I've been reading about passive solar for decades now, and I think it's been given short shrift in the solar heating community. Nice to see it's taking off again:

DARMSTADT, Germany — From the outside, there is nothing unusual about the stylish new gray and orange row houses in the Kranichstein District, with wreaths on the doors and Christmas lights twinkling through a freezing drizzle. But these houses are part of a revolution in building design: There are no drafts, no cold tile floors, no snuggling under blankets until the furnace kicks in. There is, in fact, no furnace.

In Berthold Kaufmann’s home, there is, to be fair, one radiator for emergency backup in the living room — but it is not in use. Even on the coldest nights in central Germany, Mr. Kaufmann’s new “passive house” and others of this design get all the heat and hot water they need from the amount of energy that would be needed to run a hair dryer.

“You don’t think about temperature — the house just adjusts,” said Mr. Kaufmann, watching his 2-year-old daughter, dressed in a T-shirt, tuck into her sausage in the spacious living room, whose glass doors open to a patio. His new home uses about one-twentieth the heating energy of his parents’ home of roughly the same size, he said.

Architects in many countries, in attempts to meet new energy efficiency standards like the Leadership in Environmental and Energy Design standard in the United States, are designing homes with better insulation and high-efficiency appliances, as well as tapping into alternative sources of power, like solar panels and wind turbines.

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.