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-   -   Rigid Foam in Crawl Space between Joists? (http://www.diychatroom.com/f103/rigid-foam-crawl-space-between-joists-162957/)

Bhava 11-11-2012 01:37 PM

Rigid Foam in Crawl Space between Joists?
 
I have a small vacation cabin that has rarely been used over the years. I want to start using it now in the winters, but the (fiberglass) insulation that was originally installed has been picked apart by the local critters.

I don't want to waste my time using fiberglass again; I'd rather use rigid insulation instead. What I was thinking, was to fit the insulation between the joists (with the appropriate adhesive), up against the underside of the floorboard. However, everywhere I look, it never mentions doing it this way. It always mentions using it on the inside of the skirting, which I'm also going to do, but that will be later. I'm also going to use vapor barrier on the ground.

Anyway, can I do this?

Appreciate any help...

Windows on Wash 11-11-2012 06:32 PM

To different approaches that you are referencing.

What is on the floor above?

You should be able to insulate between and cover the joists with a rigid foam.

Bhava 11-11-2012 08:30 PM

Quote:

Originally Posted by Windows on Wash (Post 1049847)
To different approaches that you are referencing.

What is on the floor above?

You should be able to insulate between and cover the joists with a rigid foam.

After looking at my post, I think I might have been a little vague. I meant to say that the insulation I want to install between the joists, is rigid-foam--not fiberglass.

My question is, do I install the rigid-foam at the top of the joists, to the vapor barrier which is under the plywood sub-floor, or to the bottom of the joists?

Also, as an afterthought, I was wondering, instead of just rigid-foam between (and at the top of) the joists, would it be acceptable to install it at the bottom of the joists, with the addition of fiberglass above it, and below the sub-floor?,

I'm asking about this extra protection because the temperatures here can drop to as low as -30C (-20F)!

Again, thanks very much for any help!

wewantutopia 11-13-2012 10:42 PM

I think WoW was suggesting filling the area between the joists with fiberglass again then attach rigid foam to the bottom of the joists. This will stop the thermal bridging of the joists, protect the fiberglass from critters, and, if the foam is thick enough and seams are taped, act as a vapor barrier. Fiberglass and rigid will really increase the r-value. Cutting the rigid to fit snugly between joists is a real pain (trust me I know!).


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