The concept of the passive house, pioneered in this city of 140,000 outside Frankfurt, approaches the challenge from a different angle. 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.
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.
There are now an estimated 15,000 passive houses around the world, the vast majority built in the past few years in German-speaking countries or Scandinavia.
It never occurred to people to always build homes this way?
Regardless, it's fortunate. Soon we'll want to have not only our water but our air filtered for contaminants -- it's de rigeur, for example, to build new houses in LA with air filters and "air tight" rooms. You don't want the automobile soot, industrial waste, military pollution and carcinogenic diesel smoke to drift in and infect your precious snowflakes and/or meaty wife, do you?