Air exfiltration and ice formation in insulation
My windows were replaced about 5 years ago with new vinyl casements. The space between the framing and the window was packed with batt insulation. This summer, I removed the interior trim around one window because I was going to renovate that room. The window has been without that trim ever since . The temperature this week has been about -15C. You can feel the cold air around the window. It’s more than just convection; there is draft around the frame. This afternoon, I removed the batt insulation and filled the gap with foam insulation. The batt insulation that I removed was packed with ice, probably due to the water vapor freezing as the air escaped through the gap. And I mean solid chunks of ice and not just a little frost. A knew that I could expect frost but was surprised by the amount of ice. Can moist air escaping and freezing in the insulation create that much ice in a wall ?
Replies
Yep, that's why there are
Yep, that's why there are vapor barriers. It was likely made worse by the fact that you probably didn't really "pack" in the insulation, but just stuffed it in sorta snug. When using fiberglass around windows like that it really needs to be PACKED tightly, so that no air can get through. And of course the foam is a better idea.
Likely the other windows in your home are in need of the same foam treatment -- it can make a significant difference.
The windows were replaced in batches by different contractors (same company but different crews). Some were done with foam; others with batt. I've been replacing the batt as I renovate the corresponding rooms.
I think it was made worse by not having the trim in place. The other windows have trim which was caulked on both edges, thereby limiting the exfiltration.
After I had removed the insulation, I could see the j-trim on the exterior. It definitively was not airtight.
It's more than just
It's more than just convection; there is draft around the frame.
Convective air flow is draft. It's one and the same. FYI
What I meant to say is that there is real air flow to the outside as opposed to a "draft" that one would feel in front of a cold window (due thermal convection and/or radiation)
That's a real fine window
That's a real fine window contractor you have there! No caulk on the outside, no foam on the inside. Makes one wonder what else was 'overlooked'?
The outside of the house is clad in aluminum siding so I would not expect caulk. There is new j-trim at the edge of the siding and the j-trim is caulked to the window frame. Without removing the siding, I realise that properly sealing the window from the exterior is difficult.
I would hope that water getting behind the siding will flow down the j-trim and drain as per a typical installation. So while water probably can't get in, moist air certainly can get out.
I plan to eventually change the siding and the windows will all be properly flashed at that time.
The contractor has since gone out of business. They had good references, had good BBB ratings, and were recommended by the window manufacturer (good windows by the way). Unfortunately, the quality of the work varied depending on which crew did the installation.