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nauko
Proper Insulation for Kitchen Exhaust Pipe

What kind of insulation should I use to wrap a kitchen range exhaust pipe vent in our attic? I went to Home Depot and came home with a fiberglass ventwrap that has foil on the outside, but now I am wondering about fire safety. Not sure how hot the exhaust vent gets, but it is a gas stove so range hood is sucking up a lot of heat.

function
Re: Proper Insulation for Kitchen Exhaust Pipe

I think the answer is none. Take the fiberglass back, but remember fiberglass does not burn.

dj1
Re: Proper Insulation for Kitchen Exhaust Pipe

As far as I know, kitchen stove vent remains uninsulated.

A. Spruce
Re: Proper Insulation for Kitchen Exhaust Pipe

It's a vent, what's the point of the insulation?

There is little to no heat in the vent itself, as the volume of air mixed with any cooking gases/heat quickly dissipates it. Even if you're worried about conditioned house air escaping, all you're doing is making sure the air gets out of the house while it's still warm.

nauko
Re: Proper Insulation for Kitchen Exhaust Pipe

I am in the Pacific NW, and have had a number of issues with condensation in our low pitch 2:12 attic. The school of thought here from energy retrofit folks is that it is important to seal and insulate any duct work in your attic so the warm air doesn't migrate into the cool attic and then cause condensation problems in the attic which has been our problem. We are hoping we have resolved all our condensation problems which involved a new ridge vent, mold removal, soon to happen insulation work in a very difficult area to reach in our eves, but we want to be sure we have dotted all our eyes so if any problems come back, I don't have the roofer pointing at the little uninisulated kitchen exhaust fan duct and saying that is the source of the problem. I also don't want to pay the insulation company a couple hundred dollars to wrap a little pipe with insulation which I can do myself in a few minutes. I am just trying to figure out what is the right material to insulate an exhaust vent that might get a little hot at times.

A. Spruce
Re: Proper Insulation for Kitchen Exhaust Pipe

In all honesty, I've heard of zero issues concerning kitchen exhaust venting and condensation. Bathroom vents, yes, but generally, the issue isn't with attic moisture, it is condensation within the pipe that runs back into the bathroom fan.

I grew up in the northwest, and again, have heard of zero issues at the time or since, and attribute anyone telling you that there is an issue more to a white elephant than anything else. I will even step this up a bit and offer that in my 10+ years here at TOH, there has not ever been one post on this subject, ever, not even from the east coasters that seem to have a whole lot more problems with humidity, moisture, condensation, etc., than we do here on the west coast.

Where I can see issues is if any exhaust vent is terminated into the attic space itself, rather than the outside air. If you exhaust moisture from the house into the attic, then yes, you're going to have issues, but as long as your vents extend to the exterior properly, you should be ok - without insulation.

Lastly, if you will feel better with wrapping your exhaust vents, the by all means, do so, whether you do it yourself or have someone else do it. Will you see any real benefits from it, not likely, but your piece of mind is worth what little you'll spend to have it done and never worry about it again.

nauko
Re: Proper Insulation for Kitchen Exhaust Pipe

Thanks for the advice. I am not disagreeing about the neccesity of doing this. I am just wanting to end this line of conversation with our roofer. Any advice on what kind of insulation would be best to use to wrap this pipe? I just wanting to make sure I put something around this duct that is fire safe. We have a gas range below that pumps out some heat which the exhaust fan is venting. Is the fiberglass duct insulation with the foil backing going to be ok? They also sell this bubble wrap looking insulation. I just want to know what to use!

guy48065
Re: Proper Insulation for Kitchen Exhaust Pipe

If it were me I would insulate any long vent through a cold attic. Fire rating isn't an issue--a range hood doesn't carry away much heat from the range (you can hold you hand over it without discomfort), but does vent away a lot of moisture.
OTOH with your low pitch roof the pipe can't be very long so vapor won't have much chance to condense.

nauko
Re: Proper Insulation for Kitchen Exhaust Pipe

Everyone has been really helpful! Thanks!

keith3267
Re: Proper Insulation for Kitchen Exhaust Pipe

Because of your other post concerning your attic issues, I would say go ahead and use the insulation you bought. It won't catch fire. If the vent got hot enough to combust anything, then your clothes would catch fire if you got anywhere near that stove.

But, the insulation is not going to do you any good if you don't seal the vent pipe, and the insulation will not provide that seal. What you need is vent mastic. Its a putty like material that you paint on all the seams in your vent. You use it where the sections of the pipe connect, the seams of the curved sections and the seam down the sides of the pipe where it is put together. Then you can put the insulation on over that if you like. I don't know if the insulation will help, but if you put the mastic on first, it won't hurt.

If you put the insulation on without the mastic, it might make matters worse. It would trap moisture that escapes from the vent and hold it against the pipe, causing it to rust out in a year or two.

http://www.homedepot.com/webapp/catalog/servlet/Search?storeId=10051&langId=-1&catalogId=10053&keyword=duct+mastic&Ns=None&Ntpr=1&Ntpc=1&selectedCatgry=Search+All

BTW, do NOT use duct tape for this.

Midge1234
Re: Proper Insulation for Kitchen Exhaust Pipe
nauko wrote:

What kind of insulation should I use to wrap a kitchen range exhaust pipe vent in our attic? I went to Home Depot and came home with a fiberglass ventwrap that has foil on the outside, but now I am wondering about fire safety. Not sure how hot the exhaust vent gets, but it is a gas stove so range hood is sucking up a lot of heat.

Hello Nauko - Just wondering what you ending up doing with your venting? We live in Midwest US and totally get condensation that drips down from our uninsulated kitchen vent ducting and wet spot forms on drywall. Sometimes even finds it way to drip down in small puddle in basement.. This only happens when it is cold out, about 20 degrees and colder. We want to get this finally fixed. We are having hard time finding someone who will go up in our attic to insulate the venting.
Hope your venting is working well.
Thanks, Midge

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