I am making final preparations to my existing firebox while I wait for my chimney liner to appliance adapter to arrive. In the diagram I've attached, the area shaded in yellow is a disgusting mess in my fireplace. It is filled with a sooty, black, grainy substance (creosote?). There are also small chunks of old firebricks and small animal bones! I have been reaching back there and scooping it out cup by cup. I seem to remember reading somewhere this area should be filled with sand. I could see sand being beneficial to keep pressure on the firebricks and also as an insulator. I don't have any sand on hand but I have plenty of roxul. Can I fill the area with roxul or should I go get some sand?
I'm installing a Jotul 550 with a full length insulated liner in an exterior chimney, if that affects the answer.
I'm installing a Jotul 550 with a full length insulated liner in an exterior chimney, if that affects the answer.