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Can installation of rigid foam on roof be done in stages?

tedsilk | Posted in General Questions on

Due to condensation in our unvented vaulted ceiling, we must remove corrugated metal roofing to install rigid foam on top of the sheathing.  We live in a remote area where there are no roofing contractors and very little help available.  It’s winter here, icy and cold, and the tin cannot be removed easily as it was applied with silicone and tacky tape.  Work can only be done for a few hours a day.  Would it mitigate the condensation at this time if the tin is removed and a new layer of felt applied?  Then could the application of the foam sheets, etc. be done when it warms up in a couple of months?

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  1. charlie_sullivan | | #1

    I think the best option for short-term condensation mitigation would be 1. Seal air leaks into the cavities above the drywall (is there drywall?) and 2. Reduce humidity in the house.

  2. Expert Member
    BILL WICHERS | | #2

    +1 for reducing indoor humidity levels. Making sure you have a good air seal will be beneficial too.

    A new layer of roofing felt won't do anything to help with condensation. The reason you have condensation is that the inside surfaces are below the dew point of the indoor air. There are two possible solutions for this: 1- lower the indoor humidity levels, which lowers the dew point of the indoor air, or 2- raise the temperature of those inside surfaces, which is what the exterior insulation will do.

    I don't really think what you are considering is a good project for bad weather season. If you have part of your roof open and a storm hits, you'll have bigger issues than just condensation. I think your best option is to lower indoor humidity levels, and possibly also raise the indoor temperature a bit, then wait for better weather. When better weather arrives, you can do your exterior insulation project from start to finish.


  3. Expert Member

    +1 on waiting until it is warmer.

    If only to reduce the project fatigue as a result of slow progress and a long duration.

    Think of it this way - if you're only working two hours a day now, that's 4x as many overheads as a single 8 hour day. Getting started and cleaning up could very well eat up an hour and a half on normal days. You'll just spin your wheels, and freeze the whole time working up on a roof in the winter.

    Spring is just around the corner!

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