So I just installed a 300CFM range hood that is going to be ducted (partially) through an attic and out the gable end of the house. The exit will be near or right beneath the gable vent for the attic. Is that a bad idea?
The gable vent has louvers, the attic has been air sealed relatively well, and the duct exit would be a metal wall cap with a damper. Also there is a ridge vent and soffit vents.
I thought there might be a code regarding the location of the range hood duct exit; and then I thought that in certain situations with the right wind the exhaust may find it’s way into the attic.
What do you think? Any advice?
Replies
Its hard to say without doing the calculations but my first thought is if the soffit and ridge vent is adequate to vent the roof then you could go ahead and block off that one gable louver
I would also insulate any duct pipe that runs through the unheated attic space or you will have condensation dripping back into the hood
I agree w/ Maverick. Backdrafting back into the attic wouldn't be a desireable thing. If you have the vent area w/ the other sources, blank off the gable vent. But you also have to think about staining the wall w/ the grease and all blowing out and then depositing on your siding. On a roof, this isn't as noticeable (although it still tends to happen).
The gable vent should exhaust air if it's done as part of the attic ventilation system--in other words, the air intakes that ventilate the attic should be in the soffit, and the warm air should rise and escape through the gable vents under normal conditions. Wind could change the flow at times.
But, even if the gable vent were to draw in some of the kitchen exhaust under certain rare conditions, what harm would it do? None I can think of. You're not a restaurant producing constant grease-laden vapors.
And, 300 CFM is a lot for a domestic range. You will be diluting any range exhaust to a point that it's not going to create any problems.
Codewise, if you're on the IRC, there's no prohibition against your installation, with the possible exception that, if the manufacturer of the exhaust fan has something against it in the installation instructions, the code always wants you to go by that.
thanks for the feedback everyone; I think I might go ahead and put the duct exhaust there then. It's the most convenient spot mechanically, but I wasn't sure about the code that stated range hoods had to exhaust 3 feet from an opening (is a gable vent considered an opening?)The duct will be very well sealed, and I plan on wrapping the run with a R13 batt and taping the seams. I also thought about slightly pitching the last portion of the run on it's way out...