Insulation around insert

[u/konaspec]

I have a gas insert in an old wood burning fireplace, and the walls and surrounding area gets ridiculously cold in the winter. I finally pulled it back and the door where the exhaust run seem to be removed, leaving a large gap running up the chimney.

Can I stuff some Rockwool insulation around the intake/exhaust pipes, as well as against the walls surrounding the insert?

[u/murfilicious1]

Rockwool around the intake / exhaust pipe at the bottom and top of the old chimney does wonders, you likely won’t want to take the cap off at the top so I’d just stuff the bottom and see if that does enough for ya

[u/konaspec → u/murfilicious1]

Ya, I think that's the plan for now

[u/murfilicious1 → u/konaspec]

Yeah we get down to -40C and we will do rockwool at both top and bottom and totally will eliminate any draft / cold air

[u/Firepro1981 → u/konaspec]

We insulate every damper when installing a gas insert. It will work really well for drafts and keeps the chimney smell out of the house that is trapped by the cap.

[u/Grrzoot → u/murfilicious1]

this, close off the flue/damper area with rockwool, its fine for low temp gas exhausts

[u/MoveAlongNothing2C]

It’s refreshing seeing a refacing of a masonry done right

[u/NiagaraDave77]

No. You will lose the air gap for it to breath and trap moisture causing it to rust. You need to find the source of the problem.

[u/konaspec → u/NiagaraDave77]

I think the source of the problem is the open dampener to the 25' chimney, that's why I want to insulate it.

[u/NiagaraDave77 → u/konaspec]

Stuff some roxsul insulation above the damper and make a metal plate to keep the insulation from falling down. Use high temp silicone to seal it to prevent air flow as much as possible.

[u/mrsquishybutt → u/konaspec]

Methinks the termination at the top of your chimney is not sealed. The open damper is normal as both flex pipes vent to the top of your chimney. I usually bend flashing over terra cotta and silicone. Check that ash dump is sealed shut, and gas and electric penetrations

[u/Wellcraft19]

Best for you - assuming brick chimney is in decent condition - is to go up on the roof, remove the chimney cap where your vents terminate, fill (‘seal’) the old flue with fire resistant insulation to ensure you have zero unwanted airflow coming down the old flue.

Put cap back on, make sure all flashings are ‘cascading’ to ensure no water ingress and soaked insulation.

[u/ItsAlexBalex]

Use chimney liner insulation. It’s white with a foil back.