Guy Marsden - insulating door and window framing

During the energy audit that we had done on the house last month they ran a blower door test to evaluate the air leakage of the building envelope. The total leakage came to about 120 square inches which is pretty good. So while the big fan was sucking air out of the building we walked all round the building looking for cold spots with our hands and a thermal camera. What we found was cold drafts coming from behind the door and window trim. The images below show the thermal camera image of the dark blue (cold) air that is blowing in around the front door trim. We marked each cold spot with a post-it note so I could deal with them later.

I removed the door trim to find that the builders had neglected to insulate the space between the framing and the door frame itself. This gap ranged from less than 1/4" to over an inch in some windows. The solution was to squirt Great Stuff foam into the gap, totally sealing and insulating the space to prevent air infiltration.

I also found several windows with huge un-insulated gaps, one that required almost a full can of Great Stuff foam to fill. I'm sure that I have removed many square inches of air leakage at this point. Some windows were packed with fiberglass which is the typical way to insulate the framing space, but I prefer the total seal that foam provides. A friend recently told me that upon opening up his walls, he found that water vapor had been condensing on the fiberglass in the trapped air space during the winter which was beginning to encourage rot in the framing of his windows. Later in the winter we noticed that we no longer needed to run a humidifier in the bedroom because the humidity level in the house was higher on average. This is a clear indication that sealing those leaks made a difference.


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