Heating garage with duct from home furnace

[Toba]

I had a friend bring this idea up to me to heat his garage. Has anyone done this? If so how well does it work?

[cavalierowner]

My gut reaction is that you wouldn't be able to raise the temperature in your garage by more than a few degrees. Even if the walls and ceiling is well insulated, the garage door(s) are going to be a huge heat loss. Even insulated, weatherstripped doors.

But there's a bigger issue and that's the code issue. The wall between the house and garage (assuming it's an attached garage) by code has to be fire rated. That would mean that any ducts penetrating that wall would need a fire/smoke damper. You would also need a return air for the system to work properly. I don't know the mechanical code, but I'm betting it wouldn't allow you to bring air back to the house that may contain carbon monoxide. But the best way to know for sure if this would meet code is to talk to the local inspector. This is a life safety issue and you don't want to bet your life it might be OK.

[CAMAN]

Not only is it a 99.99% chance it is against code, It is setting yourself up for a very dangerous situation. You never want a path from a garage to a living area that CO or other dangerous gasses can travel. Find a natural gas or propane heater if you really need to heat the garage.

[MNice]

Not 99.99% against code at all. It's 100% against code. Bad, bad idea.

[CJH]

That's a no no.

[Toba]

Once again in life there are no short cuts. Thanks guys. I guess it's time to put some more money away for an install of a heater.

[CAMAN]

Not 99.99% against code at all. It's 100% against code. Bad, bad idea.

I only said that because I figured there was probably some municipality out there with some stupid code still on the books. Yeah, probably overthinking it.

But yes, VERY.....VERY.....VERY BAD!

[Big Tom]

Had a house that had exactly this in the Garage with a wall open/close vent. The house was built in '87 and we got it in '92.

It added very little to heating the garage even when open all day and the garage was insulated.