Here’s another crawl space question.
It’s a wide open space, varies in depth from nearly 5 to eight feet. The walls are block. The floor above is joist and plywood, radiant heat, 1 1/2″ mortar, then ceramic tile. Boiler is in the crawl space.
I bought the insulation (R 11 FG) to go between joists but now I’m thinking the better place for it might be draped against the block walls. A vapor barrier against the block is a given.
So, what do you think? Walls or joists? It’s a radiant floor and we use a wood stove quite a lot. If I did the walls I’d probably pull some of the heat from the woodstove down into the crawl space to warm the floor a bit.
Thanks folks, the house is in Montana.
Lee
Replies
Hi Lee. Is there a concrete slab in the crawl? If so, I'd consider insulating the walls with either eps foam as in my basement article in FHB 169, or rigid fiberglass board insulation. Still, with radiant heat above, it probably makes sense to insulate the floor. Otherwise, you're going to raise the temp of the crawlspace considerably. That might create a large enough delta-T to call for a surprising amount of wall and floor insulation.
If there's no slab, then I'd look at the FHB archives for this article from issue 153:
SEALING A CRAWLSPACE
by Larry Janesky
Close the vents and let a heavy-duty vapor barrier keep moisture, mold and radon out of the living space
Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Nope, no slab. The budget won't allow for more insulation than what we have on hand for now. There's enough R-11 to do either the ceiling or the walls but not both. Payback is a consideration since we might list the house in the not too distant future, it's up in the air.Thanks Andy,Edit: I just looked at the blurb on Janesky's article. Moisture is not a problem here unless too little is a problem, we are in a high dessert.Lee
Edited 10/10/2005 9:56 am ET by LeeGrindinger
Moisture may not be a problem, but what about radon?
I'd still insulate the floor. Unless you insulate the ground, insulating the walls only takes you so far. The ground under your house comes close to being an infinite heat sink. And unless you spend a lot of quality time in the crawlspace, in your case I'm not sure that conditioning it makes a lot of sense. The only hesitation I have comes from your boiler being in the crawl. By insualting the walls, you wouldn't lose so much of it's scrap heat to the outside.
I can tell you from personal experience with radiant floor heat that not insulating below it affects its performance in ways you won't like. It took me a couple of months to insulate my floors after moving in. My basement walls are ICFs, about an R-30, so I figured that there was no need to insulate below the radiant. Well, I roasted in the basement until I insulated those tubes. Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Dang, I hate insulating overhead....We've been in the house around 7 years, I guess it's time.Thanks Andy.Lee
That's one reason for a Tyvek suit. Under $10 at most paint stores.Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.