Insulated Wood Headers
Question about the level of “perfection” that is required for insulating wood headers: Climate Zone 4A, 2×6 exterior walls, and I detailed the headers with the required number of vertical 2x10s (i.e., I didn’t do triple 2x10s in non-load bearing walls). The 2x10s are held to the outside face of the wall. For a single 2×10 condition (~4” void) the insulator was able to dense pack cellulose. For a double 2×10 condition (~2.25” void), I installed 2” of XPS with a half inch gap and foamed in the edges. For a triple 2×10 condition (~.75” void), I caulked the edges for air sealing.
At one location, I noticed that the rigid foam had pushed towards the inside of the house while the foam was curing, which would leave a void between the foam and the 2x10s. Should this rigid foam be removed, re-fastened to the header, and re-foamed? Or, is it okay that the foam is not perfectly flat against the header?
At the areas where I caulked, I’m assuming that air sealing is better (less just for air movement and condensation forming) than just leaving the edges uncaulked. Correct?
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Replies
David,
Q. "At one location, I noticed that the rigid foam had pushed towards the inside of the house while the foam was curing, which would leave a void between the foam and the 2x10s. Should this rigid foam be removed, re-fastened to the header, and re-foamed?"
A. Nail it with cap nails.
I agree. I’ll take this one piece of foam out, clean it out, nail it, and re-foam it tonight. But I want to make sure I understand the principle…is a small gap a bad thing (like, I tear out drywall and double check every single one) or is it okay? My gut tells me a small gap is okay, because no wood-to-insulation interface is ever going to be perfectly aligned. On top of that, there are gaps/mis-alignments in multi-ply wood headers all the time.
David,
Q. "Is a small gap a bad thing (like, I tear out drywall and double check every single one) or is it okay?"
A. It's OK.