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ERV Air Intake Duct Freezing

user-5602664 | Posted in General Questions on

I had an ERV installed in my home 2 years ago – zone 5. It works just fine with one complaint. The intake duct freezes in cold weather resulting in soggy insulation when temperatures return to normal.

At first, the installer used mostly R6 insulated flex duct. When that failed the first winter, they returned and piped the intake with rigid duct with an R8 insulation sleeve over it (picture attached). Unfortunately, there was frost where indicated in the photos, and the insulation is wet again.

Any recommendations on how I might redo the intake duct to avoid the frost buildup in colder weather?


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  1. DennisWood | | #1

    It looks like the frost is happening where the air enters the unit and also at the corner, where the duct is in close proximity to the wall.

    1. At the ERV, I don't see tape, which should be sealing the insulation sleeve to the outer ERV duct ring.

    2. At the top right corner, it looks like the duct is touching the outside wall? Likely there is a cold spot there, (that area is not being heated by interior ambient conditions) and therefore frost. You likely need to get some separation there.

    You can also insulate over the 6" duct sleeve with another 10" sleeve. You'll need to source that likely at a local HVAC supplier. Regardless, there needs to be a good air seal at the wall and ERV on both the duct itself, and the insulation sleeve!

    1. user-5602664 | | #2

      Thanks for the advice - I will give it a try!

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