Salt Lake City—The U.S. Passive House Institute recently awarded The Breezeway House, located in Salt Lake City, certification. It is the first building in the Western U.S. to receive the award.
The Breezeway House uses about 10 percent of the energy of an average existing home and about 20 percent of the energy of an average new house built to code. A Passive House can reach net-zero annual energy consumption with the addition of solar panels.
A Passive House, as certified by the Institute, essentially heats and cools itself and is designed to reduce the heating energy consumption of a building by 90 percent. The standard requires certain strategies to be implemented, including high-R walls and windows without thermal bridges, an airtight envelope, passive solar heat, air-tight construction, energy-recovery mechanical ventilation and proper solar shading.
While multifamily development has yet to include Passive House standards in the U.S., over the last 10 years, more than 15,000 buildings—including multifamily developments, as well as single-family residences, schools, office buildings and factories—in Europe have been designed or remodeled to the standard. A 149-unit apartment building in Hessen, Germany and a 361-unit development in Tirol, Germany are two such examples.
Despite this lack of building in the U.S., Certified Passive House Consultant Dave Brach, AIA, principal of Salt Lake City-based Brach Design Architecture LLC, which designed The Breezeway House, notes that the standard is actually much easier to apply to multifamily housing.
“Multifamily buildings in and of themselves [are] inherently more energy-efficient than single-family. Each individual unit is losing a lot less energy because they are not losing or gaining heat in common walls,” he points out. “The Passive House standard is about super-low energy consumption, and it’s amazing how much easier it is to meet the standard when you have multiple units. Building is just more efficient; you can get a better surface-to-volume ratio.”
In fact, Brach tells MHN, it is more difficult for single-family homes to meet the standard than it would be for multifamily, particularly since “it’s almost impossible to find equipment that’s small enough because the loads in certified Passive House-level buildings are so small…so you oversize. But with multifamily buildings, you have very low energy consumption per square foot [and] because you have five or 100 units grouped together you can use one system. You have these efficiencies of scale so you can properly size the mechanical equipment.”
According to the Institute, performance requirements for a Passive House include an airtight building shell less than or equal to 0.6 ACH (Air Changes per Hour) @ 50 pascal pressure; annual heat requirement less than or equal to 15 kWh/m2/year and primary energy less than or equal to 38.1 kBtu/sf/yr. Also, depending on climate, the buildings should have window u-values less than or equal to 0.8 W/m2/K, ventilation system with more than 75 percent heat recovery with low electric consumption and thermal bridge-free construction less than or equal to 0.01 W/mK.
A certified Passive House uses energy-modeling software, called the Passive House Planning Package (PHPP), developed by the German Physicist Wofgang Feist, who built the first passive house in Germany in 1990.
With the relative ease of which certification could be achieved for multifamily, it may be surprising that there aren’t any communities in the U.S. But, as Brach points out, there are a few reasons for this lack of multi-housing certification. Simply from a practical standpoint, the software hasn’t been available in the U.S. for very long. In addition, there is currently a lack of demand for this type of building, so designers aren’t educated about the process. Perhaps even more important is the fact that, compared to Europe, energy is cheap, so there is less of an incentive for energy-efficient measures. However, as efficiency becomes more important (particularly in the form of government mandates), perhaps the Passive House standard will begin to catch on in multifamily development.
For those interested in pursuing the standard, Brach cautions against a lack of commitment. “You have to be committed to it from the very beginning of conceptual design. Plan to be a Passive House from the very start. The other thing is, building to the air-tightness standard is very difficult—you have to have a very well-planned and executed air-tightness design. If you wait, there’s no way it can be achieved.”
