Cold Face Insulation Bricks (CFI)

A cold face insulation brick (CFI) is a highly porous, low-density brick that sits behind the working lining, not in the flame path. Its job is purely thermal: cut heat loss through the shell, lower the cold-face temperature, and reduce the heat stored in the lining so the furnace heats and cools faster. Our CFI is Group 16, rated to a maximum safe working temperature of 900°C.

CFI Group 16 is rated to a maximum safe working temperature of 900°C. That is a backup rating, not a hot-face rating: it must always sit behind a dense working lining or a hot-face insulating brick. Putting it in direct flame or slag contact will fail it quickly. If you need insulation that can take the hot face itself, use HFK 135 or HFK 140 instead.

CFI (Group 16) is a backup brick for up to 900°C, at 0.75-0.80 g/cc bulk density, that sits behind the working lining. HFK is kyanite-based and built to hold a working face itself: HFK 135 to 1350°C and HFK 140 to 1400°C. CFI is lighter, cheaper and more insulating; HFK is denser and stronger because it has to survive direct exposure. Many wall builds use an HFK hot face over a CFI backup.

Use a matching insulating mortar, never a dense fireclay or high alumina mortar. A dense mortar joint conducts heat straight through the wall and becomes a thermal bridge, which defeats the reason you specified an insulating brick. Joints should also be kept thin and consistent. We supply insulating mortar matched to the brick grade with the order.

Two ways. Low thermal conductivity slows heat escaping through the wall, so less energy is lost continuously. Low bulk density means less mass to heat up, which matters most on batch and intermittent furnaces that cycle daily. The actual saving depends on your current wall build, cycle pattern and shell temperature, so ask us to run the heat-loss calculation on your drawings.