clearance question

[wirt]

I'm in the process of adding a ceiling with insulation to my garage, I have a 45k Lennox hanging furnace and am wondering what the clearance for the the exhaust pipe should be? It's a double walled vent that goes up through the roof, is 1" enough or should there be more? Also how do you fill the gap around the pipe then?

Btw the ceiling is plywood and the insulation is typical fiberglass Matt.

Thanks

 

[metlmunchr]

Assuming this is type B vent on a gas fired furnace......

1" minimum clearance to combustibles.

Use either a firestop support or a firestop spacer at the ceiling penetration to seal it off and to maintain the pipe centered in the opening.

 

[wirt]

Thank you sir!