Drew McDowell, the Passive House Rater, came in on Saturday and performed the fourth and final blower door test. The prior tests were all done manually (I believe they’re called “single source” tests); meaning that the Rater watches fluctuating readings on the meter and uses his judgment and observation to determine an average flow rate. In this fourth test, Drew used that method as a starting point, and came up with a value of about .28 or .29 ACH. However he then followed up with a computerized test where the PC took dozens of readings in ten-degree increments (i.e. at dozens at 10 Pascals, dozens at 20 Pascals, dozens at 30 Pascals, and so on up to 70 Pascals) and then averaged and charted the results, and used the collective information to refine the computer’s 50 Pascal readings. Also, unlike the manual test, this computerized test was performed in both directions; first while blowing air out of the house (i.e. depressurization), and then while pulling air into the house (pressurization).
The result came in at .3 ACH @ 50 Pascals. Copies of the reports are visible below:
This was up a bit from the prior test (.24 ACH), which was performed before the installation of insulation. I’m not sure how that happened, being that it seems to me the insulation and drywall should have made the house tighter, if anything. But regardless, I’m very happy with the result.
Two observations worth noting.
First, as discussed in a (much) earlier post, we used a trio of products by Prosoco to seal the gap between the windows and sills. The final product in the trio, R-Guard Air Dam, is essentially a very robust caulk that is used to seal the gap after the installation of a foam backer rod.
The windows were installed about a year ago. We’ve been in the house now for almost two months, and I’ve been chipping away at the interior work as time allows. Recently, when I began working on interior trim, I noticed a small gap in the R-Guard around one window. That prompted me to inspect all of the windows, which led to the discovery on similar gaps at three others. I suspect that the gaps were due to human error at the time of installation; the thickness of the application in those areas appears to have been very thin and the product appears to have simply shrunk. Fortunately, the gaps were easy to find and seal because I hadn’t yet trimmed out any of the windows. But the discovery caused me to think that my slow pace paid off. Had the interior been finished by a hired trim carpenter, or had it been finished immediately after the drywall was finished (which was last spring), those gaps would have never been discovered. To be clear, none of the gaps were deal breakers. But collectively, get enough small gaps and I imagine it’s possible to break the .6 ACH limit.
The second point worth noting is that, during the final blower door test Drew and I went around the house with the thermal camera and smoke pen looking for leaks. The only weak points we found were the exterior doors (all ThermaTru), which I’ve talked about extensively in a prior post. Again, obviously the leaks weren’t deal breakers. But frankly I expected much better given the amount of money those doors cost. If I had the chance to do it over, I’d be looking at Intus for the doors as well as the windows.