We have some exciting news to report in the often boring subject of building construction details. We here at The Artisans Group exhaustively detail each Passive House to minimize air leakage. Through meticulous use of state-of-the-art gaskets and adhesives, we button up our houses to a degree well beyond anything seen in the rest of the building industry. To confirm that all those seals are functioning, we test our houses using a professionally calibrated third party blower door test.
What does that mean? Well, it starts with a large computer-controlled, variable speed fan that is temporarily sealed into an exterior doorway and ran to depressurize the house to 50 Pascals. This forces the outside air (now at a higher pressure than the air inside of the house) to penetrate any cracks or holes in the building envelope. The rate at which the fan needs to continue sucking the air out of the house to maintain that 50 Pascals is measured and used to calculate the outside air that is penetrating the house through any air leaks in the house. The result is measured in Air Changes per Hour (ACH). To give some perspective, an average American house will perform at around 20 ACH; the new Washington State Energy Code requires a minimum of 5 ACH; and the stringent Passive House certification program requires a minimum of 0.6 ACH. A Passive House has impressive indoor air quality, due to its constant mechanical and filtered ventilation. From an energy performance and low hanging fruit standpoint, functionally a Passive House cannot be too tight.
As a matter of course, we test our houses twice—once in the framing stage and again at completion of the project. We just finished the first of these tests on two of our projects here in Olympia, and (drum roll, please....) we got a .07 ACH on one house and a .06 ACH on the other!
Once we stopped jumping up and down patting ourselves on the back, we did some Google-hunting and found the Guinness World Record holder for lowest ACH is a little house in Alaska that measures at .05ACH. This sparked our competitive spirit, so stay tuned for the results from the final tests once the houses are completely finished. We might get to add “record-breaking” to the long list of things that make us special as a Design/Build firm!
Posted on September 05, 2014
