Furnace Supply Registers in Garage

Hi Team, I recently came across, for the 1st time, 2 Supply registers from the furnace on the back wall of a garage. I questioned if the current homeowner put these in and the realtor said that he did so cause he works out in the garage and wanted some conditioned air.
I feel that this is an issue cause any fumes can be drawn back into the system through convection.

What are your thoughts and thanks?

Cutting Edge Inspections

Morning, Alfonso. Hope this post finds you well.
Write it up.
In bold is mine.
IRC Section M1601. 6
HVAC systems that supply air , conditioned or not, to the garage shall not supply or obtain air , conditioned or not, from any other space but the garage.
HVAC systems that supply air , conditioned or not, to the living space shall not supply or obtain air , conditioned or not, from any other space but the living space.

Hope that helps.

Ditto, having a shared HVAC system that includes the garage comes under the “really bad idea” column. Significant safety issue.


I’ve called out that type of installation before. It also breaches the fire separation to the house.

Good info for you above, Alfonso… :smile:

Hi Robert, Thanks for the response, yeah 1st time came across this one and I knew it just didn’t seem right!

It’s not only about recirculation air from a garage , it is a safety issue

Agreed, bad idea! Would you consider this a defect Jeff?

There’s the proof in the pudding! Thanks for finding that Lukasz! Once I saw the registers I said to myself…that just doesn’t look right!!

I’m not Jeff…But heck yeah it’s a defect!

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Sorry Larry, Yeah I figured to mark that as a defect…Thanks!

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We may use different word but essentially they mean the same things.

Example: I don’t necessarily use the word “defect” in most cases, I use a short statement… not working as intended…not installed to industry standards, etc then I would state why it is an issue, can fail prematurely…poses as safety hazard.

In the case of the shared ducts from your post in the garage; i might state that the ducts in the garage were shared from the garage to the home and this poses a significant safety hazard that can lead to injury or worse and does not meet industry standards, followed by the statement corrective actions are needed to ensure the occupants safety.

These are somewhat common in my area because of the very hot climate. I will also find these in model homes in a subdivision where a garage was once a sales office. I write them up and with “scary words” that alternate between Bold, Red and or Both.

In addition to all the other issues mentioned, it creates a negative air pressure in the living space which will “pull” in unconditioned air and Radon in some areas.