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Green Building News

Efficiency in the Desert

A production builder adopts green building practices

Open plan brings in lots of light. Second-floor windows filter light down from above and a bank of windows along the back wall connects the indoors and outdoors. The open plan also makes ventilation easier—the ceiling fan can mix air from the registers quite easily.
Image Credit: Daniel Morrison

Energy efficiency and sustainability take center stage at two new Las Vegas developments built by Pulte Homes, one of the nation’s largest homebuilders.

Pulte’s Azure Canyon development is located in southwest Las Vegas, where the growing edge of suburbia meets the shrinking desert. Every Azure Canyon home meets the “Green Built” standards established by the local homebuilders’ association. Ranging in size from 1,788, to 2,088 square feet, the homes sell for $230,000 to $260,000.

To minimize energy losses, Pulte locates all the homes’ ducts within the conditioned space; some ducts are run through 20-in. open-web floor trusses, while others are located in the conditioned attic. All duct seams are sealed with mastic, and the tightness of every completed duct system is verified with a Duct Blaster test.

Defining the envelope

Pulte uses its own workers rather than subcontractors for electrical, plumbing, and HVAC work, and trains all workers in the importance of maintaining air-barrier integrity. “A lot of our plans have various bump-outs, some of which are just decoration,” explained Robert Broad, director of product design for Pulte Nevada. “When we define the thermal envelope, we often simplify it — some of the bump-outs are outside of the envelope. For every cantilever or a bay area, everybody needs to understand the boundary that we are sealing to. Sometimes we actually spray-paint an indication of the location of the envelope.”

Training is an ongoing process. “We do pre-insulation behind tubs and showers,” said Broad. “But sometimes we still have to fix insulation that has been moved by the plumber. We’re trying to get the guys to recognize that if they tear out some insulation to do the plumbing, they have to replace it appropriately.”

Every home gets a blower-door test

At every Azure Canyon house, Pulte workers verify the integrity of the air barrier by performing a blower-door test. “We run the blower door and go around with a smoke pencil and look where we could do better,” said Broad. “We walk around and say, ‘What else are we missing?’ ”

To meet the requirements of Environments for Living (EFL), a voluntary energy-efficiency standard, third-party verifiers perform additional blower-door tests on one out of every seven new Pulte homes. Among the services provided by the EFL program is a framework for utility bill guarantees. On all of its Las Vegas homes, Pulte provides a guarantee that covers energy for space heating and cooling. Energy used for cooking,domestic hot water use, and plug loads are excluded from the guarantee. Since it is based on kilowatt-hours of electricity and therms of gas, not dollars spent, the guarantee is independent of energy cost fluctuations.

Low heating and cooling loads

With such careful attention to air sealing, Azure Canyon homes require much smaller HVAC systems than comparable houses. Explaining the method used to calculate heating and cooling loads, Broad said, “John Spargo of Comfort Engineering does our Manual J calculations, and that requires a lot of nuance and judgment. He narrows the range on the infiltration rate and applies more specific inputs on the heat gain calculations than you would typically find. He’s playing the edge of all of those inputs. Compared to a typical HVAC contractor, his calculations are running at about 80% of Manual J.”

Still room for improvement

Azure Canyon homes have HERS Index ratings of 61 or 62, but they could be even lower. “Our HERS scores are based on a worst-case orientation,” explained Broad. Like most production builders, Pulte makes no effort to orient its homes according to passive solar principles. As a result, roof overhangs aren’t optimized for summer shading, and window orientation is random.

Broad describes the windows that Pulte uses as “your basic low-e window.” He has been trying — so far unsuccessfully — to convince his company to upgrade to SunCoat Max glazing from Cardinal, a type of glazing with improved warm-edge spacers and a lower heat-gain coefficient.

Each home gets an energy monitor

Another Pulte development is Villa Trieste, a planned community that will eventually include 185 homes measuring between 1,487 and 1,960 square feet. All Villa Trieste homes, like those at Azure Canyon, are enrolled in the Environments For Living program. The homes are equipped with efficient appliances: 15 SEER air conditioners, 92% AFUE gas furnaces, and Rinnai on-demand gas water heater.

Each Villa Trieste home is equipped with a whole-house energy monitor, or “energy dashboard,” mounted on a wall near the kitchen. These EcoConcierge meters from In2 Networks display real-time energy use and water-use data. “The dashboard is Internet-connected. If I’m at work, I can adjust the AC from my office,” said Walter Cuculic, Pulte’s director of strategic marketing. “The thought is that by paying attention to the energy dashboard,homeowners will be able to reduce their energy use by 5 or 10%.”

Solar power on every roof

Every home at Villa Trieste will include a 1.76-kilowatt photovoltaic (PV) array using SunPower SunTile roof-integrated PV modules. Pulte’s practice of ignoring orientation complicated the task of identifying the best south-facing roof slopes for the PV arrays. “It was a little bit challenging,” admits Cuculic. “For some of the lots, we had to restrict the possible elevations — for example, we may tell a customer that you can’t have a ‘Spanish’ elevation on this lot.”

The cost of installing PV arrays at Villa Trieste is being subsidized by several grants from the local utility and the U.S. Department of Energy (DOE). A portion of the $7 million DOE grant — equivalent to $37,000 per home — will be used to study whether the homes’ energy dashboards help homeowners lower their energy use.

If Pulte is successful in its goal of obtaining LEED Platinum certification for every home at Villa Trieste, the community will become the largest collection of LEED Platinum homes in the country. Since the first rated homes at Villa Trieste obtained impressive HERS Index scores of 43 or 44, the neighborhood is off to an excellent start.

More Information

See a video interview
with a Pulte sales Associate explaining how

she uses a _Quality Construction Room_ to sell the hidden features of green construction.

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