Residential E nergy Evaluation

Transcription

1 NEW Military Family Housing Residential E nergy Evaluation M anual United States Air Force Mountain Home AFB, Idaho

2 Disclaimer This Manual was prepared by Delta Research Corporation under contract by the United States Government. Neither the United States, nor the United States Department of Defense, nor any of their employees, contractors, or subcontractors makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed. The residential energy design guidelines presented in this Manual are recommendations only, and do not supersede any applicable energy conservation building code requirements. The reader is responsible for determining the applicable code requirements, and proposing a design in compliance with these code requirements.

3 Preface The United States Air Force is committed to improving Military Family Housing. This commitment is being vigorously executed through a balanced approach of renovation of existing structures and new housing construction. As an important consideration in housing design and construction, energy efficiency has become a key element in the evaluation of each contractor s proposal. The Air Force remains dedicated to improving energy efficiency in family housing, and supports the use of leading energy technology and renewable forms of energy when consistent with reliability, cost, and other design criteria. The Residential Energy Evaluation Manual (REEM) is a key part of the Air Force housing procurement process, and is designed to serve several functions. First, the Manual provides the contractor energy budgets for each type of housing identified in the Request for Proposal (RFP) for new construction. Second, the Manual provides a simple procedure for evaluating the energy effectiveness of any proposed design. The evaluation procedure is standardized for each model type, thereby providing a common method to evaluate individual proposals. If the proposed design exceeds the energy budget allowed in the REEM, the contractor must alter his design to meet or exceed the energy budget standard. Designs not meeting energy budget standards will be disqualified from contract award. The REEM also provides information on energy saving techniques which may aid the contractor in meeting energy budget requirements. The Manual offers a straightforward energy computational process that is easy for the contractor to use. The REEM uses design criteria and energy calculation procedures in a stepwise manner to guide the designer to the optimal residential energy design solution. The calculation process provided in this Manual is simple, and requires only minimal computations. The calculation process is based on state-of-the-art building energy analysis simulations and monitored building energy performance data. The procedures provided in this Manual are applicable to a wide range of energy-efficient residences including conventional, sun-tempered, passive solar, or super-insulated. This Manual is divided into four chapters. Each chapter provides a step-by-step process leading to the completion of the energy assessment required by the RFP. Chapter One provides an overview of the use of the REEM, and should be read before proceeding to any of the other chapters. i

4 TABLE OF CONTENTS List of Tables and Figures... iii Chapter One: How to Use the Manual Chapter Two: The Energy Budget Page 2.1 Overview The Energy Budget Life Cycle Energy Costs Chapter Three: Energy Conservation Measures Overview Climate Conventional Design Considerations The Building Envelope Mechanical Equipment Domestic Hot Water Solar Applications Passive Solar Considerations Site Planning Interior Design Chapter Four: Energy Calculation Procedures Overview Definition of Points Structure of Point System Interpolating Between Energy Conservation Measures Compliance with the Energy Budget Point System Point System Instructions Point System Example References... R-1 Appendix A-1 ii

5 LIST OF TABLES AND FIGURES Tables Table 2.1: Table 2.2: Table 3.1: Table 3.2: Table 3.3: Table 3.4: Page and Cooling Budgets for Single-Family Ranch Style Houses and Two-Story Duplex Houses Life Cycle Energy Cost in Dollars for Two Prototype Houses Thickness in Inches of Select Insulation and Corresponding R-Values Thickness in Inches of Select Rigid Insulation and Corresponding R-Values R-Value and Cost Index for Select Door Construction Infiltration Reduction Measures Table 4.1: Window Shading Coefficients Figures Figure 1.1 : Manual Procedure Flowchart Figure 2.1: Projected Energy Consumption by Major Category Figure 3.1: Idaho Climate Zones Figure 3.2: Building Envelope Considerations Figure 3.3: Slab Floor Construction Figure 3.4: R-19 Standard Wall Figure 3.5: R-19 Equivalent Wall Figure 3.6: R-21 Standard Wall Figure 3.7: R-30 Standard Ceiling Figure 3.8: R-38 Standard Ceiling Figure 3.9: Summer and Winter Sun Angles for Southern Idaho Figure 3.10: Solar Gain in Summer and Winter in Southern Idaho Figure 3.11: Examples of Thermal Mass

6 Chapter One How to Use the Manual This Manual is part of a larger Air Force housing procurement package. Therefore, it may be necessary to move back and forth between this Manual and other sections of the RFP. In order to help you facilitate the preparation of information called for by the RFP, refer to Figure 1.1 and the step-by-step procedures described on the pages following.

7 STEP ONE: Review RFP and REEM Your proposed design solution must satisfy the requirements described in both the RFP and this Manual. Design guidelines are presented in Chapter Three to assist you in achieving the desired level of energy performance. Individual energy-saving techniques are presented that are realistic and cost effective. It is up to the designer to choose the appropriate energy conservation measures that best fit the individual designs. STEP TWO: Identify Mandatory Energy Requirements Your proposed design solution must satisfy the energy budget requirements as defined in Chapter Two. Any design that exceeds the required energy budget will be disqualified from contract consideration. Designs that are projected to be below the required energy budget will receive additional consideration in the proposal evaluation process. You should choose the combination of energy-saving techniques that are most compatible to your design approach and cost goals. Cost effectiveness should be a major consideration when choosing the mix of energy-saving features to achieve the energy budget. STEP THREE: Design Prototypes With the energy budget defined in Chapter Two and the energy conservation measures described in Chapter Three in mind, you should now develop a conceptual energy design package that complies with the overall housing design criteria contained in the RFP. STEP FOUR: Complete Point System Worksheets Once a conceptual design for each unit type has been developed, you should complete the point system forms contained in Chapter Four. These forms must be completed for each unit type. Instructions for preparing these point system forms is described in Section 4.2, Definition of Points. YOU SHOULD MAKE COPIES OF THE FORMS PRIOR TO FILLING THEM OUT AND KEEP THE MANUAL COPIES AS MASTERS. 1-2

8 STEP FIVE: Compare Energy Performance Against Energy Budgets The energy performance of each unit/building type should be compared to the energy budget for that unit type. If your design satisfies the energy budget, then proceed to Step Six. If your design does not satisfy the energy budget, identify what elements of the unit design are causing poor performance, adjust those elements and return to Step Four as shown in Figure 1.1. STEP SIX: Complete Documentation and Submit Proposal When you are satisfied with the energy performance of each unit and the total project, complete all the required documentation and submit the final package for Air Force review. 1-3

9 Chapter Two The Energy Budget 2.1 Overview This chapter provides information about the heating and cooling energy budget and projected life cycle costs for the residential housing types identified in the RFP. These two energy products were developed to serve several functions. First, the Air Force remains dedicated to incorporating modern, energy-saving features in new and renovated Military Family Housing. As a key part of the REEM process, the energy budget technique is viewed as an effective way to encourage contractors to design and build more energy-efficient family housing. The life cycle cost summary of prototype housing is provided to assist contractors and the Air Force in developing a perspective of the effectiveness of select energy conservation measures (ECMs). As a member of the greater southwest Idaho community, has elected to incorporate in this RFP energy conservation standards consistent with regional power and gas company recommendations, as well as general recommendations from the Idaho Energy Conservation Bureau. Information from all of these sources were combined to form the basis for Section 2.2, The Energy Budget. The computation of the heating and cooling budgets and life cycle cost data is performed using Department of Energy (DOE) developed computer programs termed COSTSAFR (Conservation Optimization Standard for Savings in Federal Residences) and CAPS (Computer Automated Point System). These two programs were developed for use by federal agencies in the procurement of residential housing. Both programs are used together, and provide projected annual energy consumption levels as well as life cycle energy costs. The models take into consideration a variety of site-specific factors including geographical location, climatology, and area cost as well as the ECMs being considered for each housing type identified in the RFP. The COSTSAFR model also provides a standardized, manual process to be used by contractors and the Air Force in evaluating each prototype dwelling. The energy budget represents a maximum energy use figure for each prototype that must not be exceeded by the contractor. The contractor is encouraged to use any mix of energy-saving features consistent with the energy budget and general design 2-1

10 requirements. Use of the energy budget figure is intended to give the contractor flexibility in the planning process and encourage innovation in designing energy-efficient housing. The and Cooling Energy Calculation Worksheets in Chapter Four should be used to compare proposed housing designs with the heating energy budget. These worksheets must be submitted as part of the contractor s proposal. In some cases, if the unit or building type varies significantly in orientation, insulation level, glazing area, or other significant specification, several heating and cooling energy calculation worksheets may be required for the same unit or building type. Please refer to Chapter Four for more information on energy calculation procedures. 2.2 The Energy Budget In Tables 2.1, a separate heating and cooling energy budget is shown for each proposed building type. The tables include ECMs that meet or exceed regional and state residential construction recommendations and the COSTSAFR-recommended program for new federal residential buildings. The ECMs represent a sample set of features that will result in compliance with the respective heating and cooling budgets. The energy budgets are specified in thousands of Btus per square foot of conditioned space per year, and are the projected maximum allowable energy consumption totals for each specified building type. FOUNDATION TYPE HVAC TYPE Energy Conservation Measures (ECMs) Ceiling Insulation Wall Insulation Floor Insulation Infiltration Window Type Equipment Ratings Cooling Equipment Ratings HEATING BUDGET (KBtu/Ft 2 /Yr) COOLING BUDGET (KBtu/Ft 2 /Yr) Single-Family Ranch Style Houses R-30 R-19 R-10 for 2 Ft Average Low E & TB 90% AFUE 10.0 SEER Slab on Grade Gas/Elec. Air R-30 R-19 R-10 for 2 Ft Average Low E & TB 90% AFUE 10.0 SEER Two-Story Duplex Houses Slab on Grade Gas/Elec. Air Table 2.1: and Cooling Budgets for Single-Family Ranch Style Houses and Two-Story Duplex Houses In Table 2.1, a prototype Single-Family Ranch Style House with a slab foundation, gas heat and electric air conditioning, and ECMs as shown, is projected to require 43.4 KBtu/Ft 2 /Yr for heating and 2.9 KBtu/Ft 2 /Yr for cooling. Similarly, a Two-Story Duplex 2-2

11 House is projected to require 38.0 KBtu/Ft 2 /Yr for heating and 3.2 KBtu/F 2 /Yr for cooling. The energy budgets for heating and cooling are based on a projected 68 degree internal temperature in winter, and a 78 F temperature in summer. The minimum outdoor design temperature is 8 F, and the maximum outdoor design temperature is 97 F. 2.3 Life Cycle Energy Costs The life cycle energy costs provided in Table 2.2, below, are based on outputs from the COSTSAFR and CAPS computer models. The House Size column includes the three different size units (in net square feet) and number of bedrooms required by the RFP. These three sizes correspond to Air Force size requirements for two, three, and four bedroom Junior Noncommissioned Officer Quarters (JNCOQ). The life cycle cost figures represent the discounted cost in current year dollars in running the heating and cooling equipment and the hot water heater of the proposed unit design for 25 years at local fuel prices and projected fuel escalation rates. The discount rate used is 7 percent. The life cycle cost figures were developed based on the same ECMs used in Table 2.1. House Size Type Single-Family Ranch Style Houses Two-Story Duplex Houses Const. HVAC 950 Ft Ft Ft 2 2 BR 3 BR 4 BR Slab Gas/Elec. Air 4,296 5,492 6,207 Slab Gas/Elec. Air 4,101 5,259 5,945 Table 2.2 Life Cycle Energy Cost In Dollars for Two Prototype Houses For the houses listed in the previous tables, the window area is estimated at 12 percent. The summer and winter shading coefficients are 0.4 and 0.8, respectively. There are several aspects of Table 2.2 that merit additional comment. Upon initial review, the life cycle costs for the three prototypes may appear to be unusually low. However, the figures shown are in current year dollars. The use of then year dollars would present a much higher figure. Although Mountain Home AFB has a relatively high winter heating requirement, total energy requirements are moderated by summer temperatures that are generally cooler than many other areas of the country. The size of the houses is another factor that supports lower levels of energy consumption. The prototypes also benefit from substantial energy-saving measures and significantly lower government gas 2-3

12 and power rates than found nationwide. All of these factors combine to produce significant reductions in energy expenditures. Also, the life cycle costs shown in Table 2.2 take into account only part of the total house energy requirement. For example, in residential buildings outlined in Table 2.1, space heating and cooling account for an average of about 44 percent of total energy demand; this figure would generally be less in more moderate climates. Domestic hot water lags behind at 20 percent for all of the prototypes considered in this project. The remaining 36 percent of projected energy consumption is divided as shown in Figure 2.1, below. Figure 2.1: Projected Energy Consumption by Major Category 2-4

13 Chapter Three Energy Conservation Measures 3.1 Overview This chapter addresses three major areas: climate, conventional design considerations, and solar applications. The purpose of this chapter is to provide contractors information about energy-saving techniques that are realistic, easy to install, and cost effective. The information provided focuses on proven energy applications designed specifically to meet or exceed the energy budgets established in Chapter Two. 3.2 Climate The residents of Idaho live in a relatively broad range of climates. Since climate plays a large role in residential energy consumption, the Idaho Energy Division established three climatic zones representing the different weather regimes within Idaho. Mountain Home AFB is located at the edge of Climatic Zone 1 shown in Figure 3.1. More detailed climatic zone boundary descriptions and lists of locations within each zone are available through the Idaho Department of Water Resources Energy Conservation Bureau, telephone (208) Figure 3.1: Idaho Climate Zones More specifically, Mountain Home AFB is located in southwest Idaho at a surface elevation of 2,996 feet above mean sea level. During a typical year at Mountain Home AFB, temperatures reach an average annual high of 63 F and an average annual low of 39 F. Mountain Home AFB experiences four distinct seasons of about equal length: the warm, dry, months of summer (June through August); the dry months of fall (September 3-1

14 through November); the cold and relatively moist winter months (December through February); and the spring transitional period (March through May). The spring transition marks the end of the cloudy, cool days of winter and the start of the summer. In the spring transition, March temperatures increase from an average maximum of 52 F and an average minimum of 30 F to an average maximum and minimum of 71 F and 44 F, respectively, in May. Summer weather is characterized by warm, dry conditions and occasional thunderstorms. Maximum temperatures average between 80 F and 92 F with minimum temperatures in the mid-40s to upper-50s. By the end of November, Mountain Home experiences a transition toward winter. Frontal passages become more intense resulting in stronger winds and more abrupt weather changes. Since the mean storm tracks pass near the base during winter and farther north and east during summer, lower ceilings and visibilities can be expected to accompany winter fronts. Prevailing surface wind flow transitions from light north westerly flow in the summer, and by November, east-southeasterly flow predominates. Fall temperatures decrease from an average daily maximum and minimum of 78 F and 48 F, respectively, in September to an average maximum of 49 F and minimum of 30 F in November. Winter is characterized by cloudy, cool weather with occasional periods of rain. Frontal passages occur frequently in winter with passages expected every three to four days. Winter maximum temperatures average in the upper-30s to low-40s with average minimums in the low- to mid-20s. Mountain Home AFB has an annual average of 5,570 heating degree days and 828 cooling degree days. 3.3 Conventional Design Considerations This section provides contractors with information about energy-saving considerations that are conventional in approach. For the purpose of this Manual, the term conventional refers to proven, cost effective, off-the-shelf materials and hardware that will produce significant energy savings. A second, and equally important consideration, is that the ECMs chosen provide occupant comfort without demanding a change in lifestyle. The examples provided in the two paragraphs following highlight successful design efforts that produced dramatic reductions in residential energy use. Moreover, the designs benefitted from a conventional approach that ensured reliability, effectiveness, and user satisfaction. 3-2

15 Two homebuilders in the Greater Chicago, Illinois area have an interesting incentive for prospective home buyers: Buy from us, and we guarantee that your heating bill won t exceed $200 per year. If it does, we // pay the difference. The builder s confidence seems well placed in noting that in eight years of active homebuilding, only one has paid out any money - just $390. The homes are in the 2,500 square foot range, and a $175,000 version sells for about $3,000 (two percent) more than conventional models offered by competitors. In Tampa, Florida, a builder s 2,200 square foot house scored a 16.9 out of 100 on Florida s Energy Performance Index (EPI). The EPI provides an overall rating of ECMs incorporated into a residence, with lower values indicating better performance. Homes of comparable size with normal energy-saving treatments typically score between 80 and 90. In Pensacola, Florida, another builder is projecting an 18.9 EPI on a new model, and expects the cost to be within five to seven percent of conventionally built homes. In the Pensacola area, where heating and cooling costs for comparable homes average $79 per month, the builder is projecting $7.75 for monthly cooling and $3.78 for heating. In the cases presented above, the builders used mostly conventional building techniques emphasizing off-the-shelf products. The walls were constructed using 2 by 6 inch framing. Wall insulation was high density fiberglass batts with a super efficient R-21 rating. Also, extra insulation was installed under the exterior siding. Ceiling insulation ranged from R-30 to R-48. Thermal break doors, low-e (low-emissivity glass) windows (R-8), and 93 percent efficient gas furnaces were used. In smaller units (less than 2,200 square feet), no furnace was used. Instead, a system of metal coils similar to a car radiator was installed at the starting point of the forced air heating system. Hot water was piped from the hot water heater to the coils with air being forced over the coils to heat the house. Key leakage points were sealed with the intent to eliminate any significant uncontrolled air movement. Foam sealers were installed around plate lines, mud sills, electrical and plumbing penetrations, baseboard and band joints, and any other points penetrating the building envelope. The homes also benefitted from contractor education and emphasis on proper installation of each system. Without such involvement, improper installation techniques can dramatically reduce the maximum performance of each component, and the system as a whole. The key to success in the homes identified centers on a number of important factors. Use off-the-shelf components Build a tight envelope Use 2 by 6 inch framing with R-21 insulation and exterior sheathing Install double pane, insulated, low-e glass and insulated doors Start ceiling insulation R-values at R-30 Use R-30 insulation in raised floor construction 3-3

16 Install gas furnaces with 90 percent or greater AFUE Use air conditioning units with a SEER of 11 or higher Take the time to seal every penetration to the building envelope Make sure the installers know proper insulation installation techniques The Building Envelope The building envelope is basically the barrier that separates the outside environment from the inside environment. The building envelope refers to the outer perimeter of the structure and generally includes the foundation, floor, walls, windows, doors, ceiling, and roof. The real objective of residential energy conservation is to minimize heat flow and infiltration through the building envelope. Figure 3.2 shows factors to consider in designing and constructing the building envelope. Figure 3.2: Building Envelope Considerations Residential design considerations should emphasize a tight building envelope that minimizes infiltration or exfiltration and heat transfer. Other envelope considerations include vapor and weather barriers and adequate drainage and ventilation to compensate for moisture deposits. Enhancements to the envelope primarily deal with the following. 3-4

17 Levels and quality of insulation materials used throughout the structure. The amount of infiltration into or out of the building. The thermal mass of the building (materials that slow temperature changes inside the building such as masonry and concrete). The size, type, and shading of glass and other fenestration products. Site considerations that better use the effects of shading and insulation. The remainder of this section will take a closer look at the two principal factors impacting heat flow through the envelope: insulation and infiltration. The topics of thermal mass and site considerations are included in Section 3.4, Solar Applications. Insulation Minimum net insulation requirements for the homes identified in the RFP are contained in Chapter Two, Table 2.1. Insulation materials must comply with applicable standards regarding performance, quality, health, and safety. In most residential construction, four types of insulation are installed: batts, blankets, loose fill, and rigid board. Each type has specific attributes and applications, but all are intended to increase a home s resistance to heat transfer, and thereby lower energy requirements for heating and cooling. Selection of specific types of insulation should be based on R-Value ratings, as well as application. R-Values for select types of insulation are shown in Tables 3.1 and 3.2. Table 3.1: Thickness in Inches of Select Insulation and Corresponding R-Values 3-5

18 Type Polystyrene Expanded Extruded Polyisocyanurate and Polyurethane Phenolic R-Value for One inch Table 3.2: Thickness in Inches of Select Rigid insulation and Corresponding R-Values Slab Foundation. For slab floors, insulation is primarily intended to lessen heat transfer through the edge of the slab. Rigid insulation is normally used around the edge of slab foundations due to its strength and ease of installation, and is applied using a mastic adhesive. The perimeter insulation must also be protected from ultraviolet light exposure and physical damage. On polyisocyanurate or spray urethane, a protective coating should be installed that is durable and strong enough to avoid puncture from backfill. The slab edge insulation must have a resistance to water absorption (.3 percent) and a vapor transmission rate of no more than 2.0 perm/inch. The energy budget for Mountain Home AFB requires a minimum slab Figure 3.3 Slab Floor Construction insulation value of R-10 for two feet or downward to the bottom of the slab. See Figure 3.3 for standard slab floor construction. Walls. Framed walls must meet or exceed the net R-19 requirements in the energy budget. The R-19 requirements are generally met using 2 by 6 inch wood framed walls on 16 inch centers. The insulation (R-19 with a vapor barrier next to finished inside walls) used in walls to prevent the leakage of heat is equivalent to approximately 14 inches of solid pine, 58 layers of ¼ inch paneling, or 90 inches of common brick. When using conventional fiberglass batts in 2 by 6 inch walls, some compression occurs reducing the insulation R-Values from 19.0 to However, the net wall R-Value is increased by exterior sheathing, interior gypsum board, and interior air film to a nominal value of R-19. R-21 batts are presently available that fit into a 2 by 6 inch wall cavity (5.5 inches) without 3-6

19 compression. When coupled with 1 inch polystyrene sheathing, an R-Value of 26 is produced. R-19 walls are also attained using 2 by 4 inch framing on 16 inch centers with R-13 batts and R-4.61 insulated sheathing. Assemblies for likely wall combinations are provided in Figures 3.4, 3.5, and 3.6. Figure 3.4: R-19 Figure 3.5: R-19 Standard Wall Equivalent Wall Figure 3.6: R-21 Standard Wall Ceilings. Ceilings, or roofs separating conditioned from unconditioned spaces, must be insulated to a net value of at least R-30. The thermal R-Value of ceiling insulation of R-30 and R-38 is equivalent to approximately 16 layers of ceiling tile, 30 inches of solid wood, or 84 layers of gypsum board. Ceiling insulation is achieved through a variety of insulation types which usually include batt, blanket, loose fill, and rigid insulation. Batt and blanket insulation should be installed between joists or trusses and extend the full depth of the joists or trusses. If a higher R- Value is desired, the batts or blankets should be placed across or staggered above the underlying insulation. Loose insulation is usually blown into an attic and generally has the advantage in ease of application over batt insulation. Rigid insulation offers a relative advantage in having higher R-Values per inch of depth and structural integrity. Rigid insulation is useful in providing insulation for attic access doors and as a baffle around the attic perimeter when using blown-in insulation. Ceiling insulation should extend far enough to cover the top plate of the exterior walls. However, care should be taken to ensure that air flow from eave vents is not blocked. Blockage of eave vents could result in moisture buildup in the attic on the underside of the ceiling insulation. Moisture in the ceiling could result in structural damage, as well as compression and loss of effectiveness of the insulation. Assemblies for ceilings with insulation values of R-30 and R-38 are shown in Figures 3.7 and

20 Figure 3.7: R-30 Figure 3.8: R-38 Standard Ceiling Standard Ceiling Doors and Windows. Emphasis on energy efficiency for doors and windows (glazing) began in the energy crises of the 1970 s. As with other assemblies, heat flow through windows and doors is expressed in terms of U-Value, or the reciprocal R-Value. A higher R-Value or lower U-Value indicates better thermal insulation capabilities. Single pane windows have R-Values of approximately.9 (U-Value of 1.12). Double pane windows improve R-Values to about 2.0. Triple glazing, or gas-filled double pane windows, generate R-Values of about 4.0. Low-E, or low-emissivity glass, is effective in reducing energy losses due to radiant heat transfer which comprises one-half to two-thirds of total window energy loss. Low-E glass, combined with several innovations such as double glazing, argon gas, and improved spacing, produces a one-inch thick window with an R- Value of 8. While this figure is still substantially below wall R-Values, a new double pane window filled with tiny glass beads and using existing low-e features has been developed and is reported to give an R-Value of 16. Minimum standards for Mountain Home AFB require windows to be low-e, argon-filled with insulated aluminum or vinyl clad wood frames. The allowable infiltration rate for manufactured doors is.37 cfm/sf of door area; for windows, the maximum rate is.37 cfm/ft of operable sash crack. The total window area expected is 12 percent with a maximum allowance of 17 percent. Windows facing east and west should be limited to 2.0 to 3.0 percent of the total floor area to minimize excessive summer solar heating. In order to meet the energy budget, the maximum U-Value allowed for windows is.65. Window areas in doors must be counted as part of the total fenestration or window area. Windows must also be certified by manufacturers regarding specific infiltration and 3-8

21 exfiltration ratings. R-Values and cost factors for select door types are presented in Table 3.3. Infiltration Door cost Construction R-Value Index Hollow Core Wood Hollow Core Wood with Storm Door Solid Wood Solid Wood with Storm Door Metal-polystyrene Core Metal-urethane Core Table 3.3: R-Value and Cost index for Select Door Construction Heat loss in the typical home due to infiltration is estimated to account for about 30 to 40 percent of a home s total heating and cooling requirement. Properly installed air infiltration measures will significantly reduce energy consumption and minimize moisture buildup in insulation areas of the building envelope. Table 3.4 shows several infiltration reduction measures and their relation to the infiltration level. Infiltration Level Air Changes Per Hour Infiltration Reduction Measures Average (15 Points or Less) Tight (15-35 Points) Very Tight (Over 35 Points) Standard Infiltration Measures (Caulk and Seal All Envelope Openings) Average Infiltration Level Practices Plus: Exterior air infiltration barrier Continuous vapor retarder sheet Infiltration barrier and vapor retarder combined Foam sealed outlets and switches Windows and doors with certified infiltration rates No or insulated ceiling recessed light fixtures All duct work located within conditioned space Sealed and taped duct work Non-cornbusting heating equipment Storm doors Minimum Required.35 ASHRAE Recommended Standard Table 3.4: Infiltration Reduction Measures 3-9

22 The term points in the infiltration level column relate to values assigned to specific infiltration reduction measures used to evaluate prototype housing submitted by the contractor. More information about the measurement of infiltration levels is included in Chapter Four. Should validation of the infiltration reduction measures be required by field testing, procedures outlined in the American Society for Testing and Materials (ASTM) publication E , Standard Test Method for Determining Air Leakage Rate by Fan Pressurization, will serve as the standard. ASTM E describes a standardized procedure for measuring air-leakage rates through a building envelope under controlled pressurization and de-pressurization. In general, a fan or blower is attached to the building envelope using a door, window or other suitable opening. The fan is turned on, and a range of induced pressure differentials are established between the inside and outside of the dwelling. Typically, air flow, in cubic feet per minute, is measured at pressure differentials of 0.05 to 0.30 inches H 2 O depending on the capacity of the air handling equipment and other parameters. From data taken during the test, an overall air change per hour (ACH) figure can be established--generally the air flow (in ACH) at 0.20 inches H 2 O divided by 20. Also, the American Society of, Refrigeration, and Air-Conditioning Engineers (ASHRAE) publication , Air Leakage Performance for Detached Single-Family Residential Buildings, provides performance requirements for air leakage of residential buildings to reduce the air infiltration load. Infiltration can be significantly influenced by air and vapor barriers. Although each influences infiltration, their purposes are significantly different. Air barriers function to limit the flow of air into or out of a building. Vapor barriers serve to limit moisture flowing from the conditioned space into the building envelope. Air barriers should be placed over the inside face of frame members in the ceiling, and either inside or outside of the framing in exterior walls. If used also as a vapor barrier, air barriers must be placed between the insulation and interior wall gypsum to meet material requirements for vapor barriers. For most construction applications, continuous polyethylene sheet or wallboard with foil backing meets vapor barrier requirements. An older method for providing an unbroken vapor barrier was to use a polyethylene sheet. More current practices emphasize sealing electrical and plumbing openings in the top plate and holes around ceiling fans and fixtures. Kraft paper backed batt insulation forms a satisfactory vapor barrier if properly installed and the paper on the batt meets vapor rating requirements. Batts in framing cavities should be fastened to the face of the conditioned side of the framing member rather than the sides, as is common practice. The batt ends should also be fastened in a similar manner to ensure a continuous barrier around the wall cavity. 3-10

23 Ventilation Ventilation has a variety of impacts on residential energy consumption. Ventilation plays a major role in eliminating moisture buildup in and around the building envelope, and enhancing air quality. In attics, crawl spaces, and walls, adequate ventilation can eliminate moisture buildup which can lead to structural or insulation damage. Ventilation in attic spaces can effectively lower summer cooling costs by as much as 10 percent. For example, thermostatically-controlled attic ventilation systems are a key feature of the highly energy-efficient Florida homes identified in Section 3.3. Other important aspects of the ventilation issue are living space cooling and air quality control. Ventilation can be an important source of living space cooling under optimal climatic conditions. In climates noted for clear skies, low humidity, and relatively large nocturnal temperature changes, natural or mechanical ventilation (also called a whole house fan) can minimize or replace seasonal mechanical cooling, and operates at about 10 percent of the cost of mechanical air conditioning. Climatic conditions experienced at Mountain Home AFB support the whole house fan concept. Additionally, natural ventilation, while generally not reliable due to its dependency on surface air flow, should be a part of the design consideration and included as a cooling and ventilation option for occupants to use. Ventilation also plays a particularly important role in air quality that is usually counter to ECMs. On one hand, energy conservation is significantly aided by limiting infiltration, and super energy-efficient homes strictly limit infiltration as an energy saving technique. On the other hand, adequate ventilation (partially achieved through infiltration) is necessary to minimize contaminants and provide sufficient air quality. In very tightly constructed homes, an energy recovery ventilator (ERV) offers a solution when used in connection with a contamination sensor. The sensor activates the ERV which draws out conditioned but contaminated air, which is then used to heat or cool incoming air as the season requires. In homes with greater infiltration rates, properly designed local exhaust fans in the kitchens and baths coupled with correctly sized central heating and air conditioning systems are highly capable of ensuring adequate air quality. A minimum of.35 air changes per hour is required in housing planned for Mountain Home AFB Mechanical Equipment Natural gas heating with electric air conditioning has been identified as the type of heating and air conditioning systems acceptable to meet the energy budget requirements in this Manual. Natural gas heating amply meets energy budget requirements, as well as general energy design considerations. As a minimum, contractors will ensure the 3-11

24 following energy efficiency standards for residential space conditioning systems are included as part of their proposals. Space Conditioning Requirements and cooling load calculations Equipment sized in accordance with load calculations Equipment certification with DOE Appliance Efficiency Standards Ducts installed, sealed, and externally insulated to a minimum level of R-7 Equipment installed in accordance with manufacturer s instructions Pilotless ignition for gas-fired equipment Setback thermostats Minimum equipment efficiencies Damper controls on exhaust systems Central gas furnaces with minimum AFUE of at least 90 percent Central air conditioners with capacities less than 65,000 Btus per hour require a minimum SEER of 10.0 Two-story units require separate thermostat controls for upstairs and downstairs Mechanical Equipment Controls A key element in residential energy conservation is the lifestyle of the occupants. Adjusting the thermostat to accommodate departures from a residence, such as daily work and school schedules and sleeping periods at night, can result in energy savings of 10 to 20 percent. Automated controls make the temperature adjustments convenient, and can be a cost effective ECMs. This Manual includes provisions for setback thermostats on residential heating and cooling systems. Also required is a clock mechanism that turns off the system during periods of non-use, and allows the occupants at least two periods in 24 hours to automatically turn up or turn down the thermostat setting Domestic Hot Water For the two types of residences identified in the RFP, energy consumption for domestic hot water (DHW) is projected to consume approximately one-half the total energy requirement for heating and cooling. Figure 2.1 in Chapter Two provides a projection of total energy use in Mountain Home AFB housing. DHW, or the water produced by the hot water heater, consumes 20 percent of the total requirement; heating and cooling are projected to generate 44 percent of total demand. 3-12

25 In general, domestic hot water heaters should have either an R-12 external insulation blanket or be certified by the DOE as not requiring a blanket. DHW piping also requires insulation from R-4 to R-6 depending on the pipe diameter. For domestic hot water pipe, diameters less than 2 inches use R-4. R-6 is used for diameters over 2 inches. Cooling system piping used with temperatures below 55 F must be similarly insulated. 3.4 Solar Applications The energy crises of the 1970 s had several major and long lasting impacts. Perhaps the most immediate was a keen sense of public awareness of the need to conserve energy, in particular non-renewable resources. For a substantial period of time during the 1970 s, the public was faced with the distinct possibility of disruption of critical petroleum imports. The cost of all energy sources rose dramatically. In the 1960 s, residential ECMs were not a major factor in home design, and in many areas even minimal wall or ceiling insulation was not used. Resistance strip heating was commonplace. During the 1970 s, energy costs soared overnight and so did average monthly utility costs. bills from $200 to $400 per month were not at all unusual in areas of the North and Northeast. From the sense of awareness and concern of the 1970 s, a need arose to find ways to save energy in residential buildings. As a result, considerable effort was placed on ECMs and solar applications, and residential design and construction techniques were changed in a fundamental way. The energy-efficient homes cited in Chapter Three underscore the truly significant advances made in residential energy conservation made over the last 20 years. Solar Applications are described below emphasizing passive solar design. As in Section 3.3, Conventional Design Considerations, solar energy conservation applications that are practical, reliable, and cost effective are highlighted Passive Solar Considerations Passive solar heating deals primarily with the direct gain of energy as the sun s rays pass through glass and warm interior surfaces. These interior surfaces store energy throughout the day, then release the stored energy at night. In contrast, active solar heating uses collectors and separate storage volumes to provide heating over time. In passive solar heating applications, the major consideration involves ways to allow solar radiation to enter the building envelope in the winter and exclude it in the summer. Other considerations involve the design and placement of thermal mass areas to optimize the storage and release of energy. The key factors of site planning and interior design are indispensable elements in passive solar applications. 3-13

26 3.4.2 Site Planning Properly orienting a residence on a site to take advantage of passive solar opportunities can substantially reduce energy consumption. The long axis of the house should be oriented in an east-west fashion, with principal wall areas facing north and major glass areas facing south. This orientation will maximize exposure to the winter sun, as well as minimize the effects of the summer sun. During the summer, the sun rises at a low angle providing strong heating to the east facing of the residence. As the sun rises, it assumes an almost vertical position at solar noon. With adequate roof overhang and internal shading, the effects of the summer sun on the south side windows can be effectively controlled. During the afternoon, the west facing of the house receives full solar exposure. Figure 3.9 shows the relative angles of the sun in the summer and in the winter. Summer Sun Angie Winter Sun Angle Figure 3.9: Summer and Winter Sun Angles for Southern Idaho 3-14

27 During the winter, the sun remains relatively low on the horizon and moves through the solar noon providing extensive direct sunlight to the south side of the building. Figure 3.10 shows the relative influence of sun angle on solar gain. Figure 3.10: Solar Gain in Summer and Winter in Southern Idaho Solar collection apertures should be free from shadows from other buildings or structures that would reduce solar access in the winter. However, vegetation in the form of deciduous trees can provide effective summer shading for solar apertures, particularly east and west facings. In the winter, the deciduous trees loose their leaves allowing relatively unimpeded solar access to the building. 3-15

28 3.4.3 Interior Design Interior design is a critical element in determining passive solar effectiveness. The following three elements of interior design - thermal mass, interior zones, and solar aperture design - are examined from a passive solar standpoint. Thermal Mass Thermal mass serves to store energy as a building is warmed, and then releases that energy as the building cools. Thermal mass acts as a moderator by slowing internal temperature variations, thereby reducing energy requirements. In passive solar designs, thermal mass for heating purposes must be exposed to sufficient direct or indirect sunlight to be effective. Therefore, the location, shape, and material content of the thermal mass must be carefully selected. Typical thermal mass materials include concrete, tile, brick, or other materials with high interior mass capacity ratings. Examples of thermal mass are shown in Figure Figure 3.11: Examples of Thermal Mass 3-16

29 The amount of thermal mass required for effective passive solar residences varies with individual design. However, as a general rule for slab floor construction, thermal mass should be equivalent to 25 percent of the ground floor area of the building. For raised construction, thermal mass should be equivalent to 10 percent of the ground floor area. Thermal mass walls are most effective with a high surface thermal absorptivity (greater than 80 percent). Interior Zones The effective design of passive solar heating systems must consider heat transfer problems associated with interior thermal zones. Interior thermal zones are generally formed by walls that separate rooms, thereby causing temperature differentials. These temperature differentials can cause problems with occupant comfort unless adequate design consideration is given to heat transfer methods such as window location, zonal heat coupling, and thermal mass considerations. Solar Aperture Design Solar aperture design deals primarily with controlling solar access to the building interior. In regard to winter heating situations, the objective of aperture design is to maximize solar contact with thermal mass and selectively warm interior surfaces. In the summer, effective aperture design limits solar access, allowing thermal mass to slow the warming process and provide a comfortable living space on an otherwise warm day. The principal considerations in aperture design deal with fenestration features that provide solar access to thermal mass areas, and the placement of thermal mass to take full advantage of solar heating. Direct Gain Windows. Direct gain windows are integral to the passive solar process with size, type, and location being the primary variables. For passive solar design homes, the minimum south facing area is 6.4 percent, and the maximum total non-south facing area is 9.6 percent. The maximum U-Value for direct gain windows is Direct gain windows should be located to maximize thermal zoning and thermal mass design. Single pane windows are recommended for direct solar gain applications. Daylighting. Daylighting refers to the sunlight that enters solar apertures in the solar heating process. This beneficial side effect of passive solar design can also be an effective ECM in reducing costs associated with lighting. 3-17

30 In summary, Chapter Three contains information about ECMs that are applicable to the residential housing identified in the RFP. In Chapter Four, information is presented on the computation of points to be used in the evaluation of each housing prototype submitted. 3-18

31 Chapter Four Energy Calculation Procedures 4.1 Overview This chapter provides information on the procedures to determine compliance with the energy budget established in Chapter Two. The procedure to determine compliance is based primarily on completion of a point system worksheet which is attached at the end of this chapter. The energy budget and points system worksheets were compiled using COSTSAFR and CAPS computer programs developed by Pacific Northwest Laboratory under contract with the DOE. Both programs were developed for use by federal agencies as a part of the DOE S Interim Energy Conservation Mandatory Performance Standards for New Federal Residential Buildings. The forms used to determine compliance will hereafter be referred to as the point system. Contractors must complete the worksheets for each prototype residence submitted for consideration. Designers select ECMs that earn credit in the points system. ECMs include insulation levels, window type and area, infiltration levels, HVAC equipment, and water heating. The cumulative points from all ECMs must equal or exceed a preestablished required point total to comply with the standard. 4.2 Definition of Points Points are proportional to dollars of life cycle energy savings, and are relative to the worst (least energy efficient) level for each ECM. For example, a point total of 53 indicates that the prototype being considered generates a life cycle cost saving of $5,300 in currentyear dollars over the same prototype with minimum level ECMs. The absolute value of the points for any ECM must be taken in relative, marginal context. For example, the points awarded to foundation measures tend to be much higher than the points awarded to ceiling and wall insulation because floor measures are compared to the very inefficient minimum level of R-O (no insulation). In contrast, the minimum level for ceiling and wall insulation is R-11. The energy savings relative to R-O insulation are much larger than the energy savings relative to R-11 insulation. However, the difference in points for the foundation ECMs may be small. Therefore, the gain in points for increasing the foundation conservation levels may have little impact on the overall point total. The least energy-efficient levels for all components always have points equal to 0.0. For Mountain 4-1