and South Glass Guidelines. page minimized with careful attention winter perfonnance. 34. and Shading. page 35) to shading. East windows catch the But most of the reasons morning sun. Not enough to people want windows have very provide significant energy. but. little to do with energy. so the unfortunately. usually enough to best design will probably be a cause potential overheating good compromise between problems in summer. If the energy effiCiency and other views or other elements in the benefits. such as bright living house's design dictate east spaces and views. windows. shading should be Double-glazing of all non­ done with particular care. solar glazing is advisable. Low-e glazing on all non-solar windows may be an especially useful solution because some low-e coatings can insulate in winter and shield against unwanted heat gain in sununer. A chart is provided with the worksheets that gives typical window R-values for generic window types. When possible. however. manufacturer's data based on National Fenestration Rating Council procedures should be used. The R-values that result from procedures

Jackson. Mississippi PASSIVE SOLAR DESIGN STRATEGIES 13

4. Mechanical • Night Setback: Clock In the National AsSOCiation of Systems thermostats for automatic Home Builders' Energy-Efficient setback are usually very effective House Project, all the rooms The passive solar features in the - but in passive solar systems were fed with low, central air house and the mechanical with large amounts of thermal supplies, as opposed to the heating, ventilating and air mass (and thus a large capacity usual placement of registers conditioning systems (HVAC) will for storing energy and releasing under windows at the end of interact all year round, so the it during the night), setback of long runs. This resulted in good most effective approach will be the thermostat may not save comfort and energy performance. to design the system as an very much energy unless set The performance of even the integrated whole. HVAC design properly to account for the time most beautifully designed is, of course, a complex subject, lag effects resulting from the passive solar house can easily be but four areas are particularly thermal mass. undermined by details like worth noting in energy-efficient • Ducts: One area often uninsulated ducts, or by houses: neglected but of key importance overlooking other basic energy • System Sizing: Mechanical to the house's energy conservation measures. systems are often oversized for performance is the design and the relatively low heating loads location of the ducts. Both the in well-insulated passive solar supply and return ducts should houses. Oversized systems will be located within insulated cost more in the first place, and areas, or be well insulated if they will cycle on and off more often, run in cold areas of the house. wasting energy. The back-up All segments of ducts should be systems in passive solar houses sealed at the jOints. The joints should be sized to provide 100% where the ducts turn up into of the heating or cooling load on exterior walls or penetrate the the design day, but no larger. ceiling should be particularly Comparing estimates on system tight and sealed. sizes from more than one • System Efficiency: Heating contractor is probably a good system efficiency is rated by the idea. annual fuel utilization efficiency (AFUE). Cooling system efficiency is rated by the seasonal efficiency is rating (SEER). The higher the number, the better the performance.

JacksoD, Mississippi 14 GUIDELINES PART TWO: BASICS 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. Ordinazy vertical glazing is performance in summer will be For example, a passive solar easier to shade, less likely to compromised. The amount of system for a 1.500 sf house overheat, less susceptible to solar glazing must also be might combine 150 sf of direct damage and leaking, and so is carefully related to the amount gain glazing with 120 sf of almost always a better year­ of thermal mass. Suntempered sunspace glazing for a total of round solution. houses use no additional 270 sf of solar glazing, or 18% of thermal mass beyond that the total floor area, well within already in the wallboard, the direct gain limit of 12% and framing and furnishings of a the overall limit of 20%. For a typical house. Houses with design like this, thermal mass solar architecture must have would be required both in the additional thennal 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 window effectively in a house. The first area that should be operable to is a limit on the amount of allow for natural ventilation. glazing for suntempered houses, 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, regarcUess of how much additional thennal 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.

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

Jackson, Mississippi 16 GUIDELINES PART TWO: BASICS 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 perfonnance 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 perfonnance. also significantly increase, has good southern exposure it Glazing oriented to within 15 especially as the orientation goes wUl usually accommodate degrees of true south will west. The wanner the climate, sufficient glazing for an effective perfonn almost as well, and the more east- and west-facing passive solar system, provided orientations up to 30 degrees off glass will tend to cause the heat can be transferred to - although less effective - will overheating problems. In the northern zones of the house. stUl provide a substantial level of general, southeast orientations solar contribution. present less of a problem than In Jackson, magnetic north southwest. as indicated on the compass is actually 5 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.

JacksOD, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 17

8. Site Planning for also the figure on page 35 Solar Access showing landscaping for summer shade. ~~- The basic objective of site ...... •...... • ~ ..... planning for maximum energy performance is to allow the south side as much unshaded exposure as possible during the winter months...... ••. "...... ;...... -.~ .... ~. . As discussed above, a good Solsr Subdivision Layouts solar orientation is possible Solar access may be provided to the rear yard, the side yard or the of solar within a relatively large southern ~ 2 Story Buildings Allowed homes. arc, so the flexibility exists to

achieve a workable balance Idesl Solsr Access between energy performance and Buildings, trees or other obstructions should not be located so as to shade the south wall other important factors such as of solar buildings. At this latitude, A = 8 ft., B the slope of the site, the = 15ft.,andC=34ft. individual , the direction of prevailing breezes for Of course, not all lots are large summer cooling, the views, the enough to accommodate this street lay-out, and so on. kind of optimum solar access, so But planning for solar access it's 1mportant to carefully assess does place some restrictions shading patterns on smaller lots even on an individual site, and to make the best compromise. presents even more challenges Protecting solar access is when planning a complete easiest in subdivisions with subdivision. Over the years, streets that run within 25 developers and builders of many degrees of east-west, because all different kinds of projects all lots will either face or back up to over the countxy have come up south. Where the streets run Solsr Subdivision Layouts north- south, creation of east­ Short east-west cul-de-sacs tied into north­ with flexible ways to provide south collectors is a good street pattern for solar access. adequate solar access. west cul-de-sacs will help ensure Once again, there is an ideal solar access. Two excellent references for situation and then some degree ideas about subdivision lay-out of flexibility to address practical to protect solar access are concerns. Ideally, the glazing on Builder's Guide to Passive Solar the house should be exposed to Home Design and Land sunlight with no obstructions Development and Site Planning within an arc of 60 degrees on for Solar Access. 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 situation for providing unshaded southern exposure during the winter. See

Jackson, Mississippi 18 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR

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

Interior Space Planning Three. Uving and high activity spaces should be located on the south.

Jackson, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 19

Checklist for Good Design

r/ 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.

r/ 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.

r/ 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.

r/ 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 - but it's a fact of human nature that people like windows, and windows can be energy producers if located correctly.

r/ 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.

r/ 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.

r/ 7. Addition of thennal 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.

r/ 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 patterns and energy needs can save energy in other ways, too - for instance, using less-lived-in areas like storage rooms as buffers on the north side.

r/ 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.

JacksOD, Mississippi 20 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR

Jackson, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 21

Part Three: Strategies for Improving Energy Performance in Jackson, Mississippi

1. The Example Tables

2. Suntempering

3. Direct Gain

4. Sunspaces

o. Thermal Storage Wall

6. Combined Systems

7. Natural Cooling Guidelines

Jackson, Mississippi 22 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

1. The Example • Three numbers The R-values indicated in the corresponding to those on the Example tables are, of course, Tables Worksheets: Conservation, apprOximate and are intended to Auxillary Heat, and Cooling show how incremental In the following sections of the Performance improvements can be achieved. Guidelines, the primary passive The Example tables then show All R-values in the Examples solar energy systems - ~ow the house design could be and Worksheets are equivalent Suntempering, Direct Gain, changed to reduce winter R-values for the entire Thermal Storage Walls and heating energy by 20, 40 and construction assembly, not just Sunspaces - are described in 60%, compared to this Base for the cavity insulation itself, more detail. Case House. and take into account framing As part of the explanation of There are, of course, other and buffering effects. each system, an Example table . ways to achieve energy savings Other assumptions are noted is provided. The Examples than those shown in the for each Example. However, one present the following information Examples. The Examples are more general assumption is about a Base Case House, based designed to show an effective important to note here. When on a National Association of integration of strategies, and a the Examples were calculated, it Home Builders study of a typical useful approach to the design of was assumed that natural construction: the house as a total system. cooling strategies such as those • Insulation levels (ceilings Using any of these combinations described in these Guidelines and walls); would result in excellent were used. particularly in the • Insulation added to the performance in your area. very high-perfonnance systems. perimeter of slab-on-grade However, they are general The greater the percentage construction. ; indications only, and using the reduction in heating energy • Tightness (measured in air Worksheets will give you more needs using passive solar changes per hour, ACH); infonnation about your specific design, the more shading and • The amount of glass area on design. natural cooling were assumed. each side (measured as a The Example assumes a The Examples show passive percentage of floor area; the 1,500 sf house, but the solar strategies, but an Added actual square footage for a 1,500 percentages apply to a house of Insulation Example table sf house is also given as a any size or configuration. (achieving energy savings only reference pOint); by increasing insulation levels, • The "percent solar savings" without specific solar features) is (the part of a house's heating provided in the Summary energy saved by the solar beginning on page 87. features); and

Jackson, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 23 2. Suntempering Examples of Heat Energy Savings Both suntempered and passive Suntempered 1,500 sf Single Story House (in a specific location) solar houses: • begin with good basic Base energy-conservation, Case 20% 40% 60% R-Values • take maximum advantage of Ceiling/Roof 26 26 34 45 the building site through the Walls 14 13 18 25 right orientation for year-round Slab Edge 0 0 0 2 energy savings, and Glass .9 1.8 1.8 1.8 • have increased south-facing Air Changes/Hour 0.75 0.50 0.66 0.50 glass to collect solar energy. Suntempertng refers to Glass Area (percent of total floor area) modest increases in windows on West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% the south side. East 3.0% 4.0% 4.0% 4.0% No additional thermal mass South 3.0% 6.7% 6.7% 6.7% is used, only the "free mass" in Solar System Size (square feet) the house - the framing, South Glass 45 100 100 100 gypsum wall-board and furnishings. Percent Solar Savings In a "conventional" house, 10% 19% 22% 28% about 25% of the windows face Performance (Btu/yr-sf) south, which amounts to about Conservation 27,212 24,941 19,581 14,281 3% of the house's total floor Auxiliary Heat 24,599 20,024 15,098 10,164 area. In a suntempered house, Cooling 15,575 13,079 10,293 8,051 the percentage is increased to a Summary: Insulation values and tightness of the house (as measured in maximum of about 7% of,the 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 Note: These examples should not be construed as recommendations - the suntempering is a very low-cost 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 latitude in selecting values to use. Of course, even though the necessity for precise sizing of glazing and thermal mass does not apply to suntempertng (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 conselVation measures, room lay-out. siting, glazing type and so on are still important for perlormance and comfort in suntempered homes.

Jackson, Mississippi 24 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

3. Direct Gain houses) and 12%. depending on where the winter sun will fall how much thennal mass will be directly on it. The most common passive solar used in the design. as discussed Effective materials for floors strategy system is called direct below. include painted. colored or vinyl­ gain: sunlight through south­ covered concrete. brick (face facing glazing falls directly into Glazing brick or pavers have even higher the space to be heated. and is Double glazing is recommended density than ordinary building stored in thennal mass for direct gain glazing in brick). quarry tile. and dark­ incorporated into the floor or Jackson. The Performance colored ceramic tile lead directly interior walls. The south Potential table on page 6 shows on the slab. window area is increased above the relative performance of For houses built with the 7% limit of a suntempered different types of direct gain crawlspaces or basements. the house. and additional thennal glazing. You will note from this incorporation of significant mass is added to store the table that yield increases by 11% amounts of heavy thennal mass additional solar gains and thus between double and triple or is a little more difficult. Thermal prevent overheating. low-e glazing. Night insulation mass floor coverings over also improves energy basements. crawlspaces and perfonnance dramatically. In lower stories would generally be fact. as the Perfonnance limited to thin set tile or other Potential table shows. covering thin mass floors. the windows at night or on When more mass is reqUired. cloudy days with the equivalent the next best option is for of R-4 shades or other material interior walls interior finishes or will save almost as much energy exterior walls or interior as with R-9 material. But masonry fireplaces. When studies have shown that only evaluating costs. the dual relatively few homeowners will function of mass walls should be be diligent enough about remembered. They often seIVe operating their night insulation as structural elements or for fire to achieve those savings. protection as well as for thennal Direct Ga/n Energy-efficient glazing. on the storage. Another option is to Direct gain is the most common passive solar system in residential applications other hand, needs no operation, switch to another passive solar and therefore is a more system type such as attached Sizing Limit convenient and reliable option. slab-on-grade sunspaces or Total direct gain glass area thermal storage walls built should not exceed about 12% of Thennal Mass directly on exterior foundation the house's floor area. Beyond Thennal mass can be walls. that. problems with glare or incorporated easily into houses Sunlit thennal mass floors fading of fabriCS are more likely with slab-on-grade floors by should be relatively dark in color. to absorb and store energy to occur. and it becomes more exposing the mass. The mass is more effectively. However. mass difficult to provide enough much more effective if sunlight walls and ceilings should be thennal mass for year-round falls directly on it. Covering the light in color to help distribute comfort. mass with any insulation both heat and light more evenly. So the total south-facing material. such as carpet. greatly glass area in a direct gain reduces its effectiveness. A good Ratio of Mass to Glass. The system should be between 7% strategy is to expose a narrow simplest rule of thumb states: (the maximum for suntempered strip about 8 ft. wide along the south wall next to the windows

Jackson. Mississippi PASSIVE SOLAR DESIGN STRATEGIES 25

For each added sqjt oj sunlight, as long as it is in the The effectiveness of thermal direct-gain glass (above the same room, with no other walls mass is relative to the density 7% sW1tempering ltmit), 6 between the mass and the area and thickness. The vertical axis sqjt oj exposed mass where the sunlight is falling. shows how many square feet of surface should be added (The 8.3 value is typical, but the mass area are needed for each within the direct-gain true value does depend on mass added square foot of direct gain. space. density and thiclmess. Refer to As you can see, performance the mass thiclmess graph for increases start leveling off after a The following procedure can be more specific values to use.) few inches of thermal mass. used to determine a somewhat More south-facing glazing more accurate estimate. This than the maximum as 4O+-~~------~ procedure gives the maximum determined here would tend to 5O#/cI amount of direct-gain glazing for overheat the room, and to a given amount of thermal mass. reduce energy performance as If the amount of direct-gain well. 75#/cI glazing to be used is already l00#/cI lmown, thermal mass can be 125#/cI added until this procedure 15O#/cI produces the deSired proportions: o~----~------~-----+ • Start with a direct gain glass o 5 10 15 area equal to 7% of the house's Thickness (ilches) total floor area. As noted above, Mass Thickness the "free mass" in the house will The effectiveness of thermal mass depends be able to accommodate this on the density of the material and thickness. This graph is for wall or ceiling mass in the much solar energy. direct gain space. The ratio of 8.3 was used earlier as a representative value. More • An additional 1.0 sf of direct accurate values can be read from this graph 1:40 for Floor and used in the fourth step of the procedure. gain glazing may be added for notinSul every 5.5 sf of uncovered.. sunlit Mass Location and Effectiveness In cases in which you are still mass. Carpet or area rugs will Additional mass must be provided for south seriously reduce the facing glass over 7% of the floor area. The uncertain if thermal mass is ratio of mass area to additional glass area effectiveness of the mass. The depends on its location within the direct gain adequate, you can go to maximum mass that can be space. Worksheet III: Thermal considered as "sunlit" may be Mass/Comfort, which is more Thickness. For most materials, estimated as about 1.5 times the comprehensive. the effectiveness of the thermal south window area. mass in the floor or interior wall • An additional 1.0 square foot increases proportlonally with of direct gain glazing may be thiclmess up to about 4 inches. added for every 40 sf of thermal After that, the effectiveness mass in the floor of the room, doesn't increase as significantly. but not in the sun. A two-inch mass floor will be • An additional 1.0 square foot about two-thirds as effective in a of direct gain glazing may be direct gain system as a four-inch added for each 8.3 sf of thermal mass floor. But a six-inch mass mass placed in the wall or floor will only perform about ceiling of the room. Mass in the eight percent better than a four­ wall or ceiling does not have to inch floor. be located directly in the

JacksOD, Mississippi 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 26 25 32 39 Walls 14 13 17 21 Slab Edge 0 0 0 1 Glass .9 1.8 1.8 1.8

Air Changes/Hour 0.75 0.53 0.75 0.55

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% 7.5% 9.3% 12.0%

Added Thermal Mass Percent of Floor Area 0.0% 2.7% 13.8% 30.0%

Solar System Size (square feet) South Glass 45 111 139 180 Added Thermal Mass 0 40 206 450

Percent Solar Savings 10% 21% 28% 39%

Performance (Btu/yr-sf) Conservation 27,212 25,405 21,152 16,703 Auxiliary Heat 24,599 20,020 15,158 10,112 Cooling 15,575 13,606 12,003 11,514

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.

Jackson, Missiuippi PASSIVE SOLAR DESIGN STRATEGIES 27

4. Sunspaces sunspace to be considered truly glass-to-mass ratio. on a clear thermally isolated. winter day a temperature swing The sunspace is a very popular The sunspace should not be of about 30'F should be passive solar feature. adding an on the same heating system as expected. attractive living space as well as the rest of the house. A well The sunspace floor is a good energy performance. There are designed sunspace will probably location for thermal mass. The many variations on the basic need no mechanical heating mass floors should be dark in theme of the sunspace. and the system. but if necessary. a small color. No more than 15-25% of possibilities for sunspace design fan or heater may be used to the floor slab should be covered are extraordinarily diverse protect plants on extremely cold with rugs or plants. The lower (References 17 through 20 winter nights. edge of the south-facing include specific design ideas). The sunspace should be just windows should be no more As used in this gUide. a as tightly constructed and than six inches from the floor to sunspace is a separate direct­ insulated as the rest of the make sure the mass in the floor gain room on the south side of house. receives suffiCient direct the house. The wall that sunlight. If the windows sills are separates the house from the higher than that. additional sunspace is called a common mass may have to be located in wall. The common wall should the walls. include operable windows and Another good location for doors that may be closed so that thermal mass is the common when the sunspace is not wall (the wall separating the providing heat to the house it is sunspace from the rest of the not draining heat from the house). Options for the common house. wall are discussed in more detail The sunspace concept used later. in these Guidelines can be used Water in various types of year-round. will provide most or containers is another form of all of its own energy needs. and energy storage often used in will contribute to the energy Sunspaces sunspaces. Sunspaces provide useful passive solar needs of the rest of the house as heating and also provide a valuable amenity well. to homes. Glazing Sunspaces are referred to as Clear. double-glazing is "isolated gain" passive solar Thermal Mass recommended for sunspaces. systems. because the SUnlight is A sunspace has extensive south­ Adding the second pane makes a collected in an area which can facing glass. so sufficient large improvement in energy be closed off from the rest of the thermal mass is very important. savings. Triple-glazing or low-e house. During the day. the Without it. the sunspace is liable coatings. on the other hand. will doors or windows between the to be uncomfortably hot during further improve comfort. but will sunspace and the house can be the day. and too cold for plants have little effect on energy opened to Circulate collected or people at night. savings. heat. and then closed at night. However. the temperature in Windows on the east and and the temperature in the the sunspace can vary more west walls should be small (no sunspace allowed to drop. It than in the house itself. so more than 10% of the total should be noted that the about three square feet of four sunspace floor area) but they are common wall is often mass. and inch thick thermal mass for each useful for cross-ventilation. not necessarily suffiCient for the square foot of sunspace glazing should be adequate. With this

Jackson. Mississippi 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 common overheating. Largely. this stems masonry wall. it can also be wall if it is made of thermal directly from poor design used for thermal mass. in which mass. But energy is mainly practice and can be avoided. case it should be solid masonry 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 mUd 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 common 15% of the sunspace south-glass gain. but they can also present wall to about R-lO is a good area. big overheating problems and idea. especially in cold climates. • Windows or sliding glass become counter-productive. If An insulated common wall will doors will provide light and either glazed roofs or tilted help guard against heat loss views. The window area in the glazing are used in the during prolonged cold. cloudy common wall should be no sunspace. special care should be periods. or if the thermal storage larger than about 40% of the taken to make sure they can be in the sunspace is insuffiCient. entire common wall area. Per effectively shaded during the Probably the most important unit area. window and slider summer and. if necessary. on factor in controlling the openings are about one-half as sunny days the rest of the year. temperature in the sunspace. effective for natural convection too. The manufacturers of and thus keeping it as as are door openings. sunspaces and glazing are comfortable and effiCient as developing products with better possible. is to make sure the ability to control both heat loss exterior walls are tightly and heat gain (for example. roof constructed and well-insulated. glazing with low shading coeffiCients. shading 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.

Jackson. Mississippi 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 1,500 sf Single Story House in the summer or on warm days in spring and fall. A properly Base vented and shaded sunspace Case 20% 40% 60% R·Values can function much like a Ceiling/Roof 26 24 29 34 screened-in in late spring, Walls 14 12 15 18 summer, and early fall. Slab Edge 0 0 0 0 .9 1.8 1.8 1.8 Operable windows and/ or Glass vent openings should be located Air Changes/Hour 0.75 0.59 0.70 0.62 for effective cross-ventilation. and to take advantage of the Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% prevailing summer wind. Low North 3.0% 4.0% 4.0% 4.0% inlets and high outlets can be East 3.0% 4.0% 4.0% 4.0% used in a "stack effect". since South (windows) 3.0% 3.0% 3.0% 3.0% warm air wUl rise. These Sunspace 0.0% 6.7% 11.0% 17.0% ventilation areas should be at Solar System Size (square feet) least 15% of the total sunspace South Glass 45 45 45 45 south glass areas. Sunspace Glass 0 100 165 255 Where natural ventilation is Sunspace Thermal Mass 0 302 495 765 insufficient. or access to natural Percent Solar Savings breezes is blocked. a small. 10% 25% 35% 49% thermostat-controlled fan set at Performance (Btu/yr-sf) about 76'F will probably be a Conservation 27,212 26,782 23,479 19,989 useful addition. Auxiliary Heat 24,599 20,012 15,073 10,119 Cooling 15,575 14,875 14,439 1.5,546

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.

Jackson. Mississippi 30 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

5. Thermal Storage Selective Sur:faces Wall A selective surface is a special adhesive foil applied to the The Thermal Storage Wall­ exterior side of the mass of also referred to as a Trombe wall Thermal Storage Walls. or an indirect gain system - is a Selective surfaces absorb a large south-facing glazed wall. usually percentage of solar radiation but built of masomy. but sometimes radiate very little heat back to using water containers or phase the out-of-doors (low emittance). change materials. The masomy To be effective. selective Thermal Storage Wall. , , surfaces must be applied is separated from the glazing A thermal storage walliS an eff6f:tive, paS,SIV6 only by a air space. Sunlight is solar system, especially to proVide mghttime carefully for 100% adhesion to heating. absorbed directly into the wall the mass surface. instead of into the living space. In Jackson. Mississippi. a A masomy Thermal Storage Wall selective surface will improve The energy is then released into should be solid. and there the living space over a relatively Thermal Storage Wall should be no openings or vents performance by about 48%. long period. The time lag varies either to the outside or to the with different materials. living space. Although vents to Mass Material and thicknesses and other factors. the living space were once but typically. energy stored in a Thickness commonly built into Thermal In general. the effectiveness Thermal Storage Wall during the Storage Walls. experience has day is released during the of the Thermal Storage Wall will demonstrated that they are increase as the density of the evening and nighttime hours. ineffective. Vents between the The outside surface of a material increases. Thermal Storage Wall and the The optimum thickness of thermal storage wall should be a house tend to reduce the very dark color - an the wall depends on the density system's nighttime heating of the material chosen. but absorptance greater than 0.92 is capability. and to increase the recommended. performance is not very sensitive temperature fluctuation in the to thickness. The following The summer heat gain from house. Vents to the outside are a Thermal Storage Wall is much chart indicates the similarly ineffective. and do little recommended thickness of less - roughly 71% less - than to reduce summer heat gains. from a comparable area of direct Thermal Storage Walls made of gain glazing. various materials. As thickness Glazing is increased. the time delay of Double glazing is recommended heat flow through the wall is for Thermal Storage Walls unless increased. and the temperature a selective surface is used. In variation on the inside surface is this case. single glazing performs decreased. about the same as double . glazing. The space between the glazing and the thermal mass should be one to three inches.

Jackson. Mississippi PASSIVE SOLAR DESIGN STRATEGIES 31

Mass Wall Thickness Examples of Heat Energy Savings (inches) Passive Solar-Thermal Storage Wall 1,500 sf Single Story House Density Thickness Material (Ib/cf) (inches) Base Case 20% 40% 60% Concrete 140 8-24 R-Values Concrete Masonry 130 7- Ceiling/Roof 26 24 26 30 18 Walls 14 12 13 15 Clay Brick 120 7-16 Slab Edge 0 0 o· 0 Ltwt. Concrete 110 6-12 Glass .9 1.8 1.8 1.8 Masonry Adobe 100 6-12 Air Changes/Hour 0.75 0.69 0.51 0.61

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% Thermal Storage Wall 0.0% 6.5% 11.0% 17.0% masonry. so a smaller volume of mass can be used. In "water Solar System Size (square feet) walls" the water is in Ught. rigid South Glass 45 45 45 45 containers. The containers are Thermal Storage Wall 0 97 164 255 shipped empty and easily Percent Solar Savings installed. Manufacturers can 10% 28% 40% 55% provide information about Performance (Btu/yr-sf) durability. installation. Conservation 27,212 27,784 25,364 22,700 protection against leakage and Auxiliary Heat 24,599 20,015 15,069 10,107 other characteristics. At least Cooling 15,575 12,471 10,729 9,720 30 pounds (3.5 gallons) of water Summary: In the case of a Thermal Storage Wall, south-facing glazing should be provided for each 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.

Jackson. Mississippi 32 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

6. Combined Systems 7. Natural Cooling Fortunately, many of the Guidelines features that help maintain Although the previous sections comfort and reduce energy have presented separate The term "natural cooling" is needs in winter also work well in discussions of four different used here to describe techniques summer. For instance, systems, it isn't necessary to which help a house stay cool in additional thermal mass choose one and only one system. summer but which require little performs well year-round. In fact, passive solar features or no energy. Natural cooling Masonry materials are equally work well in combination. techniques work to help reduce effective in staying cool and For example, direct gain air-conditioning, not replace it. storing heat. If mass surfaces works very well in conjunction These techniques are useful can be exposed to cool night­ with a sunspace or thermal not only in passive solar houses, time temperatures - a storage wall. Since thermal but in "conventional" houses as technique referred to as "night storage walls release energy well. The strategies outlined ventilation" - they will help the more slowly than direct gain below - attention to the house stay cooler the next day. systems, they are useful for location, size and shading of A California utility found during supplying heat in the evening glazing, using the opportunities studies of small test buildings and at night, whereas the direct on the site for shading and that on hot summer days the gain system works best during natural ventilation, and using workmen at the facility always the day. Although using a ate lunch in the masonry test fans - can reduce air sunspace, thermal storage wall conditioning needs and increase building because it stayed much and direct gain system in the comfort even if the house has no cooler than any of the others. same house may result in passive solar heating features. (See Reference 9) excellent performance, such The additional insulation But shading is particularly combinations do require a large important in passive solar that increases winter south-facing area, and careful houses, because the same performance will also work to design to make sure the systems features that collect SUnlight so improve summer performance by are well-integrated with each effectively in winter will go right conserving the conditioned air other and with the house's on collecting it in summer - inside the house. And some mechanical system. resulting in uncomfortably hot low-e windows and other glazing with high R-value can help rooms and big air conditioning bills - unless they are shaded shield against unwanted heat and the house is designed to gain in summer. help cool itself.

Jackson, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 33

The potential of some natural and low-energy cooling Cooling Potential strategies is shown in the 8asecase 15,575 8tu/yr-sf following table for Jackson. Energy Worksheet IV: CooRng· Savings Percent Performance Level indicates Strategy (8tu/yr -sf) Savings the total annual cooling load. No Night Ventilation1 and so can give an idea of how without ceiling fans 0 0% the passive solar features with ceiling fans 4,270 27% increase the cooling load and Night Ventilation1 how much reduction is possible without ceiling fans 1,930 12% when natural cooling techniques with ceiling fans 6,100 39% are used. High Mass2 It should be noted that the without ceiling fans 410 3% Cooling Performance numbers with ceiling fans 200 1% presented in the Examples for each passive solar strategy 1 With night ventilation, the house is ventilated at night when 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 natural cooling techniques. This to the house floor area. is especially true of the higher percentage reductions; these assume better heating performance. but also better shading and other natural cooling strategies.

Jackson. Mississippi 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 Added Annual conditioning loads dramatically. Cooling Load types of low-e windows block It is generally best in terms of Orientation (Btu/yr-sf) solar transmission but also energy performance to carefully allow clear views. These North 50,240 size non-solar glazing as East 96,330 treatments are not indicated in the following table. South 80.330 recommended for south West 104,740 windows. Skylights 191,110 As the table shows. skylights Recommended Non-south present a high potential for Glass Guidelines These values are based on double glass with a shading overheating, and are usually Percent coeffiCient of 0.88. When glazing difficult to shade properly. But of Total with a different shading skylights are very popular Orientation Floor Area coefficient is used the values may be scaled proportionally. features. and they save East 4% electricity by providing good North 4% natural daylight to the house. West 2% These numbers can be reduced In some parts of the country by shading as described in the almost every new house has at next section. least one skylight. A good West-facing windows present Using special glazing or working compromise can usually particularly difficult shading window filins that block solar be achieved if skylight area is problems. If glazing is added transmission (low shading limited, and if careful attention above the levels indicated. the coeffiCient) is an option often is paid to shading. either by need for shading will become used in particularly hot trees or by devices such as roller even more critical. climates, but the more effective shades or blinds. The Cooling loads increase as they are at blocking sunlight. manufacturer can usually give window area increases. This the less clear they are. as a rule, guidance on shading options for relationship for Jackson is a particular skylight design. shown in the following table for each of the cardinal window orientations. For instance when a square foot of west area is added or subtracted. the annual cooling load increases or decreases by 104.740 Btu/yr-sf.

Jackson. Mississippi 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 designed. devices. however. Otherwise. an that blocks summer Landscaping. The ideal site for sun may also block sun in the summer shading has deciduous Landscaping for Summer Shade spring. when solar heating is trees to shade the east and west Trees and other landscaping features may be desired. and. by the same token. effectively used to shade east and west windows. Even small trees such windows from summer solar gains. an overhang sized for maximum as fruit trees can help block sun solar gain in winter will allow hitting the first story of a house. Other landscaping ideas for solar gain in the fall on hot days. Trees on the south side can summer shade: The following figure may be used present a difficult choice. Even • Trellises on east and west to determine the optimum deciduous trees will shadow the covered with vines. overhang size. solar glazing during the winter • Shrubbery or other plantings In Jackson. an ideal and interfere with solar gain. In to shade paved areas. overhang projection for a four fact. trees on the south side can • Use of ground cover to foot high window would be 14 all but eliminate passive solar prevent glare and heat inches and the bottom of the performance. unless they are absorption. overhang would be 12 inches very close to the house and the • Trees, fences. shrubbery or above the top of the window. low branches can be removed. other plantings to "channel" allowing the winter sun to summer breezes into the house. penetrate under the tree canopy. • DeCiduous trees on the east However. in many cases the and west sides of the house. as trees around the house are shown above. to balance solar bigger selling points than the gains in all seasons. 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 leaving in as many trees as possible (see page 17. Site Planning for Solar Access). South Overhang Sizinfl In Jackson, an ideally SIZed south overhang should allow full exposure of the window when the sun has a noon altitude of 39 degrees (angle A) and fully shade the window when the sun has a noon altitude of 76 degrees (angle B).

Jackson. Mississippi 36 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

A combination of carefully sized Ceiling Fans overhangs on the south windows Ceiling fans will probably save Ceiling Fan Sizes and shading devices on the other more energy than any other Minimum Fan windows will probably be an single cooling strategy. Studies Largest Room Diameter effective solution. Adjustable show that air movement can Dimension (inches) overhangs that can be make people feel comfortable at 12 feet or less 36 As seasonally regulated are another higher temperatures. a 12 - 16 feet 48 option. general rule, the thermostat can 16 - 17.5 feet 52 be set 4 degrees higher without 17.5 - 18.5 feet 56 Shading Devices. External affecting comfort if the air is 18.5 or more feet 2 fans shades are the most effective moving at 100-150 feet per 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.

Jackson, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 37

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

JacksoD. Mississippi 38 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE

Jackson, Mississippi Passive Solar Design Strategies WORKSHEETS

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

Blank Worksheets Jackson Mississippi

JackHD, Ml•• l ••lppi 40 General Project Information

Project Name Floor Area Location Date Designer

Worksheet I: Conservation Performance Level

A. Envelope Heat Loss Construction R-value Heat Description Area [Table A] Loss Ceilings/roofs + = + = Walls + = + = Insulated Floors + = + Non-solar Glazing + = + = Doors + = + = Btu/oF-h Total

B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss Siabs-on-Grade X = Heated Basements X = Unheated Basements X = Perimeter Insulated CrawlsQ§css X = Btu/oF-h Total

C. Infiltration Heat Loss X X .018 = BtufOF-h Building Air Changes Volume per Hour

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

E. Conservation Performance Level

X X = BtuIyr-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 0) Btulyr-sf

CompueLmeEtoLmeF 41

Worksheet II: Auxiliary Heat Performance Level

A. Projected Area of Passive Solar Glazing

Solar System ROU~h Frame Net Area Adjustment Projected Reference Code rea Factor Factor (Table 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 (Table F] X = X = X = X = X = X = X = + = Total Total Solar Projected Sa9ings Area Fraction

D. AuxlHary Heat Performance Level

[ 1- X = Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E]

E. Comparative AuxlUary Heat Performance (From Previous Calculation or from Table G) Btutyr-sf

Compare Lme D to Lme E

JackSOD, Mlnissippi 42 Worksheet m: Thermal Mass/Comfort

A. Heat Capacity of Sheetrock and Interior Furnishings Unit Total Heat Heat Floor Area Capacity Capacity Rooms with Direct Gain X 4.7 = Spaces Connected to Direct Gain Spaces X 4.5 = Btu/OF Total

B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ] Capacity Trombe Walls X 8.8 = Water Walls X 10.4 = EXl2Qsed Slab in Sun X 13.4 EXl2Qsed Slab Not in Sun X 1.8 = X = X = X = BtufOF Total

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ] Capacity Trombe Walls X 3.8 = Water Walls X 4.2 = X = X = X = BtufOF Total

D. Total Heat Capacity BtufOF (A+B+C)

E. Total Heat Capacity per Square Foot + = BtufOF-sf Total Heat Conditioned Capacity Floor Area

F. Clear Winter Day Temperature Swing Total Comfort ~~ected Area Factor [Worksheet II] (Table I) Direct Gain X = Sunspaces or X = Vented Trombe Walls + = Total Total Heat Capacity

G. Recommended Maxtmwn Temperature Swing Compare Line F to Line G

Jackson, Mlsslulppl 43 Worksheet IV: Summer Cooling Performance Level

A. Opaque Surfaces Radiant Barrier Absorp- Heat Gain Heat Loss Factor tance Factor Description [Worksheet I) [TableJ) [Table K) [Table L) Load Ceilings/roofs X X X = X X X = X X X = Walls X na X = X na X = Doors 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 =

East Glass X 0.80 X X

West Glass X 0.80 X X =

Skylights X 0.80 X X =

kBtu/yr Total C. Solar Glazing

Solar System ROU~ Frame Net Area Shade Factor Heat Gain Description rea Factor [Table M) Factor [Table L) Load Direct Gain X 0.80 X X =

Storage Walls X 0.80 X X =

Sunsl2ace 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. CooUng 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. CooUng Performance Level Btu/yr-sf (E -F)

H. Comparison CooUng Performance (From Previous Calculation or from Table P) Btu/yr-sf Compare Line G to Line H

JacksoD, Ml ••l ••lppl 44

Table A--coDtlDued •• Table A-EqulvaleDt Thermal Table D-Base Case CODservatioD Performance of AuembUes Performance (Btu/yr-a1) R-values (hr-F-sf/Btu) AS-Doors Base Case 27,212 Solid wood with 2.2 Weatherstripping A1-CellingslRoof. Metal with rigid 5.9 Table E-ProJected Area Attic Insulation R-value foam core AdJustmeDt Factors Construction R-60 R-3O R-38 R-49 Degrees off Solar System Type 27.9 35.9 46.9 57.9 True DG, TW, SSA SSB, Table B-Perimeter Beat Lou South WW, SSC SSD SSE Framed Insulation R-value Factors for Slabs-oD-Grade and Construction R-19 R-22 R-3O R-38 BasemeDts (Btu/b-F-ft) o 1.00 0.77 0.75 2xS at1S"oc 14.7 15.8 IS.3 5 1.00 0.76 0.75 2x6 at 24"oc 15.3 1S.5 17.1 Heated Unheated Insulated 10 0.98 0.75 0.74 2x8 at 16"oc 17.0 18.9 2O.S 21.1 Perimeter SlabHln- Base- Base- Crawl- 15 0.97 0.74 0.73 2x8 at 24"oc 17.S 19.5 21.S 22.2 Insulation Grade menlB menlB spaces 20 0.94 0.72 0.70 2x1 0 atlS"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 2x1 0 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 at1S"oc 18.8 21.0 25.5 30.1 R-7 0.3 0.7 O.S 0.5 2x12 at 24"oc 19.0 21.4 27.3 31.4 R-11 0.3 0.6 0.5 0.4 R-19 0.2 0.4 0.5 0.3 R-30 0.1 0.3 0.4 0.2 Table F-8olar System SaviDg A2-Framed Walls FraCtlODB

~~Ie Insulation R-value Framing R-11 R-13 R-19 R-25 Table C-Bea~ Degree Days F1-Dlrect Gain 2x4 at 1S"oc 12.0 13.S (F-day) Load DGC1 DGC2 DGC3 2x4 at 24"oc 12.7 13.9 Collector Double Low-e R-9 Ni~ht 2xS at 1S"oc 14.1 15.4 17.7 19.2 Ratio Glazing Glazing Insulation 2xS at 24"oc 14.3 15.S 18.2 19.8 C1-Heatlng Degree Days (Base 65°F) 400 0.08 0.09 0.10 Double Jackson 2,389 300 0.11 0.11 0.13 Wall Total Thickness (inches) Belzoni 2,707 200 0.15 0.1S 0.18 Framing 8 10 12 14 Brookhaven 2,065 150 0.19 0.20 0.23 Canton 2,570 100 0.25 0.27 0.31 25.0 31.3 37.5 43.8 Columbia 1,881 80 0.30 0.32 0.37 The R-value of insulating sheathing should be added to Greenville 2,635 60 0.36 0.40 0.46 the values in this table. Greenwood 2,716 50 0.41 0.45 0.53 Kosciusko 2,893 45 0.44 0.49 0.57 Moorhead 2,634 40 0.48 0.53 0.61 A3-lnsulateci Floors Natchez 1,941 35 0.52 0.57 0.66 Pickens 2,584 30 0.57 0.63 0.72 Insulation R-value Port Gibson 2,532 25 0.62 0.69 0.79 Framing R-11 R-19 R-30 R-38 Vicksbu~ 2,201 20 0.68 0.76 0.85 yazoo City 0.83 2x6sat 1S"oc 18.2 23.8 29.9 2,480 15 0.75 0.91 2x6s at 24"oc 18.4 24.5 31.5 2x8s at1S"oc 18.8 24.9 31.7 36.0 2x8s at 24"oc 18.9 25.4 33.1 37.9 C2-Heatlng Degree Day Multiplier F2-Trombe Wall. 2x1 0 at 1S"oc 19.3 25.8 33.4 38.1 39.8 Passive Solar TWF3 TWA3 TWJ2 TWI4 2x10 at 24"oc 19.3 26.1 34.4 Heatless Glazing Area per Load Unvented Vented Unvented Unvented 2x12 at 16"oc 19.7 26.5 34.7 39.8 2x12 at 24"oc 41.2 per Square per Square Foot Collector Non- Non- Selec- Night 19.5 26.7 35.5 Foot .00 .05 .10 .15 .20 Ratio selective selective tive Insulation These R-values include the buffering effect of a ventilated crawlspace or unconditioned basement. 12.00 1.17 1.18 1.19 1.20 1.20 400 0.06 0.09 0.08 0.05 11.50 1.16 1.17 1.18 1.19 1.20 300 0.09 0.11 0.12 0.08 11.00 1.15 1.16 1.17 1.18 1.19 200 0.13 0.16 0.19 0.14 10.50 1.13 1.15 1.16 1.17 1.18 150 0.16 0.19 0.25 0.20 A4-Wlndow. 10.00 1.12 1.14 1.15 1.16 1.17 100 0.23 0.26 0.35 0.29 Air Gap 9.50 1.11 1.12 1.14 1.15 1.17 80 0.27 0.30 0.42 0.35 114 in. 1/2 in. 1/2 in. argon 9.00 1.09 1.11 1.13 1.14 1.15 60 0.33 0.37 0.51 0.43 8.50 1.06 1.09 1.11 1.13 1.14 50 0.38 0.41 0.57 0.49 Standard Metal Frame 8.00 1.04 1.07 1.09 1.11 1.13 45 0.40 0.44 0.60 0.53 Single .9 7.50 1.01 1.04 1.07 1.10 1.12 40 0.43 0.47 0.64 0.57 DoUble 1.1 1.2 1.2 7.00 0.99 1.02 1.05 1.08 1.10 35 0.47 0.51 0.69 0.61 Low-e (e<"o.40) 1.2 1.3 1.3 6.50 0.96 0.99 1.02 1.05 1.08 30 0.52 0.56 0.74 0.66 Metal frame with thermal break 6.00 0.93 0.97 1.00 1.03 1.06 25 0.57 0.61 0.79 0.72 Double 1.5 1.6 1.7 5.50 0.89 0.94 0.97 1.01 1.03 20 0.64 0.68 0.85 0.79 Low-e (e<"o.40) 1.6 1.8 1.8 5.00 0.84 0.90 0.94 0.98 1.01 15 0.73 0.76 0.91 0.87 Low-e (e<"o.20) 1.7 1.9 2.0 4.50 0.78 0.85 0.90 0.95 0.98 Wood frame with vinyl cladding 4.00 0.71 0.80 0.86 0.91 0.95 Double 2.0 2.1 2.2 3.50 0.65 0.73 0.81 0.87 0.92 Low-e 2.1 2.4 2.5 3.00 0.56 0.67 0.74 0.82 0.88 Low-e t"o.40!e<"o.20 2.2 2.6 2.7 2.50 0.44 0.58 0.68 0.76 0.83 Low-e e<"().1 0 2.3 2.6 2.9 2.00 0.29 0.47 0.60 0.69 0.77 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 Fenasntion Rating Council procedures, should be used when available. One half the R-value of movable insulation should be added, when appropriate.

JackSDD, Miaalsslppl 45

F3-Water Walls Table H-Umt Heat Capacities Table L-Heat Gain Facton Load WWA3 WWB4 WWC2 (Btu/F-sf) Ceiling/roofs 63.4 Collector No Night Night Selective Walls and Doors 28.6 Ratio Insulation Insulation Surface North Glass SO.2 H1-Mase Surfaces Enclosing Direct Gain East Glass 96.3 400 0.09 0.06 0.07 Spaces West Glass 104.7 300 0.12 0.10 0.11 Skylights 191.1 200 0.17 0.18 0.18 Thickness (inches) Direct Gain Glazing SO.3 lSO 0.21 0.24 0.25 Material 2 3 4 6 8 12 Trombe Walls and 23.6 100 0.29 0.35 0.35 Water Walls SO 0.34 0.42 0.42 Poured Conc. 1.8 4.3 6.7 8.8 11.311.5 10.3 Cone. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 suns~ces 60 0.41 0.52 0.51 9.0 SSl 54.9 SO 0.46 0.58 0.57 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 Flarc Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSBl 54.9 45 0.49 0.62 0.60 Buider Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSCl 23.6 40 0.52 0.66 0.64 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSDl 54.9 35 0.57 0.70 0.69 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 SSEl 54.9 30 0.61 0.75 0.74 Water 5.2 10.415.6 20.8 31.2 41.6 62.4 25 0.67 0.81 0.79 20 0.73 0.87 0.85 15 0.81 0.93 0.92 H2-Rooms with no Direct Solar Gain Table M-8bading Facton Thickness (inches) Projection F4-Sunspaces Material 1 2 3 4 6 8 12 Factor South East North West Load Poured Cone. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 0.00 1.00 1.00 1.00 1.00 Collector Sunspace Type Cone. Masonry 1.6 2.9 3.5 3.6 3.6 3.4 3.2 0.20 0.89 0.95 0.92 0.95 Ratio SSAl SSBl SSCl SSDl SSEl Face Brick 1.8 3.1 3.6 3.7 3.5 3.4 3.2 0.40 0.72 0.84 0.84 0.85 Fla~ Stone 1.9 3.1 3.4 3.4 3.2 3.1 3.0 400 0.15 0.12 0.08 0.15 0.13 Buider Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 0.60 0.57 0.73 0.76 0.73 300 0.17 0.14 0.11 0.19 0.16 O.SO O.SO 0.62 0.68 0.62 200 0.22 0.18 0.15 0.24 0.21 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 1.00 0.45 0.53 0.59 0.53 150 0.26 0.22 0.19 0.30 0.25 Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.1 1.20 0.41 0.45 0.51 0.45 100 0.33 0.28 0.26 0.38 0.33 Multiply by 0.8 for low-e glass, 0.7 for tinted glass and SO 0.37 0.32 0.30 0.43 0.38 0.6 for low-e tinted glass. 60 0.43 0.38 0.37 0.51 0.45 SO 0.48 0.42 0.41 0.56 0.50 45 0.50 0.44 0.44 0.59 0.53 Table l-Comfort Facton (Btu/sf) 40 0.53 0.47 0.47 0.62 0.56 Direct Gain 870 Table N-lDtemal Gala Facton 35 0.57 0.51 0.51 0.66 0.60 30 0.61 0.55 0.56 0.70 0.64 Sunspaces and 290 Constant Component 2,9SO kBtulyr 25 0.66 0.60 0.61 0.75 0.69 Vented Trombe Walls Variable Component 1,250 kBtu/yr-BR 20 0.72 0.66 0.68 0.81 0.76 15 O.SO 0.74 0.76 0.88 0.83

Table J-Radiant Barrier Facton Table o-Thermal Mass and Radiant Barrier 0.75 Ventilation Acijuatment (Btu/yr-sf) No Radiant Barrier 1.00 Total Heat Night Night No Night No Night Capacity Vent w/ Vent w/ No Vent w/ Vent w/ No per SF Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan 0.0 5,430 1,540 3,600 -400 1.0 6,770 2,600 4,940 660 Table K-80lar Absorptances 2.0 7,360 3,190 5,530 1,260 Color Absorptance 3.0 7,610 3,530 5,7SO 1,590 Gloss White 0.25 4.0 7,720 3,710 5,900 1,780 Semi-gloss White 0.30 5.0 7,770 3,820 5,940 1,880 Light Green 0.47 6.0 7,790 3,880 5,970 1,940 Kelly Green 0.51 7.0 7,SOO 3,910 5,980 1,970 Medium Blue 0.51 8.0 7,810,3,930 5,980 1,990 Medium Yellow 0.57 9.0 7,810 3,940 5,980 2,000 Medium Orange 0.58 10.0 7,810 3,940 5,980 2,010 Medium Green 0.59 Total heat capacity per square foot is calculated on Light Buff Brick 0.60 Worksheet III, Step E. Bare Concrete 0.65 Red Brick 0.70 Medium Red O.SO Medium Brown 0.84 Dark Blue-Grey 0.88 Table P-Base Case CooliDg Dark Brown 0.88 PerforlDllDce (Btu/sf-yr) Base Case 15,575

Table G-Baae Case AuziUuy Heat PerforlDllDce (Btu/yr-d) Base Case 24,599

Jackson, Mississippi 46 General Should the estimated conservation reduced by about 50 percent to account The Worksheets provide a calculation perfonnance level be greater than for throw rugs and furnishings. procedure to estimate the perfonnance desired. the designer should consider As a rule-of-thumb. exposed slab area level of passive solar building designs. It additional building insulation or should be considered to be in the sun is recommended that the results be reducing non-south glass area. only when it is located directly behind compared to Worksheet calculations for south glazing. The maximum slab area the builder's typical house. Perfonnance Worksheet n-AuzWary Heat that is assumed to be in the sun should levels for the NAHB Base Case House Performance Level not exceed 1.5 times the adjacent south used in the Guidelines are also provided This is an estimate of the amount of heat glass area. for comparison. that must be provided each year from In Step F. the projected area of solar A separate worksheet is provided for the auxiliary heatlog system. It glazing calculated on Worksheet II is the four separate performance levels and accounts for savings due to solar energy. used to calculate the comfort associated base cases. In Step A •the user may enter the perfonnance level. The projected area of The worksheets are supported by a rough frame area of solar glazing. since it water walls and unvented Trombe walls number of data tables. The tables are is generally easier to measure the rough is excluded in this step. given a letter designation and are frame area than it is the net glazing area. A high temperature swing indicates referenced next to each worksheet entJy. The worksheet includes a net area factor inadequate thermal mass or too much when applicable. of 0.80 to account for window frames direct gain solar glazing. If the comfort The floor area used in the and mullions. If the designer enters the performance level is greater than desired calculations should not include net glass area, then the net area factor is (13°F recommended). additional thermal sunspaces. garages or other 1.00. mass should be added to the building or unconditioned spaces. The projected area of the solar energy direct gain glazing should be reduced. systems may be calculated using the Worksheet I--COnservatlon adjustment factors in Table E or by Worksheet IV-8ummer CooUng Performance Level making a scaled elevation drawing of the Performance Level This is an estimate of the amount of heat building facing exactly south and This is an estimate of the annual cooling energy needed by the building each year measuring the glazing area from the load of the building-the heat that needs from both the solar system and the scaled drawing. to be removed from the building by an auxiliary heatlog system. The projected area per square foot is air conditioner in order to maintain For Step A. it is necessary to measure calculated as the last part of Step A. comfort during the summer. the net area of surfaces that enclose This is used to determine the heatlog In Step A. only the envelope surfaces conditioned space. For walls. the net degree days adjustment used on that are exposed to sunlight are to be surface area is the gross wall area less Worksheet I. Step E. included. For instance. floors over the window and door area. The load collector ratio is calculated crawlspaces and walls or doors adjacent Rough frame dimensions are in Step B. This is used to determine the to garages are excluded. generally used to measure window area. solar savings fractions in Step C. Steps B and C of the worksheet The R-values in Table A4 are for the The solar energy systems used in Step account for solar gains. They use the rough frame window area. C should be identical to those used in rough frame area since this is easier to Heat loss from passive solar systems Step A. The first and last of measure. The worksheets include a net is excluded. The surface area of direct Step A are simply carried down. area factor of 0.80 to account for window gain glazing. Trombe walls. water walls The solar savings fraction is frames and mullions. If the net window and the walls that separate sunspaces determined separately for each type of area is used. the net area factor is 1.00. from the house are ignored. passive solar system by looking up Table M gives the shade factor for Step A includes consideration of values in Tables Fl through F4. The windows with overhangs based on a insulated floors over crawlspaces. sunspace system types are shown projection factor. The projection factor is unheated basements or garages. beneath Table F4. the ratio between the horizontal R-values are provided in Table A3 that If the auxiliary heat perfonnance level projection of the overhang from the account for the buffering effect of these calculated in Step D is larger than surface of window and the distance from unconditioned spaces. When insulation desired. the designer should consider the bottom of the window to the bottom is not installed in the floor assembly. but increasing the size of the solar energy of the overhang. When windows have rather around the perimeter of a systems or adding additional solar sunscreens. tlots or films. the shade crawlspace or unheated basement. Step energy systems. i.e. thermal storage factors in Table M should not be used. B should be used. walls. Instead. a shading coefficient should be The perimeter method of Step B is determined from manufacturers' used for slabs-on-grade. the below-grade Worksheet III-Comfort literature. portion of heated basements. unheated Performance Level basements (when the floor is not This is the temperature swing expected insulated). and perimeter insulated on a clear winter day with the auxiliary crawls paces (when the floor is not heating system not operatlog. insulated). Heated basement walls that This worksheet requires that two sub­ are above grade should be considered in areas be defined within the building: Step A. those areas that receive direct solar Slab edge perimeter. unheated gains and those areas that are connected basements or perimeter insulated to rooms that receive direct solar gains. crawlspaces adjacent to sunspaces Rooms that are separated from direct should not be included. gain spaces by more than one door The conservation perfonnance level is should not be included in either calculated as the product of the heat loss category. per degree day per square foot [Step D\ Thermal mass elements located in and the heating degree days. adjusted for unconditioned spaces such as sunspaces the heat loss and solar glazing per are not included. square foot The adjustment is taken An exposed slab is one finished with If the cooling perfonnance level is from Table C. based on data calculated vinyl tile. ceramic tile or other highly greater than desired. the designer should on Worksheet I. Step D and Worksheet H. conductive materials. Carpeted slabs consider reducing non-south glass. Step A. should not be considered exposed. The providing additional shading or exposed slab area should be further ~creasing thermal mass.

Jackson, Mississippi Passive Solar Design Strategies EXAMPLE

Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department ofEnerg,y ______47

Jackson The Worked Mississippi Exalllple 48 WORKED EXAMPLE

The Worked Example The house has a semi­ The house is equipped with a enclosed sunspace with vertical ceiling fan to help reduce the Description of glazing. The sunspace floor has air-conditioning load. North Example Bullding a four-inch thick slab-on-grade windows have an overhang with A 1.504 square foot passive with quarry tile set in a mortar a projection factor of 0.30. East solar. single-family home is used bed. The sunspace is separated and west windows are small and to illustrate how to fill in the from the conditioned portion of have no effective overhang worksheets. See sketches for the house by sliding glass doors because of the gable roof. South the building layout. A variety of and a masomy wall. windows. including the design features have been Sunspace ventilation is provided sunspace windows. have an incorporated into the house to to the outside by awning overhang with a projection factor help illustrate how to handle windows located at the top and of 0.20. different situations in the bottom of the south wall. Take-offs from the house are worksheets. South facing windows given in the worksheets. Refer The building selected has provide direct gain solar heating to the circled values in the good insulation as described on to the dining area. and worksheet tables to locate where Worksheet I. master . The south the various values which show The east portion of the house glazing in the kitchen and dining up in the worksheets come from. is slab on grade. The area provides heat to an exposed Performance is found to be and master bedroom are slab-on-grade finished with satisfactory on all four constructed over a crawlspace. ceramic tile to provide direct worksheets. gain heat storage. The house faces 10 degrees to the east of true south.

N C\J Garage

3040 3040

4040 ~

Bedroom Bedroom

Great Room 0 C') ~ 0 C\J '"0 Master '" Bedroom

4050 8020 5030 8088 8068 8088 28'

024 8 12 ~ Floor Plan -.-.. PASSIVE SOLAR DESIGN STRATEGIES 49

III

South Elevation

···· I:t :::

North Elevation

Gt'oeat Room

Section

JackSOD, Mississippi 50 WORKED EXAMPLE

JacksOD, Mississippi 51

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

Jackson Worked ExaIllple Mississippi

Jackson, Mississippi 52 General Project Information

Project Name "PASS I..r£. ~c.. ~,,_,,~ Floor Area Date Designer

Worksheet I: Conservation Performance Level

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

Ceilings/roofs i.-1D l~ A"t'\ l<- 'oB~ + 1.,." = "l~ -"-\'\ 'Ill ~~(l>. c..a1w\1oJ 6 41.0 + 'S.I = 1-"3 Walls '"L- II t 'L,- 0 S"'~~,w" tt'C\ 1- + 1')...0 = S3 ';.... ll K'i. ~'Ut."- \1.\0 + 12..0 = 12.- Insulated Floors + = + = Non-solar Glazing ~eT4'- fM....c:. J!"'t:A.~IIo~ l~EA"" ~l- + t." = "lI- '/s..'1 ~,4I.. ~A~ + = Doors ~OL.-\!> ~~ .... '-\0 + 1.. 'Z... = \6 + = 2..01 Btu/oF-h Total

B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B) Loss Siabs-on-Grade ,~~ X Q..B.O = 1'5~ Heated Basements X = Unheated Basements X = Perimeter Insulated CrawlsQaces X = 122 Btu/OF-h Total

C. Infiltration Heat Loss 11..461 X Q.~o X .018 = I' 2- Btu/oF-h Building Air Changes Volume per Hour

D. Total Heat Loss per Square Foot 24 X LI, S + ,~ = -"-$6 Btu/DO-sf Total Heat Loss Floor Area (A+B+C)

E. Conservation Performance Level

,.~6 X 'L:~B/\ X '.lO = 'I:\'iIC; 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 0) 1-11(L Btu/yr-sf

Compare Line E to Line F

Jackson, Mississippi 53

Worksheet II: Auxiliary Heat Performance Level

A. Projected Area of Passive Solar Glazlng Solar System Rouih Frame Net Area Adjustment . Projected Reference Code rea Factor Factor [Table E] Area :D(;~\ ~ X 0.80 X a·liB = 6~ 5~'-1 UJ1J X 0.80 X O·'ifl = 1" I X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = '2--"\6 t,..."J"Z.. sf Total Area Total Projected Area L">"L + ~fo4 = 0. 12: Total Floor Total Projected . Projected Area Area per Area Square Foot

B. Load Collector Ratio I_V, 24 X '-\'\$ + 'Z-'3~ = Total Total Heat Loss Projected [Worksheet I] Area

C. Solar Savings Fraction System Solar Savings Solar System Projected Fraction Reference Code Area [Table F] ",-,-1 6q X 0.4'1.... = 2...~.C\£3 ~~~ l6!:S X 0."''2.... = 66.'-\6 X = X = X = X = X = 9,·44 + '2-'1'l.. = o. '-\"L Total Total Solar Projected Savings Area Fraction

D. AuxiUary Heat Performance Level

[1 - o.'-t"Z- X \~~,q = , '''05::> Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I. Step E]

E. Comparative AuxlUary Heat Performance (From Previous Calculation or from Table G) U1~"S Btu/yr-sf

Compare Line D to Llne E

Jackson, Mississippi 54 Worksheet ITI: Thermal Mass/Comfort

A. Heat Capacity of Sheetrock and Interior Furnishings Unit Total Heat Heat Floor Area Capacity Capacity Rooms with Direct Gain ""'" X 4.7 = 7...\61 Sl2aces Connected to Direct Gain Sl2aces ~~, X 4.5 = 41..'1 Gq-S'Z.. Btu/OF Total

B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ) Capacity Trombe Walls X 8.8 = Water Walls X 10.4 = EXl20sed Slab in Sun \03 X 13.4 = \:380 EXl20sed Slab Not in Sun \~, X 1.8 = ~'1 X = X = X = \ €.l...l Btu/OF Total

C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description Ca~ci~ Total Heat (include thickness) Area ITa Ie ) Capacity Trombe Walls X 3.8 = Water Walls X 4.2 = fAc..e.. llL-W:4-. ~~. \ \ I X >.., = 411 X = X = '-\ II Btu/OF Total

D. Total Heat Capacity f!~'i0 Btu/OF (~B+C)

E. Total Heat Capacity per Square Foot B~~o + 1~V-t = Btu/OF-sf Total Heat Conditioned ".~ Capacity Floor Area

F. Clear Winter Day Temperature Swing Total Comfort PtWcected Area Factor orksheet II) [Table I) Direct Gain b'I X ~]O = f,Ot7'f.,O SunsQaces or \6l X l...'iO = 'i1'LJ 0 Vented Trombe Walls \01100 + S~~o = rZ ... ' OF Total Total Heat Capacity

G. Recommended Maximum Temperature Swing Compare Line F to Line G

JacksOD, Mississippi 55 Worksheet IV: Summer Cooling Performance Level

A. Opaque Surfaces Radiant Barrier Absorp- Heat Gain Heat Loss Factor , tance Factor Description [Worksheet I) [TableJ) [Table K) [Table L) Load Ceilings/roofs 1:1 X \.C'o X o.::f1 X 61·:1 = 1t (,2- '2..1 X 1·00 X 0.",1 X b~.~ = ~S2 X X X = Walls B~ X na D."O X U., = "62.- X na X = Doors 9 X na 2·"]0 X 1.IiI. (, = :l:I J2S~ 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 4.0 X 0.80 X 0.68 X ~().2.. = \'-\\C:t

East Glass b X 0.80 X \.0'0 X '1'·1 = 4'-1-

West Glass b X 0.80 X ,.CO X \ c7l.\.'"1 = 501

Skylights X 0.80 X X =

'l-)'~ kBtu/yr Total C. Solar Glazing Solar System Rouih Frame Net Area Shade Factor Heat Gain Description rea Factor [Table M) Factor [Table L) Load Direct Gain B6 X 0.80 X o. iI., X BO.} = so'S!

Storage Walls X 0.80 X X =

Sunsgace 'Z.P15 X 0.80 X O.S'\ X ~J.' = 1'¥\2 X 0.80 X X = 6.~z.6 kBtu/yr Total D. Intemal Gain 'l-t;60 +( \1.,.50 X 3 ) = (z'''J.o kBtu/yr Constant Variable Number of Component Component Bedrooms [Table N) [Table N)

E. CooUng Load per Square Foot 1,000 X "2..\ 1.2-\ + '5:0'-\ \"'L\~ Btu/yr-sf (A+B+C+D) Floor Area

F. Adjustment for Thermal Mass and Ventilation 541!'~ Btu/yr-sf [Table ~ ~ \(;04{' ,.JcJr. '-'I cc::u..... ~ fC.o-J OJ

G. CooUng Performance Level 9l4f. Btu/yr-sf (E -F)

H. Comparison CooUng Performance (From Previous Calculation or from Table P) \7'5'<' Btu/yr-sf Compare Line G to Line H

Jackson, Mississippi 56

Table A.-condnued •• Table A-Equivalent Thermal Table D-Base Case Conservation Performance of Assemblies Performance (Btu/yr-s1l R-values (hr-F-sf/Btu) AS-Doors Base Case 27,212 Solid wood with Weatherstripping A1-CeilingsiRoofs Metal with rigid 5.9 Table E-Projected Area Attic Insulation R-value foam core Adjustment Facto" Construction R-38 R-49 R-SO Degrees off ~ Solar System Type @27.9 35.9 46.9 57.9 True D 1..IlL.. SSA SSB, Framed Insulation R-value Table B-Perimeter Heat Loss South ,~ SSD SSE Construction R-19 R-22 R-3O R-38 Facto" for Slabs-Gn-Grade and Basements (Btu/h-F-ft) o 1.00 o. n 0.75 2x6 at 16"oc 14.7 15.8 16.3 5 ~ 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 . 0.74 0.73 2x8 at 24"oc 19.6 21.6 22.2 Insulation ments ments spaces 20 0.94 0.72 0.70 2xl 0 at 16"oc 20.1 24.5 25.7 None 0.8 1.3 1.1 1.1 25 0.91 0.69 0.68 2xl 0 at 24"oc W> 20.7 25.5 26.8 R-5 CQ5 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-l1 0.3 0.6 0.5 0.4 R-19 0.2 0.4 0.5 0.3 R-30 0.1 0.3 0.4 0.2 Table F-8olar System Saving A2-Framed Walls FnctioDS Single Wall Insulation R-value Framing R-l1 R-13 R-19 R-25 Table C-Hea~ Degree Days Fl-Dlrect Gain (F-day) 2x4 at 16"oc 13.6 Load DGCl DGC2 DGC3 2x4 at 24"oc 9fr 13.9 Collector Double Low-e R-9 Night 2x6 at 16"oc 14.1 15.4 17.7 19.2 Ratio Glazing Glazing Insulation 2x6 at 24"oc 14.3 15.6 18.2 19.8 Cl-Heatlng Degree Days (Baa. 65oF)~ 400 0.08 0.09 0.10 Double Jackson 2, 300 0.11 0.11 0.13 Wall Total Thickness (inches) Belzoni , 7 200 0.15 0.16 0.18 Framing 8 10 12 14 Brookhaven 2,065 150 0.19 0.20 0.23 25.0 31.3 37.5 43.8 Canton 2,570 100 0.25 0.27 0.31 Columbia 1,881 80 0.30 0.32 0.37 The R-value of insulating sheathing should be added to Greenville 2,635 60 0.36 0.40 0.46 the values in this table. Greenwood 2,716 50 "-"4 ,,-\1.- 0.45 0.53 Kosciusko 2,893 I. 0.44 0.49 -n15 0.57 Moorhead 2,634 40 0.48 0.53 0.61 A3-lnsulated Floors Natchez 1,941 35 0.52 0.57 0.66 Pickens 2,584 30 0.57 0.63 0.72 Insulation R-value Port Gibson 2,532 25 0.62 0.69 0.79 Framing R-ll R-19 R-3O R-38 Vicksbu!1l 2,201 20 0.68 0.76 0.85 2x6s at 16"oc 18.2 23.8 29.9 Yazoo City 2,480 15 0.75 0.83 0.91 2x6s at 24"oc 18.4 24.5 31.5 2x8s at 16"oc 18.8 24.9 31.7 36.0 2x8s at 24"oc 18.9 25.4 33.1 37.9 C2-Heatlng Degree Day Multiplier F2-Trombe Walla 2xl 0 at 16"oc 19.3 25.8 33.4 38.1 2xl0 at 24"oc 19.3 26.1 34.4 39.8 Passive Solar TWF3 TWA3 TWJ2 TWI4 2x12 at 16"oc 19.7 26.5 34.7 39.8 Heat Loss Glazing Area per Load Unvented Vented Unvented Unvented 2x12 at 24"oc 19.6 26.7 41.2 per Square per Square Foot Collector Non- Non- Selec- Night 35.5 Fool .00 .05 .10 .15 .20 Ratio selective selective tive Insulation These R-values include the buffering effect of a 12.00 1.17 1.18 1.19 1.20 1.20 400 0.06 0.09 0.08 0.05 ventilated crawlspace or unconditioned basement. 11.50 1.16 1.17 1.18 1.19 1.20 300 0.09 0.11 0.12 0.08 11.00 1.15 1.16 1.17 1.18 1.19 200 0.13 0.16 0.19 0.14 10.50 1.13 1.15 1.16 1.17 1.18 150 0.16 0.19 0.25 0.20 A4-Wlndows 10.00 1.12 1.14 1.15 1.16 1.17 100 0.23 0.26 0.35 0.29 9.50 1.11 1.12 1.14 1.15 1.17 80 0.27 0.30 0.42 0.35 Ai'j.,Gap 1.11 1.13 1.14 1.15 60 0.33 0.37 0.51 0.43 1/4 in. 1I' in. 112 in. argon ~:~ t~ 1.09 1.11 1.13 1.14 50 0.38 0.41 0.57 0.49 Standard Metal Frame Ao...!.OO 1.04 1.07 1.09 1.13 45 0.40 0.44 0.60 0.53 Single .9 ~·"-I.50 1.01 1.04 1.07 1.12 40 0.43 0.47 0.64 0.57 Double 1.1 1.2 1.2 7.00 0.99 1.02 1.05 ~ 1.10 35 0.47 0.51 0.69 0.61 Low-e (e<=O.40) 1.2 1.3 1.3 6.50 0.96 0.99 1.02 1.05 1.08 30 0.52 0.56 0.74 0.66 Metal frame with thermal break 6.00 0.93 0.97 1.00 1.03 1.06 25 0.57 0.61 0.79 0.72 Double 1.5 c1S) 1.7 5.50 0.89 0.94 0.97 1.01 1.03 20 0.64 0.68 0.85 0.79 Low-e (e<=O.40) 1.6 1.8 1.8 5.00 0.84 0.90 0.94 0.98 1.01 15 0.73 0.76 0.91 0.87 Low-e (e<=O.20) 1.7 1.9 2.0 4.50 0.78 0.85 0.90 0.95 0.98 Wood frame with vinyl cladding 4.00 0.71 0.80 0.86 0.91 0.95 Double 2.0 2.1 2.2 3.50 0.65 0.73 0.81 0.87 0.92 Low-e 1e<=o.401 2.1 2.4 2.5 3.00 0.56 0.67 0.74 0.82 0.88 Low-e e<=O.20 2.2 2.6 2. 7 2.50 0.44 0.58 0.68 0.76 0.83 Low-e e<=0.10 2.3 2.6 2.9 2.00 0.29 0.47 0.60 0.69 o.n 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.

Jackson, Mississippi 57

Table J-Radiant Barrier Facto... Table o-Thermal Mass and Radiant Barrier 0.75 Ventilation Adjustment (Btu/yr-sf) No Radiant Barrier @ 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 5,430 1,540 3,600 -400 1.0 6,770 2,600 4,940 660 Table X-80lar AbsorptanceB 2.0 7,360 3,190 5,530 1,260 Color Absorptance 3.0 7,610 3,530 5,780 1,590 Gloss White 4.0 7,720 3,710 ~1,780 5 6 I 5.0 7,770 3,820 , 1,880 •q '1 Semi-gloss White -6.0 7,790 3,880 59 , Light Green s:. A 7.0 7,800 3,910 5,980 1,970 Kelly Green 0.51 Medium Blue 0.51 8.0 7,810 3,930 5,980 1,990 Medium Yellow 0.57 9.0 7,810 3,940 5,980 2,000 Medium Orange 0.58 10.0 7,810 3,940 5,980 2,010 Medium Green 0.59 Total heat capacity per square foot is calculated on Light Buff Brick 0.60 Worksheet III, Step E. Bare Concrete Red Brick ~ Medium Red 0.80 Medium Brown 0.84 Dark Blue-Grey 0.88 Table P-Baae Case Cooling Dark Brown 0.88 Performance (Btu/sf-yr) Base Case 15,575

Table G-Base Case AuzWuy Beat Performance (Btu/yr-sf) Base Case 24,599

Jackson, Mississippi 58 WORKED EXAMPLE

JacksOD, Mississippi 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

Glossary Passive Solar: a whole building design Suntempering: an increase of south­ 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 thermal non-mechanical means. as opposed to mass beyond the "free" mass already in a AuziHary Heating System: a term for active solar techniques which use typical house -- gypsum wall board. the system (gas. electric. oil. etc.) which equipment such as roof-top collectors. framing. conventional furnishings and provides the non-solar portion of the floor coverings. house's heating energy needs. referred to Phase-Change Materials: materials as the "auxilruy heat." such as salts or waxes which store and Temperature Swing: a measure of the release energy by changing "phase". Most number of degrees the temperature in a British Thermal Unit (Btu): a unit used store energy when they tum liqUid at a space will vruy during the course of a to measure heat. One Btu is about equal certain temperature and release energy sunny winter day without the furnace to the heat released from burning one when they tum solid at a certain operating; an indicator of the amount of kitchen match. temperature: some remain solid but thermal mass in the passive solar undergo chemical changes which store system. Conservation: in addition to energy and release energy. Phase change conservatfon in the general sense. the materials can be used as thermal mass. Thermal Mass: material that stores term is used to refer to the non-solar. but few products are commercially energy. although mass will also retain energy-saving measures in a house available at this time.. coolness. The thermal storage capacity which are primarily involved with of a material is a measure of the improving the building envelope to guard Purchased Energy: although the terms material's ability to absorb and store against heat loss -- the insulation. and are often used interchangably. a house's heat. Thermal mass in passive solar air infiltration reduction measures. "purchased energy" is geneIa11y greater buildings is usually dense material such than its "auxilruy heat" because heating as brick or concrete masonry. but can Direct Gain: a passive solar energy systems are seldom 100% effiCient. and also be tile. water. phase change system in which the sunlight falls directly into the space where it is stored more energy is purchased than is materials. etc. actually delivered to the house. and used. Thermal Storage WaH: a passive solar a-Value: a unit that measures the energy system also sometimes called Glazing: often used interchangeably with resistance to heat flow through a given Trombe Wall or indirect gain system; a window or glass. the term actually refers to specifically just to the clear material material. The higher the R-value. the south-facing glazed wall. usually made of which admits sunlight, and so can also better insulating capability the material masonry but can also be made of be plastic. Double and triple glazing has. The R-value is the reciprocal of the containers of water. U-factor. refer to two or three panes. Trambe Wall: a thermal storage wall. Radiant Barrier: reflective material used referred to by the name of its inventor. Indirect Gain: a passive solar system in in hot climates to block radiant heat. Dr. Felix Trombe. which the sunlight falls onto thermal particularly in a house's roof. mass which is positioned between the glazing and the space to be heated. i.e. a U-Factor: a unit representing the heat Shading Coefficient: a measure of how loss per square foot of surface area per Thermal Storage Wall or Trombe Wall. much solar heat will be transmitted by a degree OF of temperature difference (see R-value above). Low-Emissivity: the term refers to a glazing material. as compared to a single surface's ability to absorb and re-radiate pane of clear uncoated glass. which has heat. A material with a low emissivity a shading coefficient (SC) of 1. For absorbs and re-radiates relatively small example. clear double-pane glass might amounts of heat. Low-emissivity or "low­ have an SC in the range of .88. Reflective glass might have SC's of .03- e" glass sandwiches a thin layer of .06. In general. lower shading metallic film or coating between two coefficients are desirable when heat gain panes of glass. The low-e glass blocks radiant heat. so it will tend to keep heat is a problem. energy inside the house during the Sunspace: passive solar energy system winter. and keep heat energy outside the sometimes also referred to as an isolated house during the summer. gain system, where sunlight is collected and stored in a space separate from the living space. and must be transferred there either by natural convection or by fans.

Jackson. Mississippi 82 APPENDIX

References e. Glazings: The Design Considerations Insulation Aren't As Clear As Glass f. Ideas for Passive Solar Remodeling 10. NAHB Insulation Manual, National g. Passive Homes in the Marketplace Association of Home Builders. National General (Class C Studies) Research Center. Available from NAHB h. Daylighting in Commercial Bookstore, 15th and M Streets N.W., 1. A Sunbuilder's Primer, National Buildings Washington, D.C. 20005. (202) 822- Renewable Energy Laboratory. i. Human Comfort and Passive Solar 0200: Design 2. Passive: It's a Natural, National j. Passive Design for Commercial 11. Uschkoff, James K. 11te Airtight Renewable Energy Laboratory. Buildings House: Using the Airtight Drywall k. Passive Solar. Principles and Approach. Iowa State University 3. 11te Passive Solar Construction Products Research Foundation. Available for Handbook. Steven Winter 1. Increasing Design Flexibility $14.95; Attn: Sarah Terrones, EES Associates/Northeast Solar Energy m. Utilities and Passive: Predicting the Building, Iowa State UniverSity. Ames, Center/National Concrete Masonry Pay-off IA 50011 Association/Portland Cement Association/Brick Institute of America. 12. Spears, John. Radon Reduction in Available for $29.95 plus $3.00 New Construction. Interim Guide, handling, from Steven Winter Associates, National Association of Home Builders, Attn: Publications, 6100 Empire State Environmental Protection Agency OPA Building, New York, N.Y. 10001 87-009, , August 1987. Available from the EPA or the NAHB Bookstore, 15th 4. Suntempering in the Northeast, Steven and M Streets N.W .• Washington. D.C. Winter Associates. Available from them 20005. (202) 822-0200. at the address above for $9.50.

5. Passive Solar Design Handbook, AppUances Volume I. II, III. Available from National Technical Information Service. U.S. Dept. 13. Saving Energy and Money with Home of Commerce, 5285 Port Royal Road, Appliances. Environmental Science Springfield, Va, 22161, $32.00 each for I Department. Massachusetts Audobon Society/American Council for an Energy and II, $12.00 for III. Efficient Economy. Available for $2.00 apiece from ACEE. 1001 Connecticut 6. Balcomb, J.D .• et al. Passive Solar Ave. N.W .• Suite 535. Washington D.C. Heating Analysis. This volume 20036 supercedes and expands Volume III of the Passive Solar Design Handbook (Ref. 14. The Most Energy E§lCientAppliances. 5). Available from ASHRAE, 1988 Edition. ACEEE. $2.00 apiece at Publications. 1791 Tullie Circle NE. address above. Atlanta. Ga, 30329. $30.00 for ASHRAE members. $60.00 for non-members.

7. living With the Sun (for consumers) and BuUding With the Sun (for builders), PPG Industries.

8. 11te Passive Solar lriformation Guide, PSIC.

9. Passive Solar Trends. Technical briefs fromPSIC. a. Infiltration in Passive Solar Construction b. The State of the Art in Passive Solar Construction c. Passive Solar in Factory-Built Housing d. Radiant Barriers: Top Performers in Hot Climates

JacksoD, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 83

Site Planning Sunspaces

15. Builder's Guide to Passive Solar 17. Jones, Robert W. and Robert D. Home Design and Land Development, McFarland. The Sunspace Primer. A National Fenestration Council. Available Guide for Passive Solar Heating, available for $12.00 from NFC, 3310 Harrison, for $32.50 from Van Nostrand Reinhold, White Lakes Professional Building, 115 5th Avenue, New York, N.Y. 10003 Topeka, KS. 66611 18. Greenlwusesfor Uving, from Steven 16. Site PlanningJor Solar Access, U.S. Winter Associates, Attn: Publications, Department of Housing and Urban 6100 Empire State Building, New York, Development/American Planning N.Y. WOOl, $6.95. Association. Available for $6.50 from Superintendent of Documents, U.S. 19. ConceptN, from Andersen Government Printing Office, Washington Corporation, Bayport, MN. 55003, $6.95. D.C. 20402 20. Passive Solar Greenhouse Design and Construction. Ohio Department of Energy/John Spears, 8821 Silver Spring, Md., 20910.

JackBon, MiBBiBBippi 86 SUMMARY FOR JACKSON, MISSISSIPPI

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Jacksoo, Mississippi PASSIVE SOLAR DESIGN STRATEGIES 87

Technical Basis for Los Alamos National Laboratory with and heat losses through the solar funding from the U.S. Department of aperture and, thus. correct for omitting the Builder Energy Solar Buildings Program. See the the solar components from the Guidelines references for more information. calculation of annual heat loss. 1. J. Douglas Balcomb. Robert W. Jones, Annual Heat Loss Robert D. McFarland. and William O. (Worksheet I) How the Builder Wray, "Expanding the SIR MethDd", Passive Solar Journal. Vol. 1, No.2, Guidelines Were The heat-loss calculation is based on a 1982, pp. 67-90. Available from the Produced straightforward summation of the American Solar Energy Society. 2400 traditional elements that make up the Central Ave. Unit B-1, Boulder. CO The text of the Builder Guidelines book building heat-loss coefficient (excluding 80301. is generated by merging two computer the solar components). The worksheet meso The first is a word-processor file procedure estimates the annual heat loss 2. J. Douglas Balcomb, Robert W. Jones, containing the text; it does not change by multiplying the heat-loss coefficient Robert D. McFarland. and William O. from location to location. The second by annual degree days (times 24 to Wray. Passive Solar Heating Analysis, contains numbers and text and is convert from days to hours). Degree days American Society of Heating. location dependent. This second file is for each month were determined using Refrigerating, and Air-Conditioning produced by running a computer an appropriate base temperature that Engineers, 1984. Available from program that calculates performance accounts for an assumed thermostat ASHRAE, 1719 Tullie Circle. NE, Atlanta, numbers based on long-term monthly setting of 70 degrees. an assumed GA 30329. weather and solar data compiled by the internal heat generation of 36 Btu/day National Oceanic and AtmospheriC per sq ft of floor area. and the total 3. J. Douglas Balcomb and William O. Administration for a particular location. building loss coefficient. This forms the Wray, Passive Solar Heating Analysis, The merge operation slots the numbers basis of the table of heating degree day SupplemeDt ODe, Thermal Mass and text in the second file into their multipliers. The result of the worksheet Effects aDd Additional SLK correct locations in the first me. This is is an estimate of the annual heat CorrelatioDs, American Society of then laser printed to produce the required to maintain comfort. excluding Heating. Refrigerating. and Air­ camera-ready manuscript. both positive and negative effects Conditioning Engineers, 1987. See resulting from the solar components. In ASHRAE address above. this estimate. no solar heating credit is More than a Decade of given to east, west. and north windows, Experience because it is assumed that these will be Temperature Swing protected by vegetation or other shading (Worksheet III) The concentrated effort of research, in accordance with the Builder Guideline design. construction. monitoring. and recommendations. This is a conservative The temperature swing estimate on evaluation of actual buildings that assumption because there will always be worksheet III is based on the diurnal started at the First Passive Solar some solar gain through these windows. heat capacity (dhc) method (reference 3). Conference in Albuquerque in 1976 has The method is an analytic procedure in continued up to the present. It is Annual Auxiliary Heat which the total heat stored in the estimated that more than 200.000 building during one day is estimated by passive solar homes have been built in (Worksheet II) summing the effective heat storage the United States during this time. This potential of the all the various materials wealth of experience has been reviewed The tables of passive solar savings in the building for a 24-hour periodic by NREL, the Technical Committee of fractions are calculated using the solar cycle of solar input. Rooms with direct PSIC, and by the Standing Committee on load ratio (SLR) method (references 1 and gain are assumed to have radiative Energy of the National Association of 2). Monthly solar savings fraction (SS1'1 coupling of the solar heat to the mass. Home Builders and is distilled into these values are determined using correlation Rooms connected to rooms with direct Guidelines. fits to the results of hourly computer gain are assumed to have convective simulation calculations for a variety of coupling, which is rather les!;! effective, Analysis Procedures climates. These 12 values are converted especially for massive elements. The dhc into an annual value and entered into of the sheetrock, framing, and worksheet Tables FI-F4. The SLR is approximated as 4.5 or 4.7 Btuf"F per The analysis procedures used method gives answers that agree within throughout the GUidelines were sq ft of floor area. Worksheet Tables H 1 about 5% of the hourly computer developed using simple. well-established and H2 list the increased value of simulations and within 11% of the methods for estimating the performance diurnal heat capacity for various measured passive solar performance of conventional materials that are often of passive solar heating and natural 55 bUildings monitored under the Solar used to provide extra heat storage, cooling strategies. These procedures Buildings Program. The SSF estimates (described below) were developed at the assuming these materials replace account properly for both solar gains sheetrock.

JackSOD, Mississippi 88 APPENDIX

The only numbers in worksheet III underestimates very large cooling loads worksheet can be used anywhere within that are location dependent are the in poorly designed buildings. 4 degrees of latitude of the parent comfort factors, taken from Table I. The The adjustment factors for location. direct-gain comfort factor is 61% of the ventilation properly account for The cooling estimate obtained from solar gain transmitted through vertical, maintaining comfort in hot and humid worksheet IV is specific to the location. south-facing double glazing on a clear climates. Ventilation is restricted to Within the same viCinity and within plus January day. The driving effect of times when the outside dew-point or minus 20%, the result could be sunspaces and vented Trombe walls is temperature is less than 62 OF. This adjusted, based on a ratio of cooling assumed to result in one-third this restriction avoids ventilation when high degree days. However, this adjustment is value, based on data from monitored hUmidity might cause discomfort not done automatically within the buildings. The origin of the 61 % factor is worksheet. described in the references. 4. Robert D. McFarland and Gloria Lazarus, Monthly AwdIlary CooUng Estimation for Residential Buildings, Getting Data Annual Auxiliary Cooling lA-11394-MS, Los Alamos National Heating and cooling degree-day data can (Worksheet IV) Laboratory, NM 87545, 1989. be obtained from the National Climatic The purpose of including the summer Center, Asheville, NC. Refer to cooling estimates in the Builder Notfor Sizing Equipment Climatography of the United States No. Guidelines is to (1) determine if design 81 which lists monthly normals for the elements added to promote passive solar All heating and cooling values given in period 1951-1980 on a state-by-state heating will cause excessive summer the Builder Guidelines Tables and basis. More than 2400 locations are cooling loads and (2) provide a rough numbers calculated using the listed in this data base. estimate of the effectiveness of solar worksheets are for annual heat delivered shading and natural cooling strategies. or removed by the mechanical heating or The analysis method is based on a cooling system. You cannot directly use modified monthly degree-day procedure these numbers for sizing the capacity of in which the day is divided into day and this equipment. The methods developed night periods (reference 4). All estimates by the American Society of Heating, are derived from correlations based on Refrigerating, and Air Conditioning hourly computer simulations. Solar, Engineers for sizing equipment are well­ conduction, and internal gains are established and are recommended. The estimated for each half-day period in purpose of the guidance provided in each month. Delay factors are used to these booklets is to minimize the account for heat carryover from day to operating time and resources consumed night and night to day. The results are by this eqUipment. estimates of annual sensible cooling delivered by the air conditioner and do Using the Worksheets in not include latent loads. Because the the original Los Alamos Nearby Locations monthly procedure is too complex to be The applicability of worksheets I and II implemented in a worksheet, a Simplified can be extended somewhat by using the procedure is adopted on worksheet IV. base-65 OF degree-day value for a site Heat Gain Factors and Internal Gain which is close to the location for which Factors in Tables L and N are the the worksheet tables were generated. We calculated annual incremental cooling recommend limiting such applications to loads resulting from a one-unit sites where the annual heating degree­ incremental change in the respective days are within plus or minus 10% of the heat input parameter (that is, a one-unit parent location and where it is change in UA, glazing area, or number of reasonable to assume that the solar bedrooms). The combined heat load radiation is about the same as in the resulting from all inputs is summed and parent location. The procedure 1s simple: then adjusted for thermal mass and Use the measured base-65 OF degree-day ventilation. This correction includes a value in worksheet I, line F, instead of constant required to match the the degree-day value for the parent calculated cooling load of the base-case location. building. This linearized procedure gives Worksheet III depends only slightly accurate estimates for cooling loads that on location. The only variables are the are less than about 150% of the base­ Comfort Factors in Table I, which only case building: however, it change with latitude. Thus, this

Jackson, Mississippi