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Hot attic with duct work, enclose or not?

Barry Radeka | Posted in Energy Efficiency and Durability on

I live in southeastern coastal South Carolina, zone 3a or 2a. My A/C duct work runs in my attic that I know gets well over 120 degrees. Would it be smart for me to create an enclosure for my air handler and duct work? At least most of the duct work where it would be feasible. Last year we had to replace our inside and outside A/C units and I opted for more energy efficient units but really have not seen much benefit from them. I have plenty of room to work, I just need to know if it will improve the cooling of my home.

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  1. Jesse Smith | | #1

    It's pretty expensive to fully enclose even a small attic. I'll generally use a hybrid approach. Enclose the equipment with a mix of 2" Thermax and dense-packed cellulose. Drop the ducts to the floor - usually as part of a light duct overhaul - and spray foam 2"-3" of foam over them. Then blow cellulose over the ducts outside the conditioned room. Best to quantify leakage with pre and post work duct blaster testing, or at least a blower door.

  2. GBA Editor
    Martin Holladay | | #2

    The best approach is to install spray foam insulation on the underside of the roof sheathing, to create an unvented conditioned attic. For more information, see Creating a Conditioned Attic.

    Jesse's suggested approach can work, but not all attic and duct configurations are amenable to that solution.

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