The “Passive-Aggressive” House

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Today’s world of homebuilding gives a whole new meaning to the old idiom passive-aggressive. The Passive House concept represents the highest energy standard, with the promise of slashing energy consumption for heating by an astonishing 90 percent.

Ninety percent? That’s mighty aggressive passive!

The idea for Passive Houses was developed in 1988 by the Passiv Haus Institut, Darmstadt, Germany, and today there are more than 15,000 passive buildings — homes, factories, schools and offices — in Europe. Because of the current quest for energy efficiency in America, this concept is finally catching on with U.S. homebuilders.

A Passive House is a highly insulated, virtually air-tight building that is primarily heated by passive solar energy and by internal heat gains from people and electrical equipment. Energy losses are greatly minimized.

A Passive House is a comprehensive system. “Passive” describes the system’s basic receptivity and retention capacity. Working with natural resources, solar energy is captured and applied efficiently, instead of relying on traditional cooling and heating equipment and technology to create a building that uses zero energy.

According to the Passiv Haus Institut, the first Passive House U.S. retrofit was in California’s wine country in 2010. This house has another claim to fame: It’s the first Passive House in the Golden State.

When a retired bank manager decided she wanted a comfortable, environmentally friendly home, she turned to Rick Milburn, founder of PassivWorks, Inc., who is a meticulous master builder and green building activist in nearby Vineberg, Calif. He found the perfect candidate in a cul-de-sac of early 1960s ranch houses a few blocks from the central plaza in historic downtown Sonoma. The home was vacant for more than three years.

First, Milburn created an airtight envelope 10 times that of an average house. He filled the wall cavities with high-density fiberglass insulation and added triple-pane windows from Germany. Solar panels on the roof generated enough power to supply 100 percent of the home’s electricity.

Because ventilation is  critical for a tight Passive House, Milburn selected an energy recovery ventilator (ERV) as the core of the mechanical system. An ERV is an energy recovery process that takes the exhausted air from the home and uses it to treat (precondition) the incoming outdoor ventilation.

The builder also chose a split-ductless residential system from Mitsubishi Electric Cooling & Heating, Suwanee, Ga., for backup cooling and heating. He liked this system because the Btu/h capacities for both cooling and heating are the lowest in the industry, the outdoor units are the size of a suitcase (so they are easy to conceal) and the indoor and outdoor units are so quiet that the homeowner cannot tell they are in operation.

Passive-aggressive proof was discovered in the energy bills. After the first year of living in the house, the homeowner paid just $20 a month — the equivalent of running a hair dryer every day, once a day, for 30 days.