How can I repair kitchen exhaust duct that's routed into the attic?

3 years ago

I went up to the attic and noticed that my kitchen exhaust duct is not terminated at the roof. All the kitchen air from above the stove is being ducted into the attic, just under a roof vent.

Your guess is as good as mine, but It looks like at one point it might have been routed to the roof, but later maybe the roof was replaced, and a roof vent was put in. Kitchen exhaust duct was not properly terminated for some reason and left hanging just under the roof. Or maybe it was always been this way(?)

How do I route it to the roof? Should I route it to the roof?

Does it need to be insulated? If I need to install a new roof vent for the exhaust, how do I work around the existing roof vent?

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Comments (9)

kudzu9
3 years ago
last modified: 3 years ago
Yes, it looks like it was previously vented through the hole in the plywood and whoever replaced the roof was too unprofessional to install a new roof exhaust vent. There are many vent designs and here is one example: roof vent

To fix this problem, you would need to buy a vent of the right size, cut a hole through the roofing material, run the exhaust pipe though the hole, properly install the vent, and seal all the joints with aluminum foil tape. It would also be a good idea to wrap the pipe in thermal insulation. There are a number of variables:

1. What kind of roof is this, and are there any obstructions where you would put the hole, such as a standing seam on the roof?

2. You'll need to get the pipe to jog over to the existing hole in the plywood, or cut a new hole directly above the end of the pipe. In either case, you'll need rigid wall fittings to extend the pipe up and through the hole. (Do not go with the flexible, cheap hose material that looks like a Slinky covered in plastic: these are crap, reduce air flow, and trap lint and grease more easily.)

3. You'll need to properly seal the vent against rain where its underside contacts the roofing material. How this is done will depend on the nature of the roofing material. If you have shingles, you would ideally have the hole located where the flange on the vent can slide under a row of shingles, and you will need to use sealant as well.

There are plenty of videos on YouTube on how to install a vent, so you should watch a couple of them. But if you aren't sure you have the skills and the necessary tools, you may just want to pay a professional to fix this.
PRO
GN Builders L.L.C
3 years ago
It looks like a 6" vent pipe you need a 6" Goose Neck Vent Roof Cap, you can get it at Home Depot or Amazon, I used on a few jobs the one from Amazon here is the link.

You will have to cut a hole in the roof to install it, so call a roofing contractor if you cannot DIY
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ci_lantro
3 years ago
A couple of things don't make sense.

Why the long horizontal section instead of straight up & out?

And the interior of the vent is clean as a whistle...no sign that kitchen stove exhaust has ever travelled through it. Likewise, the roof decking is clean.

When I moved the stove in my kitchen and replaced a venting microwave with a range hood, I discovered a pristine exhaust just like yours. Turned out that who ever installed the microwave didn't remove the baffle that would have allowed the exhaust to go out the vent pipe. Some regular range hoods can either filter & recirculate or exhaust. Might that be your situation?

Does it need to be insulated?

Probably not if you live in SoCal, AZ, southern NMex. Otherwise, yes. You want to try to eliminate or greatly reduce condensation.
mike_home
3 years ago
The first thing you should do is turn on the exhaust fan and verify air is coming out of this pipe. If it does not, then no need to do anything. If it does and you plan to use the exhaust, then it needs to be terminated through the roof.

The existing roof vent is there to provide ventilation to the attic. You need to drill a 6 inch diameter hole through the roof deck and install a cap similar to what GN Builders has proposed. I suggest moving it away from the existing roof vent to prevent cooking odors from entering the attic
Dennis Matveyev
Original Author
3 years ago
the vent does indeed work, when it is turned on. The air goes into the attic from the kitchen. I am not sure why there is no build-up of oil and grime on the inside of the pipe, but my vent hood does have a filter mesh.
The circumference of the pipe is about 20". Will it work with the 6" roof cap?
mike_home
3 years ago
Pipe sizes are specified by diameter. If the circumference is about 20 inches, then it should be a 6 inch diameter. Measure the diameter to make sure.
Dennis Matveyev
Original Author
3 years ago
what should I use to insulate the vent? I got to say also that the vent is not entirely made out of the 6in duct. It changes into a rectangular box next to the kitchen intake
kudzu9
3 years ago
Insulation: fiberglas batting wrapped around the pipe. Tape it or use wire to keep it in place.
mike_home
3 years ago
I used the 6 inch duct wrap from Home Depot for my bathroom fan exhaust fans. For the box you will have to customize something with at least R-6 amount of insulation.

How can I repair kitchen exhaust duct that's routed into the attic?

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kudzu9

GN Builders L.L.C

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How can I repair kitchen exhaust duct that's routed into the attic?

Comments (9)

kudzu9

GN Builders L.L.C

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