Polyurethane vs Acoustical caulk for Air Sealing?
I get that caulking interior joints, gaps, and junction points is a crucial step in air sealing a home but I’m not 100% clear on what specific caulk I should use. In particular, I’m unclear on polyurethane vs acoustical.
I’ve used acoustical caulk before to help seal up my home theater. It’s pretty ubiquitous in that realm. In particular, I used OSI SC175 and liked it. It never hardened in the time that it was still exposed, much less shrunk.
Like I said, acoustical caulk is extremely common in the theater and studio space, but I’ve not found too many references to it being used when building an air-tight home. Instead, the focus tends to be on polyurethane caulk. I don’t have any experience with that type of caulk. Cost isn’t everything but it’s also not nothing and SC175 is much MUCH less expensive than any polyurethane caulk I’ve found, so if they are comparable, then I’d much rather use acoustical.
Alas, most of the articles I’ve found compare acoustical to “normal” and polyurethane to “normal” (or silicone) but never to each other.
So what are the thoughts between the two of them? Are they comparable in the end for this purpose?
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Replies
Nothing wrong acoustical caulk. The water based ones are much easier to clean up than urethane.
I typically use Green Glue sealant around joints that will be covered. There is nothing wrong with using it as long as it is not exposed to UV.
For a joint that will see movement, you still have to install backer rod before the caulk.
Go with manufacturer recommendations. I find it notable that reputable manufacturers (like Tremco) don't recommend it for general exterior air sealing. Not clear to me why - a guess is that it is easily pushed out as a crack varies in width down to zero.
"Tremco Acoustical/Curtainwall Sealant was developed for acoustical sealing
of drywall partitions, curtainwalls, corridors and party walls. This sealant also
is used as a lap joint and perimeter sealant for polyethylene vapor barriers
over fiberglass batt or other insulations and may be used in contact with
polystyrene."