Thread: Range hood vents to attached garage

Microwave range hood vents to attached garage.

Is this a breach of the habitable space / garage separation?

Any other concerns/prohibitions other than moisture?

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It's wrong, dead wrong and I know that you know that. Report this dangerous defect and move on.

OK, supporting documentation I’ve found so far:


Per Broan “You should never exhaust air into spaces within walls, ceilings, attics, crawl spaces or garages. The humidity and grease collect in the space.”



FAQ

Still a little thin though, as most microwave hoods can be configured to exhaust back into the house (kitchen).

Nagging at the back of my mind is the suspicion that this must violate some general HVAC prohibition regarding exchange of conditioned air between the habitable space and the garage...

OK, found it, I was looking in the wrong place:


M1502.1 General. Range hoods shall discharge to the outdoors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight and shall be equipped with a backdraft damper. Ducts serving range hoods shall not terminate in an attic or crawl space or areas inside the building. Exception: Where installed in accordance with the manufacturer's installation instructions, and where mechanical or natural ventilation is otherwise provided, listed and labeled ductless range hoods shall not be required to discharge to the outdoors.

Michael,

Two guesses here:

1) The kitchen was remodeled *without a permit* and the location was changed and it now exhausts to the garage instead of outdoors.

2) The 'garage' was a 'carport' and was enclosed *without a permit*.

Does either look like it may have been done?

I may be wrong but I believe Michael was looking for why can't you exhaust in the garage.
Simple answer would be draft stop.
309.11 No duct openings in Garage

Originally Posted by Michael Thomas

Exception: Where installed in accordance with the manufacturer's installation instructions, and where mechanical or natural ventilation is otherwise provided, listed and labeled ductless range hoods shall not be required to discharge to the outdoors.

Michael,

Just verifying - that exception *does not* allow it to vent to the garage.

I raised my post / point of view not so much to answer your question, but to get you to consider those options (if you had not already done so) as they may be larger than 'just the micro wave venting into the garage'.

What Jerry is referring to is the venting into the garage may only be the tip of the iceberg? When folks remodel it usually never stops at one obvious defect and old timers go into "overdrive" when they sense such.

All this and not counting the break in the fire wall seperating the home from the garage.

Originally Posted by Brian E Kelly

All this and not counting the break in the fire wall seperating the home from the garage.

Few places have ever required it to be built like a "fire wall", it was just made up of some 'fire rated' material, such as Type X gypsum board, but it was never intended to serve as a "fire wall".

Which is probably why it is now just considered as "separation" between the garage and the living space, and that "separation wall" can have 26 gage metal duct go through it. The problem, then, becomes 'where the metal duct terminate' (the duct may only be 30 gage instead of 26 gage anyway), and it should not terminate into the garage.

Jerry Mc. is correct: "What Jerry is referring to is the venting into the garage may only be the tip of the iceberg? When folks remodel it usually never stops at one obvious defect and old timers go into "overdrive" when they sense such."

You need to be looking for the part which sank the Titanic - the part underwater you don't see.

Forget the manufacturer specs, its an open penetration in a garage fire wall.

Andrew Constantine
InspectPro Home Inspections
Charlotte NC Home Inspector