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Thread: Best roof cap for kitchen range exhaust duct?

  1. #1

    Default Best roof cap for kitchen range exhaust duct?

    I want to replace my kitchen exhaust roof cap. Is there a standard roof cap for kitchen exhausts?

    My exhaust fan is integrated with an over-the-range microwave. Looks like 6 or 8-inch galvanized duct (two elbows and about 8 feet of horizontal run). There is no backdraft damper currently. I'd like a backdraft damper and a bird screen, unless those are bad ideas.

    I have a roof jack right now (looks like this but a lot older):

    I've seen these low profile square vents. Home Depot explicitly states that they are for kitchen duct outlets, but are they the best choice?

    These are the gooseneck styles. They include a backdraft damper, but does that impede airflow?

    I like this cap, but I suspect it's not intended for exhaust ducting. More likely for a gas appliance like a water heater:

    The attic space above the kitchen is sealed (the kitchen is built out from the 2-story house), so I can't install a damper in the ductwork. It's got to be in the roof cap or just above the fan (or not at all). The cap has to fit over the duct pipe, and there's no way to seal the connection joint (unless I take apart the kitchen ceiling).

    Anyone else faced with this choice lately?

  2. #2

    Default Microwave exhaust without damper?

    Are you sure that the microwave doesn't have a damper right at the exhaust outlet? Mine does. I'd be surprised if it doesn't have one.

  3. #3
    Join Date
    Oct 2003
    Living in, not from North Carolina


    You want to avoid any "bird screening" on the duct , because of the fire risk over time, as possible "crud" builds up (same for a dryer vent) even more so since this one is on the roof and cannot be easily inspected and cleaned.
    Check to see if your over the range microwave has a built in back draft protector, my over the range is a convection and microwave oven and has one built in right at the rear of the unit as it transitions to the ducting.

    Best suited you need a roof vent that can be attached to the attic ducting, but as you mentioned your attic access is not practical,
    number one looks more like a stack pipe cap , number two is a roof vent mainly designed to vent the hot air from the attic space, number three or number four of your pictures are specifically "vent duct roof caps", , number five is a furnace or gas water heater vent cap.
    If it were me I'd be picking number four (number three has a horizontal built in damper that could easily get gummed up with oil vapors etc...) but if you have number one and it's working fine that probably a good choice as well.

  4. #4


    Okay, I'm busted. I double-checked the microwave/exhaust hood and it does have a damper at the outlet. BTW, not much of a fan, now that I look at it.

    My kitchen is built out at the front of the house, so anything on the roof is visible from the curb. That's why I wanted something discreet.

    The first picture (roof jack) is what everyone has in this neighborhood of 30 year old homes. When roofers replaced my neighbor's roof last year, they installed a new roof jack just like the old one. Some things haven't changed in 30 years, apparently.

    Guess I'll step out to the big box store and see what they have on the shelf.

  5. #5


    I just picked up a plastic roof cap for venting my kitchen stove. The stove is a gas ge cafe. The vent is also a ge with an internal blower (not exactly sure of the cfm -- I think around 400). It's a pretty straight shot through the attic (ranch house). The cap (plastic) is what the guy recommended at the hvac supply place, but someone else I was talking to said I should double check that (I think he was worrying about the heat). Of course, the manual for the hood itself doesn't offer much help.

    Thanks for any info and help.

  6. #6
    Join Date
    Oct 2003
    Living in, not from North Carolina


    I'd recommend checking on that plastic vent cap as well, I'm pretty sure you cannot use it for a gas stove. Call your local building inspector and ask him/her.

  7. #7

    Default What about this vent cap is it good for venting a microwave oven

    I found this one online. It seems to look good. Would I want to use this to vent my hood in the roof. I have been getting leaks through my current vent cap which looks like a chinamans hat
    [IMG]\\\dfs$\care-one\users\care-one_esiegel\mydocuments\My Pictures\4295_300.jpg[/IMG]

    Moderator edit
    You need to link to a image on the internet not in 'my documents' on your PC.

    Last edited by joed; April 24th, 2009 at 01:13 PM.

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