Sorry guys but I've been too swamped to help on the board recently.
I recently moved into a place with a brick fireplace with a Heatilator steel insert. The metal insert has 4 sides and tapers up to the damper and up to the chimney. Its 18 years old, the age of the house.
After closer inspection, I see yellow insulation around the top and sides of the metal liner at the front edge. There is the metal liner, a 1 inch gap with a yellow looking insulation, then the front row of bricks next to the glass screen.
My questions are: What is this insulation? Should it be there? Is it fireproof (it shows some slight charing from previous owners fires)? Is it safe to use the fireplace with it? Who else might I ask about it?
I searched the web, looked at several fireplace Q&A sites. Searched all the posts here.