Sunday, October 14, 2012

Air Sealing: Step 04 - Performance Testing

Blower door in the front door
We did our final Blower-door testing today to verify our air-sealing strategy and the house performed far beyond our best estimates! Very exciting. 

Rich Urban from E3 Home Performance Services was nice enough to come out on a sunday morning to squeeze us in before we all head back to Brooklyn. He was really great to work with and walked us through the whole process and even let me play with his super-expensive IR scanner for a little bit! The Blower-Door is a test where a fan gets installed in an opening (usually a door) and the house is either pressurized or de-pressurized by blowing air in or out. This allows you to measure the amount of air moving through the cracks in the house's envelope, mechanicals and windows and to validate all our air-sealing work. 

Rich Urban, E3 Home Performance Services

Passive House specifies that a certified house should have an Air-Change Rate (how often all the air inside a house is changed to fresh outdoor air) of 0.6 Air-Changes every hour (when measured at 50 Pascals of air-pressure). We figured that since we didn't have Passive House windows and that we had some elements, like a big wood-stove and Range vent, these would make us a little leakier than we'd have liked.

0.6 Air Changes would mean roughly 250 CFM of air infiltration. We figured that we would be somewhere north of that, possible up around 400-500 CFM if there were some spots we really screwed up. But turns out we tested at only 175 CFM! (This was testing only the envelope though - when we opened the HRV ducts and the range vent we bumped up to about 250 CFM). But still a really great performance and a big success for the house. 

174 CFM at pressure
So that was all great news and we're very happy. During the test we walked through with Rich and took a look at all the details with his IR viewer. Since the house was depressurized, infiltration air would come leaking into the house through cracks and since there was a large temperature differential between outside and inside, we were able to see the cold air leaking in pretty well (what tiny amount there was). We could also see any thermal-bridging areas or spots where we had problems (there were only a tiny few).

IR view of a window sill. Black is cold, white is hot. The metal spacers in the Marvin windows show up as the dark line around the window. 

All in all - a big success.  Lately its been getting down into the 20s at night up here, but the house was always 55 when we came into work - even without any heat at all. So we certainly knew the house was performing very well, but it is still really exciting to see that proven by the test.