Rockwool insulation

[DWBOX2000]

Do people use that around secondary pipes coming off a gas fireplace. I have a gas fireplace that the back side is in a mud room. A cold breeze blows through constantly during the winter unless fireplace on. Around the box is insulated but where the pipe comes into the fireplace there is a 1/4” space around the pipe. Cold air comes into there and goes right out the front of the fireplace. If you look through the face of the fireplace, you can see the space at the pipe. Not sure how to seal without something touching the pipe.
Thought? Thanks.

[Zeke]

Generally fireboxes and all apparatus require 1" of clearance all around (you need the installation specs). There are collars for the vent pipes that should seal that 1/4" you have. The vent should be double or triple wall so the heat transfer through the collar won't be a hazard.

I would not stuff it full of rockwool. Supposedly it won't melt or burn but you do want the vent pipe to be able to radiate some heat. There may be some silicone that can be used. For sure I'd consult the installation instructions and keep it to code for any insurance issues.

[masraum]

I would absolutely go by what Zeke says. I think he’s forgotten more about this sort of thing than I’ve ever known.

That being said, rockwool is used as the insulation on Chambers ovens and is not going to burn or melt.

[DWBOX2000]

Thank you both. I’m not sure if doubled or tripled pipes but I can put my hand on it. Hot but not burning. I’ll see what I can find out about it. It’s over 10 years old so not sure what I’ll find out.