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Community and Q&A

Unconditioned attic furnace and air conditioning

Mightymason | Posted in Mechanicals on

I have a 96% furnace with AC condenser in my unconditioned attic in Michigan.  There is heat tape,  insulation,  and angle on condensate drain.

There are ample supply and return air ducts running into both supply and return plenums. Plenums are spray foamed. R-6 flex ducts look sealed pretty well.  Drain pans with shut off sensors are installed.

Aside from the golden rule of not having a furnace in an unconditioned attic,  are there any other concerns I should address heading into my first summer in this house using the AC?

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  1. GBA Editor
    Martin Holladay | | #1

    If this were my house, I'd be developing a long-term plan to do one of the following: (a) convert the vented unconditioned attic into an unvented conditioned attic, or (b) move or abandon the attic furnace. (One possibility is to install ductless minisplits upstairs and abandon the furnace.)

    In the short term, you should be alert to possible moisture problems at your register boots. If you have galvanized register boots, and if these aren't properly covered with spray foam or well installed duct insulation, then humid outdoor air can contact the cold steel in summer, leading to condensation and drips.

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