Insulating the chimney

I installed my direct vent LP fireplace insert over the weekend and installed the vent pipe through the existing chimney flue. After installing both pipes and getting the stove situated I noticed there was quite a cap in the flue around the liners. Anyone use insulation to seal this space? Will my vent pipe get too hot for fiberglas insulation? I am just worried about it maybe melting or causing a fire in the flue. I was going to stuff some fiberglass house insulation in there (with the paper removed) anyone think this is a good idea?

Don't put insulation in contact with the chimney, the isulation should be at least three inches away. Your best bet is to caulk the gap between your ceiling or wall firestop.

I can't caulk it because it's in an existing firebox. The vent liners go up through the damper of the existing fireplace. I think what I will do is make sure there is no insulation touching the exhause vent pipe.

The manuals for the gas inserts we sell specifically say to jam fiberglass insultion up there to seal it. It is perfectly safe for the ones we install. Check the manual.

Agreed. Check the manual, typically fiberglass insulation is stuffed into the gap. What kind of unit is it? We might be able to look it up together.

Thanks guys. I looked over the install book that I got but it doesn't say anything about filling the gap with anything. The unit is an Empire Innsbrook. I appreciate all the help.

I have a 3" pipe going up an 8" insulated chimney (for a pellet insert). Can I put fiberglass insulation around the 3"?

Never mind. I read the manual and it says fiberglass is OK. Plus, this is the gas section, not pellets!

danthman,

When they installed my DV gas stove in a masonry chimney (fireplace), they put a sheet metal plate under the smoke shelf (I had no damper). The two 3" lines for the stove ran through a hole cut into this plate.

The installer said that this plate was not really needed but he liked to do it to keep cold chimney air from coming into the house when the stove is not in use and the exhaust pipe is cold. He also said that stuffing around the gaps with fiberglass insulation was OK. jmho

Are you guys talking about puting firberglass insulation all the way up the chimney between the liner and the flue or just between the liners and the damper opening?
My damper was left on but left in the opened position with fiberglass insulation stuffed between the the open damper and the liners.
I was told by the installer that this was ok and I believe,(as mentioned above), that Heat & Glow has this listed in the owners manual for my FB Grand owners manual.
Sometimes I have heard of installers using what is called a Block OFF Plate in lieu of the open damper and fiberglass insulation.

John

fiberglass insulation will not burn, after all its glass. i put it around wood stove pipe and dampers. melting point is over 1800 degrees.

You cannot put fiberglass insulation around wood stove pipe or liners, the liners are rated to 2100 deg (with proper insulation) and as you stated the fiberglass is less than that. This is why they sell special insulation for wood liners.

Fire Bug, yes just in the damper area. The FB-Grand manually specifically says to do this.

the best way to really go is the same as wood insert it is to use a sheet metal block of plate insulation is allowed in alot of cases it can get some moister in it from the summer months and can start to fall out over time i have seen it laying on top of the firebox. not my first choice.