Methods for keeping cellulose insulation from gas flue line
I am preparing for an attic project: air sealing, and blowing in new insulation.
We have a gas furnace, and its exhaust flows in a Type B vent pipe through the attic and out the roof. The Type B requires 1″ clearance to combustibles.
There is already metal around the vent pipe where it enters the attic (picture should be attached). There is some gap between the vent and the metal, which I plan to seal using high temperature caulk.
There is currently nothing to separate the vent pipe from the attic insulation. I’m having a contractor blow in cellulose insulation, so I want to make sure we have that 1″ clearance away from the cellulose. The energystar website suggests making a sort of dam using aluminum flashing. On the other hand, the contractor says they typically wrap the vent pipe with rockwool insulation, in order to create that clearance. Does anybody have experience with either method? Is the rockwool idea safe? What is the best way to maintain the 1″ clearance?
I don’t know the efficiency of the furnace (predates our ownership of the house), and I don’t know how hot those gases are, coming out of the furnace.
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