Insulating cold floor, keeping plumbing serviceable?
I have a question about a situation that a relative has encountered. Zone 5 (SE Michigan), an addition has been added to an old house. The addition has an exposed floor on piers, built with trusses. There is some pink batt insulation near the top of truss cavity, and two inches of foam (XPS) covered by plywood at the bottom. The problem is that the (pex) plumbing which runs from main house and then along bottom of floor has frozen up repeatedly. I suspect that airsealing is part of the problem, plus it's hard to avoid voids with the batt + truss combination…and now that I’ve actually opened it up to look, I see that there is a roughly 4” void above the fiberglass batts. Since the perimeter walls below have not been insulated, this void is likely the primary culprit.
So, I would like to remove the batt insulation, pack in cellulose, and reinstall the 2” foam and plywood.
1) Remove everything, install netting/screen, blow in cellulose, then cover with rigid and plywood, OR, reinstall rigid and plywood first and then blow cellulose into a confined space? I’m kinda leaning toward using netting and blowing in insulation so that I can see what is going on, especially since the trusses are more likely to create voids than dimensional lumber.
2) How to make plumbing serviceable? One of the spaces between the trusses contains a bunch of plumbing, both pex supply lines plus PVC drains. The pipes are in the upper third of the cavity, roughly, but I don’t think they can be moved up against the floor. If we choose to blow in insulation, how can we make the “plumbing chase” between the trusses serviceable? I’m thinking of stuffing that cavity with batt insulation (Roxul ComfortBatt maybe, fiberglass otherwise) prior to netting and blowing cellulose.
Oh, just to make it more fun, there is only about 18” between ground and bottom of plywood. Floor area is 8x12 feet.
Posted Aug 15, 2014 10:02 AM ET
Other Questions in Energy efficiency and durability
Can I put rigid insulation under patio pavers, and should I have a permeable system right against the house?