Energy Revolution in a Brooklyn Townhome
Air Leakage Testing a Moderate Success
We recently conducted a preliminary test of the air leakage in the house by using a blower door and an infrared camera. While we are not close to the Passive House standard of 0.6 ACH50 which for this house is 300 cfm50, the test was a success because we were able to come up with a system to address the leakage points that still exist. When we tested the house with the blower door prior to the start of construction the house was at 8500 cfm50. A blower door test that we did prior to the new year and before all of the window area, cellar, and addition spray foam was installed was a disappointing reading of 7100 cfm50. The next blower door test yielded 4100 cfm50 which is still higher than the code requirements for new construction at 5.5 ACH50 or 2750 cfm50. This was after getting the final main areas of spray foam installed.
Because we still had a long way to go we needed a method that would pinpoint our leaks more exactly. We started by using temporary heaters to bring the house temperature up to around 50-60 degrees (still significant stratification due to air leakage), and then turned the blower door on for brief periods to draw in the outside air which was around 30 degrees. With our Flir i7 infrared camera, we went around and looked for the cold points along all of the walls. The air leaks were surprisingly easy to see and it was the first time that I could prove that the spray foam insulation was not performing as well as expected in terms of a continuous air barrier. We had holes in the middle of the spray foam in some places even with 3″ of depth and many of our corners did not perform well. We used a low VOC spraypaint to quickly mark all the areas that we found and over the next week filled them all in. Once we ran the test again we got down to 2,500 cfm50.
Still a ways off, we repeated the testing method with the blower door and the IR camera and found more leak spots. Our last test as of the begining of March is at 2,100 cfm50. I would like to get the numbers down to 1,000 cfm50 prior to drywalling all of the walls. Because of the long lead time of the German windows, we can’t wait for their installation before we have to close up all of the other walls. This is nerve-wracking because it would be much better to leave everything open, install the windows in an air tight way, and then test everything again. This way we could be assured of reaching the 300 cfm50 required prior to sealing off any areas.
We are in the process this week of detailing more leak points in the envelope and will be putting a lot more man power into tackling this issue. We still have as a backup our drywall layer as a secondary air barrier which we are planning on air sealing anyway, but I don’t want to rely too heavily on that because of the large increase in surface area of the drywall layer as opposed to the exterior wall sealing.
This is an image around the chimney header just under the roof decking taken while the blower door was running. The blue area is the cold air leakage streaking across the underside of the roof deck.