San Francisco Bay Area, California
Passive Solar Design Strategies: Guidelines for Horne Building
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 BODle Building
"San Francisco Bay Area
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 legalliabillty 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. AppUcability of the San Jose Guidelines
This woIbhop and the related PSIC Guidelines year; the areas just a few miles away can center on San Jose, California. Located at the remain much more comfortable, not requiring southern tip of San Francisco Bay, San Jose is air conditioning (such as San Jose); and the characterized by stable year-round inland areas away from the cooling effects of temperatures, strongly moderated by the the afternoon seas breeze can become very hot proximity of the ocean and Bay. The average and lead to major air conditioning loads. The winter temperatures of 50 to 55 degrees dashed line shown extending roughly from Fahrenheit result from a normal minimum of Antioch northward through Fairfield 40 to 45 degrees F to a normal maximum of approximately represents the transition zone 60 degrees F. The average summer from mild summers to hot summers. temperatures are a comfortable 65 to 70 degrees F, with a diurnal variation of 25 As a result, passive solar design for those degrees F spanning between nighttime values regions inside the heavy line with roughly of 55 degrees F and daytime highs of 80 comparable winter heating conditions needs to degrees F or less. Precipitation is largely take into account the major differences in confmed to the winter months from November summer cooling requirements, and be adjusted through March. to provide the greatest energy reduction and comfort suitable to the particular microclimate. The heavy line on the applicability map There is no one passive solar design confines areas of roughly comparable winter appropriate to the entire region shown, even heating degree days (Plus or minus about though the winter months' heating 10%). It is strongly influenced by topography. requirements are very similar. Instead, the Those areas outside of the included region all principles of providing year round comfort and contain hills or mountains, leading to energy savings by passive design techniques considerably cooler winter conditions. The need to be understood and applied in a manner dashed circle represents the normal 80-mile appropriate to each microclimate. radius of applicability for the PSIC Guidelines. Much of the numeric information in the A comparison of comparable climates by Guidelines. including the Performance Potential matching heating degree days can, in this Table, the Example Tables, and the Worksheet instance, be very misleading. The heavy line Tables, are based on long-term weather data in the applicability map represents areas with taken in San Jose. The solar savings fractions roughly comparable winter heating degree days are based on solar data taken from the Typical to San Jose, even though the annual total can Meteorological Year data file for Oakland. vary by more than 20% from San Jose's total. Solar radiation could vary somewhat from one This is because the winter climate is more apt location to another within the Bay Area. to be moderated by actual weather effects (e.g. rainstorms), somewhat leveling the otherwise Worksheets I and II may be used throughout varying microclimates that are characteristic of the Bay Area provided the appropriate heating the San Francisco Bay Area. degree day value is used in WoIbheet I. See Table CI and the list below for 3O-year This situation is reversed in the summer, where average degree-day values published by the areas in immediate proximity to the sea NOAA. breezes can be quite cold (Marlt Twain once noted that the coldest winter he ever Worksheet III is applicable within a range of experienced was summer in San Francisco), latitudes from 36 degrees North to 40 degrees requiring some heating assist almost the entire North. Worksheet N is applicable in Oakland; no provisions have been made in the worksheet format for correcting these values. However, it would be reasonable to multiply the final cooling load by the ration of cooling degree days in the particular location divided by the cooling degree days in Oakland (174 COD). In any case, residential cooling requirements are minimal throughout the Bay Area; San Jose is slightly warmer than Oakland.
CITY !!QQ ~ Berkeley 2951 91 Buttonwillow 2622 1890 Cloverdale 2763 814 Coalinga 2581 1802 Colusa 2793 1373 Davis 2843 1059 Fairfield 2686 821 Handford 2736 1532 Healdsburg 2572 773 -' King City 2639 406 Lindsay 2634 1617 Lodi 2861 1001 Los Bamos 2616 1448 Los Gatos 2740 591 Madera 2673 1654 Maricopa 2302 2317 Marysville 2551 1539 Mezoced 2653 1465 Modesto 2671 1287 Napa 2749 416 Oakland 2877 174 Orange Cove 2685 1665 Orland 2824 1520 Paso Robles 2885 734 Red Bluff 2682 1931 Redding 2544 2139 Redwood City 2600 432 Richmond 2687 162 Sacramento 2398 1379 San Francisco 3161 115 San Jose 2439 498 San Luis Obispo 2498 285 San Rafael 2439 483 __ '- Stockton 2674 1448 L:' Tracy 2704 1156 ~ ..... Visalia 2460 1804 Wuco 2466 1999 Willows 2836 1429 Winters 2593 1524 Woodland 27C» 1321
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Guidelines
Part One. Introduction ...... 1 1. The Pass1ve Solar Design Strateg1es Package...... 2 2. Passive Solar Performance 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, Pass1ve Solar ...... 9 3. Improving Conservation Performance...... 10 4. Mechanical Systems...... 13 5. South-Facing Glass ...... ,14 6. Thermal Mass ...... 15 7. Orientation ...... 16 8. Site Planning for Solar Access...... 17 9. Interior Space Planning ...... 18 10. Putting it Together: The House as a System ...... 18
Part Three. Strategies for Improving Energy Performance in San Jose, California ...... 21 1. The Example Tables...... 22 2. Suntempertng...... 23 3. Direct Gain...... , ...... 24 4. Sunspaces ...... 27 5. Thermal Storage Wall ...... 30 6. Combined Systems ...... 32 7. Natural Cooling GU1delines ...... 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 Terms...... 81 References...... 82 Summary Tables...... 84 Technical Bas1s for the Builder Gu1delines...... 87
SaD lI'rancl.co Bay Area Acknowledgements whose work is the basis of the Director of National Accounts, Guidelines; Robert McFarland. National Concrete Masonry LANL. for developing and Association. Chainnan of PSIC's Passive Solar Design Strategies: programming the calculation Board of Directors during the Guidelines for Home Buad.ers 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 Philip W. America. Region 4. Chatnnan of organizations and indMduals. Fairey. FSEC. whose research PSIC's Technical Connnittee The challenge of creating an has guided the natural cooling during the development of these effective design tool that could sections of the guidelines; the guidelines; and Bion Howard. be customized for the specific members of the NAHB Standing Chatnnan of PSIC's Technical needs of builders in cities and ConnniUee on Energy. especially Connnittee 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 unstintingly of their time. areas of expertise. their long experience in building their expertise. and their Passive Solar Design energy-efficient homes; at U.S. enthusiasm. Strategies is based on research DOE. Frederick H. Morse. sponsored by the United States Fonner Director of the Office of Department of Energy (DOE) Solar Heat Technologies and Solar Buildings Program. and Mary-Margaret Jenior. Program carried out primarily by the Los Manager; Nancy Carlisle and Alamos National Laboratory Paul Notarl at NREL; Helen (LANL). the National Renewable English. Executive Director of Energy Laboratory (NREL). PSIC; Michael Bell. fonner fonnerly Solar Energy Research Chairman of PSIC. and Layne Institute (SERI). and the Florida Evans and Elena Marcheso Solar Energy Center (FSEC). Moreno. fonner Executive The National AsSOCiation of Directors of PSIC; Arthur W. Home Builders (NAHB) Standing Johnson. for technical Connnittee 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 workshop in North (lEA). Solar Heating and Cooling Carolina; Charles Eley. for his program. Task vm 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). ConnniUee. 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.
San FrancilCo Bay Area 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 STRA TEGIES 1
Part One: Introduction
1. The Passive Solar Design Strategies Package
2. Passive Solar Performance Potential
San FrancllCo Bay Area 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 Guidelines contain BuUderGuide has been develope information 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 Spec1fic examples of systems worksheets. The program requires spec1fic information and which will save various operates like a spreadsheet: the attention to the details of design percentages of energy are user ftlls 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, fill-in-the-blank method including all table lookups, and changes in a builder's standard to pre-evaluate the performance 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 Example Worksheets allows the user to systems can ahnost eliminate a demonstrates how to complete vary input values, BuUderGuide house's need for purchased the worksheets for a typical helps the user quickly evaluate a energy - but probably at a reSidence in San Jose. 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 Buil.derGuide 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 performance 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 performance can be evaluated characteristics. virtually anywhere. Passive Solar Design Strategies: GuidelineS Jor Home Builders is written to help give builders the information they need to make these decisions.
SaD Francbco Ba1' Area fJA::i::iIVE SOLAR DESIGN STRA TEGIES
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 walls and sunspaces. and for study 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 San Jose, So, many fundamental aspects The Example Tables in Part CalifOrnia 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 house is assumed small local area, and even on the can compare them to the to be built over a ventilated features of the building site. designs you are evaluating. For crawlspace, because this is Many of the suggestions in this example, the Passive Solar typical in California. section apply specifically to San Sunspace Example Case which The examples show how to Jose, California, but there is also uses 40% less energy than the achieve 20%, 400/0 and 600A> information which will be useful Base Case House (page 29) has: energy-use reductions using in any climate. • A ConselVation Performance three basic strategies: Part One introduces Passive Level of approximately 15,384 • Added Insulation: Solar Design Strategies, and Btu/yr-sf, Increasing thermal resistance presents the performance • An Aux1lJary Heat Insulation levels without adding potential of several different Performance Level of solar features. passive solar systems in the San approximately 6,764 Btu/yr-sf, • Suntempering: Increasing Jose 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 0 Btu/yr total floor area, without adding information gives a general idea sf. thermal mass (energy storage) of how various systems might In this example, the energy beyond what is already in the perform in San Jose. savings are achieved by no framing, standard floor Part Two discusses the basic increase in insulation over the coverings and gypsum wall concepts of passive solar design Base Case House, adding a board and ceiling surfaces. and construction: what the sunspace with south glazing Suntempering is combined with advantages of passive solar are, area equal to 6% of the house's increased levels of thermal how passive solar relates to floor area, and using a ceiling reSistance Insulation. other kinds of energy fan to cut some of the air conservation 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.
San FranciKo Bay Area 4 GUIDELINES PART ONE: INTRODUCTION
• Solar Architecture: 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 San Jose, CalifOrnia, Gain Factor table. Sunspace, and Thenna! 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 thennal resistance insulation. you to compare different passive perfonnance 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 perfonnance of the house. energy conservation measures guidelines have been followed, so The most effective way to use (insulation, sealing, caulking, the houses 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 windows and doors. 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 thenna! units per square foot more detailed infonnation is first calculate the perfonnance 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 II: AlIxtJIary text, and a list of other house with a variety of energy Heat Performance Level: infonnation sources can be perfonnance 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 suntempertng 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 San The Worksheets provide a contributed by passive solar. Jose, California, 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 perfonn 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 thenna! mass to assure comfort condItioning) will be. and good thermal perfonnance. The Worksheets are Worksheet ill 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 infonnation 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,
SaD FrllDclsco Bay Area PASSIVE SOLAR DESIGN STRATEGIES
• Worksheet IV: Summer 2. Passive Solar of south-faCing glass, and each CooUng Performance Level: Performance passive solar 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 not, assume that all the systems are however, intended for use in The energy peIiormance 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 peIiormance 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 peIiormance 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 peIiormance 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 peIiormance 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 peIiormance. The Percent Solar percent of the 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 peIiormance 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 11.2%, 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 peIiormance 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 floor over a crawlspace. The worksheets. A deSCription of the Base Case House has 45 sf of deSign features, along With the south-facing glazing. For the house plans, elevations and purposes of this example, the sections, is included for Suntempered house has 100 sf additional support information.
San Franclaco Bay Area 6 GUIDELINES PART ONE: INTRODUCTION
l Performance Potential of Passive Solar Strategies In San Jose, California 1,500 sf, Single Story House Yield Percent Btu Saved per Solar Square Foot of Case Savings South Glass
Base Case 11.2 not applicable (45 sf of south-facing double glass) Suntempered 24.1 116,936 (100 sf of south-facing double glass)
Direct Gain (145 sf of south glass) Double Glass 33.4 111,147 Triple or low-e glass 33.8 115,350 Double glass with R-4 night insulation 1 36.1 128,519 Double glass with R-9 night insulation 1 36.8 131,858
Sunspace (145 sf of south glass) Attached with opaque end walls2 31.6 105,309 Attached with glazed end walls2 31.1 102,365 Semi-enclosed with vertical glazing3 32.9 109,921 Semi-enclosed with 50' sloped glazing3 40.7 152,804
Thermal Storage Wall - Masonry/Concrete (145 sf of south glass) Black surface, double glazing 30.0 96,114 Selective surface, single glazing 37.8 137,500 Selective surface, double glazing 36.3 130,094
Thermal Storage Wall - Water Wall (145 sf of south glass) Selective surface, single glazing 42.7 162,735
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, roof 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.)
Ban FrancllCo Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 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
SaD I'rUlclM:O Bay Area 8 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
1. Why Passive Solar? tnsulat11n 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 tht. 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 st1llignore a lot of energy prcx1ucers instead of conducted extensive national energy saving opportunities - energy Uabilities. surveys of passive solar homes, opportunities available in the Another example: high home owners and potential sunlight fall1ng 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 300/& 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. builder 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 perfonnance 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 l1v1ng 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 fam1l1ar 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 blfh. perceive their own household Advantages of Passive Solar energy b1lls as getting smaller - quite the opposite. So a house • Energy performance: 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 oil 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
San Franct.co Bay Area PASSIVE SOLAR DESIGN SFRATEGIES 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 advantage of summer breezes, or complicated by many factors, Passive Solar landscaping for natural cooling, and has been a subj ect 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 performance 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 Thermal mass will hold warmth • EnerlY 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. 1nflltration, glazing type and In the simplest terms, 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 thermal mass - ·which are basic to both increasing south-facing window materials with a high capacity suntempered and passive 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 thermal mass. facing glass is used in the planning for solar access; • Solar Architecture: going house, the more thermal mass interior space planning; and beyond conservation and must be provided, or the house approaching to the house as a suntempertng to a complete will overheat and the solar totally integrated system. system of collection, storage and system will not perform as use of solar energy: using more expected. south glass, adding approprtate Improperly done, passive thermal mass, and taking steps solar may continue to heat the to control and distribute heat house in the summer, causing energy throughout the house. discomfort or high air • Natural CooUng: using conditioning bills, or overheat design and the environment to the house in the winter and cool the house and increase require additional ventilation. comfort, by increasing air movement and employing shading strategies. What is Immediately clear is that these categories overlap. A good passive solar design must include an appropriate thermal envelope, energy effiCient mechanical systems, energy efficient appliances and proper solar architecture, specifically the appropriate amounts and locations of mass and glass.
SaD FrancllCo Bay Area 10 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
3. Improving The thermal resistance of Slab edge Insulation should celUng/roof assembUes, walls be at least two feet deep. Conservation and floors is affected not only by extending from the surface of the Performance the R-value of the insulation floor or above. Materials for sIal 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 18 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 conservation 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 basements required. house's basic ability to conserve provide a buffering effect which Heated basement 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 attics. 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 by using blown-in insulation or upper portion. Insulation can be • AIr inftltration • 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, ceilings. roof and ventilation. If the basement walls are foundation 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 tnstallfng 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 18 hung may In.ul.Uon In an AWe 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 mJght 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.
San lI'ranclsco Bay Area PASSIVE SOLAR DESIGN STRATEGIES 11
Air Il\Iiltration 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 necessruy to around all openings to the outside or to unconditioned rooms; energy conservation as adding ./ Caulk around all windows and doors before drywall is hung; seal all insulation. penetrations (plumbing, 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, wUl 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 nonnal winter conditions. ./ Locate continuous vapor retardants located on the warm side of the insulation (building wrap, continuous interior polyethylene, etc.); Increasing the tightness of the house beyond that may ./ Install dampers and/or glass doors on fireplaces; combined with improve the energy perfonnance, 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 house!;) may perfonn 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 door 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.
San FrancllCo Bay Area 12 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
Non-80lar Glazing account for the glass. the frame. Weat windows may be the South-faCing windows are the air gap and any special now most problematic. and there are considered solar glazing. The e) coatings. few shading systems that will br 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 U'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 summer. 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. Recommended Non needs unless heat gain is considering both summer and South Glass Guidelines. page m1nimJzed with careful attention winter performance. 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 gla.zJ.ng 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 summer. 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
8aD l'rancilCo Bar Area PASSIVE SOLAR [)ESIGN STRA TEGIES 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 mass (and thus a large capacity usual placement of registers heating, ventilating and air conditioning systems (HVAC) will for storing energy and releasing under windows at the end of it during the night), setback of long runs. This resulted in good interact all year round. so the the thermostat may not save comfort and energy performance. most effective approach will be The performance of even the to design the system as an very much energy unless set 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 uninsulated ducts, or by worth noting in energy-efficient • Ducts: One area often neglected but of key importance overlooking other basic energy houses: • 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 lOOOAl where the ducts tum 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.
San FrancllCo Bay Area 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 11% 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 perfonnance in winter, but lead to overheating even in is not properly shaded. not so much that cooling winter. Ordinary 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 88 sf of direct damage and leaking, and so is carefully related to the amount gain glazing with 70 sf of almost always a better year of thermal mass. Suntempered sunspace glazing for a total of round solution. houses use no additional 159 sf of solar glazing, or 10% 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 11%. For a typical house. Houses with design like this, thermal mass solar architecture must have would be required both in the additional thermal mass. house and within the sunspace. There are three types of The Natural Cooling limits on the amount of south guidelines in Part Three include facing glass that can be used recommendations on the 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, regardless of how much additional thermal mass is provided. This limit will reduce the problems associated with visual glare or fabric fading. Further details about the most effective sizing of south glass and thermal mass for direct gain systems are provided in Part Three.
San Francisco Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 1:>
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 masomy 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 s1m1lar 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 better. 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 masomy, 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) (lbIft3) (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 reactions. Water actually has a Pavers 130 - 135 2.2 - 2.3 higher unit thermal storage Concrete Masonry 0.19-0.22 capacity than concrete or Concrete Masonry Units 80 - 140 1.3 - 2.3 masomy. Water tubes and units Brick 115 - 140 1.9 - 2.3 Pavers 130 - 150 called ''water walls" are 2.2 - 2.5 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).
San Franciaco Bay Area 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 performance reduced, but faCing south. But as a practica true south. This orientation will summer air conditioning loads matter, if the house's short side provide maximum performance. also significantly increase, has good southern exposure it Glazing oriented to within 15 especially as the orientation goes will usually accommodate degrees of true south will west. The warmer the climate, sufficient glazing for an effective perform 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. still provide a substantial level of general, southeast orientations solar contribution. present less of a problem than In San Jose, magnetic north southwest. as indicated on the compass is actually 17 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.
San FranclllCo Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 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 L perfonnance is to allow the south side as much unshaded exposure as poss1ble during the winter months. I As discussed above. a good Solar Subdivision Layouta solar orientation is poss1ble Solar access may be provided to the rear yard, the side ytird or the front yard of solar within a relatively large southern ~ 2 Story fUldings Allowed homes. arc. so the flexibility exists to achieve a workable balance Ideal Solar 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 = 12 It. the slope of the sUe. the B = 20 ft., and C = 46 ft. ' , individual house plan. 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 U's important 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 eas1est in subdivis10ns 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 countIy have come up south. Where the streets run Solar Subdivision uyouta Short east-west cul-de-sacs tied into north with flexible ways to proVide north- south. creation of east south collectors is a good street pattem for adequate solar access. west cul-de-sacs will help ensure solar access. 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 BuUder's Guide to Passive Solar the house should be exposed to Home Design Land sunlight with no obstructions and Development and Site Planning within an arc of 60 degrees on either side of true south. but jor Solar Access. reasonably good solar access will soo 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
SaD Franclsco Bay Area 18 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
9. Interior Space Another general principle 15 10. Putting it Planning that an open floor plan will allow Together: The House the collected solar heat to as a System Planning room lay-out by circulate freely through natural considering how the rooms will convection. Other ideas from effective Many different factors will affect be used in different seasons, and a house's overall performance, at different Urnes of day, can passive solar houses: • Orienting internal mass and these factors all interact: save energy and increase the mechanical system, the comfort. In houses with passive walls as north -sou th partitions that can be "charged" on both insulation, the house's solar features, the lay-out of tightness, the effects of the rooms - and interior zones sides. • Using an east-west partition passive solar features, the which may include more than appliances,and,very one room - 15 particularly wall for thennal mass. • Avoid dividing the house importantly, the actions of the important. people who live in the house. In In general, living areas and between north and south zones. • Using thennal storage walls each of these areas, changes are other high-activity rooms should possible which would improve be located on the south side to (see page 30): the walls store energy all day and slowly release the house's energy performance. benefit from the solar heat. The Some energy savings are closets, storage areas, garage it at night, and can be a good alternative to ensure privacy and relatively easy to get. Others and other less-used rooms can can be more expensive and more act as buffers along the north to buffer noise when the south side faces the street: difficult to achieve, but may side, but entty-ways should be provide benefits over and above located away from the wind. • Collecting the solar energy in one zone of the house and good energy performance. Clustering baths, kitchens and A sensible energy-emcient laundry-rooms near the water transporting it to another by fans or natural convection house uses a combination of heater will save the heat that through an open floor plan. techniques. would be lost from 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 15 a basic checklist for energy-efficient design. These techniques are dealt with in tTrue more detail, including their North impact in your location, in Part
In.t~rlor SPII~ Planning Three. LJvmg and hIgh activity spaces should be located on the south.
SaD Fraac1.co Bay Area PASSIVE SOLAR DESIGN STRATEGIES l~
Checklist for Good Design
~ 1. Building orientation: A number of innovative techniques can be used for obtaining good solar access. No matter what the house's design, and no matter what the site, some options for orientation will be more energy efficient than others, and even a very simple review of the site will probably help you choose the best option available.
~ 2. Upgraded levels of Insulation: It is poSSible, of course, to achieve very high energy-efficiency with a "superinsulated" design. But in many cases, one advantage of passive solar design is that energy-efficiency can be achieved with more economical increases in insulation. On the other hand, if very high energy performance is a priority - for example, in areas where the cost of fuel is high - the most cost-effective way to achieve it is generally through a combination of high levels of insulation and passive solar features.
~ 3. Reduced air Inflhratlon: Air tightness is not only critical to energy performance, but it also makes the house more comfortable. Indoor air quality is an important issue, and too complex for a complete discussion here, but in general, the suntempered and passive solar houses built according to the Guidelines provide an alternative approach to achieving improved energy efficiency without requiring air quality controls such as air to air heat exchangers, which would be needed if the house were made extremely airtight.
~ 4. Proper window sizing and location: Even if the total amount of glazing is not changed, rearranging the location alone can often lead to significant energy savings at little or no added cost. Some energy-conserving designs minimize window area on all sides of the house - but it's a fact of human nature that people like windows, and windows can be energy producers if located correctly.
~ 5. Selection of glazing: Low-emissivity (low-e) glazing types went from revolutionary to commonplace in a very short time, and they can be highly energy-efficient choices. But the range of glazing possibilities is broader than that. and the choice will have a significant impact on energy performance. Using different types of glazing for windows with different orientations is worth considering for maximum energy performance; for example, using heat-rejecting glazing on west windows, high R-value glazing for north and east windows, and clear double-glazing on solar glazing.
~ 6. Proper shading of windows: If windows are not properly shaded in summer - either with shading devices, or by high-performance glazing with a low shading coefficient - the air conditioner will have to work overtime and the energy savings of the winter may be canceled out. Even more important, unwanted solar gain is uncomfortable.
~ 7. Addhlon of thermal mass: Adding thermal mass - tiled or paved concrete slab, masonry walls, brick fireplaces, tile floors, etc. - can greatly improve the comfort in the house, holding heat better in winter and keeping rooms cooler in summer. In a passive solar system, of course, properly sized and located thermal mass is essential.
~ 8. Interior design for easy air distribution: If the rooms in the house are planned carefully, the flow of heat in the winter will make the passive solar features more effective, and the air movement will also enhance ventilation and comfort during the summer. Often this means the kind of open floor plan which is highly marketable in most areas. Planning the rooms with attention to use 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.
~ 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.
SaD Fraucl.c:o Bay Area 20 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
SaD Frmclsco Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 21
Part Three: Strategies for Improving Energy Performance in San Francisco Bay Area
1. The Example Tables
2. Suntemperlng
3. Direct Gain
4. Sunspaces
5. Thermal Storage Wall
6. Combined Systems
7. Natural Cooling Guidelines
San Francisco Bar Area 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: Consexvation, approximate and are intended to Auxillaxy Heat, and Cooling show how incremental In the following sections of the Performance (see page 4) improvements can be achieved. Guidelines, the prtmaIy passive The Example tables then show All R-values in the Examples solar systems - Suntempering, how the house design could be and Worksheets are equivalent Direct Gain, Thermal Storage changed to reduce winter R-values for the entire Walls and Sunspaces - are heating energy by 20, 40 and construction assembly, not just described in more detail. 60%, compared to this Base for the cavity insulation itself, As part of the explanation of Case. and take into account framing each system, an Example table There are, of course, other and buffering effects. is provided. The Examples ways to achieve energy savings Other assumptions are noted present the following information than those shown in the for each Example. However, one about a Base Case house, based Examples. The Examples are more general assumption is on a National Association of designed to show an effective important to note here. When Home Builders study of a typical integration of strategies, and a the Examples were calculated, it construction: useful approach to the design of was assumed that natural • Insulation levels (ce1l1ngs the house as a total system. cooling strategies such as those and walls); Using any of these combinations deSCribed in these Guidelines • TIghtness (measured in air would result in excellent were used, particularly in the changes per hour, ACH); performance in your area. very high-performance systems. • The amount of glass area on However, they are general The greater the percentage each side (measured as a indications only, and using the reduction in heating energy percentage of floor area; the Worksheets will give you more needs using passive solar actual square footage for a 1,500 information about your specific design, the more shading and sf house is also given as a design. natural cooling were assumed. reference pOint); The Example assumes a The Examples show passive • The "percent solar savings" 1,500 sf house, but the solar strategies, but an (the part of a house's heating percentages apply to a house of Insulation Only Example table energy saved by the solar any size or configuration. (achieving energy savings only features); and by increasing insulation levels, without solar features) is provided in the Summaxy beginning on page 42, for comparison.
Sua FrUlcUcO Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 23 2. Suntempering Examples of Heat Energy Savings Suntempered and passive solar Suntempered 1 .500 sf Single Story House houses both: • begin with good basic Base enerO'-eonlervation, Case 20% 40% 60% R-Values • take maximum advantage of Ceiling/Roof 30 29 32 41 the building site through the Walls 19 18 21 28 right orientation for year-round Floor 19 18 21 28 energy savings, and Glass 1.8 1.8 1.8 1.8 • have increased louth-faein, Air Changes/Hour 0.50 0.49 0.50 0.46 glasl to collect solar energy. Suntempertng is the simplest Glass Area (percent of total floor area) passive solar system, and refers West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% to modest increases in windows East 3.0% 4.0% 4.0% 4.0% on the south side. South 3.0% 5.3% 6.7% 6.7% No additional thermal mass Solar System Size (square feet) is necessary, only the "free South Glass 45 79 100 100 mass" in the house - the framing, gypsum wall-board and Percent Solar Savings furnishings. 26% 40% 51% 58% In a "conventional" house, Performance (Btu/yr-sf) about 25% of the windows face Conservation 14.670 15.116 13.908 11.125 south, which amounts to about Auxiliary Heat 10.791 8.985 6.790 4.593 3% of the house's total floor Cooling 3.183 2.564 1,427 1.287 area. In a suntempered house, Summary: The window area has been slightly decreased on the west. the percentage is increased to a increased Slightly on the east and north. and increased significantly on the maximum of about 7%. south. The energy savings are more modest with this system, but suntempertng is a very low-cost strategy. 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 conservation measures, room lay-out, siting, glazing type and so on are still important for performance and comfort in suntempered homes.
San FranciMlo Bay Area 24 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
3. Direct Gain Glazing incorporation of sign1ftcant Double glazing is recommended amounts of heavy thermal mass The most common passive solar for direct gain glazing in San is a little more difflcult. Thermal system is called direct gain: Jose. The Performance Potential mass floor coverings over sunlight through south-facing table on page 6 shows the basements, crawlspaces and glazing falls directly into the relative performance of different lower stories would generally be space to be heated, and is stored types of direct gain glazing. You limited to thin set tile or other in thermal mass incorporated wUl note from this table that thin mass floors. into the floor or interior walls. yield increases by 3% between When more mass is required. double and triple or low-e the next best option is for glazing. Night insulation also interior walls or interior masoruy improves energy performance fireplaces. When evaluating dramatically. In fact, as the costs, the dual function of mass Performance Potential table walls should be remembered. shows, covering the windows at They often serve as structural night or on cloudy days with the elements or for fire protection as equivalent of R-4 shades or well as for thermal storage. other material wUl save almost Another option is to switch to as much energy as with R-9 another passive solar system material. But studies have type such as attached slab-on shown that only relatively few grade sunspaces or thermal homeowners wUl be diligent storage walls built directly on enough about operating their exterior foundation walls. Direct GIIln night insulation to achieve those Sunlit thermal mass floors Direct gain is the most common passive solar system in residential applications savings. Energy-efficient should be relatively dark in glazing, on the other hand. color, to absorb and store energ: Sizing Limit needs no operation. and more effectively. However, mass Total direct gain glass area therefore is a more convenient walls and ceilings should be should not exceed about 12% of and reliable option. light in color to help distribute the house's floor area. Beyond both heat and light more evenly. that, problems with glare or Thermal Mass fading of fabriCS are more likely Thermal mass can be to occur, and it becomes more incorporated easily into slab-on difflcult to provide enough grade type buildingS as either thermal mass for year-round floor covering. walls or veneers comfort. over interior walls. If the mass So the total south-facing is placed in the floor. it will be glass area in a direct gain much more effective if sunlight system should be between 7% falls directly on it. (the maximum for suntempered Effective materials for floors houses) and 12%, depending on include painted. colored or vinyl how much thermal mass will be covered concrete. brick (face used in the deSign, as discussed brick or pavers have even higher below. density than ordinary building brick). quarry tile. and dark colored ceramic tile. For houses built with crawlspaces or basements. the
SaD PruacilCO Bay Area PASSIVE SOLAR DES/G{V STRA TEGIES 25
Ratio of Glass to Mass. The More south-faCing glazing Thickness. For most materials, following procedure can be used than the maximum as the effectiveness of the thermal to detennine the maximum detennined here would tend to mass in the floor or interior wall amount of direct-gain glazing for overheat the room, and to increases proportionally with a given amount of thermal mass. reduce energy performance as thickness up to about 4 inches. If the amount of direct-gain well. After that, the effectiveness glazing to be used is already doesn't increase as significantly. known, thermal mass can be A two-inch mass floor will be added until this procedure about two-thirds as effective in a produces the desired direct gain system as a four-inch proportions: mass floor. But a six-inch mass • Start with a direct gain glass floor will only perform about area equal to 7% of the house's eight percent better than a four total floor area. As noted above, inch floor. the "free mass" in the house will The following figure shows be able to accommodate this the effectiveness of thermal much solar energy. mass in relation to density and • An additional 1.0 sf of direct thickness. The vertical axis 1:40 for Floor gain glazing may be added for rotnSul shows how many square feet of every 5.5 sf of uncovered. sunlit mass area are needed for each Mass Location and Effectiveness mass floor. Carpet or area rugs Additional mass must be provided for south added square foot of direct gain. will seriously reduce the facing glass over 7"''{' of the floor area. The As you can see, performance ratio of mass area to additional glass area effectiveness of the mass. The depends on its location within the direct gain increases start leveling off after a space. maximum floor mass that can be few inches of thermal mass. considered as "sunlit" may be estimated as about 1.5 times the 40 south window area. .£ 5O#/cf • An additional 1.0 square foot a:til of direct gain glazing may be :g30 .'i: added for every 40 sf of thermal (J) (J) 75#/cf ~ mass in the floor of the room, C)20 ~ but not in the sun. 8 100#/cf til • An additional 1.0 square foot II) 125#/cf ~10 15O#/cf of direct gain glazing may be (J) (J) til added for each 8.3 sf of thermal ::E mass placed in the wall or 0 ceiling of the room. Mass in the 0 5 10 15 Thckness (flches) wall or ceiling does not have to Mass Thickness be located directly in the The effectiveness of thermal mass depends sunlight, as long as it is in the on the density of the material and thickness. This graph is for wall or ceiling mass in the same room, with no other walls direct gain space. between the mass and the area where the sunlight is falling. Worksheet m: Thermal Mass/Comfort should be used to make sure the house has adequate thermal mass.
San Franciaco Bay Area 26 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
Examples of Heat Energy Savings Passive Solar-Dlrect Gain 1,500 sf Single Story House
Base Case 20% 40% 60% R-values Ceiling/Roof 30 29 29 31 Walls 19 18 18 19 Floor 19 18 18 19 Glass 1.8 1.8 1.8 1.8
Air Changes/Hour 0.50 0.49 0.46 0.47
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% 5.3% 7.9% 12.0%
Added Thermal Mass Percent of Floor Area 0.0% 0.0% 5.7% 30.0%
Solar System Size (square feet) South Glass 45 79 119 180 Added Thermal Mass 0 0 85 450
Percent Solar Savings 26% 40% 54% 69%
Performance (Btu/yr-sf) Conservation 14,670 15,116 15,017 14,870 Auxiliary Heat 10,791 8,985 6,782 4,549 Cooling 3,183 2,564 2,177 4,072
Summary: South-facing glazing has been substantially increased. For these examples, added mass area is assumed to be six times the excess south glass area.
SaD Fraaci.co Ba7 Area PASSIVE SOLAR DESIGN STRA TEGIES 27
4. Sunspaces The sunspace floor is a good location for thermal mass. The The sunspace is a very popular mass floors should be dark in passive solar feature. adding an color. No more than 15-25% of attractive 11v1ng space as well as the floor slab should be covered energy performance. There are with rugs or plants. The lower many variations on the basic edge of the south-facing theme of the sunspace. and the Windows should be no more possibilities for sunspace design than six inches from the floor or are extraordinarily diverse the planter bed to make sure the (References 19 through 22 mass in the floor receives include specific design ideas). suffiCient direct sunlight. If the Sunspaces The sunspace concept used Sunspaces provide useful passive solar windows sills are higher than in these Guidelines can be used heating and also provide a valuable amenity that. additional mass will have to homes. year-round. will provide most or to be located in the wall. all of its own energy needs. and Thermal Mass Another good location for will contribute to the energy A sunspace has extensive south thermal mass is the conunon needs of the rest of the house as facing glass. so suffiCient wall (the wall separating the well. sunspace from the rest of the thermal mass is very important. Sunspaces are referred to as house). Options for the conunon Without it. the sunspace is liable "isolated gain" passive solar to be uncomfortably hot during wall are discussed in more detail systems. because the sunlight is the day. and too cold for plants below. collected in an area which can or people at night. Water in various types of be closed off from the rest of the However. the temperature in containers is another form of house. During the day. the the sunspace can vary more energy storage often used in doors or windows between the than in the house itself. so sunspaces. sunspace and the house can be about three square feet of four opened to circulate collected inch thick thermal mass for each Glazing heat. and then closed at night. square foot of sunspace glazing Single-glazing may be used for and the temperature in the should be adequate. With this sunspaces. although double sunspace allowed to drop. glass-to-mass ratio. on a clear glazing Will further improve The sunspace should not be winter day a temperature swing comfort. in terms of energy on the same heating system as of about 30'F should be savings. The performance the rest of the house. A well expected. potential table on page 6 shows designed sunspace will probably the relative performance of need no mechanical heating different types of glazing. system. but if necessary. a small Windows on the east and fan or heater may be used to west walls should be small (no protect plants on extremely cold more than 10% of the total winter nights. sunspace floor area) but they are The sunspace should be just useful for cross-ventilation. as tightly constructed and Like tilted or sloped glazing. insulated as the rest of the glazed roofs can increase solar house. gain. but they can also present big overheating problems and become counter-productive. If either glazed roofs or tilted glazing are used in the
San Francisco Bay Area 28 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE sunspace, specicl care should be Common Wall Some solar energy may be taken to make sure they can be There are a number of options transferred from the sunspace to effectively shaded during the for the sunspace common wall. the rest of the house by summer and, if necessary, on In mUd climates, and when the conduction through the commOl sunny days the rest of the year, sunspace is vety tightly wall if it is made of thermal too. The manufacturers of constructed, an uninsulated mass. But energy is mainly sunspaces and glazing are frame wallis probably adequate. transferred by natural developing products with better However, insulating the common convection through openings in ability to control both heat loss wall to about R-lO is a good the common wall - doors, and heat gain (for example, roof idea, especially in cold climates. windows and/ or vents. glazing with low shading An insulated common wall will • Doors are the most common coefficients, shading treatments help guard against heat loss opening in the common wall. If and devices, etc.). during prolonged cold, cloudy only doorways are used, the You'll note that in the periods, or if the thermal storage open area should be at least Performance Potential chart on in the sunspace is insufficient. 15% of the sunspace south-glass page 6, sunspaces with glazed If the common wall is a area. roofs or sloped glazing perform masonry wall, it can also be • Windows will also provide very well. This analysis used for thermal mass, in which light and views. The Window assumes effective shading in the case it should be solid masonry area in the common wall should summer. If such shading is not approximately 4 to 8 inches be no larger than about 40% of economical or marketable in thick. Another option is a frame the entire common wall area. If your area, you should consider wall with masonty veneer. only Windows are used, the using only vertical glazing, and Probably the most important operable area should be about accepting somewhat less energy factor in controlling the Z5% of the sunspace's total performance in winter. temperature in the sunspace, south glass area. and thus keeping it as comfortable and effiCient as possible, is to make sure the exterior walls are tightly constructed and well-insulated.
San Franclaco Bay Area Sumn'ler 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 30 29 29 29 screened-in porch. Walls 19 18 18 18 Operable windows and/ or Floor 19 18 18 18 1.8 1.8 1.8 vent openings should be located Glass 1.8 for effective cross-ventilation. Air Changes/Hour 0.50 0.49 0.48 0.49 and to take advantage of the prevailing summer wind. Low Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% inlets and high outlets can be North 3.0% 4.0% 4.0% 4.0% used in a "stack effect". since East 3.0% 4.0% 4.0% 4.0% wann air will rise. These South (windows) 3.0% 3.0% 3.0% 3.0% ventilation areas should be at Sunspace 0.0% 2.4% 6.1% 12.8% least 15% of the total sunspace Solar System Size (square feet) south glass areas. South Glass 45 45 45 45 Where natural ventilation is Sunspace Glass 0 36 91 191 insuffiCient. or access to natural Sunspace Thermal Mass 0 109 275 575 breezes is blocked. a small. Percent Solar Savings thermostat-controlled fan set at 26% 40% 56% 71% about 76'F will probably be a useful addition. Performance (Btu/yr-sf) Conservation 14,670 15,129 15,384 16,024 Auxiliary Heat 10,791 8,978 6,764 4,531 Cooling 3,183 1,743 0
Summary: Insulation and tightness (for the 60% case) 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 SSD1 of the worksheets), with its south glazing tilted at 50 degrees. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double.
San Francisco Bay Area 30 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
5. Thermal Storage Selective Surfaces Wall A selective surface is a special adhesive foil applied to the The Thennal Storage Wall - exterior side of the mass of also sometimes referred to as a Thennal Storage Walls. Trombe wall or an indirect gain Selective surfaces absorb a large system - is a south-facing percentage of solar radiation but glazed wall. usually built of radiate very little heat back to the out-of-doors (low emittance). heavy masoruy. but sometimes using water containers or phase To be effective. selective Thermal Storage Wall . . surfaces must be applied change materials. The masonry A thermal storage wall is an eff~tJve. paS.SIV6 carefully for 100% adhesion to is separated from the glazing solar system, especially to proVide mghttlme heating. the mass surface. only by a small air space. In San Jose. California. a Sunlight is absorbed directly A masoruy Thennal Storage Wall selective surface will improve into the wall instead of into the should be solid. and there Thennal Storage Wall living space. The energy is then should be no openings or vents perfonnance by about 43%. released into the living space either to the outside or to the over a relatively long period. The living space. Although vents to Mass Material and time lag varies with different the living space were once materials. thicknesses and other Thickness commonly built into Thennal In general. the effectiveness of factors. but typically. energy Storage Walls. experience has stored in a Thennal Storage Wall the Thennal Storage Wall will demonstrated that they are increase as the density of the during the day is released ineffective. Vents between the material increases. during the evening and Thennal Storage Wall and the The optimum thickness of nighttime hours. house tend to reduce the the wall depends on the densit) The outside surface of a system's nighttime heating of the material chosen. The thennal storage wall should be a capability. and to increase the following chart indicates the very dark color - an temperature fluctuation in the recommended thickness of absorptance greater than 0.92 is house. Vents to the outside are Thennal Storage Walls made of recommended. similarly ineffective. and do little various materials. The summer heat gain from to reduce summer heat gains. a Thennal Storage Wall is much less - roughly 102% less - Glazing than from a comparable area of Double glazing is recommended direct gain glazing. for Thennal Storage Walls unless a selective surface is used. In this case. single glazing perfonns about the same as double glazing. The space between the glazing and the thennal mass should be one to three inches.
San FranclllCo Bay Area PASSIVE SOLAR DESIGN STRA TEGIES ;'1
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 Block 130 7-18 Ceiling/Roof 30 29 29 29 Clay Brick 120 7-16 Walls 19 18 18 18 Ltwt. Concrete 11 0 6-12 Floor 19 18 18 18 Block Glass 1.8 1.8 1.8 1.8 Adobe 100 6-12 Air Changes/Hour 0.50 0.49 0.48 0.49
Glass Area (percent of total floor area) Water Walls West 3.0% 2.0% 2.0% 2.0% Water provides about twice the North 3.0% 4.0% 4.0% 4.0% heat storage per unit volume as East 3.0% 4.0% 4.0% 4.0% South 3.0% 3.0% 3.0% 3.0% masonry. so a smaller volume of Thermal Storage Wall 0.0% 1.9% 4.4% 8.8% mass can be used. In "water walls" the water is in Ught. rigid Solar System Size (square feet) containers. The containers are South Glass 45 45 45 45 Thermal Storage Wall 0 27 66 132 shipped empty and easily installed. Manufacturers can Percent Solar Savings provide information about 26% 40% 55% 71% durability. installation. Performance (Btu/yr-sf) protection against leakage and Conservation 14,670 15,076 15,232 15,694 other characteristics. At least Auxiliary Heat 10,791 8,982 6,774 4,543 30 pounds (3.5 gallons) of water Cooling 3,183 1,748 96 should be provided for each Summary: In the case of a Thermal Storage Wall, south-facing glazing square foot of glazing. This is and thermal mass are incorporated together. The estimates here assume equivalent to a water container a 12-inch thick concrete Thermal Storage Wall with a selective surface about six inches thick. having and single glazing. the same area as the glazing.
San FranclllCo Bay Area 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 i 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 worlanen at the facility always the day. Although using a fans - can reduce air ate lunch in the masonry test 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 But shading is particularly The additional insulation 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 b.) 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 rooms and big air conditioning with high R-value can help bills - unless they are shaded shield against unwanted heat and the house is designed to gain in summer. help cool itself.
8&D Frauclaco Bay Area PASSIVE SOLAR DESIGN STRA TEGIES 33
The potential of some natural and low-energy cooling Cooling Potential Basecase 3,183 Btu/yr-sf strategies is shown in the following table for San Jose. Energy Worksheet IV: CooUng Savings Percent Performance Level indicates Strategy (Btu/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 1,550 49% increase the cooling load and Night Ventilation1 how much reduction is possible without ceiling fans -290 -% when natural cooling techniques with ceiling fans 1,390 44% are used. High Mass2 It should be noted that the without ceiling fans 520 16% Cooling Performance numbers with ceiling fans 220 7% presented in the Examples for each passive solar strategy 1 With night ventilation, the house is ventilated at night when assume that the design also temperature and humidity conditions are favorable. 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.
San FranciMlo Bay Area 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 19,020 size non-solar glazing as East 72,240 treatments are not indicated in the following table. South 57,040 recommended for south West 67,550 windows. Skylights 117,250 As the table shows. skyUghts 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 d1fllcult 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 shadlng as deSCribed in the almost every new house has at next section. least one skylight. A good As mentioned earlier. west Using special glazing or working compromlse can usually facing windows present window fihns that block solar be achieved if skylight area is particularly d1fllcult shading transmlssion (low shading limited. and if careful attention problems. If glazing is added coeffiCient) is an option often is paid to shading. either by above the levels indicated. the used in particularly hot trees or by devices such as roller need for shading will become climates. but the more effective shades or blinds. The even more critical. they are at blocking sunlight. manufacturer can usually give Cooling loads increase as the less clear they are. as a rule. gUidance on shading options for window area increases. This a particular skyUght design. relationship for San Jose is 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 67.550 Btu/yr-sf.
San FrancilCo Bay Area PASSIVE SOLAR DESIGN STRA TEGIES
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 overhang 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 San Jose. an ideal and inteIfere 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 21 all but eliminate passive solar prevent glare and heat inches and the bottom of the peIformance. unless they are absorption. overhang would be 14 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 Overhanq Sizing In San Jose, an ideally sized south overhang should allow full exposure of the window when the sun has a noon altitude of 33 degrees (angle A) and fully shade the window when the sun has a noon altitude of 70 degrees (angle B).
San Franclaco Bay Area 36 GUlDELINEB 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 more energy than any other and shading devices on the other Minimum Far 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 seasonally regulated are another higher temperatures. As 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 2 fans Shading Devices. External affecting comfort if the air is 18.5 or more feet 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 d1sturb 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. Intertor shades must be operated, too, and have the further disadvantage of permitting the sun to enter the house and be trapped between the window and the shading device. But highly reflective interior blinds and curtains are relatively low-cost and easy to operate. Another shading "device" well worth conSidering is a porch. Especially on the east and west sides, porches add pleasant spaces to houses and are excellent for prOViding shade to windows. Carports located on the east or west are another option.
SaD FrancllCo Bay Area 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" The prevailing wind direction is are used, so that the fan would from the west during the only operate when there is less summer season. Windows, than 600Al relative humidity and stairwells, transoms and other a temperature of less than 76'F. elements should be located for Natural ventilation and maximum cross-ventilation in whole-house fans are effective at each room. The free vent area Ventllstlon for Summer Cooling removing heat, but not at Natural ventilation is often impaired by (unobstructed openings like vegetation and topography. Ventilation fans moving air. Ceiling fans, on the do not depend on surroundings to be open windows) should be effective. other hand, can often create between 6-7.5% of total floor enough of a breeze to maintain area, half located on the leeward In COOling climates, a whole comfort at higher temperatures, and half on the windward side of house fan is a good idea for and still use less power than the building. Insect screens can assisting ventilation, especially required by air conditioning. By reduce the effective free vent in houses with sites or designs using natural cooling strategies area by as much as 50%. that make natural ventilation and low-energy fans, the days Casement or awning windows difficult. On the other hand, when air-conditioning is needed have a 90% open area: double when the temperature is higher can be reduced substantially. hung windows have only 50%. than about 76'F, a whole-house Natural ventilation can help fan will not be very effective. keep houses cool and Research indicates that a comfortable at the beginning and whole-house fan should pull end of the cooling season and approximately 10 ACH. A rule of thus shorten the time when air thumb: for rooms with eight foot conditioning is required. But ceilings, total floor area natural ventilation can seldom multiplied by 1.34 will equal the do the entire cooling job, necessary CFM of the fan. For especially for less than ideal 10 foot ceilings, multiply floor sites with little natural air area by 1.67. movement.
San FrancillCo Bay Area 38 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
San FrancilCo Bay Area 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 San Jose California 40 General Project Information
Project Name Floor Area Location Date Designer
Worksheet I: Conservation Performance Level
A. Envelope Heat Loss Construction A-value Heat Description Area [Table A) Loss Ceilings/roofs + = + = Walls + = + = Insulated Floors + = + = Non-solar Glazing + = + = Doors + = + = BtufOF-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 Crawls(1aces X = BtufOF-h Total
C. Inflltratlon 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 = Btulyr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C) Day Multiplier Square Foot [Table C)
F. Comparison Conservation Performance (From Previous Calculation or from Table D) Btulyr-sf
CompueLmeEtoLmeF 41
Worksheet fi: Auxiliary Heat Performance Level
A. Projected Area of Passive Solar Glazing
Solar System Rouih Frame Net Area Adjustment pr~ected Reference Code rea Factor Factor (Table E) rea 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 Savings Area Fraction
D. Auziliary Heat Performance Level
[ 1- ] X = Btulyr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E)
E. Comparative Auziliary Heat Performance (From Previous Calculation or from Table G) Btulyr-sf
Compare~eDtoLineE 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 = BtuI"F Total
B. Beat Capacity of Mass Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ) Capacity TrombeWalls X 8.8 = Water Walls X 10.4 = EXPQsed Slab in Sun X 13.4 = EXPQsed Slab Not in Sun X 1.8 = X = X = X = BtuI"F Total
C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description c~aci~ Total Heat (include thickness) Area IT Ie ) Capacity Trombe Walls X 3.8 = Water Walls X 4.2 = X X = X = BtufOF Total
D. Total Beat Capacity BtuI"F (A+B+C)
E. Total Heat Capacity per Square Foot + = BtuI"F-sf Total Heat Conditioned Capacity Floor Area
F. Clear Winter Day Temperature Swing Total Comfort r:r~jected Area Factor [Worksheet II) [Table I) Direct Gain X = Sunspaces or X = Vented Trombe Walls + = Total Total Heat Capacity
G. Recommended Maximum Temperature Swing Compare Line F to Line G 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 = kBtulyr 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 =
kBtulyr Total C. Solar Glazing Solar System Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M) Factor [Table L) Load Direct Gain X 0.80 X X =
Storage Walls X 0.80 X X =
Suns~ce X 0.80 X X = X 0.80 X X = kBtu/yr Total D. Intemal Gain +( X ) = kBtutyr Constant Variable Number of Component Component Bedrooms [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 Ventllation Btu/yr-sf [Table 0)
G. COOling 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
8m I'nIDcleeo a.,. Area 44
Table A-cODtiDUed •• Table A-EqulvaleDt Thermal Table ~Bue Cue CODservatioD PerionDaDce of AuembUes PerfOnDaDce (Btu/yr-sf) R-values (hr-F-sf/Btu) A~OooI'l Base Case . 14.670 Solid wood with 2.2 Weatherstripping A1-CeUlngIiRool. Metal with rigid 5.9 Table E-Projected Area Allie Insulation R-value foam cora ~U8tmeDt Facton Construction R-30 R-38 R-49 R-60 Degrees off Solar System Type 27~ 35.9 46.9 57.9 True 00, TW, SSA SSB, South WW, SSD SSE Framed Insulation R-value Table B--Perimeter Beat Lou sse Construction R-19 R-22 R-30 R-38 Factors for Slabs-oD-Grade and o 1.00 0.77 0.75 BasemeDts (Btu/b-F-ft) . 5 1.00 0.76 0.75 2x6 at 16"oc 14.7 15.8 16.3 Heated Unheated Insulated 10 0.98 0.75 0.74 2x6at24"oc 15.3 16.5 17.1 15 0.97 0.74 0.73 2x8 at 16"oc 17.0 18.9 20.6 21.1 Perimeter Siabs-on- Base- Base- Crawl- 2x8 at24"oc Insulation Grade ments ments spaces 20 0.94 0.72 0.70 17.6 19.6 21.6 22.2 25 0.91 0.69 0.68 2x10 at 16"oc 18.1 20.1 24.5 25.7 None 0.8 1.3 1.1 1.1 30 0.87 0.66 0.65 2x10 at 24"oc 18.4 20.7 25.5 26.8 R-5 0.4 0.8 0.7 0.6 2x12 at 16"oc 18.8 21.0 25.5 30.1 R-7 0.3 0.7 0.6 0.5 2x12 at 24"oc 19.0 21.4 27.3 31.4 R-ll 0.3 0.6 0.5 0.4 R-19 0.2 0.4 0.5 0.3 R-30 0.1 0.3 0.4 0.2 Table F-801ar S)'Item SavlDg A2-Framed Walla FraCtlODl
~~Ie Insulation R-value Framing R-11 R-13 R-19 R-25 Table C-Beatiug Degree Days F1-Dlrect Gain (F-day) 2x4 at 16"oc 12.0 13.6 Load DGC1 DGC2 DGC3 2x4 at24"oc 12.7 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 at24"oc 14.3 15.6 18.2 19.8 C1-Heatlng Degree Day. (Base 65°F) 400 0.15 0.14 0.16 Double San Jose 2,439 300 0.19 0.19 0.21 Wall Total Thickness (inches) Berkeley 2,951 200 0.28 0.27 0.30 Framing 8 10 12 14 Davis 2,843 150 0.35 0.35 0.38 25.0 31.3 37.5 43.8 Fairfield 2,686 100 0.48 0.48 0.53 Lodi 2,861 80 0.56 0.56 0.62 The R-value 01 insulating sheathing should be added to Los Banos 2,616 60 0.66 0.67 0.73 the values in this table. Los Gatos 2,740 50 0.72 0.73 0.79 Merced 2.653 45 0.75 0.77 0.83 Modesto 2.653 40 0.79 0.80 0.86 A3-lnaulated Flool'I Napa 2.749 35 0.82 0.84 0.89 Oakland 2,877 30 0.85 0.88 0.92 Insulation R-value Richmond 2,677 25 0.88 0.91 0.94 Framing R-11 R-19 R-30 R-38 Sacramento 2.398 20 0.91 0.94 0.96 15 0.94 0.97 0.98 2x6s at 16"oc 18.2 23.8 29.9 San Francisco 3.161 2x6s at 24·oc 18.4 24.5 31.5 San Rafael 2,439 2x8s at 16"oc 18.8 24.9 31.7 36.0 Stockton 2,674 2x8s at 24"oc 18.9 25.4 33.1 37.9 F2-Trornbe Walla 2x1 0 at 16"oc 19.3 25.8 33.4 38.1 TWF3 TWA3 TWJ2 TWI4 2x1 0 at 24·oc 19.3 26.1 34.4 39.8 C2-Heatlng Degree Day Multiplier Load Unvented Vented Unvented Unvented 2x12 at 16"oc 19.7 26.5 34.7 39.8 Collector Non- Non- Selee- Night 2x12 at 24·oc 19.6 Passive Solar 26.7 35.5 41.2 Heat Loss Glazing Area per Ratio selective selective tive Insulation These R-values include the buffering effect 01 a per Square per Square Foot 400 0.12 0.15 0.18 0.13 ventilated crawlspace or unconditioned basement. Foot .00 .05 .10 .15 .20 300 0.16 0.19 0.24 0.18 12.00 1.22 1.23 1.25 1.26 1.27 200 0.23 0.27 0.35 0.28 11.50 1.20 1.22 1.23 1.25 1.26 150 0.29 0.33 0.44 0.36 A4-Wlndow. 11.00 1.19 1.20 1.22 1.24 1.25 100 0.40 0.44 0.57 0.49 10.50 1.17 1.19 1.21 1.22 1.24 80 0.46 0.50 0.65 0.57 PJrGap 1.17 1.19 1.21 1.23 60 0.55 0.59 0.74 0.67 114 in. in. in. 10.00 1.15 1p 112 argon 9.50 1.13 1.15 1.18 1.20 1.21 50 0.61 0.65 0.80 0.73 Standard Metal Frame 9.00 1.11 1.13 1.16 1.18 1.20 45 0.64 0.68 0.83 0.76 Single .9 8.50 1.08 1.11 1.141.16 1.18 40 0.68 0.72 0.86 0.80 Double 1.1 1.2 1.2 8.00 1.05 1.09 1.12 1.14 1.17 35 0.72 0.76 0.89 0.83 Low-e (8<=0.40) 1.2 1.3 1.3 7.50 1.02 1.06 1.09 1.12 1.15 30 0.77 0.80 0.92 0.87 Metal frame with thermal break 7.00 0.99 1.03 1.06 1.1 0 1.13 25 0.82 0.85 0.95 0.91 Double 1.5 1.6 1.7 6.50 0.95 0.99 1.04 1.07 1.10 20 0.87 0.90 0.97 0.95 Low-e (8<=OAO) 1.6 1.8 1.8 6.00 0.90 0.95 1.00 1.04 1.08 15 0.93 0.94 0.99 0.98 Low-e (8<=0.20) 1. 7 1.9 2.0 5.50 0.84 0.91 0.96 1.01 1.05 Wood traine with vinyl cladding 5.00 0.78 0.86 0.92 0.97 1.01 Double 2.0 2.1 2.2 4.50 0.71 0.80 0.87 0.93 0.98 Low-e {8<=0.40! 2.1 2.4 2.5 4.00 0.62 0.73 0.81 0.88 0.94 Low-e 8<=0.20 2.2 2.6 2. 7 3.50 0.51 0.64 0.74 0.82 0.89 Low-e 8<=0.10 2.3 2.6 2.9 3.00 0.39 0.54 0.66 0.75 0.83 These R-values are based on a 3 mph wind speed and 2.50 0.25 0.42 0.56 0.67 0.77 0.28 0.45 0.58 0.69 are typical lor the entire rough framed opening. 2.00 0.10 Manufacture·s data, based on National Fenes1ration Rating Council procedwes, should be used when available. One half the R-value 01 movable insulation should be added, when appropriate. 45
F3-Water Walll Table H-UDlt Heat capacitle. Table L--Heat Gain Factol1l (Btu/F-Ul Load WW~ WWB4 WWC2 Ceiling/roofs 52.3 Collector No Night Night Selective Walls 8nd Doors 25.4 Ratio Insulation Insulation Surface North Glass 19.0 Hl-Mass Surfaces Enclosing Direct Gain East Glass 72.2 400 0.16 0.16 0.17 Spaces West Glass 67.5 300 0.21 0.23 0.24 Skylights 117.2 200 0.30 0.35 0.35 Thickness (inches) Direct Gain Glazing 57.0 150 0.37 0.44 0.44 Material 2 3 4 6 8 12 Trombe Walls and - 0.8 100 0.49 0.58 0.57 0.65 Poured Conc. 1.8 4.3 6.7 8.8 11.311.5 10.3 Water Walls 80 0.56 0.66 Cone. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 Sunspaces 60 0.65 0.76 0.75 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSAI 15.4 50 0.71 0.81 0.80 8.5 8.6 8.0 7.6 SSBI 15.4 45 0.83 FI~Stone 2.1 4.8 7.1 0.74 0.84 Bui er Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSCl -0.8 40 0.78 0.87 0.86 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSDl 15.4 35 0.81 0.90 0.89 SSEl 15.4 30 0.85 0.93 0.92 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 25 0.89 0.95 0.95 Water 5.2 10.415.620.831.2 41.6 62.4 20 0.93 0.98 0.97 15 0.97 0.99 0.99 H2-Rooms with no Direct Solar Gain Table lIoI-8bacliD, Facton Thickness (inches) Projection F4-Sunspaces Material 2 3 4 6 8 12 Factor Sou1h East North West Load Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 Collector Suns pace Type Conc. Masonry 2.9 3.5 3.6 3.4 0.00 1.00 1.00 1.00 1.00 1.6 3.6 3.2 0.20 0.85 0.95 0.87 0.94 Ratio SSAl SSBl SSCl SSDl SSEl Face Brick 1.8 3.1 3.6 3.7 3.5 3.4 3.2 1.9 3.1 3.4 3.4 3.2 3.1 3.0 0.40 0.60 0.83 0.74 0.81 400 0.23 0~19 0.15 0.26 0.22 Fla~ Stone 0.60 0.41 0.70 0.60 0.67 300 0.27 0.23 0.19 Buider Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 0.32 0.28 Adobe 0.80 0.33 0.57 0.46 0.54 200 0.35 0.30 0.27 0.42 0.37 1.2 2.4 2.8 2.8 2.6 2.4 2.4 1.00 0.30 0.49 0.33 0.46 Hardwood 0.5 1.1 1.3 1.2 1.0 1.1 150 0.42 0.36 0.34 0.49 0.44 1.1 1.20 0.27 0.41 0.19 0.38 100 0.52 0.46 0.45 0.60 0.55 80 0.58 0.52 0.51 0.67 0.62 Multiply by 0.8 for low-e glass, 0.7 for tinted glass and 60 0.66 0.60 0.60 0.74 0.70 0.6 for low-e tinted glass. 50 0.71 0.65 0.66 0.79 0.75 45 0.73 0.68 0.69 0.81 0.77 Table I-Comfort FactOI1l (Btu/Ul 40 0.76 0.71 0.73 0.84 0.80 Direct Gain 850 Table N-mnmu Gain Facton 35 0.80 0.75 0.77 0.87 0.83 30 0.83 0.79 0.81 0.90 0.87 Suns paces and 280 Constant Component 1,990 kBtulyr Vented Trombe Walls 25 0.87 0.83 0.86 0.92 0.90 Variable Component 830 kBtu/yr-BR 20 0.91 0.87 0.90 0.95 0.93 15 0.95 0.92 0.95 0.98 0.96
Table J-Radiant Barrier Factol1l Table o-Thermalllolau and Radiant Barrier 0.75 VeDtilatioD AdJustmeDt (Btu/yr-U) No Radiant Barrier 1.00 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 7,560 5,250 7,720 5,540 1.0 8,630 6,670 8,790 6,960 Table K--801ar Ab.orptaDce. 2.0 9,130 7,450 9,290 7,740 Color Absorptance 3.0 9,370 7,890 9,530 8,180 Gloss White 0.25 4.0 9,490 8,130 9,650 8,420 Semi-gloss White 0.30 5.0 9,540 8,260 9,700 8,550 Light Green 0.47 6.0 9,560 8,330 9,730 8,620 Kelly Green 0.51 7.0 9,580 8,370 9,740 8,660 Medium Blue 0.51 8.0 9,580 8,390 9,740 8,680 Medium Yellow 0.57 9.0 9,590 8,400 9,750 8,690 Medium Orange 0.58 10.0 9,590 8,410 9,750 8,700 Medium Green 0.59 Tolal heat ~ty Il8r square foot is calculated on Light Bull Brick 0.60 Worksheet II~ Step E. Bare Concrete 0.65 Red Brick 0.70 Medium Red 0.80 Medium Brown 0.84 Dark Blue-Grey 0.88 Table P-Bue Cue CooUng Dark Brown 0.88 Performance (Btu/d-yr) Base Case 3,183
Table G-Bue Cue AuDIluy Heat Performance (Btu/yr-st) Base Case 10,791 46 General Should the estimated conservation reduced by about 50 percent to account The Worksheets provide a calculation performance level be greater than for throw rugs and furnishings. procedure to estimate the performance 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. Performance Workabeet D-AuzlUuy Beat 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 auxiUruy heating 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 performance 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 entIy, 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 Workaheet I-CollHl'Vlltion adjustment factors in Table E or by Work.beet lV-8ummer Cooling 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 heating system. The projected area per square foot is air conditioner in order to maintain For Step A. it is necessaJY 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 heating 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 columns 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. suns pace 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 auxiliruy heat performance 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. tints or flhns. 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 coeffic1ent should be The perimeter method of Step B is determined from manufacturers' used for slabs-on-grade. the below-grade Workabeet IIl--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 crawlspaces (when the floor Is not heating system not operating. 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. 8 crawlspaces adjacent to sunspaces Rooms that are separated from direct should not be included. gain spaces by more than one door The conservation performance level is should not be included in either calculated as the product of the heat loss category. per degree day per square foot (Step DJ 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 performance 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 provtding additional shading or exposed slab area should be further increasing thermal mass.
San I'ranclaco Bay Area 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
San Jose The Worked California Example 48 WORKED EXAMPLE
The Worked Example The house has a semi The house is equipped with a enclosed sunspace with glazing ceiling fan to help reduce the Description of sloped at 50 degrees. The air-conditiOning load. North Example Bulldlng suns pace floor has a four-inch windows have an overhang with A 1,504 square foot passive thick slab-on-grade with quarry a projection factor of 0.30. East solar, single-family home is used tile set in a mortar bed. The and west windows are small and to illustrate how to fill in the sunspace is separated from the have no effective overhang worksheets. See sketches for conditioned portion of the house because of the gable roof. South the building layout. A variety of by sliding glass doors and a windows, including the design features have been masonry fireplace wall. sunspace windows, have an incorporated into the house to Sunspace ventilation is provided overhang with a projection factor help illustrate how to handle to the outside by awning of 0.20. different situations in the windows located at the top and Take-offs from the house are worksheets. bottom of the south wall. given in the worksheets. Refer The building selected has South facing windows to the Circled values in the good insulation as described on provide direct gain solar heating worksheet tables to locate where Worksheet I. to the dining area, kitchen and the various values which show The east portion of the house master bedroom. The south up in the worksheets come from. is slab on grade. The great room glazing in the kitchen and dining Performance is found to be and master bedroom are area provides heat to an exposed satisfactory on all four constructed over a crawlspace. slab-on-grade finished with worksheets. ceramic tile to provide direct gain heat storage. The house faces 10 degrees to the east of true south.
C\J N Garage
3040 3040
4040 ;,
Bedroom Bedroom 0 (') 0 Lo'" Great Room
b ;, ("') 0 N (') 0 Master '" Bedroom 0r1ng
4050 8020 8068 5030 8088 8068 8088 14' 28' 24'
o 2 4 8 12 '7f> Floor Plan -- - PASSIVE SOLAR DESIGN STRA TEGIES
South Elevation
.. ,-.... , ...... " ...... :.:.:.. ~.~...... I
North Elevation
Section
San Franci.co Bay Area 50 WORKED EXAMPLE
San FrancllCo Bay Area 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.
San Jose Worked Example California
SaD FraDclaco Bay Area 52 General Project Information
Floor Area Location S'ArJ J." CAM Ot.UA Date Designer
Worksheet I: Conservation Performance Level
A. Envelope Heat Loss Construction R-value Heat Description Area [Table A] Loss
Ceilings/roofs ~-"3S + 3~ h~ (.IICT't \ "" IQS~ :35·9 = "'R.:]6 '!!a "~.u!..:). C.Ll~~~ ~"2..0 + z..~.S = t:l Walls :L-~~ ... ~o Slll~!d.~" ~ ~c\"L. + n.J = ~, 'U.:\5 M ti.alll!!!'£ ~'-'O + '"\.J = 6 Insulated Floors + = + = Non-solar Glazing ""I'.~~"" f:C.A-c!:. : "~1.bL G...A~'I) S"Z... + l. "5 = 'to - , I"," 6.4.. • LO-..a-:c + = ~E::r __ Doors ... If'~"'" '-l2!& '-'00 + S.9 = 1 + = Btul"F-h 'S~Total
B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss Siabs-on-Grade It..-, f'~A.wo-\ \~!:::t X c:P.:;\O = ~S Heated Basements X = Unheated Basements X = Perimeter losuiated Crawlsg§C8§ X = sa BtuI"F-h Total
C. InfUtratlon Heat Loss \ "l.J.t 6 3. X t:I..5:~ X .018 = H-z.... BtuI"F-h Building Air Changes Volume per Hour
D. Total Heat Loss per Square Foot 24 X '3-z..(J + \SO~ = 5. 'Z-3 Btu/DO-sf Total Heat Loss Floor Area (A+B+C)
E. Conservation Performance Level
S.z..'3 X ~"3q X = ''L,z.fB 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) '46'0 Btu/yr-sf
Compare Line E to Line F
SaD Fraacl.co Bay Area 53 Worksheet II: Auxlliary 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 gg ~&.c::.....l X 0.80 X 0.96 = 6~ SSc,....\ -z.ofl. X 0.80 X D.9~ = \6:t X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = "lA, Z.:~'"t..... sf Total Area Total Projected Area "l-1"2... + lS'oc.t = O.IS Total Floor Total Projected Projected Area Area per Area Square Foot
B. Load Collector Ratio 24 X ':J '2..8 + 2..:11.. '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] "bGo<:,l 6S X 0.63 S:::l·1..41 SSC-\ 163 X O.J6 = ~1-R. 2.P X = X = X = X = X = 1 + z..s"L = ".~O '¥6olal Total Soar Projected Savings Area Fraction
D. AuxlUary Beat Performance Level
[1 - 0.'3,0 X \U~ = 'Z..~U; Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, SlepE]
E. Comparatlve AuxlUary Beat Performance (From Previous Calculation or from Table G) \0'" , Btulyr-sf
CompareLmeDtoLmeE
San FrancllCo Bay Area 54 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 ~6,", X 4.7 = L\SI SQaces Connected to Direct Gain SQaces ~4q, X 4.5 = 4'"Z...."'lO 6~S'- Btu/"F 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 = EXQQsed Slab in Sun 10 3 X 13.4 = ,~sa EXQQsed Slab Not in Sun \~::z X 1.8 = 2..... ,. X = X X = l6k'l Btu/"F 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 = ~~ ,~ 4" lH X ~.::l = '-'11 X = X = '-ttl Btu/"F Total
D. Total Heat Capacity ~,+~b Btu/"F +B+C)
E. Total Heat Capacity per Square Foot + 'S~ = S., Btu/"F-sf Total~"'Ii\" Heat Conditioned Capacity Floor Area
F. Clear WInter Day Temperature Swing Total Comfort PWcected Area Factor I orksheet II] [Table I] Direct Gain X e~O '586St:> Sunsl2!!ces or lb:5'9 X 'Z.RO = '-tS.'69 Vented Trombe Walls '~~l6 + g4qG7 \'L.3. OF Total Total Heat Capacity
G. Recommended Mulmum Temperature Swing Compare Line F to Line G
SaD lI'rlUlclaco Bay Area 55 Worksheet IV: Summer Cooling Performance Level
A. Opaque Surfaces Radiant Barrier Absorp- Heat Gain Heat Loss Factor lance Factor Description [Worksheet I) [Table J) [Table K) [Table L) Load Ceilings/roofs ~O X l!OOO X O.'-lj X ~'Z.::1 = ,~"Z.. [] X \.00 X 0.4::1 X S'7...3 = C4."2..C1 X X X = Walls ~, X na 0.::10 X 'Z.S. .... = SS'- X na X = Doors 3. X na 0."30 X 'Z.&.C; = ~ "l...ISI kBtulyr Total B. Non-solar Glazing ROU~ Frame Net Area Shade Factor Heat Gain Description rea Factor [Table M) Factor [Table L) Load North Glass ~ X 0.80 X 0.")2.- X ,.,.0 = "38
East Glass , X 0.80 X O.SO X 12..1... = 1.."
West Glass , X 0.80 X O.So X ".$ = 2SS
Skylights X 0.80 X X =
9'4 kBtulyr 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 88 X 0.80 X ~.ej X 5'.0 = 334"3
Storage Walls X 0.80 X X =
Suns~ace 2AS X 0.80 X O.8.7l X = t:J X 0.80 X X = l'3'-\:t kBtu/yr Total D. Internal Gain \~~O +( 610 X :1 ) = "'46., kBtu/yr Constant Variable Number of Component Component Bedrooms [Table N) [Table N)
E. Cooling Load per Square Foot 1,000 X IOc\18 + 'SO'-t = "\'1.. C\~ Btulyr-sf (A+B+C+D) Floor Area
F. &ijustment for Thermal Mass and Ventllatlon ~1\e Btulyr-sf [Table 0) - ~o t.:) \.6 ~ "c....-"l. ~ c..£\ "",....,6 ~~ G. Cooling Performance Level - lJ.\ \~ Btulyr-sf (E -F)
H. Comparison Cooling Performance (From Previous Calculation or from Table P) :l' 6:3 Btulyr-sf Compare Une G to Line H
San Francleco Bay Area 56
Table A-contlDued .. Table Ar-Equivalent Thermal Table D-Bue Cue ConHrvation Perform&llce of Assemblies PerfOrm&llce (Btu/~ R-values (hr-F-af/Btu) AS-Doors Base Case ~ Solid wood with 2.2 Weatherstripping A1--celllngIiRoof. Metal with rigid Table E-ProJected Area Attic Insulation R-value foam core ® AdjUitment Facton Construction R-3O ~ R-49 R-60 Degrees off ~ Solar System Type 27.9 ~ 46.9 57.9 True fJYi..... SSA SSB, Table B-Perimeter Heat Lo.. South 6J SSD SSE Framed Insulation R-value Facton for Slab.-on-Grade and Construction R-19 R-22 R-30 R-38 Ba.ementl (Btu/h-F-ft) o 1.00 0.77 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 0.75 0.74 Perimeter Siabs-on Base- Base- Crawl- 15 m ~N ~73 2x8 at 16"oc 17.0 18.9 20.6 21.1 Insulation Grade ments ments spaces 20 0.94 0.72 0.70 2x8 at 24'oc 17.6 19.61P 22.2 25 0.91 0.69 0.68 2xl0at 16"00 18.1 20.1 4.. 25.7 None 0.8 1.3 1.1 1.1 2xl0 at 24'00 18.4 20.7 26.8 R-5 0.8 0.7 0.6 30 0.87 0.66 0.65 2x12 at 16"00 18.8 21.0 25.5 30.1 R-7 0.7 0.6 0.5 2x12 at 24'00 19.0 21.4 27.3 31.4 R-ll 4.Y 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-solar SlItem Saving A2-Framed Walll FraCtlODI
~~Ie Insulation R-value Framing R-ll R-13 R-19 R-25 Table C-Heating Degree Day. F1-Dll1Ct Gain (F-day) 2x4 at 16"oc 12.0 13.6 Load DGCl DGC2 DGC3 2x4 at 24'oc 12.7 13.9 ~ - Collector Double Low-e R-9Ni9ht 2x6 at 16"oc 14.1 15.4 ~ 19.2 Ratio Glazing Glazing Insulation 2x6 at 24'00 14.3 15.6 18.2 19.8 C1-H.atlng Degree Day. (Bill 65°F) 400 0.15 0.14 0.16 Double San Jose ~ 300 0.19 0.19 0.21 Wall Total Thickness (inches) Berkeley ~ 200 0.28 0.27 0.30 Framing 8 10 12 14 Davis 2,843 150 0.35 0.35 0.38 Fairfield 2,686 100 0.48 0.48 0.53 25.0 31.3 37.5 43.8 Lodi 2,861 80 0.56 0.56 0.62 The R-value of insulating sheathing should be added to Los Banos 2,616 60 0.66 0.67 0.73 the values in this table. Los Gatos 2,740 50 0.72 0.73 0.79 Merced 2,653 45 0.75 0.77 0.83 Modesto 2,653 0.79 0.80 0.86 Napa 2,749 ~ 0.84 0.89 A3-lnsulated Floors Oakland 2,877 3"~ .w.... 0.88 0.92 Insulation R-value Richmond 2,677 25 ~.88 0.91 0.94 Framing R-ll R-19 R-30 R-38 Sacramento 2,398 20 0.91 0.94 0.96 0.94 0.97 0.98 2x6s at 16"00 18.2 23.8 29.9 San Francisco 3,161 15 2x6s at 24'00 18.4 24.5 31.5 San Rafael 2,439 2x8s at 16"00 18.8 24.9 31.7 36.0 Stockton 2,674 2x8s at 24'00 18.9 25.4 33.1 37.9 F2-Trombe Walil 2xl 0 at 16"00 19.3 25.8 33.4 38.1 TWF3 TWA3 TWJ2 TWI4 2xl 0 at 24'00 19.3 26.1 34.4 39.8 C2-Heating Degree Day Multiplier Load Unvented Vented Unvented Unvented 2x12 at 16"00 19.7 26.5 34.7 39.8 Passive Solar Collector Non- Non- Selee- Night 2x12 at 24'00 19.6 26.7 35.5 41.2 Heat Loss Glazing Area per Ratio selective seleem tive Insulation These R-values indude the buffering effect of a per Square per Square Foot 400 0.12 0.15 0.18 0.13 ventilated crawlspace or unconditioned basement Foot .00 .OS .10 .15 .20 300 0.16 0.19 0.24 0.18 12.00 1.22 1.23 1.25 1.26 1.27 200 0.23 0.27 0.35 0.28 11.50 1.20 1.22 1.23 1.25 1.26 150 0.29 0.33 0.44 0.36 A4-Wlndow. 11.00 1.19 1.20 1.22 1.24 1.25 100 0.40 0.44 0.57 0.49 10.50 1.17 1.19 1.21 1.22 1.24 80 0.46 0.50 0.65 0.57 Air Gap 10.00 1.15 1.17 1.19 1.21 1.23 60 0.55 0.59 0.74 0.67 1/4 in. 1pin. 1/2 in. argon 9.50 1.13 1.15 1.18 1.20 1.21 50 0.61 0.65 0.80 0.73 Standard Metal Frame 9.00 1.11 1.13 1.16 1.18 1.20 45 0.64 0.68 0.83 0.76 Single .9 8.50 1.08 1.11 1.14 1.16 1.18 40 0.68 0.72 0.86 0.80 Double 1.1 JJ.... 1.2 8.00 1.05 1.09 1.12 1.14 1.17 35 0.72 0.76 0.89 0.83 Low-e (8<=0.40) 1.2 0.3J 1.3 7.50 1.02 1.06 1.09 1.12 1.15 30 0.77 0.80 0.92 0.87 Metal frame with thermal break 7.00 0.99 1.03 1.06 1.10 1.13 25 0.82 0.85 0.95 0.91 Double 1.5 1.6 1.7 6.50 0.95 0.99 1.04 1.07 1.10 20 0.87 0.90 0.97 0.95 Low-e (8
SaD FrancilCo Bay Area 57
F3-Water Walil Table H-UDit Heat Capacities (Btu/F-If) Load WWKJ WWB4 WWC2 Ceiling/roofs Collector No NiQht Night Selective Walls and Doors Ratio insulauon Insulation Surface North Glass H1-Mass Surfaces Enclosing Direct Gain East Glass 400 0.16 0.16 0.17 Spaces West Glass 300 0.21 0.23 0.24 Skylights 200 0.30 0.35 0.35 Thickness (inches) Direct Gain Glazing 150 0.37 0.44 0.44 Material 1 2 3 4 6 8 12 Trombe Walls and ~ 100 0.49 0.58 0.57 Poured Cone. 1.8 4.3 6.7 8.8 11.3 11.5 10.3 Water Walls 80 0.56 0.66 0.65 Conc. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 suns~ 60 0.65 0.76 0.75 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSl 15.4 50 0.71 0.81 0.80 Fla~ Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSBl 45 0.74 0.84 0.83 Bui der Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSCl 40 0.78 0.87 0.86 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSDl
Table J-Radiant Banier Facton Table o-Tberma1 Ma.. and Radiant Barrier 0.75 VeDtilatioD Ad,JuetmeDt (Btu/7I'-Ifl 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 7,560 5,250 7,720 5,540 Table K-80lar Ab.orptaDce. 1.0 8,630 6,670 8,790 6,960 2.0 9,130 7,450 9,290 7,740 Color Absorptance 3.0 9,370 7,890 9,530 8,180 Gloss White 4.0 9,490 8'13O~,8,420 Semi-gloss White 9,540 8,260 , 8,550 'i . Light Green "5.' 6 9,560 8,330 ,J Kelly Green 4.P.0 9,580 8,370 9,740 8,660 t1t 8.0 9,580 8,390 9,740 8,680 Medium Blue 0.51 Medium Yellow 0.57 9.0 9,590 8,400 9,750 8,690 Medium Orange 0.58 10.0 9,590 8,410 9,750 8,700 Medium Green 0.59 Total heat capacity per square foot is calculated on Light Buff Brick 0.60 Worksheet Ill, Step E. Bare Concrete Red Brick Medium Red Medium Brown ~0.84 Dark Blue-G rey 0.88 Table P-Baae Cue CooliDg Dark Brown 0.88 Performance (BtU/~ Base Case ~
Table G-Bue Cue Awr~1JIHeat Performance (Btu/7I'-' Base Case 10,791
San Franci.co Bay Area 58 WORKED EXAMPLE
San Franciaco Bay Area 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
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 column. 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.
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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, bathrooms and mass/comfort performance level, associated with low-mass master bedroom closet 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 utility room 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 hearth 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 dining room 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 STRA TEGIES 81
Glossary Passive Solar: a whole building design Suntemperln,: 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 AuzlUuy HeatiDg System: a term for active solar techniques which use typical house -- gypsum board, the system (gas, electric, oil, etc.) which wall 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-Cbange Materials: materials as the "awdlruy heat." such as salts or waxes which store and Temperature SwiDg: a measure of the release energy by changing "phase". Most number of degrees the temperature in a British Thermal VDit (Btu): a unit used store energy when they tum liqUid at a space will vary 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. CouervatioD: in addition to energy and release energy. Phase change conservation in the general sense, the materials can be used as thermal mass, Thermal Mus: 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 prtmartly involved with improving the bUilding envelope to guard of a materialls a measure of the against heat loss -- the insulation, and Purchaaed EDergy: although the terms material's ability to absorb and store are often used interchangably, a house's heat. Thermal mass in passive solar air infiltration reduction measures. "purchased energy" is generally greater buildings is usually dense material such Direct Gain: a passive solar energy than its "auxilary heat" because heating as brick or concrete masonry. but can system in which the sunlight falls systems are seldom 100% efficient. and also be tile, water, phase change directly into the space where it is stored more energy is purchased than is materials, etc. and used. actually delivered to the house. Thermal Storage Wall: a passive solar GlaziDg: often used interchangeably with R-Value: a unit that measures the energy system also sometimes called window or glass, the term actually refers resistance to heat flow through a given Trombe Wall or indirect gain system; a 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. refer to two or three panes. U-factor. Trombe Wall: a thermal storage wall, Indirect GaiD: a passive solar system in Radiant Barrier: reflective material used referred to by the name of its inventor, which the sunlight falls onto thermal in hot climates to block radiant heat, Dr. Felix: Trombe. mass which is positioned between the particularly Ina house's roof. glazing and the space to be heated, i.e. a V-Factor: a unit representing the heat Thermal Storage Wall or Trombe Wall. Shading CoefficieDt: a measure of how loss per square foot of surface area per much solar heat will be transmitted by a degree 'F of temperature difference (see Low-Emissivity: the term refers to a glazing material, as compared to a single R-value above). 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 .SS. e" glass sandwiches a thin layer of Reflective glass might have SC's of .03- .06. In general, lower shading metallic film or coating between two panes of glass. The low-e glass blocks coefficients are desirable when heat gain radiant heat, so it will tend to keep heat is a problem. energy inside the house during the winter, and keep heat energy outside the SUDapace: passive solar energy system house during the summer. sometimes also referred to as an isolated 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.
SaD Francisco Bay Area 82 APPENDIX
References e. Ghzlngs: 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. Daylightlng In Commercial Bookstore, 15th and M Streets N.W., 1. A Sunbu.ilder's Primer, National Buildings Washington, D.C. 20005. (202) 822- Renewable Energy Laboratol)'. 1. Human Comfort and Passive Solar 0200. Design 2. Passive: It's a Natural, National j. Passive Design for Commercial 11. LischkoIT, James K. 711e Airtight Renewable Energy Laboratol)'. Buildings House: Using the Atrtfght Drywall k. Passive Solar: Principles and Approach, Iowa State University 3. 711e 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 Masonl)' Pay-olT IA 50011 Association/Portland Cement Association/Blick Institute of Amelica. 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. Suntempertng 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, Appliances Volume I, II, Ill. Available from National 13. Saving Energy and Money with HO/Tle Technical Infonnatlon Service, U.S. Dept. of Commerce, 5285 Port Royal Road, Appliances. Environmental Science Department, Massachusetts Audobon Springfield, Va, 22161. $32.00 each for I Society/ Amelican Council for an Energ and II, $12.00 for III. Efficient Economy. Available for $2.00 6. Balcomb, J.D., et al. Passive Solar apiece from ACEE, 1001 Connecticut Ave. N.W .• Suite 535, Washington D.C. Heattng Analysts. This volume 20036 supercedes and expands Volume 1Il of the Passive Solar Design Handbook (Ref. 14. 711e Most Energy EJftctentAppliances, 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. Uving With the SWl (for consumers) and BuUding With the SWl (for builders), PPG Industrtes.
8. 711e Passive Solar Iriforma1ton Guide, PSIC.
9. Passive Solar Trends. Technical briefs from PSIC. a. Infiltration in Passive Solar Construction b. The State of the Art In Passive Solar Construction c. Passive Solar in Factol)'-Built Housing d. Radiant Barriers: Top Performers in Hot Climates
San Franciaco Bay Area PASSIVE SOLAR DESIGN STRATEGIES 83
Site Planning Sunspaces
16. Builder's Guide to Passtve Solar 17. Jones, Robert W. and Robert D. Home Design and Land Development, McFarland. The Sunspace Primer: A National Fenestration Council. Available GuideJor Passive Solar Heating, available for $12.00 from NFC, 3310 Harrison, for $32.60 from Van Nostrand Reinhold, White Lakes Professional Building, 116 6th Avenue, New York, N.Y. 10003 Topeka, KS. 66611 18. GreenhausesJor Uvlng, from Steven 16. sUe PlannlngJor Solar Access, U.S. Winter AsSOciates, Attn: Publications, Department of Housing and Urban 6100 Empire State Building, New York, Development/American Planning N.Y. 10001, $6.95. Association. Available for $6.60 from Superintendent of Documents, U.S. 19. Concept N, from Andersen Government Printing Office, Washington Corporation, Bayport, MN. 56003, $6.95. D.C. 20402 20. Passtve Solar Greenhause Design and Construction. Ohio Department of Energy/John Spears, 8821 Silver Spring, Md., 20910.
San FrancllCo Bay Area 84 SUMMARY FOR SAN JOSE. CALIFORNIA Example Tables Examples of Heat Energy Savings Passive Solar-Direct Gain Examples of Heat Energy Savings 1,500 sf Single Story House Added Insulation Base 1,500 sf Single Story House Case 20% 40% 60% R·values Base Ceiling/Roof 30 29 29 31 Case 20% 40% 60% Walls 19 18 18 19 R·valuea Floor 19 18 18 19 Ceiling/Roof 30 35 43 48 Glass 1.8 1.8 1.8 1.8 Walls 19 22 29 32 Floor 19 22 29 32 Air Changes/Hour 0.50 0.49 0.46 0.47 Glass 1.8 1.8 1.8 2.7 Glass Area (percent of total floor area) Air ChangealHour 0.50 0.48 0.46 0.45 West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% Glaaa Area (percent of total floor area) East 3.0% 4.0% 4.0% 4.0% West 3.0% 2.0% 2.0% 2.0% South 3.0% 5.3% 7.9% 12.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% Added Thermal Masa South 3.0% 3.0% 3.0% 3.0% Percent of Floor Area 0.0% 0.0% 5.7% 30.0%
Percent Solar Savlnga Solar System Size (square feet) 26% 29% 34% 42% South Glass 45 79 119 180 Added Thermal Mass 0 0 85 450 Performance (Btu/yr-sf) Conservation 14,670 12,818 10,441 7,981 Percent Solar Savlnga Auxiliary Heat 10,791 9,004 6,806 4,629 26% 40% 54% 69% Cooling 3,183 1,511 0 0 Performance (Btu/yr-sf) Conservation 14,670 15,116 15,017 14,870 Auxiliary Heat 10,791 8,985 6,782 4,549 Cooling 3,183 2,564 2,177 4,072
Examples Qf Heat En~y Savings Summary: South-facing glazing has been substantially increased. Suntemper For these examples, added mass area is assumed to be six times 1,500 sf Single Story House the added south glass area.
Base Case 20% 40% 60% R·Values Ceiling/Roof 30 29 32 41 Walls 19 18 21 28 Floor 19 18 21 28 Glass 1.8 1.8 1.8 1.8
Air ChangealHour 0.50 0.49 0.50 0.46
Glaaa 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% 5.3% 6.7% 6.7%
Solar System Size (square feet) South Glass 45 79 100 100
Percent Solar Savings 26% 40% 51% 58%
Performance (Btulyr-sf) Conservation 14,670 15,116 13,908 11,125 Auxiliary Heat 10,791 8,985 6,790 4,593 Cooling 3,183 2,564 1,427 1,287
Summary: The window area has been slightly decreased on the west, increased slightly on the east and north, and increased significantly on the south. PASSIVE SOLAR DESIGN STRA TEGIES 85
Examples of Heat Energy Savings Examples of Heat Ener~y Savings Passive Solar-Sunspace Passive Solar-Thermal torage Wall 1,500 sf Single Story House 1,500 sf Single Story House
Base Base Case 20% 40% 60% Case 20% 40% 60% R·Values R·Values Ceiling/Roof 30 29 29 29 Ceiling/Roof 30 29 29 29 Walls 19 18 18 18 Walls 19 18 18 18 Floor 19 18 18 18 Floor 19 18 18 18 Glass 1.8 1.8 1.8 1.8 Glass 1.8 1.8 1.8 1.8
Air Changes/Hour 0.50 0.49 0.48 0.49 Air Changes/Hour 0.50 0.49 0.48 0.49
Gla •• Area (percent of total floor area) Glas. Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South (windows) 3.0% 3.0% 3.0% 3.0% South 3.0% 3.0% 3.0% 3.0% Sun space 0.0% 2.4% 6.1% 12.8% Thermal Storage Wall 0.0% 1.9% 4.4% 8.8%
Solar Sy.tem Size (square feet) Solar System Size (square feet) South Glass 45 45 45 45 South Glass 45 45 45 45 Sunspace Glass 0 36 91 191 Thermal Storage Wall 0 27 66 132 Sunspace Thermal Mass 0 109 275 575 Percent Solar Saving. Percent Solar Savings 26% 40% 55% 71% 26% 40% 56% 71% Performance (Btulyr-sf) Performance (Btu/yr-sf) Conservation 14,670 15,076 15,232 15,694 Conservation 14,670 15,129 15,384 16,024 Auxiliary Heat 10,791 8,982 6,774 4,543 Auxiliary Heat 10,791 8,978 6,764 4,531 Cooling 3,183 1,748 96 Cooling 3,183 1,743 0 Summary: In the case of a Thermal Storage Wall, south-facing Summary: Insulation and tightness (for the 60% case) have been glazing and thermal mass are incorporated together. The estimates increased. North and east-facing glazing have been increased here assume a 12-inch thick concrete Thermal Storage Wall with a slightly. The sunspace assumed here is semi-enclosed selective surface and single glazing. (surrounded on three sides by conditioned rooms of the house, as in Figure SSDl of the worksheets), with its south glazing tilted at 50 degrees. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double. Cooling Potential Basecase 3,183 Btu/yr-sf
Energy Savings Percent Strategy (Btu/yr-sf) Savings
No Night Ventilation 1 without ceiling fans 0 0% with ceiling fans 1,550 49
Night Ventilation 1 without ceiling fans -290 with ceiling fans 1,390 44
High Mass2 without ceiling fans 520 16 with ceiling fans 220 7
With night ventilation, the house is ventilated at night when temperature and humidity conditions are favorable.
2 A "high mass" building is one with a thermal mass area at least equal to the house floor area.
San Francisco Bay Area 86 SUMMARY FOR SAN JOSE. CALIFORNIA
Sau Fraucleco Bay Area PASSIVE SOLAR DESIGN STRATEGIES tJ(
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 BuDder 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. How the Builder (Worksheet 1) Wray, "Expanding the SIR Method", Passive Solar Journal, Vol. I, 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 illes. The first Is a word-processor file procedure estimates the annual heat loss 2. J. Douglas Balcomb, Robert W. Jones, conta1n1ng 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, Pasalve Solar HeatiDg Analyala, 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 ASH RAE, 1719 TulUe 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, Paulve Solar Heatm, AnalyU., The merge operation slots the numbers basis of the table of heating degree day Supplement One, Thermal Man and text in the second file into their multipliers. The result of the worksheet Effect. and Additional SLR correct locations in the first file. This is is an estimate of the annual heat Correlation., 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 cast, 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 which the total heat stored in the estimated that more than 200,000 Annual Auxiliary Heat 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 (SSF) 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 less 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 furniture worksheet Tables FI-F4. The SLR is approximated as 4.5 or 4.7 Btu/"F per The analysis procedures used method gives answers that agree within throughout the Guidelines were sq ft of floor area. Worksheet Tables HI about 5% of the hourly computer developed using simple, well-established and H2 list the increased value of simulations and within II % of the methods for estimating the performance diurnal heat capacity for various measured passive solar performance of of passive solar heating and natural conventional materials that are often 55 buildings monitored under the Solar cooling strategies. These procedures used to provide extra heat storage, Buildings Program. The SSF estimates (described below) were developed at the assuming these materials replace account properly for both solar gains sheetrock.
San Franclaco Bay Area 88 APPENDIX
The only numbers in worksheet III underestimates very large cooling loads worksheet can be used anywhere within that are locatlon dependent are the in poorly designed buildings. 4 degrees of latltude 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 locatlon. south-facing double glazing on a clear climates. Ventilation is restricted to Within the same vicinity and within plus Januruy day. The driving effect of times when the outside dew-point or minus 20%. the result could be suns paces and vented Trombe walls is temperature Is less than 62 'F. 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 Awdliary Cooling Estimation for Residential Buildings. Getting Data Annual Auxiliary Cooling IA-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 Not for 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 rlight 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 'F 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 lim1ttng 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 is simple: then adjusted for thermal mass and Use the measured base-65 'F degree-day ventilation. This correction includes a value in workshect 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 1, which only case building: however. It change with latitude. Thus, this
San Franclaco Bay Area