May 23, 2014: Testing the air-tightness

Everyone knows that a leaky or drafty building can be pretty uncomfortable to live in. It can also lose a lot of heat in the winter time and end up being a bit of an energy hog. So a big part of the job of making the Greeny Flat energy efficient was to try to make it reasonably air-tight. But how to know exactly how air-tight it is???

The answer is to do a Blower Door Test. I did a lot of Blower Door Testing in my previous career as a Building Analyst in Montana in the States. But I don’t have the necessary equipment here so I called upon some friends from the University of Wollongong’s Sustainable Buildings Research Centre to come and help. Daniel Jones, who helped us with the construction of the Greeny Flat, brought his associate and Blower Door Testing specialist, Craig McLaughlan, and we spent a wonderfully geeky morning playing around with a bunch of really expensive testing equipment. See video link below.

My goal with the Greeny Flat was to reach an air-tightness level of 3ACH50. This stands for 3 air changes per hour at minus 50 Pascals. ACH50 is the standard measurement used to gauge the relative tightness or leakiness of building structures. A super-tight building like a Passive House can be as low as 0.5ACH50 and a really leaky building would be anything much over about 7ACH50. The leakiest building I ever tested in Montana was 19ACH50 but Craig says he’s tested one here in Australia that was 50ACH50. Anyway, 3ACH50 is a good level of air-tightness that is achievable without going to extraordinary lengths or expense. (It is also the “Just right air tight” level that is recommended by Joe Lstiburek who is the guru of these things at the Building Science Corporation). So we are thrilled with the result of 3.25ACH50.

As we had suspected, the major culprits for air leaks were the sliding windows and doors (the casements and awnings showed very little leakage) but given that the overall air-tightness is exactly in the right range we can happily live with things just the way they are. Yay!

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