Insulation, airtight window frames, solar power and a heat-recovery ventilation system helped Clarum Homes earn its first certification for building a passive house that the company says cuts energy use by 90 percent.
Several hundred guests, including architects and engineers, toured the home, located at 1206 N. Lemon Ave. in Menlo Park, and asked about its environmental and health benefits on June 2, five days before the 4-bedroom, 3.5-bath house went on the market.
John Suppes, CEO of Clarum Homes, along with Director of Construction Sean Misskelley and consultant Katy Hollbacher, guided visitors through the 3,300-square-foot, Mission-style home and answered questions, while visitors mingled over a sandwich buffet.
The airtight, energy-efficient home needs 90 percent less energy annually for heating than the average U.S. household, Suppes said. He added that although the California-based company has built passive-inspired houses in the past, this is its first home to meet all standards -- set by Passive House Institute US (PHIUS) -- for space-heating demand and total energy use per square foot, as well as airtightness.
Structural insulated panels retain heat by using the same material as Styrofoam coffee cups, and triple-glazed windowpanes from Austria create a thermal envelope that reduces heating costs, he said. Sealants and a liquid barrier applied to the outside of the panels maintain airtightness.
Air inside the house goes through a heat recovery ventilator that keeps temperature and humidity constant by exchanging the air nine times every 24 hours, and recovering 90 percent of the heat from air exhausted to the outside of the house, said Matt Groves, an engineer for the company that supplied the ventilator.
The home also cuts energy costs by using three solar panels on the roof to provide 90 percent of the power needed to heat water, and 40 percent to heat space, according to Clarum. In addition, solar tubes replace ceiling lights in dark areas such as closets.
Although the passive house cost 4 to 5 percent more to build than normal Clarum homes, which also feature sustainable technologies, energy savings will recapture the cost, Suppes said. He plans to build and retrofit several passive houses for clients in Menlo Park and Palo Alto in the near future.
Hollbacher emphasized that a home earns certification from PHIUS as a passive house based on the building's performance, rather than prescribed features.
"Something that's really nice about the standard is that there are three absolute numbers for heat demand, energy use and air tightness. It doesn't matter if you're in Germany, or if you're in Minnesota, Truckee or (Menlo Park), you have to meet them," she said, adding that because the passive house standards were developed in Germany, they're relatively easy to achieve in California's mild climate.
Although passive house regulations don't include a standard for water efficiency -- an area that Clarum addressed in its Menlo Park house with structured-zone plumbing, a re-circulating hot-water system that reduces time spent waiting for water to heat, and drought-resistant plants -- Suppes and Hollbacher said they believe the passive house standard is currently the most advanced standard for green building. "There's just no reason not to do this," Hollbacher said.
Construction of a second Clarum passive home, with all the features of the Menlo Park house, is set to begin in the fall, with the home to be completed in the first quarter of 2012, according to Nicole Gittleson, Clarum Homes executive vice president.
The 4,200-square-foot home, with two stories over a basement, 5 bedrooms and 4.5 baths, will be located in the Southgate neighborhood, near Palo Alto High School.
For more information, visit Menlo passive house.
For information about construction standards, visit Passive House.
A rendering of the house is viewable online.