Passivhaus comes to the U.S.

In contrast to the DIY-solar featured in my last post, I would say that Katrin Klingenberg -- an architect working to bring the German Passivhaus design standard to the U.S. - occupies the high tech end of the green building spectrum. I attended a workshop she gave at the NESEA BuildingEnergy10 conference last week.

What is Passivhaus?

Passivhaus is a voluntary standard for energy efficiency in buildings; you might think about is as the German version of LEED, except for the following key differences:

1. Unlike LEED, which tends to reward adding on green features to an existing [and not necessarily sustainable building design], Passivhaus is an integrated design process that addresses the overall plan and performance of a building.

2. Passivhaus is way stricter than LEED. Someone in the industry told me recently that a LEED-certified Platinum building wouldn't even pass regular building codes in Germany, let alone measure up to energy efficient standards.

In order to attain the Passivhaus standard, a building must have an annual heating demand that does not exceed 15 kWh/sq m per year of heating energy and 15 kWh/sq m per year of cooling energy. The total energy consumption must not be more than 120 kWh/sq m [3.79 x 10^4 btu/sq ft] per year. And the air leakage must be less than building must not leak more that 0.6

Just for reference, a house built to Passivhaus standards in the U.S. would use between 75 and 95% less energy for heating and cooling than a building that would meet today's US energy efficiency codes.

How does a Passivhaus work?

Klingenberg discussed the following principles of Passivhaus design at her NESEA workshop:

+ continuous insulation [gaps in building insulation equal heat leakage, which means inefficiency]

+ no thermal bridging [a thermal bridge is basically a break in insulation that usually happens at connection details, when two materials that are poor insulators come in contact with one another]

+ compact building shape [a building with lower surface-to-volume ratio is more efficient to heat]

+ airtightness and minimal moisture [air leakage means heat leakage]

+ balanced ventilation and heat recovery [through the use of mechanical heat recovery ventilators, HRV's, or energy recovery ventilators, ERV's]

+ optimal solar orientation [to take advantage of solar radiation energy]

+ efficient appliances and lighting [for obvious reasons]

+ user friendliness and education [because the people who occupy a building must know how to operate it in the most efficient way possible]