Family in Passivhaus; Rolf Oeser for The New York Times
Elisabeth Rosenthal visits a Passive House in Germany and describes their construction:
Using ultrathick insulation and complex doors and windows, the architect engineers [sic] 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.
Rosenthal concludes with a summary of some of the problems with passivhaus design:
Because a successful passive house requires the interplay of the building, the sun and the climate, architects need to be careful about site selection. Passive-house heating might not work in a shady valley in Switzerland, or on an urban street with no south-facing wall. Researchers are looking into whether the concept will work in warmer climates — where a heat exchanger could be used in reverse, to keep cool air in and warm air out.
And those who want passive-house mansions may be disappointed. Compact shapes are simpler to seal, while sprawling homes are difficult to insulate and heat.
Most passive houses allow about 500 square feet per person, a comfortable though not expansive living space. Mr. Hasper said people who wanted thousands of square feet per person should look for another design.
"Anyone who feels they need that much space to live," he said, "well, that's a different discussion."
New York Times
More on Passivhaus design in TreeHugger:
Denmark Debuts First Certified Passive House
The Carbon Footprint of a Renovation vs New Construction
The Third Industrial Revolution
A Passiv Haus in Urbana, Illinois