How to air-seal a range hood flute


My new kitchen included a new exterior flute for a new range hood.

Few months later, I opened the cover for some maintanace reason and saw that the flexible flute is basically going through the ceiling via a hole cut into the ceiling.

The circular hole has about 1-2" space around the pipe… see picture.

How do I air-tight this? seems like all my house heating can just fly up into the attic this way…

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I thought to use expanding foam, but not sure if that is the "right" way, also, if I do, can I use the cheap stuff or do I need the "fire" rated one? any ideas? pictures are most welcomed if you have something to show me…

Best Answer

The proper way to seal the range vent flue penetration through the drywall ceiling is is Type B Gas Vent Fire Stop/Support/Wall Plate. See this link:

The fire stop plate provides clearance for the vent from the drywall and ceiling joists, while sealing the hole to block drafts, smoke and fire. Choose a fire stop with the appropriate dimensions and install according to the mfg's instructions (see the above link). The fire stop plate can be sealed to the drywall with silicone caulk and to the flue duct with aluminum foil HVAC tape for an air tight bond. In this range vent hood exhaust application, the air temperature will be very mild compared to a gas water heater or furnace exhaust where a fire stop is normally installed.

Do verify the exhaust vent has a damper installed somewhere to prevent backdrafts on windy days.

Take care, Bob Jackson