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Community and Q&A

ERV vs HRV what size unit and which is best?

Gregory Walter | Posted in Energy Efficiency and Durability on

I have a timber frame home with sips built in 2007. At the time we put in forced air heat with an aprilaire erv system tied to a trane furnace/ac and a aprilaire dehumidifier. I have always had a problem with condensation and humidity levels in the winter time. The arpilare rep said I need a hrv not a erv? Aprilare does not make a hrv which system would work with the duct work for the aprilare system and what size system do I need for a 2000 sq foot home with two levels?

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    It's true that if your house is humid during the winter, an HRV might be better than an ERV. But if I were you, I wouldn't jump to any conclusions just yet.

    Running an ERV during the winter should lower your indoor humidity levels. If you are still having problems with high indoor humidity, in spite of the fact that your house has a mechanical ventilation system, we need to first eliminate possible problems:

    1. Does your house have unusual sources of humidity like a damp basement, a damp crawlspace, indoor firewood drying, many tropical fish tanks, or numerous house plants?

    2. Are you sure that your ventilation system is operating properly? Have you cleaned the filters and the ERV core recently? Are the ducts free of obstructions? If there are dampers in the ducts, are they in the right position? Is the fresh air intake clogged with grass clippings, dried leaves, or a bird's nest?

    3. Are you ventilating at the right rate? If you know, tell us how many cfm of ventilation your system provides.

  2. Gregory Walter | | #2

    I have a finished walk out basement as far as I can tell no problem with water. I did worry at first about the wood beams in our house however, its been 7 years since they went up. If I run the fire place in the winter when the cold would cause the windows to condensate it goes away. I have seen the erv filter freeze and it was replaced two years ago. Both the inlet and outlet for the erv are covered and I check regular The system was sized for a 4000 sq foot house and we only have a little over 2000

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Operating a fireplace has the same effect as running a ventilation system -- massive amounts of air are rushing up your chimney, and this exiting air is balanced by massive amounts of exterior air leaking into your house. So that massive air exchange solves your window condensation program.

    I still suspect that something is wrong with your existing ventilation system. See if you can find a home performance contractor or an ERV installer to test your system's performance to be sure that your ERV is providing you the air flow rate you need.

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