Hedgewood Properties Research Project

Introduction Hedgewood Properties, Inc. has been a Building America builder partner with IBACOS since 1999. They build approximately 200 homes a year in communities north of Atlanta, Georgia. All of their homes meet EarthCraft House™ guidelines, which are a blueprint for healthy, comfortable, affordable homes that cut energy and water bills and protect the environment. The Southface Energy Institute, a technical partner on the project, administers the EarthCraft House™ program. Hedgewood’s homes are typically two stories with over 3,000 square feet of floor area and may have a full basement, crawl space or slab-on-grade foundation. Detached garages are a common feature. Builder Standard House Characteristics Due to Hedgewood’s involvement in the EarthCraft House™ program, the energy efficiency characteristics of their homes are well documented. We obtained information through the Southface Energy Institute to define the Builder Standard House. The house is considered representative of Hedgewood homes in the region where the pilot home is being built. The information can be summarized as follows:
Building Envelope
•	Due to the recent building code changes, the use of low solar heat gain windows has become mandatory. Hedgewood uses windows that are wood-framed, double-glazed, with low-emissivity coating; U=0.35 and SHGC=0.34.
•	The profile of exterior walls include: cladding material, housewrap, structural sheathing, 2x4 framing, R-13 kraft-faced fiber glass insulation batts in cavities, and drywall finish. Band joists are insulated with R-13 blown cellulose insulation batts in cavities. Brick, stone and fiber cement siding are common claddings.
•	Basement foundation walls are typically framed and insulated with R-13 unfaced fiberglass batts unless the area is to be finished in which case drywall is installed around the interior wall perimeter. Penetrations through the wall can provide pathways for humid air to reach the concrete foundation wall and condense.
•	Blown-in cellulose insulation is used in the attic to achieve R-38. Unfaced R-19 fiber glass batt insulation is used in the floor of living space over the garage and floors over unconditioned spaces. Roofs have asphalt shingles.
•	There is an opportunity to improve flashing around windows and doors. The long-term durability of exterior walls could be compromised because of inappropriate flashing product usage, poor flashing techniques and inadequate integration with the drainage plane.
•	In order to meet EarthCraft House™ guidelines, homes require an average air-change rate resulting from natural infiltration lower than 0.35 ACH. Troublesome airflow pathways include overhanging fireplaces, attic chases, knee walls adjacent to attic space and penetrations through exterior walls. The main air barrier, which is the interior drywall, is usually not continuous in ceiling and exterior wall locations.
Mechanical System
•	Heating equipment uses natural gas and has an efficiency of 80% AFUE and is B-vented. In most homes there are two air handlers, with at least one in the attic. Cooling equipment has an efficiency of 12 SEER, and either 4- or 5-ton capacity (depending on house size) units are usually installed.
•	To meet EarthCraft House™ guidelines total air distribution system air leakage must have a value less than 5% of the total floor area. For a 3,000 square foot house this amounts to 150 cfm of air leakage. Floor registers and ductwork traveling through the basement serves the first floor. Ductwork serving the second floor travels through vented attic space to second floor ceiling delivery locations.
•	The hot water heaters use natural gas and typically have a 50-gallon capacity and an energy factor of approximately 0.52.
•	An insulated duct connects outdoor air to the air handler return air plenum and provides mechanical ventilation. The outdoor air is drawn into the air distribution system when the air handler operates. A mechanical damper is often placed in the duct that homeowners are asked to close on warm humid days. Exhaust fans in bathrooms remove odors and moisture when switched on.
•	Dedicated return air ductwork is common for all bedrooms.
•	Lighting fixtures predominately use incandescent lamps. Appliances have typical energy efficiency.
Analysis of Builder Standard Characteristics Based on the information provided and our observations, we determined that several opportunities exist for improving the builder’s standard practice. These include:
•	Using a basement foundation wall system that has improved thermal performance and prevents condensation from occurring at the foundation wall.
•	Improving building airtightness practices to eliminate comfort problems associated with drafts and uneven temperatures.
•	Optimizing the HVAC system with higher efficiency equipment so that it more efficiently provides comfortable temperature and humidity conditions.
•	Improving the efficiency of hot water production.
•	Providing mechanical ventilation to maintain good indoor air quality and comfortable conditions on a consistent basis. Humid outdoor air used for ventilation cannot cause discomfort.
•	Using energy efficient lighting to reduce energy consumption and increase comfort during cooling conditions.
•	Using energy efficient appliances to reduce energy consumption.
•	Optimizing window and door flashing products and techniques and integrating them effectively with the drainage plane to increase home durability.
Pilot Home Characteristics The builder decided that the model home in their new Westbrook community near Cumming, Georgia, would be the best candidate to be the pilot home since it would be able to showcase publicly the most advanced system technologies for the longest time. The pilot home was designed to achieve a minimum of 40% savings in total energy use and supply some of its electrical energy via a photovoltaic system. The home has a total of 3,643 square foot of finished floor area spread over two stories and a basement and is accompanied by a detached garage. This plan typically has two air handlers. With the input of the builder, IBACOS developed detailed final specifications for the home that are summarized as follows:
	Figure 1. Pilot home during construction. It has a front access, walk out basement. The front of the home faces east.
Building Envelope
	Windows are the same as used for all of the builder’s homes. They are wood-framed, double-glazed, with a low-emissivity coating with U=0.35 and SHGC=0.34.
	The exterior walls consist of exterior sheathing comprised of R-3 (½ in. thick) extruded polystyrene rigid board insulation sheathing or OSB structural sheathing. House wrap covers the sheathing material to enhance water drainage. Cellulose spray insulation provides R-13 thermal performance, within 2x4 exterior wall assemblies and band joists, and R-19 thermal performance for 2x6 exterior wall assemblies, which are located in the basement.
	Unfinished sections of basement walls will be insulated on the inside with R-8 (1¼ in. thick) polyisocyanurate foam board insulation glued directly to the foundation wall. An interior 2x4 framed wall will be adjacent to the foam board insulation and its cavities will contain cellulose spray-in insulation (R-13 thermal performance).
	The air-change rate due to natural infiltration will be a maximum of 0.35 ACH. To improve building airtightness, emphasis will be placed on draftstopping large holes to ensure air barrier continuity. In particular, draftstopping will be conducted at exterior wall and ceiling locations where no cellulose insulation will be installed. This includes areas such as behind tubs, the overhanging fireplace, and duct chases. The numerous penetrations through the envelope will need to be sealed as well.
	Long-term durability of the building shell will be enhanced with the greater use of flashing and rainwater control measures. Flexible flashing membrane will be used around window and door rough openings and integrated with the drainage plane.
	Blown-in cellulose insulation will be used in the attic to the R-38 level.
Mechanical
	One direct vent natural gas furnace with 94% AFUE, 120.0 MBH input, 1900 cfm (high fan speed @ 0.60 in. ESP) design airflow will be used and located in the basement. A 14 SEER, 5-ton capacity condensing unit will provide cooling.
	Hot water is provided by a two natural gas fired tankless units each with 175 MBH input and an energy factor of 0.82. The units will be direct vented.
	Total air distribution system air leakage target is 10% of system airflow (190 cfm) with air leakage to the outside less than 5% of system airflow (95 cfm). As much of the sheet metal and insulated flex ductwork as possible will be located within the conditioned space of the home. A central, fully-ducted return system will serve each floor with dedicated return air ductwork serving each bedroom to keep room pressures balanced.
	A ventilation dehumidifier provides mechanical ventilation. The system will run continuously drawing outdoor air at a maximum flow rate of 220 cfm (@ 0.10 in. ESP), which is dehumidified before entering the supply air trunk. ASHRAE 62.2 ventilation requirements for the house are 70 cfm.
	We recommend that 90% of lighting in the home should be from fluorescent fixtures, compact, and linear.
	Appliances meeting Energy Star® requirements will be used.
	A 2 kW photovoltaic system will be installed to generate electricity.

Advanced System Costs and Benefits

Energy Use

We used EnergyGauge USA software version 2.1 to calculate end-use site energy for the Hedgewood Properties pilot home and to compare the pilot home with the Builder Standard House (as defined earlier) and the Building America Benchmark Definition version 3.1. Energy use values are noted in Table 1 and are based on site orientation averaged for the four cardinal directions. Total annual site energy estimates without plug load usage are subtotaled for easy reference and comparison.

Table 1. Summary of Estimated End-Use Site Energy for Hedgewood Properties Project DesignAnnual Site Energy
	BA Benchmark		Builder Standard Home		Pilot Home Design
End-Use	KWh	therms	KWh	therms	KWh	therms
Space Heating	561	796	491	676	222	349
Space Cooling	5532	0	3958	0	2406	0
DHW	0	188	0	195	0	89
Lighting	3360	0	3360	0	2380	0
Appliances	2610	-	2610	-	2000	-
Subtotal	12062	983	10419	871	7008	438
Plug Loads	5334	-	5334	-	4334	-
Total Usage	17396	983	15753	871	11342	438
Site Generation	-	-	-	-	2340	-
Net Energy Use	17396	983	15753	871	9002	438

A summary of electric and natural gas consumption components for various end uses for the pilot home are noted in Table 2.

The estimated annual electrical and natural consumption in Table 1 was used to calculate the estimated source energy consumption and savings using the following equations:

Source MBTU = kWh * 3.412 * Me/1000 + therms * Mg/10

Where: Me = 3.16 = Site to source multiplier for electricity (DOE, 2002b)

Mg = 1.02 = Site to source multiplier for natural gas (DOE, 1995).

In Table 3, two columns estimate the savings percentage for each end-use category realized in the pilot home and compared to the benchmark and builder standard homes. In the last two columns the estimated savings for each end-use category realized in the pilot home is determined as percentage of total source energy used for either the benchmark or the builder standard home.

The analysis determined that the pilot home built to the design specifications (not including the contribution of the photovoltaic system) will save 42% with respect to the Building America Benchmark Definition and 35% with respect to the Builder Standard Home for total end-use source energy. These savings rise to 50% and 45% respectively when the contribution of the photovoltaic system is included.

If plug loads were not considered, since homeowner purchasing decisions determine the appliances selected, the pilot home would save 47% with respect to the Building America Benchmark Definition and 40% with respect to the Builder Standard Home for source energy consumption.

Table 4. Summary of Estimated End-Use Source Energy with Pilot Home Design
Annual Source Energy				Estimated Source Energy Savings
				Percent of End Use		Percent of Total
End-Use	BA Benchmark (MBTU)	Builder Standard (MBTU)	Pilot Home (MBTU)	BA Benchmark	Builder Standard	BA Benchmark	Builder Standard
Space Heating	87	74	38	56%	49%	17%	14%
Space Cooling	60	43	26	57%	39%	12%	6%
DHW	19	20	9	53%	54%	4%	4%
Lighting	36	36	26	29%	29%	4%	4%
Appliances	28	28	23	20%	20%	2%	2%
Subtotal	230	201	121	47%	40%	38%	31%
Plug Loads	58	58	47	19%	19%	4%	4%
Total Usage	288	259	168	42%	35%	42%	35%
Site Generation	-	-	-25	-	-	8%	10%
Net Energy Use	288	259	143	50%	45%	50%	45%

Estimated savings for different advanced system design improvements to the pilot home with respect to the builder standard are noted in Table 5. Energy costs are based on Swanee EMC average rate for electricity of $0.07/kWh, and Scana Energy average rate for gas of $.869/therm. A discussion on the application, benefits, and costs of different advanced system improvements follows.

Table 5. Estimated Savings for Incremental Improvements with Pilot Home Design with respect to Builder Standard
					Builder Standard
	Site Energy		Source Energy		Energy Cost		Measure Package
Improvement Increment	KWh	therms	MBTU	Savings%	$/yr	Savings%	Value ($/yr)	Savings ($/yr)
BA Benchmark	17396	983	288		$2,072
Builder Standard (BS)	15753	871	259	10%	$1,859
(1) = BS + 2x4 Exterior Wall + Basement Improvements	15406	714	239	8%	$1,699	9%	$161	$161
(2) = (1) + Air Infiltration Improvements	15125	600	224	14%	$1,580	15%	$119	$280
(3) = (2) + Optimized & High Performance HVAC	14246	530	208	20%	$1,457	22%	$123	$402
(4) = (3) + Tankless DHW	14247	424	197	24%	$1,365	27%	$92	$494
Final = (4) + Energy Efficient Lighting, Appliances	11342	438	168	35%	$1,181	37%	$184	$679
Final + Site Generation	9002	438	143	45%	$1,017	45%	$164	$842
Final + 2x6 Exterior Wall Improvements	11257	369	160	38%	$1,109	40%	$71	$750

Exterior Wall Thermal Performance

Exterior wall thermal performance improvements decrease heating and cooling loads and increase homeowner comfort and is focused on two areas: basements walls and main floor walls.Since grade level for the pilot home slopes from back to front it will have its basement walk out at the front of the house. Basement walls are either constructed of 6 in. thick concrete (against soil), 2x6 wood framing (at walk out area) or a combination of both systems (at transition points in grade). A total of 743 square feet of basement floor area is finished. All concrete basement foundation walls will be insulated on the inside with R-8 (1¼ in. thick) polyisocyanurate foam board insulation glued directly to the wall with 2x4 wood framing placed adjacent to it and insulated with R-13 cellulose within cavities. Wood framed basement walls will be insulated with R-13 cellulose. This practice is different from their current practice, which consists of uninsulated walls in unfinished basement areas (and the basement ceiling insulated) or an insulated (R-13) wood frame wall installed around the interior foundation wall perimeter in finished basement areas. The foam board insulation will be applied directly to the foundation wall and have its joints sealed with a suitable tape thereby creating a vapor retarder which limits the possibility of humid indoor air interacting with a cooler foundation wall, thereby reducing the potential for condensation to occur. The builder estimates that there will be a $1,000 upgrade cost (labor and materials) for using the directly applied foam board insulation system. The main exterior walls for the Hedgewood home will consist of exterior sheathing, 2x4 framing and R-13 cellulose insulation within cavities. In the pilot home, R-3 (½ in. thick) extruded polystyrene rigid board insulation sheathing will be used as much as possible as the exterior sheathing material (wall coverage was assumed to be about 40%). OSB will be the exterior sheathing used for the balance of the walls. No cost increase is expected for the insulating sheathing usage. The predicted annual source energy savings increment for all exterior wall thermal performance improvements are 8% resulting in annual cost savings of $161 for the homeowner. This saving was achieved at a total upgrade cost of $4,000. Simple payback for the improvement is 24.8 years.

2x6 Exterior Wall Thermal Performance Strategy

A strategy to improve the exterior wall’s thermal performance beyond that exhibited in the pilot home was considered. The strategy consisted of R-5 (1 in. thick) extruded polystyrene rigid board insulation sheathing applied over the entire wall surface. 2x6 wood framing installed at 24 in. centers with cavities insulated to R-19 would complete the strategy. This approach would result in annual source energy savings increment of 3% with respect to the pilot home and lead to $71 in additional annual cost savings for the homeowner. The estimated upgrade cost for this strategy is $1,000. Simple payback for the improvement is 14.1 years. This strategy would have to been used if energy savings in end use areas such as appliances and plug loads were not realized in order to achieve the minimum 40% total energy saving target.

Exterior Wall Durability Improvements

A strategy to improve the water shedding capability of the exterior walls of the pilot home will be implemented. A building envelope that has good water shedding capability prevents rainwater entry into the wall assembly of the house. Water in building assemblies can cause wood rot or mold growth, which is not desirable from a durability and indoor air quality perspective.A thorough strategy for improving exterior wall durability was developed and includes installing exterior sheathing closely together to prevent water entry and applying plastic house wrap overtop to create an effective drainage plane. Integrating window and door flashing practices with the drainage plane completes the strategy. Installation of the drainage plane and flashing materials will promote water movement away from the house. The builder estimates that there will be a $200 upgrade cost (labor and materials) for improving flashing practices. House wrap usage is standard practice and no cost increase is expected.

Building Airtightness

Exterior walls that are more airtight have less outdoor air coming through them and the exfiltration of conditioned air is hindered. Large amounts of air leakage can adversely affect comfort levels and increase energy consumption in the house (to compensate for discomfort). Maintaining continuity of the air barrier is critical for improving airtightness in building envelope components. The main air barrier would be on the inside face of exterior walls and ceilings and consists of drywall. The use of cellulose insulation in exterior walls is expected to greatly lower air infiltration in that building component. Draftstopping details were developed for areas on exterior walls and ceilings that would not normally be drywalled in order to make a continuous air barrier. This included walls at bathtubs, behind the fireplace and at the top of chases, which would be insulated with fiberglass batts (and not benefit from the use of celluloseinsulation). These measures should result in fewer comfort complaints related to drafts and temperature swings, which customers have sometimes noticed in these areas. The numerous penetrations through the envelope will be sealed as well. The builder estimates that there will be a $150 upgrade cost for draftstopping work and $300 in extra costs for sealing of penetrations. The predicted annual source energy savings increment for the building airtightness improvement is 6% resulting in annual cost savings of $119 for the homeowner. This saving was achieved at a total upgrade cost of $450. Simple payback for the improvement is 3.8 years, the second lowest of any improvement.

Optimized Heating and Cooling System

The high efficiency furnace (94% AFUE) and 14 SEER condensing unit are energy efficiency upgrades for Hedgewood. High efficiency equipment provides the same amount of cooling or heating as lower efficiency equipment but uses less energy in doing so. In order to promote greater use of such equipment, a local HVAC supply company donated Rheem® equipment for the project. An engineered HVAC system analysis conducted on the pilot home determined the heating and cooling loads for the home. The thermal performance characteristics of the home including exterior wall improvements, reduced building envelope air leakage and effect of mechanical ventilation were used to determine the heating and cooling load. Since the home would be used as a model, above average lighting usage was also assumed. Loads were reduced to the extent that two separate HVAC systems, the typical case for a home of this size, were no longer needed. Furthermore, the one furnace used will be within conditioned space, whereas in the typical case one of the two units is located in the unconditioned attic. A zone control system is being used, so that separate areas of the home will be afforded individual temperature and humidity control. Each floor, including the basement, has its own zone. A furnace with 89,000 Btu/h output was selected to provide heating. A 5-ton condensing unit and evaporator coil were determined to be sufficient to meet cooling loads, handle humidity and provide adequate air distribution.If the load calculations produced by the HVAC subcontractor, done to their typical practice, were to be used, the total capacity of cooling equipment installed would be 8 tons, with two units being used instead of one. A 5-ton unit would only serve the basement and first floor areas. A detailed duct layout based on calculated loads and predicted air flows was developed to ensure that correctly sized ductwork could efficiently move air from the furnace in the basement to all spaces that needed to be conditioned. This approach is critical to ensure that comfort conditions are maintained. To promote good distribution of cool air in the summer on the second floor, while keeping ductwork within conditioned space, a design strategy of keeping duct registers in high wall locations was initiated. But, due to the lack of suitable interior framed walls on each floor to accommodate ductwork pathways, this design strategy was abandoned. Instead we decided (regretfully) that the only feasible way to condition the second floor was through ducts traveling through vented attic space to ceiling registers. To facilitate the placement of the main duct truck leading up to the attic space from the basement mechanical room, an interior chase was designed. With some ductwork in attic space, duct airtightness would be critical. Therefore UL-181 approved mastic sealant is being installed on all joints between all pieces of ductwork as well as joints in the furnace, and joints between ductwork and the furnace. A total air leakage goal of 10% for the air distribution system has been established. No more than 5% of air leakage can go to the outside.The predicted annual source energy savings increment for the optimized heating and cooling system improvement is 6% resulting in annual cost savings of $123 for the homeowner. The estimated upgrade cost for all HVAC improvements, including mechanical ventilation (see below), is $1,500. Simple payback for the improvement is 12.2 years.

Mechanical Ventilation

Mechanical ventilation is needed to enhance indoor air quality. It is particularly important to have a mechanical ventilation system in an airtight home since it receives a reduced amount of outdoor air through natural infiltration.The builder will install a ventilation and dehumidification unit. The unit will draw outdoor air at an intermittent rate as governed by the ventilation timer component of the control module. To meet ASHRAE 62.2 ventilation requirements, the house needs 70 cfm of outdoor air on a continuous basis. In addition, as determined by the humidity level set on the control module, the unit will draw indoor air from a register located in a breakfast area high wall location and dehumidify it to the set point level. The EnergyGauge USA analysis tool is not able to quantify the energy usage of this system and its impact on air handler run times due to its dehumidification performance, therefore for energy modeling purposes the pilot home was considered as having no ventilation system. As noted in KAAX-3-33410-04.C.2.2, Detailed Field Test Plan 2, we will evaluate the performance of the system verses its energy consumption and recommend modeling assumptions. The estimated upgrade cost for the mechanical ventilation system for the pilot home is $1,000.

Domestic Hot Water Improvements

Two direct vent, tankless, gas-fired water heaters with an EF of 0.85 will be installed. Each unit has an input of 175.0 MBH and is capable for producing 4.7gallons per minute for a 60°F rise. (This assumes a 60°F average ground water temperature for Atlanta and a water outlet temperature of 120°F.) One unit will be located in a second floor closet and serve the hot water needs of the second floor, while another unit will serve the balance of the house from its basement location. Two tankless water heaters manufactured by Bosch and donated to the project (retail cost $750 each) will be installed as per the builder’s request. The builder is unfamiliar with this water heating technology and remains cautious that one unit would have adequate capacity to serve a house with four full bathrooms. As noted in Detailed Field Test Plan 2, we will evaluate if one tankless unit is sufficient to handle the hot water load. A tankless water heater unit reduces the energy consumption associated with domestic hot water use because of its good recovery efficiency rating and also because it eliminates the stand-by losses associated with a large storage tank full of hot water. Because the water heater is directly vented and has minimal clearances to combustible products, it can be located in many different places in the conditioned space of the house. The predicted annual source energy savings increment for the domestic hot water system improvement is 4% resulting in annual cost savings of $92 for the homeowner. This saving was achieved at a total upgrade cost of $1,100 (which includes credit for power vented hot water tank). Simple payback for the improvement is 11.9 years.

Energy Efficient Lighting

We developed an advanced lighting systems plan for the pilot home including exterior lighting. The plan is a combination of two approaches and is based on making improvements to hard-wired fixtures. The first approach is a fixture change-out strategy that replaces low efficiency incandescent fixtures with higher efficiency fluorescent fixtures. The second approach is an advanced residential lighting design that is a comprehensive design of the lighting system based on the function of the space and also architectural characteristics. The design focuses on the use of energy efficient fixtures. We estimate that 29% in source energy savings will be realized by following the plan (refer to Table 3). This savings level is based on an annual use schedule developed for each fixture. The estimated upgrade cost for all lighting improvements is $300.

Energy Efficient Appliances and Plug Loads

An Energy Star® labeled dishwasher, clothes washer, and refrigerator are being installed in the pilot home. Hot water usage is expected to decrease on average by 4 gallons per day due to the Energy Star® labeled dishwasher and 14 gallons per day due to the Energy Star® labeled clothes washer. A clothes dryer that is predicted to use less than 974 kWh/yr of energy annually (the Building America Benchmark value for this appliance) and a range/oven that uses less than 604 kWh/yr of energy annually (the Building America Benchmark value for this appliance) will be installed. It is estimated that these five appliances can be obtained for a total annual energy use not to exceed 2000 kWh/yr. This will result in 20% energy savings from the appliance end use category.In order to reduce plug loads, other/miscellaneous Energy Star® labeled appliances will be installed in the pilot home (when it will be used as a model) and suggested for use to the eventual homeowner. Other/miscellaneous appliances include televisions, VCRs, DVDs, cable/satellite boxes, cordless phones, and home computers. Assuming that three televisions will be installed, it is estimated that 1,000 kWh/yr of energy savings, with respect to the Building America Benchmark value, can be achieved in the plug loads end use category.No additional costs to the builder are predicted for using energy efficient appliances since they are widely available. The predicted annual source energy savings increment for energy efficient lighting, appliance and plug load improvements is 11% resulting in annual cost savings of $184 for the homeowner. These improvements collectively represent the measure with the largest energy savings impact and can be obtained at an estimated upgrade cost of $300. Simple payback for the improvement is 1.6 years, the lowest of any improvement.

Photovoltaic System

High efficiency solar modules will provide electricity. The system will be connected to the utility grid to allow for net metering. The system will have a maximum power output of 2 kW and sit on the home’s roof. We estimated annual production of electricity to be 2,864 kWh. The estimated cost for the photovoltaic system is $13,000. The predicted annual source energy savings increment for the photovoltaic system improvement is 10% resulting in annual cost savings of $164 for the homeowner. Simple payback for the improvement is 79.3 years, the highest of any improvement.