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More than one HRV in a house?

GBA Editor | Posted in General Questions on

Does it make sense to install more than one HRV in house where a whole-house system would be difficult and costly to retrofit? Would there be a problem running two small, simple, unbalanced HRVs in different areas of a house? It’s a 1400sqft split level. Thanks Gart.

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  1. GBA Editor
    Martin Holladay | | #1

    A 1,400-square-foot house is relatively small. HRVs are relatively expensive. If I were you, I would be inclined to install a single HRV, even if the ducting were imperfect.

    Ideally, you would draw exhaust air from at least one bathroom, and deliver it to the living room and at least one bedroom. But even if you end up with only one exhaust grille and one supply grille, you will still be greatly improving your IAQ.

    If you do decide to install two HRVs, be sure that they are properly commissioned and that their air flows are measured. Adjust the programming of the HRVs to be sure your house isn't overventilated -- or else you will incur an energy penalty.

  2. Doug McEvers | | #2

    What year was this house built, I have some experience with split levels and they are about the leakiest homes going short of the 1 1/2 story with knee walls. Are you sure you need ventilation?

  3. Riversong | | #3

    You might consider using the a couple of the new Panasonic Whisper Comfort ceiling mounted mini HRV, which can replace a bath fan.

  4. Gart | | #4

    Thanks for the responses. Very helpful. Martin, I hadn't thought of the energy penalty involved with two HRVs, but you're right. If that makes sense in terms of layout, I'll have to check to see if it makes sense in terms of watts burned and total CFM transferred.

    Doug, The house was built in '85, we just bought the place last spring. I'm not sure exactly how tight it is, but the energy audit rated the place at 73. Both the inspector (at time of purchase) and the energy auditor recommended addressing ventilation. We have mold/mildew problems in the bathrooms, but improving/increasing exhaust at those points is likely to move air in from the crawl space (according to the auditor who thought the place was moderately tight), which is not desirable. Fresh 80's were recommended at the very least, as well as tightening access to crawl-space, or a retro HRV fit.

    And Robert, yes I did look at the Whisper Comfort -- unfortunately that is an ERV, and not well rated by it's own zoning map for this climate (Alaska). I guess they don't perform well when it's cold. If Panasonic would make a Whisper Comfort HRV -- that might be a great option for this house.

    For now I'm leaning toward an exhaust-only ventilation system to immediately solve IAQ issues (we have two very young children) but would like to plan heat recovery to the make the place a better home in the long run.

    Thanks, Gart

  5. Anonymous | | #5

    So, Gart, we live in Alaska and have similar concerns. What did you finally install?


  6. Gart | | #6

    @Ted -- we've ended up just going with an exhaust-only solution. I installed a panasonic whisper-green continuous low-flow fan in each bathroom (2) and a fresh 80 in the den away from the bathrooms to get some cross ventilation through the house. probably not the most efficient solution, pumping warm air out of the house, but has made a tremendous improvement in IAQ and also really dried out the bathrooms.

  7. Riversong | | #7


    I'm glad the simple solution worked for you. It's the kind of system I install in my super-insulated houses. Simple is often best.

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