How to fill gap around range hood vent pipe base

Question

How do you fill a gap between a range hood exhaust and the cabinet?

My stove range hood is affixed to the underside of a cabinet, and inside this cabinet is an opening on which rests the base of the vent pipe.

Unfortunately, the rectangular base (for lack of a better descriptor) is slightly smaller than the opening in the cabinet. There is a 1/8"-3/8" gap that i’d like to close because it’s not air tight.

What should i use? Wood shim, duct tape, foil tape, foam, tuck tape?

Note: the base is smaller than the cabinet hole, but it is larger than the range hood’s vent opening. It sits on the metal surface of the hood, so, it’s not just hanging in the air.

The whole thing was a mess of duct tape before, which i removed. I drew in red where the rim of the base sits. There is a lip and it just sits on that. No screws, no sliding on anything, no friction, no flange. it just lays there with gravity, supported partly by the rigid vent pipe elbow above.

Answer 1

High-temperature Silicone caulking.

When contemplating the choice of what to use on a kitchen exhaust vent, you always need to consider that it might be containing a grease fire at some point in time, so things like foam and the plastic alleged duct tape that were on there before are right out. Foil duct tape might be an alternative, but the HT silicone is suitable for things like pellet stove vents, etc. and will make a more positive seal in this situation.