We have a coal-effect gas fire with a flue that goes straight out through the wall. Unfortunately, there is a considerable draught coming into the room from behind the fire, which rather defeats the purpose of having it. Presumably, the hole in the breeze-block inner wall is much too large. It doesn't seem possible to dismantle the fire from the inside, because the flue is screwed onto the main chamber, and then the flue is cemented in place from the outside. I would like to avoid having to knock a few bricks out from the outside (which seems to me the only way to get access to the gap), and I was wondering if there is some kind of filler that would suit this application. I see there is a product called firefoam, but I don't know if it's meant to be used in a situation where it will get hot for repeated periods over the years. Does anyone think this would be suitable, or is there anything else I could use?
Thanks.