Ventilation for Small Space
I’m currently finalizing the contract with my GC for finishing a currently-unfinished in-law space over a 2-car garage (SE PA, border 4A/5A)
It’s about 400 sq ft with vaulted ceilings, and will have a 400 cfm hood for a hot plate and a bathroom vent fan. We’ve already installed a 1-ton Hyper Heat split unit with ceiling cassette.
My original thinking was to spray closed-cell foam on the walls, ceiling, and under the floor (the ceiling of the first floor of the garage) in order to ensure a good air barrier, but my GC is suggesting doing batts in the floor because they’re concerned we’ll end up so tight that we’ll need MUA for the hood and bathroom fan.
They raise a good point, and now I’m also concerned about IAQ if we go the full-spray route. With that said, it feels off to deliberately leave the place leaky rather than be specific about where and how our fresh air makeup is taking place.
I wonder if we should be thinking about, rather than an intermittent-use ventilation fan in the bathroom, having some kind of always-on (whole-house ventilation) fan paired with MUA or even just doing a (very small) ERV somewhere.
According to this article https://www.greenbuildingadvisor.com/article/multi-speed-bath-fans-for-whole-house-ventilation
… we’re looking at << 20 CFM for always-on ventilation, which seems quite tiny and might only be available in a few specialized SKUs I can’t find right now.
Or should we put batts in the floor and air-seal decently well and assume we’ll be leaky enough to not worry about MUA? GBA anathema I know but bears asking.
Any thoughts on this? Products I should be looking at?
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