Dryer vent gap

[appdude]

Its been a long time since i've last been here. Anyway, we recently switched out our old dryer vent hood because the old one had broken flaps. Though the new one does look nice, on the inside, there is now a gap between the vent and the wall. I'm not concerned about insulation because there is fiber glass surrounding the pipe. Now to fill in the gap, i seen people recommend using spray foam. The only problem I have with spray foam is its flammability. There is very hot air passing through the vent and I'm concerned about using this. Has anybody used this? Or is there an alternative?

 

[Rayh78]

Its been a long time since i've last been here. Anyway, we recently switched out our old dryer vent hood because the old one had broken flaps. Though the new one does look nice, on the inside, there is now a gap between the vent and the wall. I'm not concerned about insulation because there is fiber glass surrounding the pipe. Now to fill in the gap, i seen people recommend using spray foam. The only problem I have with spray foam is its flammability. There is very hot air passing through the vent and I'm concerned about using this. Has anybody used this? Or is there an alternative?

Well just use Great Stuff fire block formula, but good luck if you ever have to replace the vent and pipe again.
If the wall is already insulated why not just caulk a trim ring in place.

 

[Sponsor]

 

[Dana]

The Great Stuff Fire Block formula's ignition temp is a bit on the low side , and is the same as all of their other can-foams) and lousy choice for sealing up a dryer vent:

"CAUTION: When cured, these products are combustible and will burn if exposed to open flame or sparks from high-energy sources. Do not expose to temperatures above 240ºF (116ºC)."

I'm not sure what the max operating temp would be that wouldn't prematurely age it, making it brittle & crumble, but it's probably not much more than 150F.

The primary difference between the FireBlock and the other versions of Great Stuff is that it's orange, which makes it easy for the inspectors to see in jurisdictions where fire codes require every electrical, plumbing, and duct penetrations between floors or framing to be air-sealed for fire safety.

Caulking a non-flammable ring in place with a fire-rated caulk such as RTV silicone would make more sense.

 

[appdude]

I actually would prefer if the trim ring was there, however I have not been able to find it at all.