Passive homes are radical about saving energyby Michele Lerner
Imagine rarely switching on your air conditioning in summer or your heat in winter. If you own a “passive house,” your heating and cooling needs are regulated by the extremely well-insulated yet ventilated design of your home.
Over the past two decades, thousands of homes have been built in Europe using the passive house concept. In certain portions of Germany, for example, according to David Peabody, a certified passive house consultant with Peabody Architects in Alexandria, Va., the passive house program has been adopted as the energy standard for all new construction. In the U.S., says Peabody, approximately 50 homes have been built using the passive house program, clustered primarily in California, Vermont, New York, the Pacific Northwest, and in Illinois, where the first U.S. passive house was built.
According to the Passive House Institute of the U.S., “A Passive House is a very well-insulated, virtually air-tight building that is primarily heated by passive solar gain and by internal gains from people, electrical equipment, etc. Energy losses are minimized. Any remaining heat demand is provided by an extremely small source.”
Main goal: Save money on energy
Just how much can you save on energy costs? Peabody says a passive house typically uses 90 percent less heating and cooling energy than a standard house. But since homes have other utility costs such as lighting, appliances and electronics, the Passive House Institute estimates overall energy savings is closer to 60 to 70 percent compared to a standard home.
The passive house concept uses high-performance, triple-glazed windows, extra-thick insulation, an airtight building shell and a mechanical ventilation system which provides a back-up system for air filtration. Doors and windows in a passive house open and close like any other house.
Additional benefits of a passive house
Experts say that not only do passive homes reduce your energy bills, they provide a healthier living environment.
“Passive Houses are more comfortable because you don’t have any drafts and there is no stratification of temperature from one level to the next,” says Peabody. “They are also healthier because you have good air filtration with a mechanical ventilation system that kicks in during the seasons when you don’t have your windows open. The purified air coming in through the ventilation system has less carbon dioxide and also eliminates many of the impurities in the air that can trigger asthma and other allergy attacks.”
The ventilation prevents the build-up of moisture that can cause mold and mildew and keeps the humidity in your home at optimal levels.
Costs of passive house construction
Peabody says it is less costly to build a passive house in an area like California that has minimal heating and cooling needs, or in an area like Vermont which really only has heating needs. However, passive homes have also been built in the Washington, D.C. area which experiences both summer and winter extremes.
Peabody estimates that the construction costs of a passive home are approximately seven to 10 percent higher than standard building costs. While any architect can work with a consultant or with passive home software to make design changes, Peabody says it is much easier to work with an architect who has been trained in passive home design and who can easily incorporate the concept from the design phase. To become a certified passive house consultant, architects must take a nine-day training program from the Passive House Institute, which costs $2100, plus take an exam that costs $250.
Homes can also be renovated and retrofitted to meet passive house guidelines, but Peabody says this costs 20 to 25 percent more than a standard renovation. He expects costs to come down as passive-house construction practices become more common.
Peabody says the passive house concept represents a “growing up of green building” that focuses highly on the structure of a home from the design phase through construction in order to reduce demand for energy.
(The photo above is courtesy of David Peabody. Mr. Peabody was the architect for the passive house [pictured], located in Bethesda, Md.)