The "Passive House," an Antidote to the Massive House

In Germany's Darmstadt region, a new twist on the design of traditional row houses is nearly undetectable to the eye from the outside in the winter months, until you look in the windows. Inhabitants of these homes born of revolutionary building design gather around in their homes bearing tee shirts and bare feet in the dead of winter, cold tile floors a mere memory of childhood past, and with neither furnace nor fireplace in site. These are the "Passive Houses," Germany's solution to energy conservation that uses one-twentieth the energy of a traditional home of the same size. Even on the coldest night, while others hover around pot-bellied stoves and crank up their electric heating, Passive House dwellers get all the heat and hot water they need from the amount of energy that would be needed to operate a hair dryer.

The concept of the Passive House was pioneered in this city outside Frankfurt by architects intending to meet new energy efficiency standards like the ones in the United States. Using ultra-thick insulation and complex door and window designs and materials, the home is engineered as an airtight shell that allows for nearly no warm air to escape and barely any cold to sneak in. Additionally, a passive house is warmed by the sun, indoor appliances, and the warmth of occupants' body temperatures. In Germany, the cost of building a passive house is only about 5 to 7 percent more than that of a conventional home, making the design efficient not only for energy, but for the wallet as well. The premise of "recycled heating" is one that works, as compared to earlier failed attempts at sealed solar-heating homes. Contrary to the stagnant air and mold resulting from those designs, passive houses use an ingenious central ventilation system that allows the warm air going out to pass side-by-side with the cold air coming in at the same rate, exchanging heat with 90 percent efficiency.

An estimated 15,000 passive houses have been built worldwide, mostly in German-speaking countries or in Scandinavia. Even some schools in Frankfurt are built with this technique. As for the United States, California architect Nabih Tahan, who worked in Austria for over a decade, is completing his family's Berkeley home and heads up a group of 70 Bay Area architects and engineers who encourage wider acceptance of the standards. The irony, however, is that inspectors at the Berkeley home did not designate it as having met "green" codes, as the heat exchanger is an uncommon device in the U.S. and could not get credit in the inspection.

Although in Germany the added construction costs of passive houses are modest, the sophisticated windows and heat-exchange mechanisms needed to make the houses work are not readily available in the United States, therefore the construction of such designs is likely to evoke a much higher price tag. And because a successful passive house requires the interplay of the building with the sun and the climate, architects must be mindful of site location. Researchers are examining the likelihood of the concept working in warmer climates in the reverse, keeping cool air in and warm air out. Those wishing for a "massive passive" house may be disappointed. Quite simply, sprawling homes are difficult to insulate and heat, leaving the ideal size of a passive home at 500 square feet per occupant, a comfortable but not expansive living space. Again, the design is based on conservation, so modesty and practicality seem to encapsulate the list of attributes, as well as to seal the passive home into an airtight module. Sound cozy?