okay to vent OTR microwave into adjacent garage?

reesegirl · 07-20-2009, 09:42 PM

I have an over the range microwave that currently vents back into the kitchen.
The problem with that is that the filters underneath don't really work all that well
and I end up with a greasy film on my cabinet doors. My microwave can be converted to vent to the outside. I can't go up so would have to go out through the garage to the outside. The run would be about 20 feet long. Is it against code to let it vent out into the garage? It currently vents into the kitchen. Whats the diff? Grease in the garage or grease in the kitchen.

Plumber101 · 07-20-2009, 09:55 PM

With that short of run to the outside you should be fine. Just don't vent into the garage, make sure it goes outside

hvac122 · 07-20-2009, 10:34 PM

It is against code to vent into the garage as the garage has a fire rating from the house. No penetrations like that aloud around here. Another reason is that is would let carbon monoxide into the house when you start the car.

Plumber101 · 07-20-2009, 10:43 PM

Can you quote me section and code refference for this?

hvac122 · 07-21-2009, 09:43 AM

I am not disagreeing with you. It would be OK to go through the garage to the outside as you said, just don't vent into the garage.

reesegirl · 07-21-2009, 10:07 AM

Thanks for the responses. I hadn't thought of the carbon monoxide angle.
I will definitely vent to the outside or just let the grease fly in my kitchen.

Scuba_Dave · 07-21-2009, 10:47 AM

Venting over a long distance is not a good idea either
Grease will build up in that vent
In addition a longer vent will decrease performance
The more turns the lower cfm you will end up with
I'm going to have the same issue with my new kitchen setup

Chucky Jesus · 07-21-2009, 12:12 PM

I did a similar thing a few years back, but vented up above the ceiling, across the ceiling to the outside and then down through the soffett. (The range was against an inside wall (bad) but the ceiling joists went the right direction (good).) If you are using galavnized duct work to do the venting, I suggest you orient the duct with the long seam facing up and seal each and every joint with mastic or other sealant. Also seal each of the joints in those adjustable elbows. Any grease or moisture that is trapped or condenses in the duct work will STAY in the duct work. It's probably a good idea for all duct work.

Plumber101 · 07-21-2009, 07:08 PM

HVAC122,

I wasn't either trying to cause a fuss, you just brought up a very good point about penatration of a fire rated wall and I thought I just missed something

Scuba_Dave · 07-21-2009, 07:32 PM

Just thought of another thing
I'm going to have to run my dryer vent out the wall to the garage & then outside. Just a short distance
So if anyone has any knowledge of that firewall speak now !!

Leah Frances · 07-21-2009, 10:30 PM

Wow! Maybe it's because I still wax my 1986 volvo 240 with 400,000 miles on the ODO, but WOW!

I know you have a sticky situation, I have sympathy for that. But, do you really want to blow smoke and grease onto your cars (or whatever it is you keep in your garage)?

hvac122 · 07-22-2009, 08:42 AM

Here, the garage has a 1 hour fire rating from the rest of the house. If we run anything from the house through the garage it either has to be 26 gage and fire caulk the penetration or a soffit built and drywalled around the pipe to make it part of the house.
I am sure it is different in other areas but this is what they make us do here in Nebraska.