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Community and Q&A

Basement fresh air

user-7160310 | Posted in Mechanicals on

Hi All

I live in New York (downstate) and am considering installing either an ERV or dehumidifier in the basement to help eliminate musty odor. My hvac contractor believes  that a fresh air system is not a good because it introduces outside (humid) air. The home is pretty tight (exceeds current ACH code). I am not sure if a dehumidifier is the right way to go or if a fresh air system to eliminate stale air is better. (We have a fresh air system and dehumidifier they cover first and second floor). Thanks.

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  1. Expert Member
    Akos | | #1

    I'm with your HVAC contractor, you can go with an ERV but than you would still need something to dehumidify.

    Why not add a stale air pickup to your existing ERV?

    If your basement is musty, it might still need additional dehumidification. Dry basements are rarely musty.

  2. Expert Member
    Dana Dorsett | | #2

    It's true that summertime outdoor dew points in downstate NY are much higher than the subsoil temps, which leads to higher relative humidity in basements. A dehumidifier would remove that moisture, converting the latent heat of vaporization to sensible heat (temperature) in the air. (A heat pump water heater would convert it to sensible heat in the water inside the tank.)

    As long as the relative humidity at mid-height in the room stays below 60% there won't be much mold risk, except for susceptible materials such as rugs or cardboard boxes in direct contact with the cool slab.

    If the upstairs is being maintained at 75F/50% RH, the dew point of the upstairs air would be about 55F. If the basement is 65F and ventilated with same air the RH downstairs jumps to a mold-friendly 70% RH, so simply tying the basement in to the upstairs ventilation & humidity control isn't necessarily going to work.

    What is the temperature at mid height in the basement?

    What is the temperature at floor/slab level?

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