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How To Further Insulate On Top Of Spray Foam

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Posted by: from Oro
11/7/2011 at 7:37:14 PM

We have just bought an old cabin and the main flour was built with block foundation. It was insulated with pray foam about 2-3 inches. We would like to have a grater R value than that and wonder how do you put more insulation?

And whats the best to use on top of the pray foam. Because we got to thinking if we put up plastic, we will end up with two vapor barriers and there may be other problems we dont know about.

Thanks so much :)

REPLIES (2)
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Joe in Ottawa
Date/Time11/10/2011 at 10:22:12 AM

Spray foam on top of spray foam is not a problem, however there is a couple of things to find out first.

If its open cell you need to see if they applied a spray on barrier, if so then there are procedures that need to be observered

- If its closed Cell then your application will somewhat be hassle free

- All dirt and or grime is removed,

- No moisture is present on the surface when applying your top coat of Foam

At Three inches the existing should have an vapour barrier providing it was 2 lb foam to begin with. By applying foam over the exsiting foam it will only add R value along with increasing your vapour barrier resistance.

A closed-cell spray foam that I would recommend is Tiger Foam. They will be able to help you with any questions you may have related to your application.

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Date/Time11/15/2011 at 7:12:51 PM

Hi Anitsa

Not sure about you meaning of block foundation, but i am assuming that the building is block , with 2 by framing inside, spray foam between the studs, coverd with drywall, i hope (fire issue if not). If your talking about the crawl space walls then you have a problem, and need to insulate the floor instead, or cover them according to code.

Assuming its block wall with framing, i would use regular insulation in the stud cavity,if there's not enough room for the r value you need strap the walls. NO !!! vapor barrier, this will allow any vapor to dry to the inside, and cover with drywall. If you intend to use wood as a covering, you can getaway with fire rated insulation instead (safe and sound) over the foam, but no foam can show, it's not code approved, but it works as a fire stop. Note; all foam insulation must be covered with gypsum in a heated space.

John Miller

Superior Handyman

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