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Community and Q&A

ERV mold

Shawnnixon1 | Posted in General Questions on

I can’t decide between HRV and ERV
I live in montreal quebec where we have dry cold winters and humid summers. ERV makes the most sense but I read reviews online that the ERV core is a magnet for mold since it gets humid there?

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  1. user-5946022 | | #1

    Have two ERV's installed in a hot humid environment, and neither core shows any sign of mold.

  2. Expert Member
    Akos | | #2

    I'm in Toronto, I haven't tested it for mold but can't see any of the standard signs (little black spots) on the ERV core. Looks pretty clean, well as clean as it can be after many years.

    I have a feeling the mold issue is mostly on systems that cycle. If the ERV is running 24/7, there is less chance of moisture buildup.

    1. andyfrog | | #3

      This commenter wrote that their system was run continuously and also developed mold.

  3. DennisWood | | #4

    I'd have zero worries about an ERV in cold climate. I've run one here at where temps go down to -35 issues over 5 years. That said, if for some reason your intake/exhaust (again cold climate) is not 100% well sealed and insulated, insulation can get very wet, very quickly and would be the more likely spot for mold to develop.

    Your ERV/HRV intake and exhaust ducts need to be sealed, insulated, and also vapour sealed with very careful attention paid at the ERV/HRV boots. That is why the insulated flex duct with a plastic (or non permeable cover) is typically used. If any mold showed up in these systems, the first place I would look at would be the HRV/ERV intake/exhaust ducting.

    Consider that on the fresh air intake, a small leak in the duct vapour barrier (with poorly sealed ducts) will pull warm moist air from the home into contact with potentially cold air (I'm talking cold climates here) and generate a large amount of moisture that will first soak the insulation and then keep it wet!

    With an HRV, properly functioning drains are also 100% required. I just sorted a drain issue due to short horizontal tubing runs (required due to tight quarters) at lower than 1/2" ID. I only point this out as someone reporting mold in an ERV/HRV has likely not explored the full cause of that issue...and there are a few possibilities.

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