I ran across this today. The flue for the gas furnace is against the closet wall. The exterior of the flue where it touched the wall was around 100 degrees. I think the flue should be routed so it’s away from the wall. Could this be a fire rated material on the closet wall? It’s brown, about a 1/4 of an inch thick? The other thing here is the logo and lettering on the furnace cabinet. It’s upside down. Is it posible to install a furnace upside down? HA HA.
G2426.4 (502.4) Insulation shield.
Where vents pass through insulated assemblies, an insulation shield constructed of not less than 26 gage sheet (0.016 inch) (0.4 mm) metal shall be installed to provide clearance between the vent and the insulation material. The clearance shall not be less than the clearance to combustibles specified by the vent manufacturer’s installation instructions. Where vents pass through attic space, the shield shall terminate not less than 2 inches (51 mm) above the insulation materials and shall be secured in place to prevent displacement. Insulation shields provided as part of a listed vent system shall be installed in accordance with the manufacturer’s installation instructions.
This section of the IRC is talking about where B-vent passes through a wall. The B-vent should also be kept 2" away from any combustable materials. If the wall is drywall, then that is not considered a combustable material. If studs are present near the opening of the drywall or any NMC, then that would be an issue. Hope this helps.
I believe B-vent components need only 1" clearance to combustibles.
Is’nt it things like this that make you think and say, hell it might not make the house burn down, but couldn’t they have tried to make the stinking thing right to begin with and save someone else some money to pay someone in pointing that out?
Amazing isn’t it?
Marcel 
isnt the paper backing on drywall a combustible?
First paragraph of page 2 of Manufacturer’s PDF sheet and read NFPA info of WORD doc.
I would guess then that a b vent touching fiberglass insulation would be ok since fiberglass is non-combustible. Correct?
Correct…but watch out for the paper or foil backed batts.
Not acceptable