I use a Lopi Revere insert. It is installed into an old Heatilator steel fire place box. The 6" flex pipe for the stove comes through a slot cut in the damper and top of the fire place box. The pipe is insulated and the gap around the pipe and damper is insulated. I have the 12" trim around the stove. I think a lot of heat is being trapped in that space a between the stove and fire place box. I'm thinking about cutting some slots or get a metal guy to cut some kind of design in the top piece of trim so that heat can escape into the room. Thoughts/comments/suggestions
Do you have a good block off plate and the chimney filled with insulation, not just an insulated liner but poured full of insulation around the liner?
I would bet that there is not as much heat being trapped back there as you think as long as you have the insert fan running