Best roof cap for kitchen range hood vent?

collins designApril 6, 2009

Hi- hope this is the right forum to post this in...

We're installing a 600 CFM range hood in a one-story ranch house in southern Maine.

The guy at the appliance store was saying something about "if you can afford it, get one of those chef-hat type spinning roof caps". He thought that the lower-profile ones might cause ice dams because they spit the hot air right onto the roof... and/or that snow on the shallow roof pitch (5:12) might cover and block the low-profile type. Is he being overly cautious?

Clearly we want our vent to work as optimally as possible and avoid roof leaks, but we're also on a budget (and DIY.)

Related question: what type of damper is best and where to install it? I have read to install it at the thermal break, i.e. at the attic insulation level. Comments on that?

Thank you!!

STacey

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john_com

>>The guy at the appliance store was saying something about "if you can afford it, get one of those chef-hat type spinning roof caps". He thought that the lower-profile ones might cause ice dams because they spit the hot air right onto the roof... and/or that snow on the shallow roof pitch (5:12) might cover and block the low-profile type. Is he being overly cautious?

We have a very standard I think Broan low profile type you speak of. Ice dam? oh yeah. Minnesota. Something I never thought of. It was existing so we used it. We had a small mountain last year so now I have to remember to use the roof rake after it snows. Post a link of the chef hat style you mention.

    Bookmark   April 6, 2009 at 11:51AM
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antss

The rotating chef hats are for venting hot attic air not appliances. You really need to consult your HVAC guy. A lot depends on the location the vent will penetrate and even more on the type of roof you have.

    Bookmark   April 6, 2009 at 2:22PM
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PRO
collins design

Well, we are DIY but I will go to the HVAC supply store and ask my local experts there... DH is a systems tech (plumbing, electrical, HVAC, mechanical) but in the marine industry. He's perfectly competent to install and service stuff, but things like this we need advice on!

    Bookmark   April 7, 2009 at 3:20PM
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kaseki

I would doubt that ice dams of any significance would occur for any roof steeper than 4:12, and plausibly for even lower pitches. Not only is the heated area small, but the heat (BTUs per hour times hours of use) exhausted due to cooking is much less than the household heat passing into an attic in cases where ice dams are a problem. I had a major ice dam this winter at the edge of the roof over my kitchen, but the kitchen ceiling was insulated by only a tarp.

However, the question of blockage is an interesting one.

A sufficiently wet and heavy (yet blowing) snow might pile up in a way that reduces the aperture of the style roof cap that Broan, say, uses for the larger model fans. However, these fans have overhang at the exit (down side) and I doubt that total blockage would occur. So long as some air can pass, then pushing out warm air should clear a larger hole as needed. I won't be able to attest to that until next winter, but I can say that here in southern NH, when in use a Nutone mushroom style exhaust fan with an air exit point about 10-inches above a 5:12 roof, has never been blocked by snow in 20-some years.

If a snowstorm were found to be depositing snow that was suspected of being perverse in the blockage sense, then running the fan during the storm should maintain sufficient air clearance to allow the fan to work when the snow hardens up.

kas

    Bookmark   April 8, 2009 at 9:44AM
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antss

The engineers that design remote blowers and caps for venting co.'s are way smarter than your local appliance salesman.

Don't you think that they considered their firm might sell a cap/blower to someone that lived in an area that had heavy snow? Think they figured that they should design their system and install instructions to deal with that?

Still think your appliance guy has a clue?

    Bookmark   April 8, 2009 at 4:11PM
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PRO
collins design

Thanks folks--- Yeah, I was doubtful of his advice and that's why I wanted to run it by this forum!!! He had that air oftrying too hard to be the expert.... but you never know, and I am certainly not an expert! Thanks for the feedback!

    Bookmark   April 8, 2009 at 7:45PM
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mojua

just a thought...is there any way you might be able to vent out the side of your house instead of the roof? I'm probably only about an hour south of you, and when our vents (hood, bath, dryer, etc.) were being installed, the HVAC guys did everything possible to NOT punch them through the roof...specifically because of the potential for ice damming...

    Bookmark   April 8, 2009 at 7:59PM
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