I’m a little late to this party, but so-called “passive houses” have been lighting up in the blogosphere in the wake of this New York Times article:
> 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.
In the ideal case, passive houses require no furnace, no air conditioners, and, in fact, no thermostat. The airtight dwellings maintain a perfectly even and comfortable temperature by means of a ventilation system that automatically brings fresh air in from the outside, heating it to the proper temperature via exchangers and other low-energy systems. Even in fairly harsh climates, such homes “get all the heat and hot water they need from the amount of energy that would be needed to run a hair dryer.”
Passive homes have three essential elements:
1. Superinsulation. Although not strictly necessary, passive houses usually have a boxy exterior shape that makes it easier to maintain a good thermal envelope.
2. Efficient heat recovery. Passive homes have ventilation systems that draw a continuous supply of fresh air. Incoming air passes through heat exchangers that reclaim the energy in outgoing warm air. If necessary, incoming air can also be passed through underground ducts to pick up geothermal energy.
3. Passive solar heating. Southern-facing, unobstructed windows with “triple low-
emissivity glazing and superinsulated frames” capture more solar energy than they let out.
Although tuning and perfecting the systems has taken over a decade, all of these technologies fall into the category of “not rocket science,” allowing passive homes to achieve enormous energy savings with only slightly increased construction costs:
The Passive House Institute has conducted a fair amount of research into user acceptance of the system. That is, do homeowners like their houses, and how well do they adjust to the mild behavioral changes such houses impose? The answer appears to be that they like them quite well. Passive houses keep a more even temperature than traditional houses — no more cold bathroom tiles or hot, stuffy rooms. And owners of passive houses tend to spend some of their energy savings on increased comfort. That is, they keep them a bit warmer than owners of traditional homes. Given that their houses have no radiators, that’s a bit of warmth they’ve earned.