Passive Houses require a fraction of the energy to heat and cool as traditional designs, so why aren't we all living in one?

I've been reading a great book about energy in the United States, Maggie Koerth-Baker's Before the Lights Go Out, over the last couple of days. I'll talk more about the book next week, but it introduced me to an idea that's so cool I couldn't wait to share it--Passive Houses.

The concept of the Passive House is straightforward. It's a home that's designed and built in such a way that it gets most of the energy it needs for heating from passive solar or ambient internal sources--warm stuff inside the house, like people, lighting, computers, or cooking. As a result, typical Passive Houses require minimal or no active heating or cooling, even in cold climates. What's the benefit? Passive Houses will require 90% less energy to heat than a similar size house that uses traditional construction techniques.

Photo Credit: Flickr user PG via Creative Commons

As someone who lives in a 50s-era house with virtually no insulation and single-pane glass, this sounds like magic to me. It doesn't really get cold in California, and we still have to run the heat all the time. Here's how it works.

Passive House builders follow voluntary standards established by the Passivhaus-Institut in Darmstadt Germany to achieve this efficiency. During construction, the homes are built differently than standard houses--they have thicker walls, much more insulation, and they're airtight.

To circulate air in and out of the house and avoid perils like radon gas, the houses are equipped with a controlled ventilation system. Depending on the climate, the ventilation system uses heat exchangers and fans to exhaust the air in the house every few hours, and warm inbound air in the winter and cool it in the summer along the way.

Image Credit: Passive House Institute US

The windows are placed to take most advantage of solar heating and minimize leakage--the largest windows face the equator and windows on the opposite side are typically very small. Additionally, the windows use triple-pane glass and include insulated seals and frames, which are uncommon in typical construction.

Passive House construction also removes thermal bridges between the inside and outside of the house. Thermal bridges, like fireplace chimneys, clothes dryer vents, and holes punched for wiring, allow warm air to escape the house and let cool air in. Removing drafts makes these houses feel much warmer, but making your home airtight requires some novel technology--clothes dryers that operate using a different principle than the one's your familiar with, and they may not work as well.

Passive houses come in all shapes and sizes, modern and traditional designs. There are 10,000 to 15,000 Passive Houses in Germany, Austria, and Scandinavia today, but only a handful in the US. They're more expensive to build than a traditional house, but the long-term benefits are fairly large. Of course, if you're only going to live in a house for a few years, you may not care about long-term benefits as much.

If Passive Houses are something you're interested in, post a comment below, and we'll see if we can track one down to visit and take a tour.