Spray foam into window weight cavity

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Joined: Mon Nov 14, 2005 8:58 am

Spray foam into window weight cavity

#1 Post by dhs » Mon Nov 14, 2005 10:09 am

Hi everyone,

First post here. I have found this board to be extremely helpful in dispelling some myths and backing up some claims of the salesmen I have spoken to about doing replacement windows on my house. Thank you for this board and the knowledgeable posters who make it what it is! I am sure my decision on who to go with would be full of a lot more pitfalls without it.

I tried a search on this but did not find a specific answer to this question. Is it considered a good thing to fill the window weight void with expandable foam before installing replacement windows? None of the salesmen I have spoken to say this is a standard step as part of their install.

thanks for any input,

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Location: Kingsport, TN

#2 Post by Profx » Mon Nov 14, 2005 4:14 pm


This is not really a standard step. I have filled them several times and I think it definately needs to be done, but it is time consuming, which brings another charge. The exterior of your wood windows are probably cased out with a 1" x 5", both sides of your opening-the 1"x 5"'s will need to be pulled off, weights removed, and r-11 w/facing placed in there. I couldn't imagine how many cans of foam it would take to fill those voids. After the r-11 is placed in I usually screw the 1 x 5's back in place. If you suggest you would like this method done to a company, I couldn't see it being more than a $20 - $30 addt'l charge per window.

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#3 Post by romr » Mon Nov 14, 2005 5:03 pm

I heard this was a no no. What someone told me is that if foam is used then it voids your warranty. The reason I was told was that the foam won't expand and contract with the window thus making it more prone to fail. Does anyone know if this is correct? Geez, what a pain in the butt to try to find a decent window.

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