By peter di benedetto from oxford ,ma --01540 on December 16, 2011
i have a 12" gal pipe with a liner s.s. 8" inside hookup to a fire place. It goes up in the wall approx 2'x2' space up 2 floors to the attic. There is over a 2'' space held from the floor and ceiling joist -with metal fire stops at each floor. The insurance company wants us to put in attic insulation shields around this 12"" pipe to keep back the cellulose insulation. Do i need a shield? There is a 2" fiber glass wrap around it now - can cellulose insulation start a fire if it is up against the pipe?
By Collin C. - NFI Master Hearth Professional on December 16, 2011
Answer:The primary concern with insulation being against the vent pipe is with the transfer of heat. The insulation, while noncombustible by nature, can heat up and transfer heat to adjacent framing members. This can cause the wood to dry out over time, possible scorching it and causing a fire.
You can remove the insulation from around the pipe, but a insulation shield is recommended.
We do not carry shields for a 12", as this is quite large and usually not used in a residential application. However, shields can be produced from 24 gauge sheet metal for this application. A metal collar would need to be wrapped around the pipe and riveted along the seam. You would then need to create a metal ring to cover the collar and keep insulation from falling down inside. There needs to be at least 2" of space all the way around the pipe between the outside wall and the inside of the fabricated shield.