Single wall vent clearance from duct board

[jfrederick (Joshua Frederick)]

I think I’ve asked this before, but here goes again (as I couldn’t find it searching): Does the 5" or 6" (can’t remember which) clearance apply when the material is duct board?
Thx in advance.

[lkage (Larry Kage, CMI)]

@jfrederick

I think I’ve asked this before, but here goes again (as I couldn’t find it searching): Does the 5" or 6" (can’t remember which) clearance apply when the material is duct board?
Thx in advance.

Single wall vent pipe needs 6" to combustibles.

[jfrederick (Joshua Frederick)]

@lkage

Single wall vent pipe needs 6" to combustibles.

I know, I stated that ;-). Is duct board combustible and/or is this set up incorrect due to proper clearances not being in place?

[ddagostino (Dominic DAgostino, CMI HI3957)]

It depends on the ASTM rating of the duct board.

Chances are, it isn’t rated as such.

Dom.

[eschmidt (Erik Schmidt)]

Is that duct board supply or return? If it is supply duct it should have a fire rating.

[grusk (Gary RUSK)]

Fire-Rated Assemblies
Mat-Faced Micro-Aire, SuperDuct RC or Micro-Aire Type LP duct board
1" (25 mm) thick is accepted in lieu of sheet metal duct in many fire-rated
assemblies. See UL Label for design numbers.

Gary