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This article was originally published in the March/April 1998 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.

 

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Home Energy Magazine Online March/April 1998


TRENDS

5 Steps to Tract Home Success

This Pulte home was the first house in Nevada to receive a 5-star rating from the state's new home energy rating program.
Making energy efficiency improvements in a tract home development isn't easy. Not only does the builder have to know how any changes will affect all of the house systems, but all of the subcontractors have to be re-educated. Pulte Homes, a high-volume builder in Las Vegas, found that the best way to build more efficient homes was to make five simple changes to the construction process that the subs could follow easily, and institute a rigorous series of quality assurance checks.

Pulte wanted to reduce the houses' utility costs by 30%, says David Beck, director of construction, but they didn't want to change the size, shape, aesthetics, or livability of the homes in the development. And most importantly, Pulte didn't want to raise the ticket price of the houses, so any improvements had to be cost-effective.

Beck consulted with Joseph Lstiburek of Building Science Corporation (BSC), who came up with five changes the builder could make without increasing costs or changing the house dimensions or aesthetics. Now called the Pulte Five-Step Energy System, the program was put to the test in three model homes in 1996. Pulte built two houses using Lstiburek's recommendations and compared them with a third control home on the same lot.

The five steps of the system are:

1. Move insulation from the attic floor to the underside of the roof to increase air conditioning efficiency and install ducts inside the thermal boundary, eliminating the need for a vented attic.

2. Reduce the tonnage of the air conditioning unit.

3. Use the domestic hot-water system to heat the home, reducing the need for a furnace.

4. Install highly efficient windows.

5. Install controlled ventilation.

Ventilated attics are certainly more conventional, but Lstiburek's research in the Pulte subdivision showed that the hot, humid climate was better served by an unvented attic. Vented attics in the Las Vegas climate actually provide an entrance for moisture. Hot, damp air from the outside can condense on the mechanically cooled surfaces inside the vented attic. The drying direction in a warm climate is to the inside, Lstiburek says. It's stupid to vent attics in hot, humid climates because it only serves to bring moisture in (see Conditioned Attics Save Energy in Hot Climates, HE May/June '97, p. 6).

Beck says, We moved the insulation to the roofline. Now if the duct leaks, it doesn't matter, because [heating and cooling] is leaking into the envelope itself. Sealing ducts tight was not as simple as it sounded (see Discovering Ducts, HE Sept/Oct '93, p. 23).

Lstiburek, along with Armin Rudd of Florida Solar Energy Center, reported in the Energy Efficient Building Association 1996 Conference Proceedings that the duct systems for the sealed attic houses had an average of 41% less total air leakage, and most important, no measurable air leakage to the outdoors. The attic method alone, Lstiburek wrote, could save 10% on space conditioning energy.

With leakage into the unconditioned attic accounted for, Pulte could downsize their standard air conditioning unit to a smaller system that was cheaper to run. Now they had cut costs in two areas--the sealed attic had saved them money on roof vents, and the smaller air conditioner was cheaper than their previous unit. We could eliminate roof venting, since there was no attic space to vent, Beck says. The savings there helped offset other costs.

We then went to the next item and changed glazing systems. We switched to a vinyl window with low-e glass, which allows natural light in but eliminates thermal transference. This helped reduce the heating and cooling load. Pulte took the savings from the ventless attics and smaller air conditioner and applied them toward the windows and a hydronic heating system. The system has a larger, more efficient water heater that takes potable water for the house and runs it through a fan coil to heat the home. This not only heats the home, Beck says, it means more hot water for the homeowner.

The last step of the Pulte System is ensuring the indoor air quality of the houses. We found that once homes become so sealed, we needed a fresh-air exchanger, Beck says (see Mechanical Ventilation for the Home, HE Mar/Apr '96. p. 13).

Positive test results were returned from BSC, so Pulte Homes went ahead with a full subdivision of houses built according to Lstiburek's energy efficiency strategy, guaranteed by a seven-section quality assurance checklist. The first check occurs at the footings/pre-slab phase, and the next covers framing and structural members. The third inspection is done before the drywall goes up; the fourth, before painting; the fifth, before flooring. The sixth check looks at cabinetry, countertops, and final trims, and is followed by the final overall inspection. One in every five homes is also checked by a quality assurance inspector from BSC, who acts as a third-party inspector to qualify Pulte for the Energy Star Homes program.

Our goal was to not change the aesthetics or livability of our homes, Beck says. But I wanted to pass on a home that was as much as 30% more efficient than my competitors. If I can sell one more home a month [because it's more efficient], then that's my niche in the market. My whole house costs are only up $150. I feel that once I'm in full-blown production, I will even eliminate that. We paid more for windows, insulation, and hydronic heat, and saved on the air conditioner and attic ventilation. The actual ticket price on the house hasn't changed.

The Pulte home received a Five Star rating from Nevada's home energy rating program, the first home to achieve a Five Star rating in the state. According to Dave McNeil, the home energy rating system program manager for the Nevada State Energy Office, Because the Pulte home's high energy rating qualifies its buyers for an energy-efficient mortgage, the homes are within the reach of many more Las Vegas families. McNeil adds that according to a study by the U.S. Environmental Protection Agency, an Energy Star mortgage 5% qualification ratio stretch would increase home ownership by 15%. This would mean an additional 70,690 Las Vegas Valley families would qualify for home ownership with such an energy-efficient mortgage.

Pulte Homes operates in 40 housing markets across the nation, building 12,456 homes per year. The company received the National Home Builders Association's 1997 America's Best Builder Award.

With strategies like the Pulte System, cutting back energy use isn't totally dependent on the consumer. Says David Beck, I've forced people into energy conservation whether they want it or not.

--Polly Sprenger

 


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