RandallBagsyFoot t1_iug8rrn wrote on October 31, 2022 at 2:12 AM

HVAC guy here. Looks like the Microwave vent was added either as a renovation or as a last minute fix during construction. It should be buried in the studying, not sitting atop it. That vent won't reach high temperatures at all, so any sealant is fine. Depending on your climate, insulating the vent with pink fibreglass could be a good idea. #1 to prevent condensation dripping down the wall cavity and growing mold and #2 for heat loss.

***Ah, "newly installed microwave" I see.

RatArmy OP t1_iuhpo5r wrote on October 31, 2022 at 12:48 PM

Yeah the microwave itself is new that I'm putting in. But there was an older microwave there and the vent was previously installed.

When I took the old one down, that's what I noticed that the vent was basically uninsulated.