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  1. #1

    ERV or Dehumidfy with exhaust??

    We currently live in Ohio and are moving to Charleston, South Carolina this summer. We currently have an HRV attached to our Lennox variable speed gas furnace with the 16 MERV media filter. We are receiving conflicting opinions from some of the HVAC people down in Charleston about the benefits of the ERV. They say that it doesn't do enough to control humidity when the temp is in the mid-high 70s and the A/C isn't actively running, while our low-speed fan and ERV will be. They say that the ERV uses an exchange of air to try to dehumidify the incoming fresh air. I've been advised by one to forget the ERV and go with a dehumidification system that is always active and that will draw in outside air, dehumidify with drainage, and then exhale the old house air separately. My main concern is the indoor air quality of the house with a son with severe asthma. I realize that humidity will be a much bigger issue down there, but we will want to open our windows and doors more often with the mild weather. Suggestions?

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,538
    Keeping the indoor %RH below 50%RH is important to avoid mold and dust mites. Erv/HRVs are unable to keep the home dry during cool, damp weather. Opening the windows can also make your home damp enough for dust mites to grow.
    I agree with fresh air when the home is occupied and maintain <50%RH all of the time. You will need about 90 cfm of fresh when the home is occupied. With the mild weather, you not get much benefit from and ERV and will also need dehumidifier during low/no cooling loads. Much more practical to get a ventilating dehumidifier. I work for ULtra-Aire/Therma-Stor. We sell both ERVS and dehumidifiers. I agree with your a/c contractors. No pay back on the ERV and the make-up air fresh helps the bath fans and clothes drier to operate. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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