mudroom floor and wall insulation ideas

I’m trying to find the best DIY insulation strategy for a small mudroom – maybe 10×10. The attic above it will be blown cells. I need to insulate 3 walls and the floor. One wall is shared with the garage – DW on both sides. All 2x construction, vintage 1960. One wall outside wall has the electrical panel. I don’t see bringing a foam guy in for this of small a room.
I thought about Mooney but it really only works for maybe two of the 3 walls, because the 3rd wall can’t be thickened for a variety of reasons – in particular problems with the inswing exterior door. Also I can’t find a rental cell blower that is strong enough to dense pack – they are all 110v and I hear you need 220v or gas for dense. I’m left with cutting sheets of polyiso to fit between and foaming gaps but there still a lot of thermal shorts that way. How well does that work anyway? Any other suggestions? I’m fine with all 3 walls being different techniques – just whatever works best for each.
Also I’m unsure of how to do the floor best because its cantilevered over a crawl space (crawlspace has a concrete floor). I thought of nailing foam to the undersides of the joists. But mudrooms tend to be wet places at times and if any water gets through the finished floor (or leaks from a pipe below the finished floor) I don’t want it trapped on the topside of the foam – next to the joists. Is there some way to make this a little safer from that point of view – some sort of drainage/drying system. Any ideas would be great.
Thanks for any help.
-Brian
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Rigid foam panels with expanding foam around the perimeter is really good stuff for wall cavities. Better than dense-pack, but more costly and labor intensive. Good solution for a small area, where the framing is irregular, or there are a lot of small cavities.
I have dreams of a mudroom with a floor that pitches to a floor drain. That way you could hose it down.
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I'm really more concerned about a pipe leak below the finished floor but above the rigid insulation. A floor drain would be nice but I think you'd need a vent stack and I don't really want to get into all that.Have you used the rigid foam in a wall cavity? I think it would be nice for the garage wall because of the DW on both sides, but I'm not sure how error prone the installation would be.
Edited 7/31/2006 1:53 pm ET by grandizer
"Have you used the rigid foam in a wall cavity? I think it would be nice for the garage wall because of the DW on both sides, but I'm not sure how error prone the installation would be."
I do this frequently. Actually, I was doing it yesterday.
Technique is foolproof in the sense that there is near zero air movement within the cavity. Just cut the panels a bit small to allow enough clearance for your expanding foam straw or gun (gun is better) nozzle. Temporarily secure in place with screws (+ fender washers) or scraps of wood. Inject expanding foam completely around the perimeter. Once hard, use "snap-off" utility knife to trim flush. Slower going than other insulation methods, but the results are tough to beat.
Pipes would ideally be enclosed in a foam chase but with no foam on the warm (inside) side.
I'm not sure you can't dense-pack with a rental machine. It might take a while, but if you close down the material flow as much as possible, I'd think it would work. It doesn't have to be that dense to stay put - Anything above the natural settled density of cellulose (I think that's about 2.5 lbs/cubic foot, but check around) and you're good. You can verify what you're getting by calculating the volume of a couple of stud bays and seeing how far a bale or two takes you.
Andy
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