Insulation levels in crawlspace?
Wondering what the recommended insulation levels are for a crawlspace in a mixed climate (IL… bad winter can be -20, bad summer 100+).
I will be insulating the perimeter (along the crawl block walls and across the crawl floor) rather than insulating between the first floor joists. Looking at bug-resistant foamboard (XPS/EPS). The “Tu Tuff 4” vapor barrier will go down first (across the crawl floor and 2/3 to 3/4 of the way up the wall).
I was thinking of about R10 on the floor and maybe R10-20 on the walls.
jt8
“The cynic is one who knows the price of everything and the value of nothing.” –Oscar Wilde
Replies
The R20 on walls sounds good but I don't know about the R10 across the dirt floor. I might consider a 3-5' skirt similar to an outside skirt for around the interior floor perimeter.
I'm researching the same basic thing, and what I've seen so far (old threads here and by googling various word combos) is that XPS is the preferred type. With a sealed crawl space (sounds like you're going to seal yours) I think you need to pay closer attention than normal to the rim joist space insulation. Slickest way to take care of that seems to be set your rim joist in a bit and install strips of rigid on the OUTSIDE of the rim joist, under the sheating, building paper and siding. Works well with "I" joists where you can fit a stip of XPS on both sides.
OR, after the joists are laid and before the sub floor goes down, have a spray foam contractor come in and foam the rim space with closed cell poly.
OR, crawl in there afterwards and put in blocks of 2" rigid and seal with foam.
Important detail is to make sure that you seal the edges of the vapor barrier to the block walls. Don't know exactly how you would do this... bead of acousti-seal and lathe powder nailed in to the block? Maybe just the acousiseal would hold but I wouldn't count on it. Or go all the way up to the plate and acousti-seal and staple.
Nice detail is to wire for plenty of lights in there. Important for annual inspections and in case you need to access utility lines in there.
Edited 12/6/2005 3:14 pm ET by johnnyd
OR, crawl in there afterwards and put in blocks of 2" rigid and seal with foam.
That had been my original plan for insulating the rim joist, however that got a wrench thrown at it with the discovery of 'little white ants' (which are being treated as we speak). So that means whatever I install around the rim joist will need to be removeable so that it can be inspected for 'little white ants' at a later date.
Important detail is to make sure that you seal the edges of the vapor barrier to the block walls. Don't know exactly how you would do this... bead of acousti-seal and lathe powder nailed in to the block? Maybe just the acousiseal would hold but I wouldn't count on it. Or go all the way up to the plate and acousti-seal and staple.
The lady at Sto-Cote recommended using Great Stuff to seal it to the block walls, and their special tape to seal seams. I think in a FHB article they screwed pt 2x4's to hold it up and then accoustic sealed the edges.
Nice detail is to wire for plenty of lights in there. Important for annual inspections and in case you need to access utility lines in there.
That was also my first thought. Put some flourescent shop-light type lights down there and they all fire on one switch. Really l light the place up. Upon reflection...maybe i should just put a 20 watt incandescent in that 99 cent porcelin fixture. After all, I'm gonna be selling it and I wouldn't want them to see TOO well ;)
jt8
"The cynic is one who knows the price of everything and the value of nothing." --Oscar Wilde