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Installing foam insulation in shingle style house

Posted by elsewhere (My Page) on
Mon, Sep 26, 11 at 11:33

I have an old 1890 era shingle style house with a finished 4th floor (cathedral ceiling, 8" rafters). As it's time to reroof, I'm getting estimates for putting insulation up - there is currently no insulation in the roof. I'm comparing 1) foam boards with R15 put in cavity at time of shingling, 2) open cell foam insulation (about R32) with an all roof ice & water barrier, and 3) closed cell foam insulation (up to R38+) with no barrier. I'm in a cold, wet climate.

My questions - are 2) and 3) preferable, despite the much greater cost? would 2) present a problem with vapor condensation?

And finally, what are your experiences, if you have insulated a similar home?

Follow-Up Postings:

RE: Installing foam insulation in shingle style house

Your insulation is below minimum recommended R Values. See charts in this thread.

Ice and weather shield should be on the roof, running from the eaves to three-six feet up the roof. It has nothing to do with R Value, but protects the roof against ice damming.

Since you're re-roofing you could well consider insulation both above and below the sheathing.

Finally, sealing your home will do as much or more than increased insulation levels to make your home more energy efficient. (See Link Below)

Here is a link that might be useful: Attic Air Sealing Guide

RE: Installing foam insulation in shingle style house

Thanks for the advice, I'm in zone 5 with a Cathedral ceiling - R30-38 is recommended.

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