Rockwool plus MemBrain or rockwool plus airtight drywall?
knh1vt
| Posted in Energy Efficiency and Durability on
I live in central Vermont – zone 6. House is 1974 mostly renovated 2 x 4 construction. North wall on ground floor is all original and from what we’ve seen elsewhere on the house, probably has remnants of moldy fiberglass insulation.
Siding is clapboard. No idea what’s under it (we bought the house recently).
What’s the most energy efficient way to insulate that wall? We will rip out the wallboard and start from there.
Instead of rockwool (possibly) I’ve been looking at the wood fiber insulation coming out of Maine. We don’t want to use foam.
Can anyone advise? Given the IRA incentives we’ll hire it done.
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Replies
On the IRA rebate, Rockwool brand is Energy Star rated. ThermaFiber mineral wool is not Energy Star listed.
The wood insulation, while might be great, is also not listed on the Energy Star website.
https://www.energystar.gov/saveathome/seal_insulate/certified_insulation/certified_insulation_products
I think it needs that certification to be submitted for the rebate.
If you'll be replacing the siding and adding rigid foam, and assuming you go with at least the recommended minimum R value of rigid foam for your walls, then you don't really need the interior side vapor retarder -- although using it will provide additional insurance against moisture problems. If you are NOT going to be using exterior rigid foam, then you NEED the interior side vapor retarder to keep moisture out of the wall. I'd detail the drywall airtight in either case.
BTW, my preference is to use more-than-minimum levels of exterior rigid foam, and also an interior side smart vapor retarder (typically MemBrain, because it's cheapest), to make for a more robust assembly. I always detail the interior drywall airtight on exterior walls. On interior walls, I only detail the drywall airtight when it matters, which isn't usually in all areas.
Bill