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Community and Q&A

How far apart must my HRV fresh air intake be from exhaust?

lewberg | Posted in Building Code Questions on

Just had an HRV installed and was expecting the fresh air intake to be on the front of my house because my furnace and water heater are vented on the corner of the side of my house. The installer used a 2 in one vent cover where the stale air and fresh air intake come out of one vent cover that is located 2 1/2 feet away from the first exhaust pipe. Is this safe or legal? How about if he adds snorkels to either the intake or the exhaust?

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  1. Expert Member
    Michael Maines | | #1

    They should be at least 6' apart. I don't think there are specific requirements in the building code but most manufacturers spec 6', and 10' is better. It's not unsafe, it just won't do what it's supposed to do if they are too close together.

  2. KeithH | | #2

    Hopefully a real expert jumps in for you but ... (I'm just a DIYer)

    I know that LifeBreath offers a "dual hood" so that setup isn't necessary improper.

    However, 2.5' from a combustion appliance exhaust sounds inadequate. Here is a BuildIng Science article about placement of the HRV vents.

    From the article:
    "Wall intakes must be located at least 10 feet from any appliance vent or any vent opening from a plumbing drainage system. Wall intakes must also be 10 feet from any exhaust fan discharge outlet unless that outlet is 3 feet or more above the intake location. (IRC 2006, Section M1602.2)."

    Can anyone quote from the ASHRAE Standard (62.1?) ? Looks like it says 15' minimum?

    It doesn't sound like a snorkel would help much if you are only 2.5' away.

    Was the install inspected? Did it pass?

    I think the experts around here will want to know what HRV, what equipment is exhausting 2.5' away, etc.

  3. GBA Editor
    Martin Holladay | | #3

    The first thing to check is the installation instructions provided by the HRV manufacturer. These should be available online.

    Installing equipment in a way that doesn't follow the manufacturer's instructions is a code violation.

  4. lewberg | | #4

    seems to go HRV, furnace, furnace then water heater. Perhaps he is planning to put snorkels on exhaust to put them over 3 feet above intake......He mentioned something about snorkel when I asked.

  5. Anon3 | | #5

    You'll have bug problems with intake that close to the ground.

  6. Balazs_F | | #6

    ASHRAE 62.1 calls for a minimum separation of 10 feet between fresh air intake and Class 2 exhaust. Toilet room exhaust, exhaust from residential kitchen hoods, laundry dryer exhaust are all classified as Class 2. General exhaust from a dwelling unit is Class 1 which has no minimum distance requirement. However, state or provincial building codes often include more relaxed requirements for single family, low rise residential construction.
    In Ontario, the minimum distance to potential sources of contaminants, such as gas vents or oil fill pipes is set at not less than 3 ft. In addition, fresh air intake openings are to be located at minimum 18" above ground level or the depth of the expected snow accumulation, whichever is greater. I find these values to be reasonable for residential buildings. Side-by-side or concentric intake/exhaust arrangements will result in some level of recirculation of exhaust, especially in windy conditions, and should be avoided. I would keep a larger distance (10 feet) to exhaust containing combustion products such as furnace and fireplace exhaust.

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