Efficiency in the Desert
A production builder adopts green building practices
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 spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. ; 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 BlasterCalibrated air-flow measurement system developed to test the airtightness of forced-air duct systems. All outlets for the duct system, except for the one attached to the duct blaster, are sealed off and the system is either pressurized or depressurized; the work needed by the fan to maintain a given pressure difference provides a measure of duct leakage. test.
Defining the envelope
Pulte uses its own workers rather than subcontractors for electrical, plumbing, and HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. 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 testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas.
At every Azure Canyon house, Pulte workers verify the integrity of the air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both. 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 green building program that focuses on building science to improve home energy efficiency and comfort. EFL is administered by Masco Contractor Services. (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 gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. 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-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. window.” He has been trying — so far unsuccessfully — to convince his company to upgrade to SunCoat Max glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. 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(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. air conditioners, 92% AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. 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 LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. 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.
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.
- Daniel Morrison