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Green Living Journal #26 Fall 2014 : Page 21

House buildings using a computer program developed at the Passivhaus Institute in Germany. Building component specifica-tions are combined with climate data to predict the heating de-mand of the building. This is called performance based design because design decisions are based on the predicted perfor-mance. For a Passive House to meet the certification criteria, it will typically use a tenth of the energy to heat as a convention-www.greenlivingpdx.com The O2 Haus, Portland, OR. Photo courtesy of airbnb.com ally built home. To give a sense of how far building technology has come over the past 30 years, here’s an example. The windows that I am using on my current Passive House project in Middlesex Vermont, have an R-value around 10. A Thermopane top of the line window from the 1970s would have had an R-value of 2.5. Making this single change in the window specifications would more than triple the heat loss of the building. Windows, the smooth transparent vertical surfaces, are the furnaces of Passive Houses. Learning to use this simple yet unpredictable energy source, Passive House designers stand on the shoulders of those who came before from the Modernist architects who carefully studied the effects of solar radiation on their glass curtain wall buildings, to the Passive Solar trailblazers who envisioned a new low-impact way of building. Solar radiation is free for everyone, so whether it’s simply taking the advice of Socrates and orienting the building to the south, or building to the Passive House standard, in cold climates passive harvesting of energy from the sun is a must in the 21st century. Indigo Ruth-Davis is a Passive House Institute US Certified Passive House Consultant and builder. He is a partner at Montpelier Construction, one of central Vermont’s leading building performance companies. Issue 26 Fall 2014 21

Port of Skamania

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