Sunday, November 4, 2007

Passive House Conference: Moving Toward Zero-Energy Homes

I attended the Second Annual North American Passive House Conference last weekend in Urbana, Illinois and my head is still spinning from all the presentations, demonstrations and conversations about ways of reducing and even eliminating carbon emissions from homes that stay warm in the winter and cool in the summer.

The essential component of these super-efficient homes is a structural envelope that is superinsulated (with up to 15 inches of insulation in exterior walls) and super airtight. Passive solar energy from large south-facing windows is used as the main form of heat. And an energy recovery ventilator (such as the RecoupAerator) is used to provide fresh air from the outside without cooling (in winter) or heating (in summer) the house.

Passive Houses are quite common in Germany and Austria where energy costs are very high. But they are not yet well known in North America. The conference drew together builders, architects, engineers and other sustainability-minded folks from all over the United States and Canada together with a number of Germans and Austrians living either in Europe or the U.S. who are involved in some fascinating projects in the U.S. and Europe.

Urbana's own Katrin Klingenberg, an architect who learned about Passive House concepts in Germany (where it is known as Passivhaus) organized the conference and showed attendees the two Passive Houses that she has built in Urbana and another under construction. Katrin is the director of the Ecological Construction Laboratory (e-co lab) in Urbana and also heads Passive House Institute US (PHIUS).

A Passive House can be built for 10 to 20% more than a conventional house of the same size with typical energy savings of 80 to 90%. Some speakers at the conference showed how adding other renewable energy sources such as solar electricity, solar hot water, wind and geothermal energy could reduce energy consumption to zero.

Some interesting technology that I learned about at the conference include research at the Univeristy of Illinois by Ty Newell on using CO2 as a refrigerant, vacuum insulating panels that provide an insulation value of R-30 per inch (such as Vacupor), and indirect evaporative coolers that can cool air down to its dew point (instead of just to its wet-bulb temperature), making these practical for more humid locations such as parts of the midwest and northeast U.S. (see products made by Coolerado). Other technology exhibited at the conference can be found here.

Passive House technology looks like an obvious move in a world where housing and buildings consume vast amounts of non-renewable, greenhouse-gas-producing energy.