The Complete Handbook of Heating Radiator Reflectors

Chapter 1: Understanding Heating Radiator Reflectors

Heating radiator reflectors are not a new or exotic technology, and that is precisely why they are often misunderstood. They are simple devices: a sheet of material placed between a radiator and the wall it is mounted on, intended to reduce heat loss through that wall and redirect some of that heat back into the room. The concept has been around for decades, and the materials are not complex. Yet the difference between a reflector that saves a meaningful amount of energy and one that is a waste of money comes down to a few specific physical principles and a handful of practical installation details. This chapter is about those details.

Let us start with the problem they solve. A radiator heats a room by two mechanisms: convection and radiation. Convection is the process where air in contact with the radiator heats up, becomes less dense, and rises, setting up a circulation loop. Radiation is the direct transfer of heat in straight lines from a hot surface to a cooler surface, without heating the air in between. For typical hot-water radiators running at 70 degrees Celsius, roughly half of the heat output is radiated in the form of infrared energy. The other half goes into the air via convection. Both mechanisms are important, but the radiated half is the one that a reflector addresses.

When a radiator is mounted on an exterior wall, its back surface faces that wall. The back surface of a