I hope to hang my furnace this week or next. This is forced air gas (Modine type) and when I run the B vent flue through the attic will I need to establish a barrier around it so the loose fill insulation doesn't touch it? The B vent will be 5", I though I'd just put a piece of snap lock around it (anchored in some fashion) to hold the loose fill back, unless I don't have too. Not sure which loose fill I'll use, but I'm leaning toward fiberglass.

I think they require 1" space around it.    The issue with the insulation  is corrosion on the pipe from condensation that cannot dry off.   While fiberglass won't burn other types may.   Roly

Fred, that vent flue should be triple walled in the attic. In which case, it will be cool to the touch and, under normal circumstances, won't sweat. 

6 minutes ago, Gene Howe said:

Fred, that vent flue should be triple walled in the attic. In which case, it will be cool to the touch and, under normal circumstances, won't sweat. 

 

but it will still need a shield to keep the insulation away from it...

normal atmospheric conditions will cause condensation...

5 minutes ago, Stick486 said:

 

but it will still need a shield to keep the insulation away from it...

normal atmospheric conditions will cause condensation...

Never had a condensation problem but, it's AZ. 

1 hour ago, Gene Howe said:

Never had a condensation problem but, it's AZ. 

 

that happens any place that has high(er) humidity...

Thanks, guys. I'll plan on putting some clearance around the flue.