The metal firebox is lined with refractory panels that look like masonry. These panels are manufactured with high thermal properties, generally are 1/2 in to 3/4 in thick. There are four panels for the back, bottom and sides. Their purpose is to withstand the high heat of a fire, protecting the surrounding metal firebox. Without this protection, heat can transfer to the metal enclosure and cause it to warp, weaken, or worse; transfer heat to the surrounding combustibles, which is obviously a fire hazard. You don’t need a flame to create a fire, you just need an ignition point hit. Years of heat transferring to the surround wood consistently lowers that ignition point, increasing the likelihood of a house fire.
Why do they deteriorate?
Fireplace refractory panels are a common repair. They are not meant to last forever. Years of heat and usage cause wear and tear, stress and heat cracks, abrasion and pitting, all of which can compromise the effectiveness of this safety barrier. They are made to be relatively easily removable and replaceable. Each manufacturer sells prefab panels for this eventuality. There are also aftermarket panels that can be cut to fit, if the make and model cannot be determined or if the fireplace is no longer made.
When should they be replaced?
One should consider replacing the refractory when large cracks occur. If the crack is larger than 1/16 inch (thickness of a nickel) the refractory should be changed. Also, if the refractory starts to crumble and fall apart in chunks, you should replace it. Not only will this replacement provide a safe burning environment, it also will increase your unit’s efficiency creating a more enjoyable fire.
New Refractory panels:
Will transform and refresh the appearance of your fireplace
Will prevent heat from penetrating the metal firebox causing unseen damage
Will revert the fireplace to its original safety standards
Will reflect heat, from the fire, back into the room providing alternative heat to the home