I just installed blown in cellulose insulation in the attic of my home. As I was in a hurry to get the insulation installed, I forgot to install flashing around the furnace exhaust vent and the stove chimney to keep the insulation away.

My question is: Is it necessary to install shields to keep the insulation away if both the furnace and the chimney are of the double wall type? Both vents have an inner tube that is actually doing the venting and the outer tube that seems to be just for heat shielding purposes. Any pros that can weigh in on this one?

Thanks.

Yes, even on double wall pipe you must have at least 1 inch clearance around the pipe... A good way to do this is to use aluminum flashing and surround the pipe in a cone to at least 6" higher than the insulation is expected to be. Then seal that to the flue with high temp caulk.

Thanks for the recommendation. I did a lot of research and came up with the same answer of course.

I like the cone idea. Good way to keep the inslation out for good.

I'll be installing the shields this morning.