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Recommendations for Intake / Exhaust Vents for HRV

Salesi | Posted in General Questions on

Is there a best intake and exhaust vent installed through the rim joist of a house. My HRV will be installed in the crawl space. The intake and exhaust will be 4″ installed in the rim joist. I am wondering if there is a better vent to use than one with just a flapper for the exhaust. Does anyone have a recommendation? Thanks.

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  1. Expert Member
    Michael Maines | | #1

    Do you live in a place where it snows? If so, the intake and exhaust should be placed higher than the snow line. They should also be at least 6' apart, 10' is better. The intake should not be close to sources of odors or otherwise contaminated air.

  2. Salesi | | #2

    Michael: Thank you for the response. We are where it snows but I do not believe this should be an issue blocking the intake or exhaust. I am interested in finding the best mechanical fixture that will be installed in the rim joist and connected to the HRV. A dryer vent with a hood and flapper seems like a poor choice due to it not sealing properly on the intake side and allowing mice, etc. in on the exhaust side. I would like to know if there is a better vent mechanism to install in the wall.

  3. user-723121 | | #3

    The intake and exhaust for ERV/HRV I am familiar with do not have dampers and have hardware cloth screens. A better intake than this would be nice because the hardware cloth gets covered with cotton from trees and then does not let in fresh air. The intake vents are not cleaned regularly by most and a lack of fresh air is the result.

    1. Salesi | | #5

      Are these just dryer vents with add on hardware cloth added?

  4. charlie_sullivan | | #4

    You don't need a damper flap, as it will run continuously (or nearly so), but you do need a critter-proof mouse. This is a plastic version but you might want metal.

  5. jrpritchard | | #6

    We like these all metal terminations from Broan. The screens are easy to clean and the dampers are removable if you don’t need them.

  6. user-1140531 | | #7

    I used 6" PVC pipe for intake and outlet piping. I left most of it unglued, except for joints that were subjected to gravity pull. I ran them out horizontally through the basement concrete block walls just above the exterior ground surface. At their outside terminations, I cut them off square. For each pipe, I cut out a disc of wire mesh with about 1/8" square openings. That is fairly heavy wire, so the disc stays flat and rigid.

    The disc was cut to match the O.D. of the pipe, and I friction fitted it into the I.D. of a 6" PVC coupling. Then I pushed a coupling with the screen disc onto each of the pipes. So the screen was captured between the end of the pipe and the midway internal ring flange of the coupling. I left it unglued, but there was plenty of friction to hold it in place.

    The discharge outlet always melted all the snow away from it, but the intake could occasionally get blocked with snow or plugged with cottonwood tree fiber. I could pull it apart to get the screen out for cleaning or just reach into it with the shop vac.

    For each coupling, I also took short piece of the PVC pipe and cut it off at about 60 degrees to the pipe centerline axis. I pushed that into one end of each of the two couplings. The angle cut on those shorter pipes were at the exterior termination of the two pipes and were intended to act as rain hoods.

    It could be assembled so you only take off that short angled pipe to remove the screen or you take off the short angled pipe and the coupling without separating them from each other. Both joints at each pipe end were just friction fitted. Then, with the right primer, I spray painted all the piping gloss black.

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