Air-Sealing and Insulating Floor on Piers
Hi,
I’m looking for advice to fix my cold floor on piers. We’re in zone 4a.
Current assembly is: carpet, pad, 3/4″ plywood, 9- 1/2″ TJI 16″ OC, fiberglass batt, 5/16″ fiber cement Hardie Panel
This space is the master bedroom which was an addition from 2004. We’ve disconnected the HVAC pipes which are run in two joist bays and located a mini-split into the closet. All of the HVAC is now in the conditioned space.
Blower door shows leaks along the plywood seams in the floor and around the room perimeter at the floor. Plan to tape plywood seams with Tescon Vana and caulk perimeter with Contega HF when the carpet is replaced.
Looking for advice on how to best air seal/insulate the floor. The addition is on a slope and is approximately 6′ to 14′ off the ground. Floor space is approximate 17′ x 17′.
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Replies
Any thoughts on dense packing cellulose?
mgensler,
While you have the underside open to insulate (and I don't think it makes much difference whether you use cellulose of batts), I'd add a continuous layer of EPS foam before replacing the cement board. That will reduce thermal bridging, reduce air-leakage, and up the R-value of the floor.
Thanks. I was wondering if I could get by with drilling holes and having it dense packed, leaving the batts in place. If that isn't recommended, I would remove the Hardie and batts..I would air seal the rim joists with closed cell, install mineral wool, eps or polyiso, and then install Hardie.
mgensler,
I don't have enough experience with dense-packing to know if that would work. I suspect you will end up with voids, or uneven coverage, but I'm just guessing. Exposed floors are a bit unique in that they are one of the few places you constantly touch - and 91/2" isn't much depth to protect them. Even in my mild PNW climate I always include underside foam.
You don't need closed-cell spray foam to get good air sealing. Open cell can work at least as well.
It is sometimes possible to remove batts without completely opening the bottom--just open a 1-foot strip and pull them out.
Thanks. All good ideas. I will do some exploration to see if the batts will pull out. Hate to demo the whole thing as working safely on the slope won't be easy.
I agree. I'd explore all options to avoid working over your head on a sloped site. It's probably the job I hate most, and it's very difficult to maintain good workmanship.