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Fritz
spray foam for crawl and roof

we're looking into SPF for these spaces.
The crawl is very tight, probably 6" to 18" below the joists, which are 6".
T or F? For crawl space, close cell is better idea for water resistance and R value?
Are all SPF close cell products basically the same?

Our roof will be a project this year.
It is a cathedral with probably 6" joists also.
If we redo the sheathing, is spray in a good choice or SIPs?
And what Is the best idea for preventing ice dams on the roof?
We're on Long Island and just last week we had an ice dam that ripped off and twisted part of a gutter.

scfd529
Re: spray foam for crawl and roof

Spray foam should be great for both of those applications. Not only does it give good R values and seal ALL air voids, but there is nothing for moisture to feed on and end up creating mold. I would say you wouldn't go wrong with that application.

I'm from Kansas and though we do get a lot of snow and such, i've never had to deal with ice dams. I think they make metal....i guess you would call them flashings, that slip under the shingles and clip onto the inside of the gutter and allow rain to drain into the gutters still at a rate of over 2 inches an hour but also let snow and ice slide off easier. Might look into something like that.

canuk
Re: spray foam for crawl and roof
Fritz wrote:

we're looking into SPF for these spaces.
The crawl is very tight, probably 6" to 18" below the joists, which are 6".
The joists are only 6 inches?
6-18 inches is very tight and actually I would be concerned with that little space between the underside of the joists and the ground.
It would be a heck of a job for someone to get in there to spray the underside of the floor.
In this case it might be better to spray the perimeter walls of the crawlspace.
T or F? For crawl space, close cell is better idea for water resistance and R value?
Do you have issues with water ?
Generally speaking ---- closed cell foam is more resistant to water infiltration and typically has more R value per inch.
Are all SPF close cell products basically the same?

Again generally speaking ---- closed cell SPF products have basically the same performance.

Quote:

Our roof will be a project this year.
It is a cathedral with probably 6" joists also.
If we redo the sheathing, is spray in a good choice or SIPs?
And what Is the best idea for preventing ice dams on the roof?
We're on Long Island and just last week we had an ice dam that ripped off and twisted part of a gutter.

Boy if you could go with SIPS go for it.
Otherwise --- you might consider SPF.
Also, apply a 2 inch thick layer of rigid foam on the exterior sheathing then add a second layer of sheathing to attach the roofing material to.

Basically ice damns are caused by warmth from the interior warming the underside of the roof. This melts any snow from the underside, the water runs down and freezes when exposed to the cold air.
To prevent this-- keep the warmth from inside from reaching the underside of the roof.

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