2516 Energy Performance Townhouses

A DVANCED H OUSING T ECHNOLOGY P ROGRAM M ONITORING AND E VALUATION OF THE E NERGY P ERFORMANCE OF THE ST 21 C ENTURY T OWNHOUSE U NITS

Subcontract No. 86X-SC895C and 62X-SC895C

Prepared for: Martin Marietta Energy Systems, Inc. Oak Ridge, TN 37831-6501 by: NAHB Research Center, Inc. 400 Prince George’s Boulevard Upper Marlboro, MD 20774-8731

June 1997

INTRODUCTION ................................................................................................................... 1 STRUCTURAL CHARACTERISTICS OF TOWNHOUSE UNITS ................................ 3 TOWNHOUSE UNIT 7—STRUCTURAL INSULATED PANELS ......................................... 3 Foundation ....................................................................................................... 3 First and Second Levels .................................................................................. 3 Exterior Finish ................................................................................................. 4 Attic/Roof ......................................................................................................... 4 Mechanical/Plumbing ..................................................................................... 4 TOWNHOUSE UNIT 8—INSULATING CONCRETE FORMS ............................................. 5 Foundation ....................................................................................................... 5 First and Second Levels .................................................................................. 5 Exterior Finish ................................................................................................. 5 Roof/Attic ......................................................................................................... 5 Mechanical/Plumbing ..................................................................................... 5 TOWNHOUSE UNIT 9—STEEL FRAME.......................................................................... 6 Foundation ....................................................................................................... 6 First and Second Levels .................................................................................. 6 Exterior Finish ................................................................................................. 6 Attic/Roof ......................................................................................................... 6 Mechanical\Plumbing ..................................................................................... 6 TOWNHOUSE UNIT 10—AUTOCLAVED AERATED CONCRETE .................................... 7 Foundation ....................................................................................................... 7 First And Second Levels ................................................................................. 7 Exterior Finish ................................................................................................. 8 Attic/Roof ......................................................................................................... 8 Mechanical/Plumbing ..................................................................................... 8 MODEL CODE ENERGY ANALYSIS ................................................................................ 8 DATA AND METHOD FOR THE ANALYSIS OF INDIVIDUAL TOWNHOUSE UNITS .......... 9 Townhouse Unit 7 .......................................................................................... 12 MEC Analysis Results ......................................................................... 14 Energy Consumption Estimates .......................................................... 15 Townhouse Unit 8 .......................................................................................... 17 MEC Analysis Results ......................................................................... 19 Energy Consumption Estimates .......................................................... 20

Townhouse Unit 9 .......................................................................................... 22 MEC Analysis Results ......................................................................... 24 Energy Consumption Estimates .......................................................... 25 Townhouse Unit 10 ........................................................................................ 27 MEC Analysis Results ......................................................................... 29 Energy Consumption Estimates .......................................................... 30 ENERGY SIMULATION ANALYSIS ............................................................................... 32 TOWNHOUSE ENERGY PERFORMANCE MONITORING–COOLING SEASON ............... 35 Air Conditioning Energy Consumption ...................................................... 35 Performance of Individual Townhouse Units ............................................. 36 Townhouse Unit 7— Structural Insulated Panels ............................... 36 Townhouse Unit 8— Insulating Concrete Forms ................................ 41 Townhouse Unit 9— Steel Frame with Spray Foam Insulation .......... 45 Townhouse Unit 10— Light Weight Autoclaved Aerated Concrete .................................................................................. 50 Building Temperature Profile ...................................................................... 55 Temperature Response ................................................................................. 57 TOWNHOUSE ENERGY PERFORMANCE MONITORING–HEATING SEASON ............... 62 Performance of Individual Townhouse Units ............................................. 63 Townhouse unit 7— Structural Insulated Panels ................................ 63 Townhouse Unit .................................................................................. 65 8— Insulating Concrete Foam Forms ................................................. 65 Townhouse Unit 9— Steel Frame with Spray Foam Insulation .......... 69 Townhouse Unit 10— Lightweight Aerated Autoclaved Concrete .................................................................................. 73 Summary ........................................................................................................ 76 VISITOR SURVEYS ....................................................................................................... 77 Likelihood of Adoption ................................................................................. 78 Attributes Influencing Adoption of Innovations ........................................ 81

INTRODUCTION st

The NAHB Research Center (Research Center) built four 21 Century Townhouses in its Research Home Park as part of the Research Center’s research home program. The principal objective of the program is to: Test, demonstrate, and gain experience with innovative home building products, systems, and technologies to aid the movement of innovative products and systems into the mainstream of home construction. st

Products incorporated in the 21 Century Townhouses feature two themes: • •

innovative structural systems in home building and approaches to achieving advanced residential energy efficiency.

The objective of Task 2 of the U.S. Department of Energy’s (DOE) Advanced Housing Technology Program (AHTP); is to “initiate the monitoring and evaluation of the performance of selected energy-related technologies included in the townhouses.” This task begins with the selection of technologies or attributes of units to be studied. It then proceeds with the development and initiation of an overall analytical approach to the technical analysis and monitoring protocols. In this report, the Research Center evaluates the results to date and synthesizes the findings. This report focuses on the second theme, the analysis and evaluation of energy-related technologies as they affect residential energy efficiency. A comprehensive survey of visitors’ reactions to the Photovoltaic (PV) solar system in one of the townhouses was initiated in October 1997 and completed in March 1997. Subsequently, another more general survey pertaining to the other energy-related technologies was implemented in March 1997. The initial results of the survey of PV technology will be included in a separate report devoted to building integrated photovoltaics (BIPV). The initial results of the general survey to-date is included as part of this report. st

The NAHB Research Center’s 21 Century Townhouse project consists of four townhouses. In keeping with the objective of demonstrating innovative products, a minimal amount of dimensional lumber framing was used in the construction of the townhouses. The construction materials include high and low density foams, oriented strand board (OSB), structural insulated panels with insulating foam, high and low density concrete, and steel framing. According to Prince George’s County’s original lot number designations, individual townhouse units in this report are referenced as units 7, 8, 9, and 10. Their significant features are as follows: •

Townhouse unit 7 walls and roof are constructed of Structural Insulated Panels (SIPs) consisting of two panels of OSB sheathing enclosing an

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• • •

•

expanded polystyrene (EPS) core. This unit uses a gas fueled heat pump for both heating and cooling. The foundation walls of units 7, 8, and 9 are constructed using insulating concrete forms (ICFs) provided by ICE, which uses forms made of EPS that are stacked, reinforced with metal rebars, and filled with concrete. The main feature of unit 8 is its construction using ICFs, from foundation to gable. This townhouse uses an integrated hot water/furnace unit for heating and an electric outdoor unit for cooling. Unit 9 is characterized by its steel frame construction with Icynene spray foam insulation in the wall and ceiling. This townhouse unit uses a ground source heat pump for both heating and cooling and includes a hot water desuperheater. Unit 10 features walls that are constructed using Hebel’s lightweight autoclaved aerated concrete (AAC) blocks. The roof is wood truss framing insulated with spray foam and blown fiberglass. The foundation walls are constructed using Superior Wall’s pre-formed concrete panels. A PV solar system, with inverter and battery storage, supplements the utility electric supply. The home uses an integrated hot/water furnace unit for heating and an electric outdoor unit for cooling, similar to townhouse unit 8.

In summary, units can be identified either by their numbers or their most significant structural feature: • • • •

unit number 7—SIP construction unit number 8—ICF construction unit number 9—Steel Frame construction unit number 10—AAC construction

Townhouse units are designed with common walls between the units. Units 8 and 9, have an ICF common interior wall with each other; units 7 and 10, share a common wall with an unconditioned garage as an adjoining unit. In this respect, units 7 and 10 have more in common with detached housing units than attached units typical in townhouse construction. Unit 7 was occupied during the period of performance. Unit 8 was occupied for a portion of the period of performance, and units 9 and 10 were unoccupied during the entire period of performance. Each of the units were available for numerous tours and each contains appliances and lighting which may have been operational throughout the period of performance.

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STRUCTURAL CHARACTERISTICS OF TOWNHOUSE UNITS This section contains the detailed structural characteristics of each of the townhouse units which is useful in interpreting the results of the energy analyses. TOWNHOUSE UNIT 7—STRUCTURAL INSULATED PANELS Foundation The foundation wall consists of the ICE Block stay-in-place concrete wall forming system to form an 8' basement. The ICE Block walls have a stated R-value of 26. The forms consist of expanded polystyrene (EPS) foam with a light-gauge steel web connecting interior and exterior form walls. The total wall thickness measures 11-1/8" with the concrete core a structural equivalent of an 8" conventional reinforced concrete wall. Window and door block-outs consist of 2 x 12 pressure-treated lumber left in place after concrete placement to serve as a means for attaching doors and windows. A 2 x 12 pressure-treated sill plate was fastened to the top of the foundation wall with anchor bolts. The floor of the walk-out basement is an uninsulated concrete slab reinforced with wire mesh. The slab is stepped 6" to divide the one-car garage and family room. A double 18 gauge steel frame wall separates the garage and living areas. Inner and outer walls consist of 3.5" 18 gauge steel studs with a 5/8" type-X fire-rated gypsum wallboard between the inner and outer steel stud wall. A 1" void separates the wallboard surface from the outer wall. The outer wall stud bays and space between walls are insulated with the Icynene Insulation System, a modified urethane spray-on foam. Windows and a single patio door in the basement are low-E glazed, argon-filled Andersen units with a U-value of 0.32 (R-3). The door between the garage and living area is a steel ThermaTru unit with an R-9 foam filled core and steel frame, carrying a 90 minute fire rating. The 8' x 7' garage door is supplied by Masonite. The below-grade exterior walls are treated with EPRO water-based foundation waterproofing system in lieu of a petroleum based coat that would cause the foam to melt. Both sides of the interior wall separating garage and living area were clad with 5/8" type-X gypsum wallboard, completing the fire-rating required by code. All other interior walls were 1/2" gypsum wallboard attached by screwing directly into a light gauge steel flange embedded in the ICE Block form. First and Second Levels The floor decks consists of 16" 125 series TrusJoist I-beams (TJIs) set on the foundation sill plate, running front to back. Joists are spaced 24" on-center with a 3/4" plywood rim joists. The flooring consists of 3/4" Weyerhaeuser Structurboard oriented strand board (OSB) with tongue and groove edges. Floor sheathing is fastened to joists with construction adhesive and nails. To decrease air infiltration, the rim joist area is sealed with Amoco's Infi Seal, a gasketed air barrier that is set under the sill plate and wraps over the joist onto the floor deck. The

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interior overlap is then attached to the wall surface under the wallboard. The rim joist area is insulated with the Icynene Insulation System spray-in foam to an R-19 value. The joist bays above the unconditioned garage are also insulated with the Icynene Insulation System. The exterior wall is constructed of stress skin insulated panels. Wall panels consists of a 3-5/8" (EPS) foam core sandwiched by layers of 7/16" OSB. Typically, stress-skin panels have no interior wall studs or headers. Some do recess the foam between OSB faces at the top, bottom, and sides, and window and door openings sufficient to place a nominal 2 x 4 stud that facilitates attachment. However, the local fire code required the panels to be manufactured with 2 x 4 studs at least every 8 feet vertically and horizontally as draft/fire stops. Wall height for both floors is 8'. Interior partition walls are framed with 25 gauge metal studs. Windows and patio door are Andersen low-E, argon-filled units with a U-value ranging from 0.33 to 0.35 (R-3). The front door is an R-9 Therma-Tru fiberglass insulated door. The single patio door opens onto a potential deck/balcony at the rear of the unit. Interior walls and ceilings are clad with 1/2" gypsum wallboard except the party wall separating interior living area with the garage of another unit, which is two layers of 5/8" type-X fire-rated gypsum wallboard. Intermediate load bearing capacity for the second level floor is provided by a pair of beams. A flush Micro=lam laminated veneer lumber (LVL) 1-3/4" x 16" beam supports half the floor. The other half is supported by a dropped beam consisting of a single of 3-1/2" x 12" Parallam which has been incorporated into the kitchen bulkhead. Exterior Finish A United States Gypsum (USG) exterior insulation and finish system (EIFS) was used on the exterior walls. A 1" layer of expanded polystyrene (EPS) foam was attached with mastic and Windlock fasteners to all wall surfaces. The foam serves as a base for the USG base coat and mesh. A pre-colored finish was trowel-applied over all base coat areas. Attic/Roof The roof is constructed with 8" sandwich insulated panels with an R-value of 30, making the unfinished attic conditioned space. It is covered with 30 pound asphalt roofing felt and an ATAS standing seam metal roof system. The gable ends are constructed of the same sandwich panels as the walls. Mechanical/Plumbing Heating and air conditioning will be provided by York Triathlon gas-engine heat pump. The water heater will also be a gas unit. Basement and second level supply registers are located in the ceiling and the first level supply registers are in the floors. A combined sprinkler system with all ceiling heads was also installed.

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TOWNHOUSE UNIT 8—INSULATING CONCRETE FORMS Foundation The foundation of unit 8 uses the same ICE Block system described for townhouse unit 7 to form a walk out basement. The floor consists of a concrete slab and the finished ceiling height is 9' 4". EPRO waterproofing is applied on below grade exterior walls. The interior is clad with 1/2" gypsum drywall. Windows and the patio door are Andersen argon-filled with low-E glazing. The majority of the basement is devoted to a single recreation room with a closet and a utility room completing the balance. All but 12' of the east-facing basement wall is shared with unit 9. The 12 foot segment has an exterior exposure. First and Second Levels All exterior walls are constructed of 9 1/4" ICE Block (6" equivalent core). The east-facing wall of the first and second level is shared with unit 9. Interior partitions are framed with 25 gauge steel studs. Interior walls and ceilings are covered with 1/2" gypsum wallboard. The first floor deck is framed side to side with 135 Series 16" deep TJIs spanning the 22' 6" width of the unit spaced 24" on center. The joists are hung on Micro=lam ledges that are attached to the exterior walls with two 1/2" x 8" j-bolts every two feet. The floor sheathing is 3/4" Weyerhaeuser Structurboard OSB. The front door is an R-9 Therma-Tru fiberglass door. Windows and rear patio door is are Andersen argon-filled, low-E glazed units. Exterior Finish The same USG EIFS system used on unit 7 was applied on exterior walls. Roof/Attic The roof is framed using wood trusses with raised heels, often referred to as an energy truss. This design allows an even distribution of insulation to its full height to the edge of the attic space. The insulation will be 15" of blown-in Certainteed InsulSafe Fiberglass providing an R-value of 38. The roof is sheathed with 7/16" Weyerhaeuser OSB and covered with 30 pound roofing felt and a ATAS standing seam metal roofing. Mechanical/Plumbing The heating plant is a Lennox Complete Heat gas furnace system which also provides domestic hot water. Air conditioning is a Lennox high-efficiency 12 SEER electric unit. Basement registers are in the ceiling, first level registers are in the floor, and second level registers are located in the floor and ceiling and are selectable so that either system or both are being used. A GFX drainwater heat recovery system was installed in the drains of the two upstairs showers. The warm shower drain water tempers the incoming cold water, which feeds the cold side of the shower diverter valve. Also, a combined sprinkler system using blazemaster orange and copper pipes with central supply heads was installed in this townhouse. NAHB Research Center, Inc.

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TOWNHOUSE UNIT 9—STEEL FRAME Foundation The foundation of unit 9 is identical to unit 8, sharing the west-facing wall except for a 12' section, which has a below-grade exposure. First and Second Levels The first floor is supported by Mitek Posi-Strut steel floor trusses. The trusses span 22' 6" and are top chord bearing on one end and supported by hangers on the other. Floor sheathing consisted of 3/4" Weyerhaeuser Structurboard OSB. Exterior walls are constructed with 2 x 6 light-gauge steel framing members with an actual wall depth of 5-1/2". Walls are sheathed with Durock cement board except for the west-facing wall shared with unit 8. Exterior frame walls are insulated with the Icynene Insulation System described in the section on unit 7, with wall stud bays filled with a 5-1/2" (R-19) layer of sprayed-in foam. Interior walls consist of 25 gauge steel framing covered with 1/2" gypsum wallboard. Exterior window and door openings were lined with pressure-treated 2 x 6 lumber to facilitate attachment. Windows and patio doors are Andersen argon-filled, low-E glazed units with a Uvalue of 0.32 to 0.35, or about R-3. The front door is a Therma-Tru fiberglass unit, and the door leading to the garage is a Therma-Tru steel door, both with R-9 foam cores. Exterior Finish The exterior walls feature the USG EIFS textured finish identical to the system used on unit 7 except for its use of USG Durock sheathing on first and second level steel frame walls. The 1" EPS foam layer served as the EIFS base and provided the 1" thermal break recommended for steel stud walls. Attic/Roof The roof trusses are Mitek Ultra-Span light gauge steel with a raised-heel design. The roof is sheathed with 7/16" Weyerhaeuser OSB and attached with Enrico pins, which are pneumatically driven nails. The ATAS standing seam metal roof is placed on a base of 30 pound roofing felt. The attic is insulated with a 3-1/2" layer of Icynene foam with an additional layer of Certainteed InsulSafe blown-in fiberglass insulation. Mechanical\Plumbing The forced air heating and cooling system features a Waterfurnace ground-source heat pump with three 180' vertical wells. Domestic hot water is also provided by this unit. The basement and second floor registers are located in the ceiling, and the first floor registers are located in the floor. Individual air returns are located on the second level. A GFX drainwater heat recovery system pre-heats water to the cold water side of the showers and the water heater intake. A combined fire sprinkler system was installed with side wall heads.

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TOWNHOUSE UNIT 10—AUTOCLAVED AERATED CONCRETE Foundation Unit 10 has a Superior Wall pre-cast concrete foundation wall set on a gravel footing. The design of the Superior Wall foundation is based on the principles of optimum value engineering, conserving concrete, and steel reinforcement by strategically placing it in loadbearing vertical studs, reinforced top and bottom plate, and a 1-1/2" concrete exterior surface. A 1" layer of extruded polystyrene is cast between the exterior wall surface and vertical "studs" and serves as a thermal break between exterior and interior walls. The resultant wall has cavities that can be insulated additionally with fiberglass batt insulation. Window and door block-outs consist of 2 x 8 lumber and serve as a nailing surface for easy attachment. The foundation forms a walk-out basement. The concrete slab floor is stepped between garage and living areas identical to unit 7. The doubled steel frame wall between interior living and garage areas is configured, insulated, and finished identically to unit 7 steel basement wall. Interior walls are framed with 25 gauge steel studs and interior walls are finished with 1/2" gypsum wallboard. Windows and the patio door were Andersen argon-filled, low-E glazed units. The garage has an 8' x 7' Masonite door and the door separating the living area from the garage is a Therma-Tru R-9 steel unit with steel frame. First And Second Levels The entire first and second level exterior walls were built with the Hebel Wall System, consisting of a lightweight AAC block that contains a load bearing structure, insulation, and interior and exterior wall substrates in a single material. A reinforced concrete bond beam was cast between the first and second level and at the top of the Hebel wall using a hollowed Hebel AAC unit form that corresponds to a U-block in conventional masonry construction. Loadbearing lintels were constructed over all openings from the same materials. The width of the Hebel wall is 8". Wall openings were lined with 2 x 8 pressure-treated lumber, a traditional mechanism for attaching doors and windows. The first and second level floor systems used TrusJoist International engineered wooden Ibeams for floor support. Each joist has a 3" fire cut at the end bearing on the exterior walls. A layer of roofing felt was placed between joist and concrete beam to protect the joist against water absorption. The Hebel material extended to the top of the foundation, so cut-outs were made in the Hebel material 24" on center to accommodate the joist. The floor sheathing is Weyerhaeuser 3/4" OSB. The joist bays over the unconditioned garage were filled with the Icynene Insulation system (R-19). As with unit 7, Micro=lam and Parallam LVL beams were used as intermediate load-bearing support for the second level floor. Windows and patio doors are identical to unit 7. The front door is an R-9 Therma-Tru insulated fiberglass model. Interior walls are framed with 25 gauge steel studs and doors are lined with 2 x 4 lumber to facilitate attachment. The interior Hebel wall surface was finished with the Litewall interior plaster supplied by Elite Cement Products, Inc. Interior walls were clad with 1/2" gypsum wallboard.

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Exterior Finish The exterior finish system consists of the Litewall one-coat stucco system supplied by Elite Cement Products, Inc. The Portland cement-based stucco contains fibrous reinforcement and polymers to inhibit cracking and to ensure proper adhesion. The mix, designed for use on AAC, also contains lightweight aggregates to insure the same thermal expansion coefficient as AAC. The stucco mix was spray-applied as a 3/8" base coat troweled to a smooth surface. The same mix, which contains texturing aggregates, was hand applied and floated to a textured 1/8" finish. Attic/Roof The roof was framed with raised heel lumber trusses, sheathed with 7/16" OSB, and covered with 30 pound roofing felt and an ATAS standing seam metal roof. The attic was also insulated with Certainteed InsulSafe blown-in fiberglass insulation. The east-facing gable is composed of Hebel building material and finished with the same exterior finish system. The east-facing gables are clad with OSB, a 1" foam substrate, and USG fiberglass mesh and base coat. The finish coat was supplied by Elite Cement Products, Inc. Mechanical/Plumbing The mechanical system features the Lennox Complete Heat gas furnace and domestic hot water system. Air conditioning is a Lennox high-efficiency electric unit. Basement and second level registers are located in the ceiling, and first level registers are located in the floor. This townhouse is fitted with the electronics for supplying the home with solar-generated electricity pending the delivery and installation of a roof-mounted photovoltaic module array.

MODEL CODE ENERGY ANALYSIS In the construction of the townhouse units, a major focus on increased energy efficiency is realized. The increased efficiency is attributed primarily to the building envelope and space conditioning equipment. One evaluation which seeks to quantify the increased energy efficiency is a comparison of the townhouse construction with the minimum requirements of the Model Energy Code (MEC)1. This particular analysis highlights the benefits of specific building materials. A short-coming of the basic MEC analysis is that certain aspects of energy efficiency such as HVAC efficiency, infiltration, and duct losses are not specifically accounted for in the analysis. Each of the four units is considered individually. A set of basic thermal transmittance (U) or 2 thermal resistance (R) requirements are established for each unit . These basic requirements are derived directly from the 1993 MEC. An analysis of each townhouse unit has been performed to develop specific U-and R-values for the wall, floor, and ceiling/roof subsystems. The results of this analysis are then used to compare to the requirements on a subsystem by subsystem basis. The results of the comparison are shown in tabular and graphical form. 1

The analysis uses the 1993 MEC with the notable exception that each planar basement wall is considered separately. This approach is consistent with recent changes in the MEC. 2 The higher the U value, the greater the heat transfer across the particular subsystem.

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Compliance with the MEC is established when each of the subsystems meet the requirements 3 established for a standard MEC compliant building. The primary influence on the basic UA requirements is the location of the building and the associated heating degree days (HDD) for the locality. In a MEC analysis, compliance of individual subsystems helps assure compliance of the building as a whole. In the event that one subsystem is not in compliance, a method is available for "trading off" a better performing subsystem for a lesser performing subsystem, but it is limited. 4

A computer software package, MECcheck , developed at the Pacific Northwest Laboratory, establishes a base UA requirement for the building according to the wall areas; other features are included in the design. A whole building performance UA is thus established for the townhouse unit and compared to the required UA. When the townhouse unit UA is less than the minimum required UA, the building is in compliance with the 1993 MEC. The software also includes an option to derive the benefits for a more efficient HVAC plant, a feature not part of the 1993 MEC. DATA AND METHOD FOR THE ANALYSIS OF INDIVIDUAL TOWNHOUSE UNITS 5

•

Using the BOCA terminology, the four townhouse units are analyzed as Group R (residential), Type A-1 (detached), and Type A-2 (attached). As noted above, the two end units are separated from the attached two center units by an unconditioned garage. The energy analysis is most accurately reflected by considering the units as two detached single-family homes and one two-family home. However, according to building officials with Prince George’s County (the local jurisdiction), the units are technically considered townhouses.

•

Weather data used in the analysis is based on ASHRAE 1989 (except for the Heating Degree Days [HDD] ), for Andrews Air Force Base and includes the following data: winter dry-bulb temperature = 14°F summer dry-bulb temperature = 90°F design wet-bulb temperature = 76°F Heating Degree Days (ASHRAE 1981, 65°F base) = 4224 6 Heating Degree Days used in analysis = 4459

•

The geographic coordinates are 38° 5' Latitude and 76° 5' Longitude.

•

The type A-1 Maximum Wall Uo7 = .2188-(4459*.00001555) = .149

•

The type A-2 Maximum Wall Uo = .215

•

The type A-1 and A-2 Maximum Roof/Ceiling Uo = .036-[(4459-3900)*.00000476] = .033

3

the thermal transmittance (U) times the area (A) Version 2.0 5 The regional model building code. 6 the heating degree day value is consistent with that used in the MECcheck program 7 based on the 1993 MEC chapter 8 requirements 4

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•

The type A-1 and A-2 Maximum Floor Over Unheated Space Uo = .050

•

The type A-1 and A-2 Maximum Basement U = .205-(4459*.0000233) = .101

•

The type A-1 and A-2 Minimum Unheated Slab On Grade R = 4.0

The MEC permits an increase in the Wall thermal transmittance (Uo) requirement if the wall system exhibits as thermal mass characteristics. The basis of the qualification is a calculation 2 of the heat capacity (HC) of the wall exceeding 6 Btu/ft -°F. The heat capacity is found by the following formula from the MEC: Heat Capacity = Weight * Specific Heat Two of the townhouse units are constructed using wall materials which may qualify as thermal mass. Unit 10 is constructed using lightweight AAC by Hebel Southeast, and unit 8 is constructed using the ICE foam concrete forms filled with high density concrete. Both systems are analyzed below for qualification as thermal mass: •

8

Hebel Light Weight AAC 8" block characteristics are as follows: Density Conductivity R-value Weight Specific Heat MEC HC value

3

32.0 lb/ft 2 0.9 Btu-in/h-ft -F 9 9.0 (static) 2 26.0 lb/ft 0.250 Btu/lb-°F 2 6.5 Btu/ft -F

Since the AAC HC value is greater than 6.0, it satisfies the criterion for 10 thermal mass using MEC Table 502.1.2c : Uo for non-mass wall Uw non-mass wall Uw from table (interpolated) Maximum Uo for ICE Block Mass Wall •

0.149 11 0.127 0.167 0.177

12

ICE Foam Form Concrete Block characteristics are as follows: Density of concrete Specific Heat of concrete Weight of 6" form MEC HC value (6" form) Weight of 8" form MEC HC value (8" form)

150 lb/ft3 0.200 Btu/lb-°F 56.4 lb/ft2 11.28 Btu/ft2-°F 76.1 lb/ft2 15.22 Btu/ft2-°F

8

Hebel Block From Hebel literature, an “effective” R-value of 30 is also included in the literature 10 the lightweight AAC is considered a mass wall with mixed insulation and mass 11 using formula in note 6, table 12) 12 manufactured by ICE Block 9

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Since the ICE Block foam form HC value is greater than 6.0, it satisfies the thermal mass criterion in regard to thermal mass for both the 6” and 8" forms. MEC Tables 502.1.2a and b were used in the calculation since the insulation is on both sides of the mass: Uo for non-mass wall Uw non-mass wall Uw from table (interpolated) Maximum Uo for ICE Block Mass Wall

0.149 13 0.122 14 0.152 0.174

•

The level of duct insulation required for ducts on the inside of the building envelope (not necessarily in conditioned spaces), with a temperature difference 15 (TD) greater than 40 is an R 5.0 ft2-°F-hr/Btu. The ducts in the townhouses are insulated with a minimum R 6.0.

•

The HVAC equipment for each townhouse unit must meet the minimum equipment efficiencies specified. A comparison of the heating and AC equipment with the basic requirements are shown in Table 1: Table 1 HVAC Equipment Installed

HVAC Equipment

Unit

Heating

Water Furnace Ground Source Heat Pump

9

COP = 3.50

York Triathlon Natural Gas Heat Pump

7

COP = 1.26

8,10

AFUE = 90%

Lennox Complete Heat

Cooling 1

EER = 14.7

3

SEER = 15.6

4

SEER = 12.0

3

3

2

1

estimate based on 50 kBtu/hr load and 60F temperature difference estimate based on 27 kBtu/hr load and 20F temperature difference 3 manufacturer's data 4 based on proposed method to calculate SEER using fuel cost for gas & electricity 2

•

Gas water heaters installed must comply with MEC section 504.

The following analyses for each townhouse unit are based on: • • •

Calculation of the Uo- and R-values necessary for compliance with MEC requirements given the unique material characteristics and local climatic data. Performance of a MEC analysis of each townhouse using MECCheck software. Completion of a MEC analysis of the house as built, using REM Design’s estimation software to derive annual heating and cooling energy use estimates and costs.

13

using formula in note 6, table 6) average of MEC Table 502.1.2a, Uw = 0.162 and MEC Table 502.1.2b, Uw = 0.142 15 refer to chapter 5 of the MEC 14

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As noted earlier, the units are technically considered townhouses from a building code standpoint and must comply with MEC requirements for multifamily townhouses, but actually the two end units, separated from the rest of the units by an unconditioned garage, can be considered one-family detached units and the two middle units that share a common wall can be considered two-family units or duplexes. Consequently, in computing compliance with MEC requirements in the tables that follow, the more strict MEC requirements for one- and two-family houses were also derived for comparison purposes. Townhouse Unit 7 The MEC minimum requirements for each subsystem in unit 7 are shown in Table 2. 16

Table 2 Subsystem U and R Requirements

Space Conditioning Mode

Building Subsystem

One- and TwoFamily

Multifamily/ Townhouses

Uo

Uo

Walls

Heating or cooling

0.149

0.215

Roof/Ceiling

Heating or cooling

0.033

0.033

Floors over unheated space

Heating or cooling

0.050

0.050

R-value

R-value

NA

NA

R-value

R-value

4.0

4.0

U-value

U-value

Heating or cooling

0.101

0.101

Heating or cooling

NA

NA

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

Heating

Heating

2

U-values in BTU/hr×ft ×°F; R-values = 1/U

Unit 7 is constructed with ICE Block foundation system enclosing the basement. The SIPs, manufactured by Insulspan Co., enclose the first and second floors. One-inch expanded polystyrene (EPS) board is added as insulation to the outside of the SIPs for application of the wall finishing system. Also, SIPs eight inches thick are used for the roof system.

16

Adapted from Table 502.2.1 1993 MEC

NAHB Research Center, Inc.

12

June 1997

Table 3 describes the physical dimensions of unit 7. Wall sections representing different construction materials are included separately. Table 3 Construction Features of Unit 7

Wall/Ceiling Surface

Area

1

U-value

UA-Value

Subscript

ICE Block

182.85

0.068

12.39

w1

2

17.54

0.081

1.42

w2

1703.03

0.046

77.84

w3

245.04

0.112

27.40

w4

331.62

0.055

18.38

w5

Garage/Basement Wall (Steel)

217.09

0.069

14.87

w6

Windows (U=0.32)

197.97

0.320

63.35

g1

Windows (U=0.35)

144.00

0.350

50.40

g2

Windows (U=0.31)

24.00

0.310

7.44

g3

5

Fireplace Opening

14.33

0.855

12.25

fp

Door (U=0.16)

21.07

0.160

3.37

d1

Door (U=0.14)

21.64

0.140

3.03

d2

Sliding Door (U=0.32)

20.00

0.320

6.40

d3

Top Plate SIP Wall

Wood wall framing members

3

Framed Gable Sections 4

Total Gross Wall Area (Ao)

3375.30

6

Overall U-value (Uo)

o 0.092

Roof (8" SIP) Floor Over Unheated Space 7

Basement Walls

1049.00

0.029

356.83

0.046

349.50

0.068

o

R-value 8

Slab Edge (24" insulation depth)

14.76

2

Note: All U-values in Btu/hr-ft -°F 1 basement wall sections less than 50 percent below grade 2 pressure treated wood (nominal 2" x 10.75") 3 nominal 2x4 typical 4 double 3 1/2" steel wall with Icynene thermal break 5 use steel insert, fully enclosed flue box (U-value = steel + air space) 6

Uo =

[(UA)w 1+(UA)w 2+(UA)w 3+(UA)w 4 +(UA)w 5+(UA)w 6)+(UA)g1+(UA)g 2+(UA)g 3+(UA)fp +(UA)d 1+ (UA)d 2 + (UA)d 3] Ao

7

basement wall sections more than 50 percent below grade slab edge of basement walls considered in Gross Wall Area

8

NAHB Research Center, Inc.

13

June 1997

The data on unit 7 in Table 2, are compared with the MEC requirements for multifamily townhouses and single- and two-family units in Table 4, showing the difference in the Uoand R-values of various components of the building as built and as required by MEC. Table 4 Townhouse unit 7 MEC Compliance Record

Building Element

As Built

One- and Two-Family

0.149

% difference 39

0.215

% difference 57

0.029

.033

12

.033

12

0.046

.05

8

.05

8

R-value

R-value

R-value

NA

NA

NA

R-value

R-value

R-value

14.76

4.0

U-value

U-value

0.068

0.101

NA

NA

Uo

Uo

Walls

0.092

Roof/Ceiling Floors over unheated space

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

Multifamily / Townhouses

73

Uo

4.0

73

U-value 33

0.101

33

NA

2

U-values in BTU/hr*ft *°F *Percent reduction in Uo from MEC requirement

MEC Analysis Results The MEC analyses results in Table 4 indicate that each component of unit 7, not only fully comply with the 1993 MEC, but has substantially lower U-values than required by MEC, which could contribute to significant increases in energy performance. The exact contribution to the whole house energy usage depends on the relative importance of each building element in the total structure. See Appendix A for results of the analysis performed using MECCheck software.

NAHB Research Center, Inc.

14

June 1997

Energy Consumption Estimates Energy simulation analysis software was used to evaluate the thermal and energy 17 performance of the whole townhouse. The software package, REM/Design , provides energy consumption data and an estimate of the annual energy cost for the unit. The energy analysis calculates the energy performance attributable to the efficiency of the building envelope components, the HVAC plant, and includes infiltration losses, and duct performance. A comparison of the estimated energy consumption is also made based on the 1993 MEC. The software analysis for unit 7 shows: • •

A MEC minimum required overall Uo of 0.113 compared to an overall Uo of 0.072 as built. The 1993 MEC maximum energy consumption requirements for heating and cooling of 46.1 million Btu. As compares to an estimated 36.2 million Btu consumed by the unit as built, a 22 percent reduction.

Figures 1 and 2 graphically summarize the annual component energy consumption estimates resulting from the software analysis. Figure 3 shows the MEC comparison of heating and cooling energy consumption and estimated annual cost between the townhouse as constructed and a similar house constructed to code minimums as analyzed by the software. Figure 1 Structural insulated Panels Subsystem Heating Consumption Estimate

Other

Doors

Subsystem

Ceilings/Roofs

Slab Floors

Foundation Walls

Glazing

Above Grade Walls

Infiltration -6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Annual Consumption (Millon Btu)

17

Version 6.05 by Architectural Energy Corporation

NAHB Research Center, Inc.

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June 1997

Figure 2 Structural Insulated Panels Subsystem Cooling Consumption Estimate

Other

Infiltration

subsystem

Above Grade Walls

Ceilings/Roofs

Ducts

Internal Gains

Glazing

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Annual Consumption (Million Btu)

Figure 3 Structural Insulated Panels $500

40.0

$450

35.0

Annual Fuel Consumption (MMBtu/yr)

$400 30.0 $350 25.0

$300 $250

20.0

$200

15.0

$150 10.0 $100 5.0

$50

0.0

$0 Heating, MEC Base Case

NAHB Research Center, Inc.

Heating, MEC As Designed

Cooling, MEC Base Case

Cooling, MEC As Designed

16

Cost, MEC Base Case

Cost, MEC As Designed

June 1997

Townhouse Unit 8 The MEC requirements for each subsystem, included in Table 5, include any benefits as a result of the use of thermal mass in the above grade wall systems. 18

Table 5 Subsystem U and R Requirements

Building Subsystem

Space Conditioning Mode

One- and TwoFamily

Multifamily / Townhouses

Uo

Uo

Walls

Heating or cooling

0.174*

0.215**

Roof/Ceiling

Heating or cooling

0.033

0.033

Floors over unheated space

Heating or cooling

0.050

0.050

R-value

R-value

NA

NA

R-value

R-value

4.0

4.0

U-value

U-value

Heating or cooling

0.101

0.101

Heating or cooling

NA

NA

Heated slab on grade Unheated slab on grade Basement wall Crawl wall

Heating Heating

2

U-values in BTU/hr*ft *°F, R-values = 1/U * Increase in Uo requirement from 0.149 due to thermal mass credit ** No increase in Uo-value for A-2 residential construction

Unit 8 is constructed with ICE Block foundation system enclosing the basement, first and second floors. A nominal 8" block is used for the basement and a nominal 6" block is used for the first and second floors. Raised heel roof trusses are used for the roof system.

18

Adapted from Table 502.2.1 1993 MEC

NAHB Research Center, Inc.

17

June 1997

Table 6 describes the physical dimensions of unit 8. Wall sections representing different construction materials are included separately. Table 6 Construction Features of Townhouse Unit 8

Wall/Ceiling Surface

Area

U-value

UA-Value

1

319.33

0.068

42.73

w1

1377.93

0.071

98.46

w2

40.65

0.120

7.87

w3

Windows (U=0.32)

8.83

0.320

2.83

g1

Windows (U=0.35)

105.00

0.350

36.75

g2

Windows (U=0.31)

72.00

0.310

22.32

g3

Windows (U=0.30)

25.00

0.300

7.50

g4

Door (U=0.16)

21.07

0.160

3.37

d1

Door (U=0.14)

21.64

0.140

3.03

d2

Sliding Door (U=0.32)

53.89

0.320

17.25

d3

ICE Block

2

ICE Block

3

Wood Window/Door Jambs Rough Framing

Total Gross Wall Area (Ao)

2045.34

4

Overall U-value (Uo)

o 0.117

Ceiling Area

807.20

0.026

NA

NA

630.54

0.068

Floor Over Unheated Space 5

Basement Walls

Subscript

o

R-value 6

Slab Edge (24" insulation depth)

14.76

Note: All U-values in Btu/hr-ft2-°F 1 basement wall sections less than 50 percent below grade, 8" ICE Block 2 6" ICE Block 3 2 x 8 wood typical 4

Uo =

[(UA )w 1+(UA )w 2+(UA )w 3)+(UA )g 1+(UA )g 2+(UA )g 3+(UA )g 4+(UA ) fp +(UA )d 1+(UA )d 2+(UA )d 3] 5base Ao

ment wall sections more than 50 percent below grade 6 slab edge of basement walls considered in Gross Wall Area

NAHB Research Center, Inc.

18

June 1997

The data on unit 8 in Table 6, are compared with the MEC requirements for multifamily townhouses and single- and two-family units in Table 7, showing the difference in Uo and RValues of various components of the building as built and as required by MEC. Table 7 Townhouse Unit 8 MEC Compliance Record

Building Subsystem

Space Conditioning Mode

One- and TwoFamily

Multifamily / Townhouses

Uo

Uo

% Difference

Uo

% Difference

Walls

0.117

0.174

33

0.215*

46

Roof/Ceiling

0.026

.033

21

.033

21

NA

.05

.05

R-value

R-value

R-value

NA

NA

NA

R-value

R-value

R-value

14.76

4.0

U-value

U-value

0.068

0.101

NA

NA

Floors over unheated space

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

73

4.0

73

U-value 33

0.101

33

NA

U-values in BTU/hr*ft2*°F * No increase in Uo-value for A-2 residential construction due to thermal mass ** Percent reduction from MEC requirement

MEC Analysis Results The MEC analysis results in Table 7 indicate that each component of unit 8 fully comply with the 1993 MEC, but has substantially lower Uo-values than required by MEC, which could contribute to significant increases in energy performance. The exact contribution to whole house energy performance depends on the relative importance of each building element in the total structure. See Appendix A for results of the analysis performed using MECCheck software.

NAHB Research Center, Inc.

19

June 1997

Energy Consumption Estimates Energy simulation analysis software was used to evaluate the thermal and energy 19 performance of the townhouse. The software package, REM/Design, provides energy consumption data and an estimate of the annual energy cost for the unit, and compares results with MEC minimum requirements (see Appendix A). The software analysis calculates the energy performance attributable to the energy efficiency of the building envelope components, the HVAC plant, and includes infiltration and duct losses. The software analysis for unit 8 shows: • •

A MEC required minimum overall Uo of 0.110 compared to an overall Uo of 0.083 as built. A 1993 MEC maximum energy consumption required for heating and cooling of 80.6 million Btu compares to an estimated 33.9 million Btu consumed by the unit as built, a 58 percent reduction.

Figures 4 and 5 summarize the annual energy consumption estimates resulting from the software analysis. Figure 6 shows the MEC comparison of heating and cooling energy consumption between the townhouse as constructed and a similar house constructed to code minimums as analyzed by the software. Figure 4 Insulated Concrete Forms Subsystem Heating Consumption Estimate

Other

Doors

Subsystem

Ceilings/Roofs

Slab Floors

Foundation Walls

Glazing

Above Grade Walls

Infiltration -15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

Annual Consumption (Million Btu)

19

version 6.05 by Architectural Energy Corporation

NAHB Research Center, Inc.

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June 1997

Figure 5 Insulated Concrete Form Subsystem Cooling Consumption Estimate

Other

Infiltration

subsystem

Above Grade Walls

Ceilings/Roofs

Ducts

Internal Gains

Glazing

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Annual Consumption (Million Btu)

Figure 6 Insulated Concrete Form 80.0

$900

70.0

$800

Annual Fuel Consumption (MMBtu/yr)

$700 60.0 $600 50.0 $500 40.0 $400 30.0 $300 20.0 $200 10.0

$100

0.0

$0 Heating, MEC Base Case

NAHB Research Center, Inc.

Heating, MEC As Designed

Cooling, MEC Base Case

Cooling, MEC As Designed

21

Cost, MEC Base Case

Cost, MEC As Designed

June 1997

Townhouse Unit 9 The MEC requirements for each subsystem in unit 9 are shown in Table 8. 20

Table 8 Subsystem U and R Requirements

Space Conditioning Mode

Building Subsystem

One- and TwoFamily

Multifamily / Townhouses

Uo

Uo

Walls

Heating or cooling

0.149

0.215

Roof/Ceiling

Heating or cooling

0.033

0.033

Floors over unheated space

Heating or cooling

0.050

0.050

R-value

R-value

NA

NA

R-value

R-value

4.0

4.0

U-value

U-value

Heating or cooling

0.101

0.101

Heating or cooling

NA

NA

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

Heating

Heating

2

U-values in BTU/hr*ft *°F, R-values = 1/U

Unit 9 is constructed with ICE Block foundation system enclosing the basement. The first and second floors are framed using steel construction insulated with Icynene spray insulation. Additional insulating 1" EPS board is used for the finishing system. Raised heel roof trusses are used for the roof system.

20

Adapted from Table 502.2.1 1993 MEC

NAHB Research Center, Inc.

22

June 1997

Table 9 describes the physical dimensions of 9. Wall sections representing different construction materials are included separately. Table 9 Construction Features of Unit 9

Wall/Ceiling Surface

Area

U-value

UA-Value

Subscript

1

227.13

0.068

15.39

w1

2

210.75

0.071

15.06

w2

1202.20

0.087

104.03

w3

10.66

0.022

0.24

w4

50.54

0.096

4.83

w5

Windows (U=0.32)

12.00

0.320

3.84

g1

Windows (U=0.35)

135.00

0.350

47.25

g2

Windows (U=0.31)

48.00

0.310

14.88

g3

Windows (U=0.30)

25.00

0.300

7.50

g4

Windows (U=0.29)

6.00

0.290

1.74

g5

Door (U=0.16)

21.07

0.160

3.37

d1

Door (U=0.14)

21.64

0.140

3.03

d2

Sliding Door (U=0.32)

36.67

0.320

11.73

d3

ICE Block ICE Block

Exterior Steel Framed Walls Bulk Head Area Wood Window/Door Jambs

3

Total Gross Wall Area (Ao)

2006.66

4

Overall U-value (Uo)

o 0.116

Ceiling Area

804.00

0.026

NA

NA

721.96

0.068

Floor Over Unheated Space 5

Basement Walls

o

R-value 6

Slab Edge (24" insulation depth)

14.76

2

Note: All U-values in Btu/hr-ft -°F 1 basement wall sections less than 50 percent below grade, 8" ICE Block 2 6" ICE Block 3 2 x 6 wood typical 4

Uo =

[(UA)w 1+(UA)w 2+(UA)w 3+(UA)w 4 +(UA)w 5) +(UA)g 1+(UA)g 2+(UA)g 3+(UA)g 4+(UA)g 5+(UA)fp+(UA)d 1+(UA)d 2+(UA)d 3] Ao

5

basement wall sections more than 50 percent below grade slab edge of basement walls considered in Gross Wall Area

6

NAHB Research Center, Inc.

23

June 1997

The data on unit 9 in Table 8, are compared with the MEC requirements for multifamily townhouses and single- and two-family units in Table 10, showing the difference in Uo- and R-values of various components of the building as built and as required by MEC. Table 10 Unit 9 MEC Compliance Record

Building Subsystem

As Built

One- and Two-Family

Multifamily / Townhouses

Uo

Uo

% Difference

Uo

% Difference

Walls

0.116

0.149

22

0.215

46

Roof/Ceiling

0.026

.033

21

.033

21

NA

.05

.05

R-value

R-value

R-value

NA

NA

NA

R-value

R-value

R-value

14.76

4.0

U-value

U-value

0.068

0.101

NA

NA

Floors over unheated space

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

73

4.0

73

U-value 33

0.101

33

NA

U-values in BTU/hr*ft2*°F * Percent reduction from MEC requirement

MEC Analysis Results The MEC analysis results in Table 10 indicate each component of unit 9 not only fully comply with the 1993 MEC, but has substantially lower Uo-values than required by MEC, which could contribute to significant increases in energy performance. The exact contribution to whole house energy performance depends on the relative performance of each building element in the total structure. See Appendix A for results of the analysis performed using MECCheck software.

NAHB Research Center, Inc.

24

June 1997

Energy Consumption Estimates Energy simulation analysis software was used to evaluate the thermal and energy 21 performance of the townhouse unit. The software package, REM/Design , provides energy consumption data and an estimate of the annual energy cost for the unit comparing results with MEC requirements (see Appendix B). The energy analysis calculates the energy performance attributable to the energy efficiency of the building envelope components, the HVAC plant, and includes infiltration and duct losses. The software analysis for unit 9 shows: • •

A MEC required minimum overall Uo of 0.111 compared to an overall Uo of 0.084 as built. A 1993 MEC maximum energy consumption requirement for heating and cooling of 24.9 million Btu compared to an estimated 11.0 million Btu consumed by the unit as built, a 56 percent reduction.

Figures 7 and 8 summarize annual energy consumption estimates resulting from the software analysis. Figure 9 shows the MEC comparison of heating and cooling energy consumption between the townhouse as constructed and a similar house constructed to code minimums as analyzed by the software. Figure 7 Steel, Spray Foam Insulation Subsystem Heating Consumption Estimate

Other

Doors

Subsystem

Ceilings/Roofs

Slab Floors

Foundation Walls

Glazing

Above Grade Walls

Infiltration -1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Annual Consumption (million Btu)

21

Version 6.05 by Architectural Energy Corporation

NAHB Research Center, Inc.

25

June 1997

Figure 8 Steel, Spray Foam Insulation Subsystem Cooling Consumption Estimate

Other

Infiltration

subsystem

Above Grade Walls

Ceilings/Roofs

Ducts

Internal Gains

Glazing

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

Annual Consumption (Million Btu)

Figure 9 Steel, Spray Foam Insulation 25.0

$500 $450 $400

Annual Fuel Consumption (MMBtu/yr)

20.0

$350 15.0

$300 $250

10.0

$200 $150

5.0

$100 $50

0.0

$0 Heating, MEC Base Case

NAHB Research Center, Inc.

Heating, MEC As Designed

Cooling, MEC Base Case

Cooling, MEC As Designed

26

Cost, MEC Base Case

Cost, MEC As Designed

June 1997

Townhouse Unit 10 The MEC requirements for each subsystem in unit 10 are shown in Table 11, taking into account benefits from thermal mass in the above grade wall systems, calculated according to procedures explained above. 22

Table 11 Subsystem U and R Requirements

Space Conditioning Mode

Building Subsystem

One- and TwoFamily

Multifamily / Townhouses

Uo

Uo

Walls

Heating or cooling

0.177*

0.215**

Roof/Ceiling

Heating or cooling

0.033

0.033

Floors over unheated space

Heating or cooling

0.050

0.050

R-value

R-value

NA

NA

R-value

R-value

4.0

4.0

U-value

U-value

Heated slab on grade

Unheated slab on grade

Heating

Heating

Basement wall

Heating or cooling

0.101

0.101

Crawl wall

Heating or cooling

NA

NA

U-values in BTU/hr*ft2*°F, R-values = 1/U * Increase in Uo requirement from 0.149 due to thermal mass credit ** No increase in Uo-value for A-2 residential construction

Unit 10 is constructed with a Superior Wall foundation system for the basement wall. A lightweight AAC system, manufactured by Hebel Southeast, forms the walls of the first and second floors. Additional wall insulation is not installed. Raised heel roof trusses are used for the roof system.

22

Adapted from Table 502.2.1 1993 MEC

NAHB Research Center, Inc.

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June 1997

Table 12 describes the physical dimensions of unit 10. Wall sections representing different construction materials are included separately. Table 12 Construction Features of Unit 10

Wall/Ceiling Surface

U-value

UA-Value

170.27

0.071

12.16

w1

45.28

0.106

4.78

w2

2073.51

0.098

203.89

w3

77.17

0.115

8.90

w4

Garage/Basement Wall (Steel)

184.11

0.069

12.61

w5

Windows (U=0.32)

197.97

0.320

63.35

g1

Windows (U=0.35)

120.00

0.350

42.00

g2

Windows (U=0.31)

48.00

0.310

14.88

g3

5

Fireplace Opening

14.33

0.855

12.25

fp

Door (U=0.16)

18.56

0.160

2.97

d1

Door (U=0.14)

21.63

0.140

3.03

d2

Sliding Door (U=0.32)

20.00

0.320

6.40

d3

Superior Wall Sections

1

2

Concrete Bond Beam Hebel AAC

Wood Window/Door Jambs

3 4

Total Gross Wall Area (Ao)

Area

Subscript

2990.83

6

Overall U-value (Uo)

o 0.129

Ceiling (flat and cathedral)

870.60

0.026

Floor Over Unheated Space

350.14

0.046

329.42

0.071

7

Basement Walls

o

R-value 8

Slab Edge (24" insulation depth)

5.2

2

Note: All U-values in Btu/hr-ft -°F 1 basement wall sections less than 50 percent below grade, excluding 1 3/4" top bond beam 2 including Superior Wall top bond 3 2 x 8 pressure treated wood typical 4 double 3 1/2" steel wall with Icynene thermal break 5 use steel insert, fully enclosed flue box (U-value = steel + air space) 6 7

U = o

[(UA )w 1+ (UA )w 2 + (UA )w 3 + (UA )w 4 + (UA )w 5)+ (UA )g 1+ (UA )g 2 + (UA )g 3 + (UA ) fp + (UA )d 1+ (UA )d 2 + (UA )d 3]

nt wall sections more than 50 percent below grade 8 slab edge of basement walls considered in Gross Wall Area

NAHB Research Center, Inc.

baseme

A

28

June 1997

The data on unit 10 in Table 11, are compared with the MEC requirements for multifamily townhouses and single- and two-family units in Table 13, showing the difference in Uo- and R-values of various components of the building as built and as required by MEC. Table 13 Townhouse Unit 10 MEC Compliance Record

Building Subsystem

As Built

One- and Two-Family

Multifamily / Townhouses

Uo

Uo

% Difference

Uo

% Difference

Walls

0.129

0.177

27

0.215*

40

Roof/Ceiling

0.026

.033

21

.033

21

Floors over unheated space

0.046

.05

8

.05

8

R-value

R-value

R-value

NA

NA

NA

R-value

R-value

R-value

5.18

4.0

U-value

U-value

0.071

0.101

NA

NA

Heated slab on grade

Unheated slab on grade

Basement wall Crawl wall

23

4.0

23

U-value 29

0.101

29

NA

2

U-values in BTU/hr*ft *°F * No increase in Uo-value for A-2 residential construction due to thermal mass ** Percent reduction from MEC requirement

MEC Analysis Results The MEC analysis results in Table 13 indicate each component of unit 10 fully complies with the 1993 MEC with respect to the total house, but has substantially lower Uo and R-values than required by MEC, which could contribute to significant increases in energy performance. The exact contribution to whole house energy performance depends on the relative performance of each building element in the total structure. See Appendix A for results of the analysis performed using MECCheck software.

NAHB Research Center, Inc.

29

June 1997

Energy Consumption Estimates Energy simulation analysis software was used to evaluate the thermal and energy 23 performance of the townhouse unit. The software package, REM/Design , provided energy consumption data and an estimate of the annual energy cost for the unit comparing results with MEC requirements (see Appendix B). The energy analysis calculates the energy performance attributable to the energy efficiency of the building envelope components, the HVAC plant, and includes infiltration and duct losses. The software analysis for unit 10 shows: • •

A MEC required overall Uo of 0.113 compared to an overall Uo of 0.091 as built. A 1993 MEC maximum energy consumption requirement for heating and cooling of 97.4 million Btu, compares to 61.0 million Btu consumed as built, a 37 percent reduction.

Figures 10 and 11 summarize the annual energy consumption estimates resulting from the software analysis. Figure 12 shows the MEC comparison of heating and cooling energy consumption between the townhouse as constructed and a similar house constructed to code minimums as analyzed by the software. Figure 10 Lightweight Concrete Subsystem Heating Consumption Estimate

Other

Doors

Subsystem

Ceilings/Roofs

Slab Floors

Foundation Walls

Glazing

Above Grade Walls

Infiltration -10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

Annual Consumption (million Btu)

23

Version 6.05 by Architectural Energy Corporation

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June 1997

Figure 11 Lightweight Concrete Subsystem Cooling Consumption Estimate

Other

Infiltration

subsystem

Above Grade Walls

Ceilings/Roofs

Ducts

Internal Gains

Glazing

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Annual Consumption (Million Btu)

Figure 12 Lightweight Concrete 90.0

$1,000

80.0

$900 $800

Annual Fuel Consumption (MMBtu/yr)

70.0

$700 60.0 $600 50.0 $500 40.0 $400 30.0 $300 20.0

$200

10.0

$100

0.0

$0 Heating, MEC Base Case

NAHB Research Center, Inc.

Heating, MEC As Designed

Cooling, MEC Base Case

Cooling, MEC As Designed

31

Cost, MEC Base Case

Cost, MEC As Designed

June 1997

ENERGY SIMULATION ANALYSIS A simulation using REM/Design Software was performed for each unit to determine Rvalues for non-standard wall sections. The structural and material characteristics of each unit were explicitly detailed, using either manufacture's data such as glazing U-values or actual measured envelope dimensions. Blower door tests provided infiltration data and the results for each unit are shown in Table 14. Table 14 Infiltration Testing Results *

ACHwinter

**

Unit

ACH50

ACHsummer

7

4.8

0.41

0.27

8

3.8

0.23

0.14

9

2.3

0.15

0.09

10

5.0

0.42

0.28

***

* Air Changes per Hour @ 50 pascals ** Air Changes per Hour (natural) for Winter months (Dec.-Feb.) *** Air changes per Hour (natural) for Summer months (Jun.-Aug.) Note: the estimated ACH (natural) for summer and winter months determined from a model developed at the Lawrence Berkeley Laboratory.

The REM/Design software simulation estimates building annual energy consumption. Building wall materials and R-values were used as inputs into the simulation. The existing database of standard wall sections does not always contain information on the innovative wall systems used in the construction of the townhouses. In such cases, the program had the capability of estimating the wall R-value. A parallel path estimate was used to develop the overall R-value for the wall section using the above inputs. Table 15 indicates the areas of some of the wall and floor sections used in the analysis. Units 7 and 10 are mirror images of each other as are units 8 and 9, but some differences still exists. For example, the slab floor areas are larger for units 8 and 9 since they do not include an unconditioned garage as part of the house structure. The differences in roof areas between units 7 and 10 are accounted for by the use of additional sloped ceilings in unit 7.

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June 1997

Table 15 Townhouse Comparative Statistics

Feature

Unit 7

Unit 8

Unit 9

Unit 10

2938.8

1679.7

1733.3

2713.3

428.6

307.5

305.4

426.1

529

875

804

529

1049

807

804

871

Rim/Band Joist Area (ft )

252.7

0

0

45.3

Foundation Wall Length (ft)

74.6

95.6

95.6

75.0

357

0

0

350

2

Above Grade Wall Area (ft ) 2

Window/Door Opaque Area (ft ) 2

Slab Floor Area (ft ) 2

Roof Area (ft ) 2

2

Frame Floor Area (ft )

The software estimates the annual energy consumption of the building. An estimate of the lights and appliance use is include in the energy consumption analysis. The program makes use of fuel rates supplied by the user to estimate the annual cost of energy. All energy calculations are based on Btu energy use. Table 16 shows the results of the simulation for the four townhouses. Caution is advised in drawing conclusions from a direct comparison of the townhouses since the nature of the orientation, connecting walls, duct location, infiltration rates, and other variables can result in significant variations in any analysis. For example, units 7 and 10 have much larger glazing areas than units 8 and 9 resulting in greater energy losses and higher energy consumption.

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June 1997

Table 16 Compiled Results of Simulation Runs

Description Area of Conditioned Space

ft

2

Unit 7

Unit 8

Unit 9

Unit 10

2102

2293

2352

2193

Annual Heating Load

million Btu/yr.

47.1

31.7

32.4

56.4

Annual Heating Consumption

million Btu/yr.

36.3

35.2

9.8

62.6

278.29

271.51

175.49

471.95

Annual Heating Cost

$/yr.

Annual Cooling Load

million Btu/yr.

35.8

23.5

20.1

37.7

Annual Cooling Consumption

million Btu/yr.

7.8

6.7

4.7

10.7

196.20

167.04

116.76

268.59

Annual Cooling Cost

$/yr.

Annual Water Heating Load

million Btu/yr.

19.7

18.7

16.8

18.7

Annual Water Heating Con.

Million Btu/yr.

25.9

19.1

8.3

19.1

Annual Water Heating Cost

$/yr.

205.59

152.30

172.11

150.42

million Btu/yr.

25.24

25.3

25.3

25.3

$/yr.

406.51

408.14

410.20

406.62

Annual Lights and Appliance Consumption Annual Lights and Appliance Cost Peak Heating Load

thousand Btu/hr

30.2

22.7

21.1

37.0

Peak Cooling Load

thousand Btu/hr

Area Normalized Heating Consumption Area Normalized Cooling Consumption

40.5

25.2

23.0

44.0

2

17.3

15.4

4.2

28.5

2

thousand Btu/ft /yr.

3.7

2.9

2.0

4.9

Area Normalized Heating Cost

2

$/ft /yr.

0.13

0.12

0.07

0.22

Area Normalized Cooling Cost

2

$/ft /yr.

0.09

0.07

0.05

0.12

$/million Btu

7.75

10.47

20.16

10.10

Annual Space Conditioning Costs

thousand Btu/ft /yr.

Figures 1 through 12 above, compare the estimated losses attributed to each component. In the heating estimates, the above grade walls and infiltration losses make up the largest percentage of losses. In cooling energy requirements, glazing and internal gains account for most of the cooling energy requirements. The comparative value of the results in Table 16 of the simulation analysis are affected by the following utility, operation, and construction factors and result in substantial differences in energy consumption among the units: • • • • •

The cost of electricity is slightly more than $0.08/kwh while the cost of natural gas is about $0.82/therm. The HVAC set point is kept constant at 72°F. Units 8 and 9 have a common wall decreasing the wall area exposed to the 2 outdoors by over 1000 ft compare to the other two units. 2 The opaque openings are over 125ft larger for units 7 and 10. The infiltration rates for units 8 and 9 are at least half of the other units.

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June 1997

Cooling fuel consumption cost estimates for townhouse unit 7 are based on an electric compressor unit operating at an estimated SEER-value of 15.6. TOWNHOUSE ENERGY PERFORMANCE MONITORING–COOLING SEASON Each of the townhouse units were monitored for heating and air conditioning energy consumption, indoor temperature, and north and south wall surface temperatures. The outdoor ambient air temperature was also recorded. The data is gathered in ten minute intervals, averaged, and logged. In the three units which had gas fuel for heating and/or air conditioning, consumption was logged by recording the number of pulses from the meter every ten minutes. Each pulse represented one cubic foot of natural gas. This value was then converted to therms using the gas company’s conversion factor, listed on the monthly billing. The energy used by the geothermal heat pump is recorded by a watt meter on the unit power supply. The amount of time the compressor was running was recorded for the two townhouses with outdoor air conditioning compressors. Manufacturers’ data were then used to determine the energy consumed by the air conditioning system, including the blower motor. Operational data was logged for each unit at ten minute intervals and averaged. The analog output of the transducer was recorded at ten minute intervals and averaged to obtain real power measurements. For compressor operating time, the sum of all the minutes during the ten minute period in which the compressor operated was recorded. For gas consumption, a pulse was recorded per cubic foot rotation of the two-cubic foot dial on the gas meter. Periodically, the utility electric meter data was recorded. Air Conditioning Energy Consumption The air conditioning equipment was activated in the beginning of June 1996, since prior to this date, little, if any, air conditioning use was required; moreover, building construction was completed at this time and operation of each unit was more stable without interference from contractor use. Three of the four units were unoccupied; unit 7 was occupied by two people. The energy consumption of the air conditioning equipment was derived by either directly logging data or from calculations based on compressor "on-time" data. The air conditioning energy consumption data was totaled for each day and plotted against the average daily difference between the indoor and outdoor temperature readings. The plot indicates indoor temperature range for various performance indicators such as hourly daily use.

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June 1997

Performance of Individual Townhouse Units Townhouse Unit 7—Structural Insulated Panels The space conditioning equipment consisted of a gas engine powered air-source heat pump unit with a manufacturer's SEER rating of 15.60. The SEER rating is developed by the manufacturer using the proposed ANSI standard Z-21 which relates an equivalent SEER for the gas engine heat pump to a comparable electric-powered unit. The comparison is based on fuel costs in a given geographic area. The rated capacity is 36,000 Btuh. A dedicated gas meter was installed to record the gas supplied to the gas engine separate from other gas appliances. The gas meter was located downstream of a pressure reducing valve. A plot of the data provided during four months of operation is shown in Figures 13 and 14. This data indicates the energy consumption trend based on the temperature difference between the indoor and outdoor daily average temperatures. This townhouse was occupied and the thermostat operation included a night setback of about four degrees Fahrenheit (2.2C), from 74°F to 70°F. The measured indoor temperature range over the full period was between 67.4°F and 77.0°F. For the narrow cooling period under analysis, the trend in energy consumption indicates approximately 0.1 therms per degree temperature difference between the outdoor and indoor average temperature. The balance point is that outdoor temperature at which no space conditioning is required. It differs from the thermostat set-point, which is influenced by internal gains. Note the cooling season balance point for this particular townhouse occurs when the average outdoor temperature is 10.5°F below the average indoor average temperature. (see Figure 13)

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June 1997

Figure 13 Structural Insulated Panels Cooling Season Performance 4.5

4.0

therms (excluding blower fan operation)

3.5

112 Day Period Indoor temperature Range 67.4 - 77.0 F

3.0

2.5

2.0

1.5

1.0

0.5

0.0 -18.0

-16.0

-14.0

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

degree F Temperature Difference (Outdoor - Indoor)

Figure 14 Structural Insulated Panels Cooling System Performance 3.0

therms (excluding blower fan operation)

2.5

2.0

1.5

1.0

26 Day Period Indoor temperature Range 71.8 - 75.0 F

0.5

0.0 -10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

degree F Temperature Difference (Outdoor - Indoor)

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June 1997

Figures 15 and 16 respectively show a five- and two-day period of operation. The effect of temperature setback is evident in the indoor temperature and the cooling system operation in that the bulk of air conditioning operation follows the daytime peak temperature. The peak cooling load for the period was approximately 30,000 Btuh. At an interior set point of 72°F, the estimated peak cooling load was 40,500 Btuh for the software analysis.

Figure 15 S tru c tu ra l In s u la te d P a n e ls 0 .3 0

9 0 .0

8 5 .0 0 .2 5

0 .2 0

degree F

7 5 .0

0 .1 5

7 0 .0

6 5 .0 0 .1 0

Cooling System Operation

8 0 .0

6 0 .0 0 .0 5 5 5 .0

238

237

236

235

0 .0 0 234

5 0 .0

5 D a y p e rio d b y h o u r a v e ra g e th e rm s

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A m b ie n t

In d o o r A ir

June 1997

Figure 16 Structural Insulated Panel days 237-238, 1996

0.0600

85.0

80.0

75.0

degree F

0.0400 70.0 0.0300 65.0 0.0200 60.0

air conditioner operation (therms)

0.0500

0.0100

55.0

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

12:10 AM

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

0.0000 12:10 AM

50.0

hour (by 10 minute averages)

Ambient

Inside Air

therms

Figure 15 shows the relationship between air conditioning demand and the outdoor and indoor temperatures. Since the townhouse is operated with thermostat setback, a larger demand occurs in the evening at the setback period and little demand occurs following the setback period. The operation of the air conditioning unit coincides closely with the outdoor temperature and solar gains. Townhouse unit 7 has the largest amount of west facing glazing of all the units which will result in increased heat-gains penalties not evident in other units.

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June 1997

Figure 17 shows the hourly average temperatures for two days during the summer cooling period. The peak south wall exterior temperature precedes the peak interior south wall temperature by two to three hours. Since exterior air temperatures remain relatively high during the night, the wall surface and air temperatures tend to converge during the night time. Due to the incident solar gains at the peak period, the surface temperature of the south facing wall rises 31.7°F above the ambient air temperature.

Figure 17 Structural Insualted Panels Days 236-237 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0 Inside Air

S Wall Ext

S Wall Int

Ambient

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0 hour averages

Actual consumption has exceeded the predicted consumption of the simulation software by about 50 percent. To determine actual consumption, estimates of consumption were made for missing data points. The difference in consumption is attributed to the complexity of accurately determining a SEER rating for a gas-powered air conditioner.

NAHB Research Center, Inc.

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June 1997

Townhouse Unit 8—Insulating Concrete Forms The HVAC equipment in unit 8 consists of a gas forced-air furnace and an air conditioning outdoor unit with a manufacturer's rating of SEER=12.0. The rated output capacity is 30,000 Btuh. Data for the unit’s operation was logged through monitoring of the time the air conditioning compressor was in operation. The time was then multiplied by the manufacturer's energy consumption rating, which included the blower fan, to obtain overall energy consumption. A plot of the data available during four months of operation is shown in Figures 18 and 19. These figures show energy consumption in relation to the temperature difference between the outside and inside air temperatures. For the narrow 41-day period under analysis, the trend in energy consumption indicates approximately .40 kWh per degree temperature difference between the outdoor and indoor average temperatures. The significant amount of data scatter is indicative of thermally massive walls. During the 41-day period, the indoor air temperature was stable within a 2°F range with an average indoor temperature of about 74.3°F. Figure 18 Insulated Concrete Forms Cooling Season Performance 20

18

16

98 Day Period Indoor Temperature Range 61.0 - 78.2 F

kilowatthours

14

12

10

8

6

4

2

0 -20.0

-15.0

-10.0

-5.0

0.0

5.0

10.0

degree F Temperature Difference (Outdoor - Indoor)

NAHB Research Center, Inc.

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June 1997

Figure 19 Insulated Concrete Forms Cooling System Performance 10

9

8

kilowatthours

7

6

5

4

3 41 Day Period Indoor Temperature Range 73.3 - 75.4 F

2

1

0 -12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

degree F Temperature Difference (Outdoor - Indoor)

A five- and two-day period of operation is shown in Figures 20 and 21, respectively. The relationship between the air conditioning unit operation and the outdoor and indoor temperatures is consistent for the period in that the air conditioning operation follows the daytime peak temperature. The one exception is the rise in the indoor temperature on day 237. On this day, the rise in temperature is coincident with the air conditioning operation possibly due to direct solar gains. Air conditioning operation appears to be dependent on what is assumed to be solar gains which is inferred by an indirect correlation between air conditioning operation and exterior temperature of the wall. (“S Wall Ext" in Figure 22) This temperature is dependent on solar radiation falling on the wall surface.

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June 1997

Figure 20 Insulated Concrete Forms 90.0

1.20

85.0 1.00

0.80

degree F

75.0

70.0

0.60

65.0 0.40

Cooling System Operation

80.0

60.0 0.20 55.0

238

237

236

235

0.00 234

50.0

5 Day period by hour average kWh

Ambient

Indoor Air

Figure 21 Insulated Concrete Form days 237-238, 1997 85.0

3000

80.0

2500

degree F

2000 70.0 1500 65.0 1000

A/C operation (watts)

75.0

60.0

500

55.0

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

12:10 AM

10:40 PM

9:10 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

0 12:10 AM

50.0

hour (by 10 minute averages) Ambient

NAHB Research Center, Inc.

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Inside Air

watts

June 1997

The air conditioning operation was less variable when the ambient temperature fell below the indoor temperature or when the direct solar gain was minimized. The thermal massiveness of the wall system was considered to be the primary controlling factor, mitigating the immediate impact of the outdoor conditions. Operation of the compressor rarely approached a 50 percent duty-cycle for one hour with most of its operation about 15 percent per hour. Significant periods of compressor off time were also common. The air conditioning operation is estimated to have used approximately 689 kWh (2.35 24 million Btu) of energy in the four months of operation . The house was unoccupied and minimal appliance and lighting loads were in effect. A simulation run based on 72°F thermostat set point predicted a cooling energy consumption of 6.7 million Btu. The average indoor temperature was measured at 73.8 °F. Figure 22 shows the relationship between the ambient outdoor, the inside air, the south wall exterior, and interior temperatures. The south wall interior temperature remained flat and closely followed the inside air temperature. The large thermal mass mitigated transmission of diurnal variations in temperature. During the night, the south wall surface temperature remained above the ambient temperature due to heat flow from the thermal mass to the exterior. The north wall surface temperatures in Figure 23 indicate a much closer relationship between the ambient air conditions and the surface temperatures. During the cooling season, the north wall received a small amount of solar radiation. Figure 22 Insulated Concrete Forms Days 236-237 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0 Ambient

Inside Air

S Wall Ext

S Wall Int

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0 hour averages

24

451 kWh actually measured with the remaining estimated from curve fit equations

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June 1997

Figure 23 Insulated Concrete Forms Days 236-237 95.0

90.0

85.0

degree F

80.0

75.0

70.0

65.0

60.0 Ambient

N Wall Ext

N Wall Int

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0

Townhouse Unit 9—Steel Frame with Spray Foam Insulation The HVAC equipment in unit 9 consists of a geothermal-source heat pump unit with a manufacture's EER rating of 14.70. The rated capacity is 33,000 Btuh. Data on energy use is accomplished through a power transducer monitoring the power supply feed to the HVAC unit. All power used by the HVAC unit including the ground loop pump, the blower motor, and associated electronics was included. A plot of the data available during four months of operation is shown in Figures 24 and 25. In the narrow 58-day period under analysis the trend in energy consumption, indicates approximately a .65 kWh per degree temperature difference between the outdoor and indoor average temperature. The significant amount of data scatter in this case was a result of the large fluctuations in the indoor air temperature. During the 58-day period, the indoor air temperature was stable varying in a 1.4°F range with an average indoor temperature of about 73.8°F.

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June 1997

Figure 24 Steel, Spray Foam Insulation Cooling Season Performance 18.000

16.000 121 Day Period Indoor Temperature Range 68.9 - 75.2 F 14.000

kilowatthours

12.000

10.000

8.000

6.000

4.000

2.000

0.000 -16.0

-14.0

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

degree F Temperature Difference (Outdoor - Indoor)

Figure 25 Steel, Spray Foam Insulation Cooling System Performance 10.000

9.000

8.000

kilowatthours

7.000

6.000

5.000

4.000

3.000

2.000 58 Day Period Indoor Temperature Range 73.1 - 74.5 F

1.000

0.000 -12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

degree F Temperature Difference (Outdoor - Indoor)

NAHB Research Center, Inc.

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June 1997

A five- and two-day period of operation is shown in Figures 26 and 27, respectively. The relationship between the air conditioning unit operation and the outdoor and indoor temperatures is consistent for the period, in that air conditioning operation follows the daytime peak temperature, except for small indoor air fluctuations. Similar to the previous unit, the sharp increase in air conditioning system operation occurring on day 237 is most likely attributed to direct solar gains. Air conditioning operation appears to be dependent on what is assumed to be the solar gain which is inferred by an indirect correlation between air conditioning operation and exterior temperature of the wall (“S Wall Ext" in Figure 28). This temperature is dependent on solar radiation falling on the wall surface. Figure 26 shows a direct relationship between the outdoor ambient air temperature and the air conditioning system operation. Due to the low thermal mass of the light frame construction, during the night the air conditioning system operates minimally. Figure 26 Steel, Spray Foam Insulation 2.50

90.0

85.0 2.00

degree F

75.0

1.50

70.0 1.00

65.0

Cooling System Operation

80.0

60.0 0.50 55.0

238

237

236

235

0.00 234

50.0

5 Day period by hour average kWh

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Ambient

Indoor Air

June 1997

Figure 27 Steel, Spray Foam Insulation days 237-238 90.0

2500

80.0

60.0 degree F

1500 50.0 40.0 1000 30.0 20.0

A/C operation (watts)

2000

70.0

500

10.0

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

12:10 AM

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

0 12:10 AM

0.0

hour (by 10 minute averages) Ambient

Inside Air

watts

The measured energy consumption is 689 kWh (2.35 million Btu) for the four month period. This includes a four day period when the interior temperature set point was changed to below 68°F. For the period the average indoor temperature was 73.1°F within a 6.3°F range. A simulation run based on an interior set point of 72°F estimated consumption during the cooling period of 4.7 Million Btu. The actual energy consumption of the building was lower because the townhouse was unoccupied, reducing the appliance and lighting loads.

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June 1997

Figures 28 and 29 show the relationship between the wall surface temperatures and the air temperatures of the townhouse. During the night, the exterior wall surface temperature approaches the interior conditions especially as the temperature difference between the outdoor and indoor is small. Figure 28 Steel, Spray Foam Insulation Days 236-237 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0 Ambient

Inside Air

S Wall Ext

S Wall Int

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0 hourly averages

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June 1997

Figure 29 Steel, Spray Foam Insulation Days 236-237 95.0

90.0

85.0

degree F

80.0

75.0

70.0

65.0

60.0

Ambient

N Wall Ext

N Wall Int

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0

Townhouse Unit 10—Light Weight Autoclaved Aerated Concrete This townhouse is constructed using a lightweight AAC wall system, incorporating thermal mass and insulation in a homogeneous wall structural material. The HVAC equipment is identical to that used in townhouse unit 8, except for capacity. The manufacturer's rating is SEER=12.0 and the rated capacity is 42,000 Btuh. A plot of the data available during four months of air conditioning operation is shown in Figures 30 and 31. In the narrow 80-day period under analysis, the trend in energy consumption indicated approximately a 1.91 kWh per degree temperature difference between the outdoor and indoor overall temperatures. The scatter data was limited in this case, as a result of an equilibrium in the wall system and equipment operation. During the 80-day period, the indoor air temperature set point was increased by 2°F with an average interior air temperature of 67.5°F within a range of 65.2 to 71.5°F.

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June 1997

Figure 30 Lightweight Concrete Cooling Season Performance 40

35 100 Day Period Indoor Temperature Range 62.5 - 73.4 F 30

kilowatthours

25

20

15

10

5

0 -12.0

-7.0

-2.0

3.0

8.0

13.0

degree F Temperature Difference (Outdoor - Indoor)

Figure 31 Lightweight Concrete Cooling System Performance 40

35

30

kilowatthours

25

20

15

80 Day Period Indoor Temperature Range 65.2 - 71.5 F

10

5

0 -6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

degree F Temperature Difference (Outdoor - Indoor)

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June 1997

A five- and two-day period of operation is shown in Figures 32 and 33, respectively. The relationship between the air conditioning unit operation and the outdoor and indoor temperatures was consistent for the period in that high daytime temperatures and solar gains caused increased operation of the air conditioning system. The indoor air temperature fluctuated considerably even with the electronic thermostat. This townhouse has a large amount of east facing glazing compared to the other townhouses. The air conditioning system operation was extensive throughout the day resulting in a lower indoor air temperature. The importance of the thermal mass in the lightweight concrete appears to be evident during the afternoon period when the solar gains were limited and the air conditioning system operation decreased. Figure 32

3.00

75.0

2.50

70.0

2.00

65.0

1.50

60.0

1.00

55.0

0.50

50.0

0.00

Cooling System Operation

80.0

238

3.50

237

85.0

236

4.00

235

90.0

234

degree F

Lightweight Concrete

5 Day period by hour average kWh

NAHB Research Center, Inc.

52

Ambient

Indoor Air

June 1997

Figure 33 Lightweight Concrete days 237-238, 1997 4000

85.0

3500

80.0

3000

degree F

2500 70.0 2000 65.0 1500

A/C operation (watts)

75.0

60.0 1000 55.0

500

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

12:10 AM

9:10 PM

10:40 PM

7:40 PM

6:10 PM

4:40 PM

3:10 PM

1:40 PM

12:10 PM

9:10 AM

10:40 AM

7:40 AM

6:10 AM

4:40 AM

3:10 AM

1:40 AM

0 12:10 AM

50.0

hour (by 10 minute averages) Ambient

Inside Air

watts

The measured energy consumption based on actual indoor air temperatures was 2204 kWh (7.52 Million Btu) including estimates for the periods when data was unavailable. A simulation based on an interior set point of 72°F resulted in an estimated consumption of 10.7 Million Btu for the cooling period. The difference between the interior set point and the actual recorded temperature was significant. The house was unoccupied and had minimal appliance and lighting loads. Figures 34 and 35 show the relationship between the interior, exterior wall, and air temperatures. The south exterior wall temperatures, and to some extent the north exterior wall temperatures, track the incidence of solar radiation. The south wall showed a thermal lag of six to seven hours between the temperatures on the exterior and interior surfaces.

NAHB Research Center, Inc.

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June 1997

Figure 34 Lightweight Concrete Days 236-237 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0 Ambient

S Wall Int

S Wall Ext

Inside Air

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

11

9

7

5

3

1

55.0 hourly averages

Figure 35 Lightweight Concrete Days 236-237 95.0

90.0

85.0

degree F

80.0

75.0

70.0

65.0

60.0 Ambient

N Wall Int

N Wall Ext

54

23

21

19

17

15

13

11

9

7

5

3

1

23

21

19

17

15

13

9

NAHB Research Center, Inc.

11

7

5

3

1

55.0

June 1997

Building Temperature Profile The wall surface temperatures on the south and north facing exterior wall surfaces were monitored in two or three locations. The interior north and south wall surfaces were each monitored in one location. Five consecutive days were selected for comparison since these days are representative for each townhouse. The south and north wall interior and exterior temperatures and the indoor and outdoor temperatures are compared. Table 17 lists the maximum and minimum daily average temperatures from day 234 to day 238. Table 17 Maximum and Minimum Temperatures Days 234 to 238

Unit

Outdoor Ambient

Indoor Air

South Wall Exterior (SWExT)

South Wall Interior (SWInT)

North Wall Exterior (NWExT)

North Wall Interior (NWInT)

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

7

82.3

63.3

76.6

71.7

103.3

69.1

74.7

70.2

92.1

69.1

74.7

70.0

8

82.3

63.3

76.9

75.7

100.5

72.6

78.0

77.0

86.8

70.2

76.6

75.7

9

82.3

63.3

74.5

73.4

103.6

72.1

75.0

73.0

92.9

70.9

75.3

73.7

10

82.3

63.3

69.1

67.4

96.0

68.8

72.4

70.1

82.9

68.3

68.3

66.6

7

86.3

64.2

77.5

71.8

113.1

70.6

75.6

70.5

95.6

70.0

75.0

70.0

8

86.3

64.2

77.3

75.8

104.4

73.3

78.6

77.1

90.7

71.0

77.0

75.7

Day 234

Day 235

9

86.3

64.2

74.4

73.8

109.6

73.3

75.2

73.8

95.0

72.3

74.9

73.8

10

86.3

64.2

69.0

67.7

100.7

70.2

73.1

70.5

85.9

69.8

70.5

66.6

7

88.8

65.7

77.6

71.8

120.5

71.0

76.1

70.6

96.4

71.3

74.7

70.0

8

88.8

65.7

77.6

75.8

111.3

74.1

79.0

77.2

90.4

72.0

76.9

75.8

9

88.8

65.7

74.4

73.8

117.5

73.7

75.4

73.9

95.3

73.2

74.9

73.5

10

88.8

65.7

69.0

66.9

108.9

70.6

73.1

70.9

87.1

70.3

71.5

65.9

7

83.2

66.7

77.1

71.7

117.5

73.2

75.8

71.7

93.1

72.7

74.6

69.7

8

83.2

66.7

79.1

75.9

109.3

76.0

78.8

77.6

89.0

73.1

77.4

76.0

Day 236

Day 237

9

83.2

66.7

74.4

73.5

113.5

76.1

75.2

73.2

94.3

74.8

77.8

72.1

10

83.2

66.7

68.8

66.8

105.9

73.4

73.0

70.8

84.2

72.7

69.0

65.9

7

80.9

59.8

79.3

71.5

118.3

66.1

75.5

70.1

90.8

66.8

75.2

69.9

8

80.9

59.8

77.3

75.8

108.8

71.6

78.7

77.3

86.6

68.8

76.8

75.8

9

80.9

59.8

74.3

73.4

113.3

68.6

75.5

72.7

86.7

67.7

74.3

73.1

10

80.9

59.8

69.0

67.1

105.0

66.5

72.7

70.2

80.4

66.1

73.3

66.0

Day 238

NAHB Research Center, Inc.

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June 1997

The following findings were observed based on the data contained in Table 17: •

The minimum temperature of the exterior north and south walls were similar and only a few degrees above minimum ambient temperatures, suggesting heat flow to the outdoors during lower night ambient temperatures.

•

The maximum south wall interior temperature was within 1.5°F of the maximum indoor air temperature in units 8 and 9, indicating the high level of insulation in the exterior walls. The maximum south wall interior temperature was about 4.0°F above the indoor air temperature for unit 10, indicating the influence of the combination of thermal mass and static Rvalue in making the transmission of the outdoor temperature to indoors more pronounced. Townhouse unit 7 interior wall temperatures were below the interior air temperatures due to the effects of the setback regime imposed by occupants.

•

The impact of thermal mass may be seen by comparing the minimum south wall interior temperature with the minimum interior air temperature in units 8 and 10. The higher minimum wall temperature compared to the minimum interior air temperature indicates the effect of heat storage in the south facing mass walls. The same comparison for the light frame walls of unit 9 revealed a negligible difference suggesting no thermal mass effects.

•

The minimum interior wall surface temperatures for the north facing walls, were approximately equal to the minimum interior air temperature except for unit 10 where the interior north surface temperature appeared to have a pronounced response to the effects of the outdoor temperature.

NAHB Research Center, Inc.

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June 1997

Temperature Response Unit 7 air conditioning operated under a 4°F setback which influenced the inside wall surface temperature. The temperature of the inside wall floated to a higher level influenced by the air conditioning operation rather than by the effect of the solar gain on the exterior surface. The time lag between the exterior surface temperature and the interior surface temperature was five to six hours, but this was largely due to the effect of the thermostat setback. Figure 36 shows unit 7’s five-day temperature profile. Figure 36 Structural Insulated Panels Days 234-238 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0

238

237

236

235

234

55.0

Day (by hour average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall Ext

57

S Wall Int

June 1997

Unit 8’s temperature profile revealed barely identifiable temperature time lag between the interior and exterior wall surfaces, due to the high level of concrete thermal mass in the exterior walls. This mitigated the direct effects of the solar gain on the wall surface from changes in diurnal temperature. Figure 37 shows unit 8’s temperature profile for day 234 to day 238. Figure 37 Insulated Concrete Forms Days 234-238 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0

238

237

236

235

234

55.0

Day (by hour average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall Ext

58

S Wall Int

June 1997

Unit 9’s temperature profile indicated that solar gains on the south surface in a short period of time resulted in an increase in interior temperatures. This light frame wall system with little thermal mass rapidly transmitted changes in ambient conditions indoors. Figure 38 shows unit 9’s temperature profile for day 234 to day 238. Figure 38 Steel, Spray Foam Insulation Days 234-238 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0

238

237

236

235

234

55.0

Day (by hour average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall Ext

59

S Wall Int

June 1997

Unit 10’s temperature data indicates a time lag of seven or eight hours for outdoor wall surface temperatures to be transmitted to the interior due to the integration of thermal mass with the insulation of the AAC wall. Figure 39 shows townhouse unit 10’s temperature profile for day 234 to day 238. Figure 39 Lightweight Concrete Days 234-238 125.0

115.0

degree F

105.0

95.0

85.0

75.0

65.0

238

237

236

235

234

55.0

Day (by hour average) Ambient

NAHB Research Center, Inc.

S Wall Int

S Wall Ext

60

Inside Air

June 1997

Figure 40 compares the hourly average temperature difference between the inside and outside north wall surface temperatures. In the diurnal cycle, high daytime temperature differences were clearly visible. Three townhouses exhibit similar traits or peak daytime temperature differences while the temperature levels in the townhouse constructed with ICFs has shifted downward with a smaller range of variation. Figure 41 shows a similar diurnal peak temperature difference for the south wall surface temperature. Figure 40 North Wall Surface Temperature Difference Days 234-238 SIP ICF SSF AAC

20.0

degree F (Outside - Inside)

16.0

12.0

8.0

4.0

0.0

-4.0

117

113

109

105

97

101

93

89

85

81

77

73

69

65

61

57

53

49

45

41

37

33

29

25

21

17

9

13

5

1

-8.0

hour of day

NAHB Research Center, Inc.

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June 1997

Figure 41 South Wall Surface Temperature Difference Days 234-238 SIP ICF

42.0

SSF AAC

degree F (Ouside - Inside)

32.0

22.0

12.0

2.0

21

17

9

13

5

1

21

17

9

13

5

1

21

17

9

13

5

1

21

17

9

13

5

1

21

17

9

13

5

1

-8.0 hour of day

TOWNHOUSE ENERGY PERFORMANCE MONITORING–HEATING SEASON The energy consumption and wall surface temperatures of the heating system of each of the townhouses was monitored for the period from November to April. Unit 8, built with SIPs, was monitored for wall temperatures but not for energy consumption since the space heating equipment did not function for much of the monitoring period. The thermostat setting for the SIP, ICF, and SSF townhouse units was 68°F. The heating degree days assumed for the simulation was 4459 using a base temperature of 25 65°F. Calculated degree days for the 181-day period was 4414 .

25

Calculated on the average of the daily maximum and minimum and a 65°F base temperature

NAHB Research Center, Inc.

62

June 1997

Performance of Individual Townhouse Units Townhouse unit 7—Structural Insulated Panels The heating system for unit 7 is a gas engine heat pump unit. The engine input is rated at 45,000 Btuh and the auxiliary heat input (boiler) is rated at 75,000 Btuh. During the entire heating season, the operation of the heating equipment was interspersed with periods of equipment outages. The available data, shown in Figure 42, indicates the periods when the heating system was operating. Figure 42 Structural Insulated Panels Note: Operation of the heating system equipment intermittant throughout period

90.0

6.0

80.0 5.0 70.0

4.0

50.0 3.0 40.0

30.0

therms

degree F

60.0

2.0

20.0 1.0 10.0

120

114

108

96

102

90

84

78

72

66

60

54

48

42

36

30

24

18

6

12

366

360

354

348

342

336

330

324

318

312

0.0 306

0.0

day of year Ambient

NAHB Research Center, Inc.

63

Inside Air

Heat Fuel Consumption

June 1997

Even with the minimal operation of the central heating system, a temperature profile is available for the townhouse. Figure 43 shows the relationship between the exterior and interior wall and air temperatures. Changes in the north wall exterior temperature closely followed the outdoor ambient temperature, but averaged 9.1°F above the ambient air temperature. Both the interior north and south wall temperatures cycles appear to be influenced by indoor air temperature. In the north wall however, the impact of heat transfer to the outside surface was clearly evident since the wall temperature was below the indoor air temperature. This was observed in the south wall surface, where the south interior wall temperatures were affected by exterior wall cycles. Figure 43 Structural Insulated Panels days 17 - 19, 1997 90.0 80.0 70.0

degree F

60.0 50.0 40.0 30.0 20.0 10.0

9:30 PM

11:40 PM

7:20 PM

5:10 PM

3:00 PM

12:50 PM

8:30 AM

10:40 AM

6:20 AM

4:10 AM

2:00 AM

9:40 PM

11:50 PM

7:30 PM

5:20 PM

3:10 PM

1:00 PM

8:40 AM

10:50 AM

6:30 AM

4:20 AM

2:10 AM

9:50 PM

12:00 AM

7:40 PM

5:30 PM

3:20 PM

1:10 PM

8:50 AM

11:00 AM

6:40 AM

4:30 AM

2:20 AM

12:10 AM

0.0

hour (by 10 minute average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall out

N Wall out

64

S Wall in

N Wall in

June 1997

Townhouse Unit 8—Insulating Concrete Foam Forms Unit 8 was heated using equipment which integrates domestic hot water with the furnace operation. The hot water from the domestic hot water tank was circulated through a heat exchanger in the blower cabinet. The rated heating output was 90,000 Btuh with a maximum of 94,000 Btuh. Figure 44 shows the operation of the heating system for the 181-day period. The townhouse unit was unoccupied November to December (days 306 to 366), after which the townhouse was occupied by two people. Since the hot water use was integrated with the heating system, an estimate of energy consumption was made to subtract the portion of the fuel consumption attributed to water heating. Figure 44 Insulated Concrete Form 80.0

7.0

70.0

6.0

60.0 5.0

4.0 therms

degree F

50.0

40.0 3.0 30.0 2.0 20.0

1.0

10.0

120

114

108

96

102

90

84

78

72

66

60

54

48

42

36

30

24

18

6

12

366

360

354

348

342

336

330

324

318

312

0.0 306

0.0

day of year Note: 0.35 therms/day subtracted for water heating

NAHB Research Center, Inc.

Heat Fuel Consumption

65

Ambient

Inside Air

June 1997

Diurnal changes in the outdoor ambient conditions were indicative of the stabilizing influence of the thermal mass. Days 17-19 are shown in Figure 45. For example, the regular and periodic on/off operation of the heating system is clearly observed throughout the day and night, constantly cycling to keep the indoor temperature stable. Figure 45 Insulated Concrete Form Days 17-19 70.0

0.1000 0.0900

60.0 0.0800 50.0

degree F

0.0600 40.0 0.0500 30.0 0.0400

furnace operation

0.0700

0.0300

20.0

0.0200 10.0 0.0100

2340

2130

1920

1710

1500

1250

830

1040

620

410

200

2350

2140

1930

1720

1510

1300

840

1050

630

420

210

2400

2150

1940

1730

1520

1310

850

1100

640

430

10

0.0000 220

0.0

hour-minute therms

NAHB Research Center, Inc.

66

Inside Air

Ambient

June 1997

A simulation performed on this unit using an indoor thermostat setpoint of the measured average indoor temperature, estimated a peak heating load of 21,300 Btuh. Total 26 consumption for the period was measured at 308.1 therms or 30.81 Million Btu. The consumption estimate based on the simulation was 29.1 Million Btu. The measured fuel consumption was decreased by 0.15 therms per day to account for water heater losses and was decreased by an additional 0.35 therms per day to account for the domestic water heater consumption for the period when the townhouse was occupied. Figure 46 shows an approximately linear relationship existed between fuel consumption and the difference between the inside and outside air temperature, since the fuel consumption is directly related to changes in ambient temperatures. Figure 46 Insulated Concrete Form 7.0

6.0

5.0

therms

4.0

3.0

2.0

1.0

0.0 0

10

20

30

40

50

60

degree F (Inside Air-Ambient)

26

Portions of the measured data are estimated during periods when actual data was missing.

NAHB Research Center, Inc.

67

June 1997

A three-day period during the coldest part of the season in Figure 47 shows the relationship between the exterior and interior wall and air temperatures. Changes in the north wall exterior temperature followed the outdoor ambient temperature closely but averaged 12.6°F above the ambient air temperature within a range from 6.6 to 18.6°F. Changes in the interior north and south wall temperatures follow the inside air temperature but were less. The temperature profiles were much different since the inside south wall temperatures were affected by the solar gains on the exterior surface. A subtle rise in the south wall interior temperature was observed which may be attributable to the solar gains on the exterior wall during the day. The delay is on the order of a few hours and is greatly attenuated. Figure 47 Insulated Concrete Form days 17 - 19, 1997 90.0 80.0 70.0

degree F

60.0 50.0 40.0 30.0 20.0 10.0

9:30 PM

11:40 PM

7:20 PM

5:10 PM

3:00 PM

12:50 PM

8:30 AM

10:40 AM

6:20 AM

4:10 AM

2:00 AM

9:40 PM

11:50 PM

7:30 PM

5:20 PM

3:10 PM

1:00 PM

8:40 AM

10:50 AM

6:30 AM

4:20 AM

2:10 AM

9:50 PM

12:00 AM

7:40 PM

5:30 PM

3:20 PM

1:10 PM

8:50 AM

11:00 AM

6:40 AM

4:30 AM

2:20 AM

12:10 AM

0.0

hour (by 10 minute average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall out

N Wall out

68

S Wall in

N Wall in

June 1997

Townhouse Unit 9—Steel Frame with Spray Foam Insulation This townhouse is heated using a closed loop geothermal heat pump with three ground loops in a vertical well configuration. The rated heating output is 36,200 Btuh with 11.4 kW of electric back-up heat. Figure 48 shows the operation of the heating system for the 181 day period. The townhouse was unoccupied for the entire period except for periodic tours. Figure 48

kilowatthours

120

114

108

96

102

90

84

78

72

66

60

54

48

42

0 36

0.0 30

5

24

10.0

18

10

6

20.0

12

15

366

30.0

360

20

354

40.0

348

25

342

50.0

336

30

330

60.0

324

35

318

70.0

312

40

306

degree F

Steel, Spray Foam Insulation 80.0

day of year Heating Fuel Consumption

Inside Air

Ambient

The walls were constructed of steel framing with spray foam insulation in the cavities and Cchannels. In addition, a one-inch foam board was attached to the exterior of the framing members. ICF construction formed the common wall with adjacent townhouse unit 8. Diurnal changes in the outdoor ambient conditions were reflected in the heating system operation, suggesting little influence from a stable wall system. Days 17-19 in Figure 49 show the operation of the heating system was clearly dependent on the external conditions throughout the day and night. Day 19 is shown expanded in Figure 50 and indicates the rapid response of the heating system to changes in outdoor ambient conditions, a typical feature of low-mass wall construction.

NAHB Research Center, Inc.

69

June 1997

Figure 49 Steel, Spray Foam Insulation Days 17-19 2500

70.0

60.0

degree F

50.0

1500

40.0

30.0

1000

20.0

Geothermal system operation

2000

500 10.0

2340

2130

1920

1710

1500

1250

830

1040

620

410

200

2350

2140

1930

1720

1510

1300

840

1050

630

420

210

2400

2150

1940

1730

1520

1310

850

1100

640

430

10

0 220

0.0

hour-minute watts

Ambient

Inside Air

Figure 50 Steel, Spray Foam Insulation Day 19 2500

70.0

60.0

50.0

degree F

1500 40.0

30.0 1000

20.0

Geothermal System operation

2000

500 10.0

2330

2240

2150

2100

2010

1920

1830

1740

1650

1600

1510

1420

1330

1240

1150

1100

1010

920

830

740

650

600

510

420

330

240

150

10

0 100

0.0

hour-minute watts

NAHB Research Center, Inc.

Ambient

Inside Air

70

June 1997

A simulation of the operation of this unit using an indoor thermostat setpoint of the measured average indoor temperature, estimated a peak heating load of 20,300 Btuh. Total consumption for the heating period was measured at 3289 kWh or 11.22 Million Btu. The simulation estimated energy consumption of 8.8 Million Btu. The unit was unoccupied and internal heat gains were minimal. According to the simulation, internal gains should have reduce the building load by about 20 percent. Figure 51 shows that linear relationships existed between the heating system operation in kWhrs and the temperature difference between the inside and outside air. Figure 51 Steel. Spray Foam insulation 40.0

35.0

30.0

kilowatthours

25.0

20.0

15.0

10.0

5.0

0.0 0.0

10.0

20.0

30.0

40.0

50.0

60.0

degree F (Inside Air-Ambient)

NAHB Research Center, Inc.

71

June 1997

A three-day period during the coldest part of the season in Figure 52 shows the relationship between the exterior and interior wall and ambient air temperatures. Changes in the north wall exterior temperature closely followed the outdoor diurnal cycle of ambient temperature, but averaged 10.8°F above the ambient air temperature within a range of 7.3 to 15.2°F. Changes in the interior north and south wall temperatures followed a diurnal cycle of high day and low night temperatures, but the temperature levels were less. The profiles, however, were much different since the inside south wall temperatures were affected by the solar gains on the exterior surface. A distinct rise in the south wall interior temperature was observed and may be attributed to the solar gains on the exterior wall during the day. The delay was about two hours and was attenuated, but not as much as in the thermal mass wall construction. Thermal mass changes the way the exterior temperatures are transferred indoors, making a more even operation of equipment possible. Figure 52 Steel Framing, Spray Foam Insulation days 17 - 19. 1997 90.0

80.0

70.0

degree F

60.0

50.0

40.0

30.0

20.0

10.0

9:30 PM

11:40 PM

7:20 PM

5:10 PM

3:00 PM

12:50 PM

8:30 AM

10:40 AM

6:20 AM

4:10 AM

2:00 AM

9:40 PM

11:50 PM

7:30 PM

5:20 PM

3:10 PM

1:00 PM

8:40 AM

10:50 AM

6:30 AM

4:20 AM

2:10 AM

9:50 PM

12:00 AM

7:40 PM

5:30 PM

3:20 PM

1:10 PM

8:50 AM

11:00 AM

6:40 AM

4:30 AM

2:20 AM

12:10 AM

0.0

hour (by 10 minute average) Ambient

NAHB Research Center, Inc.

Inside Air

S Wall out

N Wall out

72

S Wall in

N Wall in

June 1997

Townhouse Unit 10—Lightweight Aerated Autoclaved Concrete Unit 10 was heated using equipment similar to townhouse unit 8 which integrated domestic hot water with the furnace operation. The hot water from the domestic hot water tank was circulated through a heat exchanger in the blower cabinet. The rated heating output was 90,000 Btuh with a maximum of 94,000 Btuh. Figure 53 shows the operation of the heating system for the 181-day period. The townhouse was unoccupied for the entire period except for periodic tours. Figure 53

therms

120

114

108

96

102

90

84

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Lightweight Concrete

day of year Heat Fuel Consumption

Inside Air

Ambient

The walls were constructed of lightweight AAC with traditional stucco on the exterior and plaster on the interior. Diurnal changes in the outdoor ambient conditions were reflected in the heating system operation suggesting little influence from the relatively stable wall system. The data for days 17-19 in Figure 54 show the operation of the heating system was dependent on the external conditions throughout the day and night, but the operation of the system appears to be much more constant than the other townhouses. Day 19, shown in detail in Figure 55, indicates the constant operation of the heating system. The inside air temperature was stable during the period, except for a brief period when the electricity was not supplied to the house loads.

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Figure 54 Lightweight Concrete Days 17-19 70.0

0.12

60.0

0.10

degree F

0.08 40.0 0.06 30.0 0.04

heating system operation

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0.00 220

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hour-minute therms

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Figure 55 Lightweight Concrete Day 19 70.0

0.12

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degree F

0.08 40.0 0.06 30.0 0.04

heating system operation

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hour-minute therms

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A simulation of the operation of this unit using an indoor thermostat setpoint of the measured average indoor temperature, estimated a peak heating load of 33,700 Btuh. Total consumption for the heating period was measured at 534.1 therms or 53.41 Million Btu. The simulation consumption estimate was 47.7 million Btu. The unit was unoccupied and internal heat gains were minimal. The simulation indicated that internal gains would have reduced the building load by about 22 percent. Figure 56 indicates an approximately by linear relationship between the heating system operation in therms and the temperature difference between the inside and outside air temperatures. Figure 56 Lightweight Concrete 8.0

7.0

6.0

therms

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degree F (Inside Air-Ambient)

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A three-day period during the coldest part of the season is shown in Figure 57 indicating the relationship between the exterior and interior wall and air temperatures. Changes in the north wall exterior temperature followed the outdoor ambient temperature closely but averaged 12.1°F above the ambient air temperature within a range of 7.4 to 16.3°F. Both the interior north and south wall temperatures followed inside air temperature but the temperature levels were less. The profiles, however, were much different since the inside south wall temperatures were affected by the solar gains on the exterior surface. A distinct rise in the south wall interior temperature was observed which may be attributed to the solar gains on the exterior wall during the day. The delay was five to six hours and was highly attenuated. Figure 57 Lightweight Aerated Concrete days 17 - 19, 1997 80.0

70.0

60.0

degree F

50.0

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9:30 PM

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0.0

hour (by 10 minute average) Ambient

Inside Air

S Wall out

N Wall out

S Wall in

N Wall in

Summary Observations for days 17-19 for townhouse units 8, 9, and 10 can be summarized as follows: •

North wall exterior temperatures follow the high day and low night temperatures of the diurnal cycle.

•

North wall interior temperatures follow the cycle of the interior temperatures, but are always less due to the heat transfer to the exterior wall surface.

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•

Exterior south wall temperatures match the exterior north wall temperatures however, during the day, surface heating due to solar gains are clearly evident.

•

Interior south wall temperatures changes are relatively limited, presumably due to the heat capacity of the wall.

•

Thermal lag is observed for all of the units, including light-frame walls, with the thermally massive concrete unit (ICFs) showing the largest attenuation and the light-frame (steel), the least and the AAC falling in between; however, the light weight concrete is observed to have a distinct thermal lag much higher than the light frame steel construction or the massive ICF construction.

VISITOR SURVEYS st

The 21 Century Townhouses have been open to the public since June 1996 and will remain open through August 1997 for scheduled tours. Eighty tour participants completed comprehensive surveys of the photovoltaic (PV) array during a six month period, yielding approximately 13 surveys per month in regularly scheduled tours. The results will be analyzed in a separate report on the building integrated PV program. A general townhouse survey of all key technologies was developed in March 1997 and distributed beginning in April 1997. Surveys were typically completed during standard 1.5 hour regularly scheduled tours. Regularly scheduled tour was canceled to make way for a special tour for members of the National Council of the Housing Industry (NCHI) and Remodelers Council. Other such special tours were conducted for the Bowie Chamber of Commerce and the Vinyl Siding Institute. Consequently, 22 surveys were completed on key technologies. Because the large special tours were abbreviated and conducted on mass, participants were not asked to complete surveys. It is anticipated that a “Last Chance” publicity drive will be conducted during June to increase interest and participation in July and the beginning of August. The following key technologies were highlighted and explained during the one and one-half hour tour, after which respondents were asked to complete a questionnaire (see Appendix B): • • • • • •

Structural Insulated Panels Insulating Concrete Forming System - ICE Block Light Gauge Structural Steel Framing - American Iron and Steel Institute (AISI) Drain Water Heat Recovery System - water Film Energy, Inc. Natural Gas Engine Heat Pump - York International Environmental Systems Ventilation and Dehumidification Equipment - Thermo-Stor Products

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• • • • •

Lightweight Autoclaved Aerated Concrete - Hebel USA Ground Source Heat Pump Photovoltaic System - Energy Conversion Devices, Inc. Home Automation - Smart House, Inc. Gas Refueling System

Visitors were asked about their likelihood of incorporating these technologies in their house in terms of four categories or responses: very likely, somewhat likely, don’t know, and not likely. The attributes of each technology that were thought to be advantageous were listed and visitors were asked to indicate which were most important. The results of the survey are summarized in Table 17. The following are the key findings from the survey (see Table 17 and Appendix C) Likelihood of Adoption •

Insulating Concrete Forms, Ventilation and Dehumidification Equipment, Autoclaved Aerated Concrete, Structural Insulated Panels, Home Automation, in order, were the top five ranked technologies among all visitors surveyed.

•

Insulating Concrete Forms’ (ICFs) high rating (rank 1) was due largely to the relatively high percentage of respondents who stated they did not know enough about the product (rank 1) to give a definitive response and the relatively low percentage of respondents who stated they were not likely to adopt (rank 2). ICFs ranked third in other response categories. Although ranked high overall, some uncertainty exists about this product and there is a need for more information.

•

Ventilation and Dehumidification Equipment’s high overall ranking (rank 2) was due to the large percentage (rank 1) of respondents who stated they would very likely adopt this innovation and the lowest percentage (rank 1) who definitely would not adopt the innovation. It ranked low (rank 7) in terms of the percentage of respondents who did not know whether they would adopt. Respondents were most positive and felt more certain that they would adopt this innovation compared to any other and seemed to be confident that they had the information they needed.

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18 22 23 25 29

GSHP

Drain Water Ht.

PV

Gas Eng. HP

Gas Refuel

9

8

7

6

5

5

21

15

14

15

13

13

11

7

6

5

6

4

4

3

0

6

10

14

14

18

14

18

9

41

14

%Total

7

6

4

3

3

2

3

2

5

1

3

Rank

Very Likely

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79

Sum of Very Likely, Somewhat Likely, Don’t Know, Not Likely rankings from most positive (1) to least positive (9). Sum of all rankings that were not negative- excludes “Not Likely” 3 Technology with lowest percentage reporting “Not Likely” received a positive rank of 1, etc.

1

18

Lt.Gg.Steel

4

2

14

10

Home Autom.

4

14

SIPs

10

2

3

1

13

7

Rank

AAC

1

Score2 3

9

Rank

Total Positive

Vent & Dehumid.

ICFs

Score1

Total

June 1997

10

19

36

18

27

32

64

36

45

45

45

9

7

4

8

6

5

1

4

2

3

3

Rank

Somewhat %Total

Table 17 Survey of Visitors to Townhouse (n=22)

19

29

14

23

23

14

9

23

27

9

32

%Total

5

2

6

4

4

6

7

4

3

7

1

Rank

Don’t Know

71

42

45

45

36

36

18

23

18

5

9

%Total

8

6

7

7

5

5

3

4

3

1

2

Rank3

Not Likely

•

Lightweight Autoclaved Cellular Concrete’s (AAC) relatively high ranking (rank 3) was due to the relatively large percentage of respondents who stated they were somewhat likely to adopt (rank 2) the innovation. This contrasts with the moderate score (rank 5) in regard to those who would very likely adopt. It ranked relatively high in other categories (rank 3) “don’t know” and “not likely” to adopt. In general, respondents were open to adopt this innovation, but were uncertain and needed more information.

•

Structural Insulated Panels’ (SIPS) relatively high score (rank 4) was due to the proportion of respondents who said they would very likely (rank 2) adopt this innovation. It was rated relatively high (rank 4) in all categories of response. Respondents appeared quite certain in their positive response to this innovation, although the rankings were generally lower than the top three rated innovations.

•

Home Automation’s relatively high rating (rank 4) was largely due to the large proportion of respondents who had a lukewarm reaction (rank 1) to this innovation, in that they were somewhat likely to adopt. At the same time, a relatively low percentage (rank 7) did not know now whether they would adopt this information or stated they would not likely adopt this innovation. Respondents seemed to have definite opinions about this innovation, but they were only moderately positive.

•

Light Gauge Steel’s rating was moderate (rank 5) due largely to the relatively high percentage of respondents (rank 2) who stated they were very likely to adopt this innovation. A relatively moderate share of respondents (rank 5) however, stated they were not likely to adopt this innovation.

•

The Ground Source Heat Pump’s score was moderate (rank 5) due to a relatively high rating (rank 3) from those respondents who said they would very likely adopt this innovation. Other ratings of this innovation were relatively moderate to low. A very high proportion of respondents stated they would not likely adopt this innovation.

•

Ratings of the drain water heating equipment, PV, gas engine heat pump, and gas refueling were generally low. The drain water heating unit ranked relatively high (rank 3); however, among respondents who said they would very likely adopt this innovation. Uncertainty about the gas engine heat pump was relatively high (rank 2). A relatively high percentage of respondents said that they would not likely adopt PV, yet it ranked relatively high (rank 4) in regard to those who would very likely or would be somewhat likely to adopt this innovation.

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Attributes Influencing Adoption of Innovations (See Figures 1–11 in Appendix C) •

Energy Efficiency was the most important attribute influencing, in order, the use of SIPs, ICFs, Gas Engine Heat Pump, Ground Source Heat Pump, and Drain Water Heat Reclaim unit.

•

Health and Comfort, respectively, were the most important attributes that would lead to the adoption of the Ventilation and Dehumidification System.

•

Security was the most important attribute influencing the adoption of home automation.

•

Price stability was the most important factor cited as affecting the adoption of Light Gauge Steel.

•

Back-up power during outage and operating cost respectively, were the most important attributes influencing adoption of PV.

•

Environment was the most important reason cited for the likely adoption of gas refueling.

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APPENDIX A

APPENDIX B

TOWNHOUSE UNITNUMBER7

TOWNHOUSE UNITNUMBER 8

TOWNHOUSE UNITNUMBER 9

TOWNHOUSE UNITNUMBER 10

APPENDIX C

APPENDIX D