What insulation is best for the arch?

[philkasza]

I have a 5x12 arch that had fire brick in it and I was wondering what insulation to put in instead of fire brick.

[Matt Hatch]

k wOOL MADE BY lYN INDUSTRIES IS GOOD STUFF PLUMBING AND HEATING SUPPLY STORES CAN GET IT. GOOD LUCK !

[Fred Henderson]

Ceramic wool , 8lb density.