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I am looking to install an ERV in my house and am currently trying to determine good locations for the intake and exhaust vents. While I have identified other candidate locations for the exhaust vent, by far the easiest candidate location is to vent it into our attached, unfinished garage.

I have not seen anything in my building code (Western NY, USA) that explicitly prohibits this, but I am by no means an expert. My local township has advised me that they place no additional constraints on ERV installation save to follow manufacturer guidelines.

Is there anything I may have missed that makes venting the exhaust into the garage a poor idea or not allowed?

Thanks in advance.

Edit: For clarity, the intake vent will run outside, only the exhaust vent will run to the garage.

Andy Hall
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    They are suppose to bring in fresh air into the house, usually required for a very well seal house. A garage with a car warming up in it will probably defeat this propose. If the two vents are separated and only the exhaust is in the garage, with intake outside, then it should be okay. I imagine the garage does get aired out often. – crip659 Nov 21 '23 at 22:29
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    That seems like a huge violation of fire walls, as it will pull smoke from inside the garage and maybe even admit flame. – Harper - Reinstate Monica Nov 23 '23 at 00:53
  • You are aware that you are going to dump ~1 garage worth of air there every hour, 24/7? The garage will require sizeable holes for this to work at all. But if you do have/plan those, I don't see any relevant issues beyond the fact it will be fairly drafty in there. – Zizy Archer Nov 23 '23 at 22:13

2 Answers2

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I am sure it would be against code.

If it isn't always running and your ERV doesn't have a damper on the exhaust then you've introduced a nice path for CO to enter from your garage into your house. I'd say for that reason alone it would violate whatever the code is that requires some kind of air tightness from the garage to the house. Code is often about protecting against the dumbest user and someone could just un-install or unplug the ERV and then you've got ducting from the garage directly into bathrooms and kitchen ( ERV exhaust vent locations ).

Fresh Codemonger
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  • If only the exhaust/return goes into the garage, then this answer is incorrect. – MikeB Nov 23 '23 at 10:18
  • @MikeB is an exhaust duct magic and without pressure can somehow prevent the movement of air into it? – Fresh Codemonger Nov 23 '23 at 19:23
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    ERVs are generally running 24/7, except for those few minutes when you exchange filters. This path for CO is a non-issue - without pressure the amount of CO that would go over all these ducts is negligible. You have like several meters of somewhat narrow tubing and a dust filter in between. – Zizy Archer Nov 23 '23 at 20:36
  • @ZizyArcher right but code is meant to keep things safe in as many scenarios as possible and removing the appliance or unplugging it then creates a hazard. Unplugging an appliance should not create a hazard. If the HRV stops working, breaker trips, motor dies, etc then you end up in potentially fatal hazard situation. All you need to do is create a pressure imbalance in the house ( turn on your dryer / range hood / co device ) and you'll be sucking air in from the garage if the hrv is off. – Fresh Codemonger Nov 23 '23 at 20:43
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    You could make the same claim on the value of an air sealed door leading from the house to the attached garage. The amount of CO that is going to come in around the door jamb is minimal without a pressure difference but that air sealed door is code required. – Fresh Codemonger Nov 23 '23 at 20:45
  • Code generally prevents typical stupid things, not a perfect storm of many issues at once. Door is next to the house, distance = 0m. Even no pressure difference gets CO from the garage to the house. Ordinary door is perfectly safe if you have a long corridor before your bedroom and living room ... but if your garage is next to the bedroom you might suffocate. – Zizy Archer Nov 23 '23 at 21:25
  • For an issue with ERV you need: car running in the garage AND ERV not working AND fume hood working and venting outside without ERV bypass AND a sealed house so air travels over ducts instead of gaps. And even if all of that holds true, you are still awake in the kitchen, not asleep in bed, so it isn't even a "go to sleep and never wake up" scenario. You will smell the garage and feel bad way before CO level gets high enough to be dangerous. – Zizy Archer Nov 23 '23 at 21:33
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Unless your ERV also exchanges humidity, you are putting relatively humid air into the cool space of the garage. Even in my dry climate (Alberta, 16" of precip/year) the aphorism "rust never sleeps" runs true in my garage. And it has an open garage door most of the time.

Clearly you don't want to have your intake in the garage. Run your car, and poison the house.

Can your continue the duct across the garage and exit the other side of the garage?

Responses to comments.

Jmac My limited and dated experience with heat exchangers of any kind is that 70% is the sweet spot in terms of economics. Which means that there is still a fair amount of water in the exhaust air.

Tiger Guy Mostly on the underbody of the car. It's common to come in with 40-50 lbs of slush on the bottom of the car. Warm engine warms up the body enough for most of it to fall off. I live outside Edmonton, Alberta. Most years we have snow on the ground for 5-6 months.

If the ambient temperature in the garage is -20C, it takes very little additiona water vapour to saturate the air at that temperature.

Screwtop My garage doors don't fit well. My brother-in-law has an insulated heated garage. While garage doors don't fit as tightly as most houses' front doors, they are tight enough to make the garage heatable. Most people will heat them to between 45 and 50 F.

Sherwood Botsford
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  • This is a very good argument even if the garage isn't considered a garage for cars, for example by not having a big door. I've considered this as mine is more of a workshop and bike shed, and the ceiling is lower than my van's roof anyway – Chris H Nov 22 '23 at 09:06
  • If the ERV doesnt exchange humidity, it would be a HRV. That's the big difference between the two. So assuming OP isnt calling a HRV an ERV, it will exchange humidity. – JMac Nov 22 '23 at 13:01
  • unless you have moisture coming up from the slab, where is your moisture in your garage coming from? I think you are getting rust because you don't close the garage door. – Tiger Guy Nov 22 '23 at 14:12
  • In my experience, garage doors are far from airtight, and the indoor dew point will track the outdoor one fairly closely. Especially if the garage space is cool, and depending on the climate, the relative humidity can easily be high enough for rust to form. Also, combustion engines release a lot of water, so if you're starting and parking a motor vehicle, that will contribute too. – screwtop Nov 23 '23 at 23:00