Elisabeth Rosenthal examines the new German Passive Houses, which “get all the heat and hot water they need from the amount of energy that would be needed to run a hair dryer”:
Using ultrathick insulation and complex doors and windows, the architect engineers a home encased in an airtight shell, so that barely any heat escapes and barely any cold seeps in. That means a passive house can be warmed not only by the sun, but also by the heat from appliances and even from occupants’ bodies.And in Germany, passive houses cost only about 5 to 7 percent more to build than conventional houses.
Decades ago, attempts at creating sealed solar-heated homes failed, because of stagnant air and mold. But new passive houses use an ingenious central ventilation system. The warm air going out passes side by side with clean, cold air coming in, exchanging heat with 90 percent efficiency.
A market has developed in Germany for the sophisticated windows and heat-exchange ventilation systems needed to make passive houses work properly, but they are not readily available in the United States yet — and US residential building tend not to even have ventilation systems.