Type of insulation between exhaust flue and chimney flue?

Question

We converted a wood stove to a propane fireplace. It's a direct vent but we're only using the exhaust insert. The intake air will come from the interior.

Anyways, as such, we have a gap around the new flue insert and the flue. What kind of insulation can I use to plug up that gap at the bottom to prevent cold air from pouring down in the winter?

Answer 1

Mineral or rock wool is what it is called, I believe Roxul is a brand of that. Check its properties to make sure it can handle that kind of heat. It is approved for firestopping in framing of homes.

Here is a video of it's benefits

http://www.youtube.com/watch?v=7rbRYs0XEAM