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Community and Q&A

HRV and Basement Combustion Air

jimhar | Posted in General Questions on


I have a new single family home built late 2021 with HRV air exchanger.  I am looking to finish basement where the furnace will be in an enclosed unfinished mechanical room.

Would I still need to address combustion air requirements for the furnace since I have a HRV?

If so, would a couple of 6″ vents on wall opposing the mechanical room be acceptable?


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  1. Expert Member
    Akos | | #1

    Combustion venting is not the same as house ventilation even though both are called venting. An HRV will not provide combustion air.

    Check the manual for your furnace and water heater. They will show the required vent grill sizes needed. If in doubt, install a louvered door on the utility room.

    1. jimhar | | #2


      Is it a correct assumption that return vents don't count as combustion air? I have a return vent that will be enclosed within the room with the furnace. I was planning on extending that out to wall that encloses room.

      I was planning on a louvered door, but unsure if that is enough. I have seen some basement examples where they put two huge 16x16 grilles a foot off ceiling and floor to provide combustion air.

      1. Expert Member
        Akos | | #3

        The HVAC vent is not a combustion supply of any kind. Depending on the gas appliance combustion air is either taken form the home or directly from the outdoors. The louvered door has a larger free open area than a set of grills.

        If your gas appliances are newer, there is a good chance it will be two pipe direct vented. This means it gets its combustion air from the outdoors.

  2. jimhar | | #4

    Thanks again. It does look like I have a direct vent 2-pipe system. It appears there are 2 pipes going out the side of my house and ends in the type of vent shown in attached picture.

    It appears, then, that I would not need to worry about combustion air requirements.

    1. Expert Member
      Akos | | #5

      You also need to check your water heater. Some are only one pipe and will need supply air. Also check the installation manual of your furnace, even some direct vented one still require high/low grills.

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