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Can a HPWH be installed into a unity closet with venting in and out of a garage?

xSPARExSTEWx | Posted in Building Code Questions on

I am looking at getting a HPWH for a house that is above my detached garage. The furnace and water heater is in a little closet in the garage, and would not be big enough air for the HPWH. I would like the exhaust and return be from the garage and only the exhaust being vented with the return being just a vent without the ducts. Since the closet is sealed off of the garage and is not from the house would this cause an issue? Would the only way be exhaust and return to outside or would I have to put ducts on the return if I did want it venting through the garage?

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  1. Expert Member
    Peter Engle | | #1

    You can probably supply and return from the garage with a few important caveats:
    1. You need to watch your fire separations. If the closet is currently part of the garage, you're probably OK. But if the closet is part of the house, the ducting from the garage to the HPWH must be sheet metal and airtight.
    2. A garage is pretty small for supplying heat to the HPWH. If you are in a colder climate, you won't get great performance from the HPWH. In a warmer climate, this might work well and keep the garage more comfortable to boot.

    1. xSPARExSTEWx | | #2

      The closet is tied to the house so I would need to duct the return and exhaust then? The garage is 2 car, around 1000sqft, and should be decently warm in the winter as it looks like there is no insolation between the garage and the house above it. I will also have my electric car charging in it at night which has been known to heat it up a bit too.

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