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bigdoglover

Help please -- flex duct in range hood

14 years ago

Last night I read PeterH2's comment not to use flex duct in a range hood because of possible grease build-up/fire hazard.

"Moving a range hood by a few inches" by dee850,

http://ths.gardenweb.com/forums/load/kitchbath/msg121718033887.html?7

Yesterday I had my exhaust fan insert installed in my wood mantle hood, and he did use flex duct! I questioned that and he said he couldn't use rigid duct because there were no doors on the front of it, so it was not possible to get up in there to do it. This seems unlikely -- how many range hoods must there be that don't have doors! Then he said flex duct is in compliance code.

The stove backs up to an exterior wall, so the exhaust vent (which he also installed just yesterday -- builder had not done so) goes pretty much straight out. I'm not sure how long the run from the fan is vertically, but can't be more than a few inches to a foot.

So, does this make a difference re grease/fire hazard? Does what my installer said have merit? My hood is basically a big square box, easy to stand up in and move around some. Should I ask him to come back and change to the rigid flex that Peter was talking about?

Unfortunately the granite is now installed so he's going to have a much harder time getting up in there than he did yesterday, when he could stand on a piece of plywood on the cabinets. I'm not about to let him stand on my granite or on my new cooktop.

The exhaust fan also vibrates a lot at top speed, so much that the wood hood can be felt vibrating. I'm wondering if this is because of the air resistance against the flex duct. It is a Faber 600cfm exhaust fan.

Comments (12)

  • 14 years ago

    I can tell you that it is against code here in SF, CA.

    And you are right not to let him stand on the granite/cooktop. Mine was cracked when someone did that :( Luckily my fab fabricator fixed it and no one can tell.

  • 14 years ago

    Thanks Marcy, I'm going to call our City Code Department right now.

  • 14 years ago

    No, this isn't a losing battle. It doesn't matter what everyone else does, it's against code, period, get the installer to come back and fix it. Assuming you needed permits for the work and will have an inspection, you won't pass. Tell the installer he is in violation of city code and it needs to be fixed or you will report him. This isn't just a petty bureaucratic issue, it's a safety issue. It may also become an insurance issue if you have a fire and your insurance company refuses to pay out. Hold your ground and demand that the work be done correctly. Good luck!

  • 14 years ago

    Oh, I love that line, "this is what everyone does." I ran into that once during my reno. I didn't want to sound b@tchy, but had to insist that I knew what the code was and what he was trying to do wasn't code. Just because the guy has gotten away with what he's doing, doesn't make it right.

    It doesn't sound like you have a GC who can talk to the installer, right? Put on your no nonsense pants and insist the work be done to code. I like Weissman's suggestion of reporting the guy, or at least the threat of it. :)

  • 14 years ago

    I'm in Southern Louisiana, it's against code here. I'm currently switching out my builder-installed, against code, flex ducted vent hood system to a rigid pipe, new liner, new inline blower.

    I have an *amazing*, old school, perfectionistic kitchen contractor and a great vent hood specialist (from Coburn's, you have at least a couple Coburn's stores in TX if you choose to bring someone else into the job). My contractor was *disgusted* when he saw the flex pipe. He brought me into the attic to show me all the problems it can cause, then brought me into the attic of another of his customers with properly installed rigid pipe. It was a great lesson.

    From what they've taught me, and my own research/recent crash course, it's a big deal in a few ways- the fire hazard, and the fact that wherever that flex duct bends you're losing the benefit of the full circumference of the pipe. So a 10" pipe bent (and therefore squished down below 10") at a 90 degree angle even once makes the whole system louder, less efficient, etc. That causes noise and efficacy issues. You could duct tape everything down, but that's like a band-aid. I'd insist on rigid pipe installed by someone who cares about doing it right. Proper installation can make a huge difference in noise, etc.

    As for the safety hazard, I've already had 1 cooking-related house fire. Stand your ground, my friend! You don't need to be worried about a potential fire.

  • 14 years ago

    Well THANK you Weissman, Breezy and Madeline for your strength on this! I'm recharged to have it done properly, according to Code. DH is on board with this too. We do not have a GC so will have to take the stand ourselves.

    Madeline, I was unaware of Coburn's. The closest one is in Athens TX, about 1.5 hours away, but I'm going to call them tomorrow. Thanks so much for sharing that. At least mine does not go up into the attic -- it is all self-contained in the hood itself, and goes straight out the wall behind the hood. But your point is well-taken -- one squish or kink in the flexduct and that can ruin the whole reason for having it.

    One more question for you: I see his problem. There is no access panel, so how is he supposed to get his hands up there to connect the unit to the rigid duct after he has pushed it up into the wood hood? Thus he's saying he needs the flexduct to dangle down... BUT, don't you think that with precise measurements and good care, he could arrange and position the rigid pipe so that it mates up perfectly with the unit when he pushes it up there?? Or should the cabinetmaker have made some kind of access panel on the front of the hood? I see a lot of pics of hoods that definitely don't look like they have access panels.

    I've just spoken to our plumber about this, who's coming tomorrow to hook up the sink etc., and he thinks the above is do-able (mate the two pipes as the unit is being pushed up and positioned.) What's your experience on this?

    Thank you again, I'm so glad I asked.

  • 14 years ago

    The cabinet maker should have created an access panel since you were venting out the wall. It would have made things a lot easier. If you were venting straight up, you would have access from the attic and be able to attach a piece of rigid ducting to the vent and raise it straight up into position and make the final connections in the attic. Venting straight out the wall is harder on the HVAC person, but the attachment can be done with the asphalt based mastic instead of metal tape. You have to have patience, and it'll be stinky for a good while, but it's doable. Is this person a professional HVAC person? If not, that's where I'd start----after this guy refunded your money.

  • 14 years ago

    Do you still have money held back that is payable after all items pass inspections? If so, that will make it easier for you to either get your money refunded or to get they installer back to correct this issue.

    My GC tried to pull the same thing with my venting, using small flex duct, though he knew it was against code. We had agreed to cover all inspections from day one as BF is retired, and pointed out the ducting to the inspector who promptly failed the installation. Bottom line was that the installer had to buy the correct parts and make it work to pass inspection. I'm sure that once he is forced to do it correctly, he will quickly figure out the parts to the puzzle.

  • 14 years ago

    I am glad you are standing your ground. I am appalled that the contractor is willing to risk your and your family's life so his task could be easier. I am also appalled that others that you speak to in your area seem to back him up.

    Things sure do vary by region. When I had my hood installed, the flex duct was there from the previous owner. At the time, I wasn't educated about hoods, so I didn't think a thing about it. When the appliance store installer came to install my hood, he said he would have to replace the flex duct, whether I wanted it or not. He said he would not be permitted by his employer (the appliance store) to leave my house with flex duct still there, or he'd be fired. He also explained that if I refused to allow him to replace the flex duct, he would not install the hood, and take it back to the store, and they would refund my money for the hood. Of course I told him he could go ahead and replace the flex duct with rigid duct. There is a cabinet door above the hood that gave access. The extra charge was about $30, mostly for time/labor, as duct is pretty cheap.

  • 14 years ago

    thanks so much lwo, katsmah, and shannon. No, he was not an HVAC person and thank you for that suggestion lwo. We got our HVAC guy out here and he's working on it. Meanwhile, turns out we got a real bum steer with the original person (yeah, obviously!) and are working on getting at least part of our $$ back. katsman, no, we stupidly paid the whole thing. Good news is he has not cashed the check, so I put a stop on it while DH works this out with him. I hated doing that, but would have no leverage any other way.

    The good news is we found a very good appliance installer in the process. I don't know if it's the new location (Texas) or if things have gone downhill everywhere since we moved here 4-1/2 years ago, but we are finding out the hard way that there are a lot of contractors out there who just don't know what they're doing.

    I appreciate all the help here. :-) Yes, I can still smile.

  • 14 years ago

    Bigdoglover,

    So glad to hear you had the opportunity to stop the check!

    As far as access panels, I can only say that my contractor says it's far preferable--he's putting them in for me--but it it can be worked around if they're not there.

    It sounds like you have some great people to work with. Best of luck, and if you want to talk to my Coburn's guy, just email me anytime!