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Venting experts: Does this seem OK to you?

Posted by Ginny20 (My Page) on
Sun, Aug 5, 12 at 11:39

When we redid the kitchen last year it turned out that, due various factors, the only way to vent to the outside was to go in the wall, down to the basement, across the basement ceiling, then out. I thought this was pretty ingenious of the GC. I understand that a run this long and with so many turns isn't optimal, but my hood seems to draw well anyway.

But when I run it, I notice that the basement smells like whatever I'm cooking. This suggests to me that the duct work isn't completely sealed. (Another possibility is that the vent outside is near the cellar door or window, and the smell is getting back in that way. But the basement doesn't smell like smoke when we grill out there, so I think that's less likely.) DH says it's virtually impossible to seal ducts enough so there is no leak. So do you think I have a problem or not?

Follow-Up Postings:

RE: Venting experts: Does this seem OK to you?

Yes, you have a problem. The design is pretty sub optimal to begin with and needs to be checked to make sure the CFM are adequate for such a long twisty run as well as the ductwork is large enough. Then the ductwork needs to be inspected at the joins as well as the exit location. Was this inspected by a codes enforcement inspector from your municipality?

RE: Venting experts: Does this seem OK to you?

I have plenty of cfm - it started at 800, and it's only induction. It sucks like crazy and I don't even run it on high. The ductwork is 10". But I do wonder about whether it's leaking at the joints.

I don't think anyone actually has a code enforcement inspection on remodels around here, unless you're actually building out new foundation.

RE: Venting experts: Does this seem OK to you?

Try using metal-based duct tape [not duck or gaffer tape] around all the joints.


RE: Venting experts: Does this seem OK to you?

an HVAC guy might suggest mastic for the joints.

I'll also wager you did not install any MakeUp Air. This would mean that as you run the fan there is negative pressure inside your house. The exhaust is probably finding it's way back into the basement through door or some other leakage point.

RE: Venting experts: Does this seem OK to you?

No, you're right,we don't do MUA around here. But the house is old and very far from air tight. There's a keyhole (for an old skeleton key) in the door to the garage maybe 6 ft away from the hood, and you can see right through it. I know air comes in that way, plus around that door. Your suggestion is possible, though. We have one of those old fashioned cellar doors right next to where the exhaust comes out, so it could be coming back in there. That wouldn't bother me as much as if the duct isn't sealed.

I'll see what the joints are sealed with. My GC was not an HVAC guy, and I may need one to get this right.

Thanks for all your suggestions.

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