• All America Homes of Gainesville

All America Homes has been in business for 17 years and builds 10 homes each year in the Gainesville (FL) area. After providing design assistance for the award wining 2002 home (Figure 3) during the 4 th budget period, BAIHP provided additional assistance to All America for a second home with solar and energy efficiency concepts during the 5 th budget period. The home was built with a photovoltaics (PV) system, and achieved a HERS rating of 90.6.

Figure 3 All America Homes of Gainesville, 2003 Energy Value Housing Award, Silver Medal, Custom Home/Hot Climate.

This home serves as a model for the hot-humid climate using a combination of on-site power generation and energy efficiency to reach near-zero utility demand, similar to the home built in 2002 (Table 3).

It incorporates energy efficient air conditioning, hydronic solar water heating, excellent air distribution design and construction (pressure tested for validation) and right sizing of the heating and cooling capacity. It also incorporates envelope improvements in the roof, ceiling, walls, windows and infiltration control. A passive fresh sir ventilation system provides filtered outside air to the return side of the mechanical system during operation. See Appendix C, Florida H.E.R.O. Standard Technical Specifications.

• AMJ Construction

Florida Home Energy Rating Organization (Florida H.E.R.O.) provided an engineered duct system for 26 models in the Regents Park Townhouse development. This downtown urban infill project will result in 54 units with Building America features including ductwork in the conditioned space, outside air ventilation, and combo hydronic heat and 13 SEER cooling.

• Applegren Construction, Eastern Dakota Housing Alliance (EDHA)

EDHA set a goal of achieving up to 50% energy savings over the 1993 Model Energy Code with superior indoor air quality (AIQ). Phase I (March 2003) and Phase II (Feb 2004) each included two twin homes (duplexes) for a total of eight homes.

Figure 4 Selkirk Twin Homes, Grand Forks, ND.

The two story dwellings (Figure 4) include an insulated basement with air circulation to the main house, suitable for conversion to living space. Features of the Phase I and Phase II homes are summarized in Table 5 which also shows a theoretical base case house using local conventional construction and code minimums modeled in DOE2 to determine energy savings and cost effectiveness. Estimated combined gas and electric utility savings ranged from 25% on Phase I homes to 35% on Phase II homes over the base case. The homes also met the BA goal of 40% savings compared to the Benchmark house.

Annual Energy Use

A performance comparison of the base case and improved structures is shown in Table 5. The DOE2 model predicts the need for very little cooling, however many new homes in this area, including these, are being built with central air conditioning.

Moisture Issues

Phase II of construction added a layer of R-10 rigid extruded polystyrene (XPS) to the exterior side of the wall assembly. The low water vapor permeance of rigid XPS foam sheathing (1.1 perms) presents a dilemma in this climate where an interior vapor barrier (usually 6-mil polyethylene) is considered mandatory to minimize moisture diffusion from the conditioned space into the wall cavity. The installation of two vapor barriers leaves the wall vulnerable to moisture accumulation should water unintentionally enters the cavity. One BAIHP recommendation calls for removing the interior vapor barrier and relying on two coats of latex paint on the interior to limit diffusion from the conditioned space into the wall. This option allows the wall to dry to some extent in both directions, but was not chosen by the builder.

Ventilation

A heat recovery ventilator (HRV) mounted in the basement provides controlled mechanical ventilation with an energy penalty estimated at $45/year. The unit contains an 80-watt fan that introduces 75 CFM of outside air while exhausting a similar amount at a heat transfer efficiency of 70%. The HRV can operate either continuously or on an intermittent 20 minutes on, 40 minutes off cycle. Intermittent operation was simulated to meet the old guideline. Attempting to meet the new ASHRAE 62.2 standard (ASHRAE 1999) would require 42 CFM of continuous ventilation. For these simulations however, the old ASHRAE guideline of 0.35ACH was used, calling for a continuous rate of 25 CFM.

Cost Analysis

Tables 6 (Phase I) and 7 (Phase 2) show the cumulative effect of All Measures in comparison to the base case home. The heat recovery ventilator (HRV) is also shown separate from the other measures because the HRV is an essential IAQ feature, yet it increases energy use by $45/year. With the exception of the HRV all measures show a positive cash flow on a 6%, 30 year fixed rate mortgage beginning in the first year.

The higher savings of Phase II over Phase I arise from two energy saving measures unusual for this region: XPS foam sheathing with 2x4 framing and tankless gas water heating. Simple paybacks for these measures were 8.3 and 13.3 years respectively. Electric water heaters are the current norm in the Grand Forks area, but with electricity 26% below the national average and natural gas prices on the rise, simple payback on the tankless model was relatively long. In addition, fluctuating natural gas prices complicate the economic analysis. Initial concerns of how the tankless water heater would perform in this extreme climate were met with positive feedback through the first winter, which was colder than normal including an all-time record low of -44ºF set at the Grand Forks International Airport on January 30, 2004.

Four more dwellings (two duplexes) are slated for completion in the summer of 2004. See also Cold Climate Case Study: High Efficiency North Dakota Twin Homes on www.baihp.org .

• Atlantic Design and Construction

Atlantic Design & Construction (AD&C) is a production builder located in Gainesville, Florida, who builds about 50 homes a year. Though initially producing homes better than the Florida Energy Code minimum, Florida HERO worked with AD&C to increase their efficiency to Energy Star and then to Building America standards. (Table 8). The new upgrades resulted in homes achieving an average HERS score of 89.

Figure 5 Atlantic Design and Construction home in the Mentone neighborhood.

Savings from the increased the cooling system efficiency more than offset the additional $250 to $375 needed for improved duct sealing and insulation and air sealing protocol adjustments. This savings, while sufficient to offset those costs, were not enough to pay for all implemented measures. Instead, increasing the price of the home by $1,250 was sufficient to cover the additional costs and derive an excellent profit margin. Despite adding $1,250 to $2,500 to home buyer costs up-front, AD&C's award-winning development, Mentone, has been the best-selling subdivision in Alachua County for four years running (Figure 5).

Kenny Brekenridge, AD&C Project Manager, says that the company believes with energy costs continuing to rise that it makes sense to build energy efficient, and that they emphasize the Building America improvements in their sales literature and discussions.

• Avis American Homes

In the summer of 2003, Avis American Homes tested an alpha prototype Status and Control System (STACS) developed by the UCF Constructability Lab researchers (BAIHP Partner). The system is a real-time shop floor labor data collection and reporting system. Production workers use wireless laser scanners to report their current work assignment. STACS reporting is web based and provides both real time manufacturing status and summaries of historical production performance (Figure 6). While labor represents a relatively modest fraction of production cost, typically 10-15%, it has a profound impact on operations, including product quality, cycle time, material waste, and labor productivity.

Figure 6 STACS system components and relationships.

Avis American employees tested STACS in drywall finishing operations. Test results demonstrated that production workers could operate the system effectively and that the system accurately captured scanned activity.

See also Penn Lyon Homes (Technical Assistance section) and Status and Control System (STACS) (Research Section III).