Unlike fireplaces made of brick and mortar, pre-fabricated fireplaces are made of thin sheets of metal. If they get too hot, they warp, permanently damaging the fireplace and resolved only with its complete replacement. They can also transfer heat to the wood frame of your home and set the house on fire.
Refractory cement insulating panels are used to prevent this from happening, absorbing most of the heat and keeping the metal sheeting cooler. They wear out over time and have to be replaced, and homeowners should not start fires if cracks or damage is evident in these panels. They need to be inspected by a certified chimney sweep and in all likelihood replaced.
Many homeowners are uncertain of the signs that it is time to replace these insulating panels. Among the things to look for are chimney spalling, where chunks of brick or cement have fallen off, and a panel that gives when you press it lightly. Further, if a credit card can fit into the crack, the panel needs to be replaced.
As the installation of zero clearance fireplaces has soared, pre-fabricated replacement panels have come into increased demand. Consequently, custom patterns are available and, for relatively little expense, homeowners can restore their fireplaces to good condition. It is usually easiest to simply replace all of the panels even if only one is damaged, since matching it would require finding that exact model. This is unlikely, with many manufacturers of existing fireplaces having gone out of business.
Since cracks in refractory panels can result in serious hazards and even lead to house fires, they need to be addressed promptly. Again, fires should not be started until cracked or warped panels have been replaced. Intended to reflect heat back into the house and away from the firebox, preventing heat from damaging it, these panels play an integral part in a fireplace safety.