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Insulating behind window trim vs sealing around window trim

pshyvers | Posted in Green Building Techniques on

I went and sealed around the edges of my window trim a while back, after thermal imaging demonstrated leaking & we had already hit all the other big leaks. I did the side casing to wall, and side jamb to window casing.

I’ve noticed a few cracks I missed (side casing to side jamb) that have dust accumulation, clues showing where air is actively (not just theoretically) leaking out of the building.

But since I did the sealing, I learned that I probably was “supposed” to pull the trim and seal the gap between the window & frame, instead.

At this point, should I go ahead and seal the side casing to side jamb with caulk? Should I strip all the caulk I already laid and seal behind the trim instead? Does the insulating value of expanding foam provide any meaningful benefit? I am generally very attracted to “correctness”, and I like the sharp clean edges of the uncaulked wood trim, but it seems I’m likely to do some damage trying to strip the old caulk.

I’m definitely committing to sealing it as best I can one way or another- as discussed elsewhere, I put in a humidifier for medical reasons, so continuing air sealing remains very important work even though we’ve already got the envelope “pretty tight”. Thanks.

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  1. pshyvers | | #1

    I always forget to add specifics, haven't blower door tested recently but estimate ~1.7ACH, Zone 5 in Colorado (dry, cold climate), two story with basement.

  2. GBA Editor
    Martin Holladay | | #2

    It's hard to get a good seal with the method you chose; after all, casing expands in the summer and shrinks in the winter. Sealing between the rough opening and the window frame is the right way to do it.

    You're right that removing the casing (especially now that the casing is caulked in place) is likely to damage either the casing, the wall finish, or both. Unless you are willing to repair what gets damaged, you'll probably have to live with the results of your mistake.

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