Question on venting a range hood — 6" round to 3.5" x 10" rectangular okay?

Eric Scheidler

Hello there. I hope this is an appropriate question for this forum.

I'm a homeowner who is having his kitchen gutted and renovated. One quandry we're facing is how to vent the range. We plan to use a wall-mount range hood, which requires a 6" round vent. However, the ductwork will have to sneak through a drop ceiling, with only 4" of space.

My proposed solution is to switch from 6" round duct going up through the chimney to 3.5" x 10" rectangular duct going through the ceiling, and then down through a cabinet and into the wall to the vent to the outside.

Will this provide enough volume for the vent hood motor to do its thing?

This is the range hood we've picked out (CFM 400).

Here's a picture of the location, with a drawing of my proposed ductwork. Please ignore both the 2x4s that are in the way (they'll be removed and headed off), and the BX that's also in the way (also going to be moved over).

Larry Weingarten

Hi, The area of the 3.5" by 10" duct is a bit more than the area of the 6" round duct, so you should get decent air flow. The tight 90 degree bend in the rectangular duct doesn't really help, but as the duct has more area, it isn't a fatal flaw. Is the outlet of your range hood 6"? Often they are 7".

Yours, Larry

mattmia2

Even if you were reducing it, it will still work, you'd just get less flow than the spec.

EBEBRATT-Ed

you should be fine

Eric Scheidler

Larry Weingarten said:

Is the outlet of your range hood 6"? Often they are 7".

Yes, the outlet is 6" for this range hood.

Eric Scheidler

Thanks for confirming this approach to the problem, y'all!