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Hot spots in open cell foam, humidity in attic, what are the best steps to take?

suect | Posted in General Questions on

Texas home with summer approaching.  We have had some concerns with humidity in the past, using a dehumidifier.  I have also noticed the more the HVAC system works humidity and temperature in the attic increases as well.

I decided to rent a Flir to check the insulation performance and noticed quite a few hot spots throughout the attic.

I have had HVAC professionals and an energy Rater suggest a supply and return. In light of this new discovery, I’m not sure if this would be an approach to take.

Is this common occurrence with spray foam insulation?  Any suggestions on how to work with what we have and keep a dry, cooler attic?

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  1. JC72 | | #1

    Moisture will diffuse from the rest of the house up into the attic. At that point, depending on the type and thickness of the foam, it will either become trapped in the attic or slowly move through the foam and into the decking at the ridge. It's common in high humidity climates.

    Typical solutions are to dehumidify or condition (supply, or supply & return) the attic.

    Of course removing the affected spray foam is part of the solution but IMO it's not an either or situation.

    1. suect | | #4

      Thank you.

  2. Jon_R | | #2

    Cooling the attic combined with the unavoidable stack effect infiltration can increase attic moisture. You have tried a dehumidifier in the attic?

  3. suect | | #3

    I have used a dehumidifier in the past and have decided to return to it. I also have a whole house dehumidifier. I was advised to have it at 45% but there was changes to the home. I have a fresh air intake which is bringing humidity in but concerned about negative pressure as another source of humid air.

    Would sealing all the flexible ducting be considered in light of your advise?

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