When you think of a traditional radiator, what comes to mind? If it's a big, clunky cast iron radiator taking up plenty of space against a wall, you're not alone. Cast iron radiators are the original hot water heating system in North America.
Built to last forever, millions of them are still in perfect working condition. You might wonder, with all the technological advancements in heating, is there a better way? Would baseboard heat be just as effective with plastic or wood baseboard heater covers?
Metal is an important elelment to the success of baseboard heating. It's all about the conductivity and retention of heat energy.
Why Steel is Necessary Rather than Plastic or Wood Baseboard Heater Covers
Finned tube element heating, also known as baseboard heating, uses the exact same convection and radiant heating principles as the larger cast iron radiators do. When the thermostat calls the boiler for heat, the boiler turns on and heated water flows through to the emitters in the heating loop. The slow moving air currents in the room will encounter the fins, the air will be heated, will rise and then eventually cool and fall to the floor. This process is cyclical. What happens when the thermostat tells the boiler to shut down after the set temperature has been reached? The water in the system stops flowing and eventually cools. It is at this stage of the cycle where the presence of steel close to the emitter makes a huge difference.
Steel is an excellent conductor of heat energy. Wood and plastic on the other hand, not so much. After the boiler shuts off, the steel baseboard heater covers will still retain warm and the rooms convection air currents will continue to circulate for a certain period of time until the temperature in the room drops. Delaying the call for heat results in an overall fewer number of calls for heat to the boiler, which reduces the consumption of fuel and boosts efficiency when compared to naked finned tube element or when insulating materials like plastic or wood baseboard heater covers are used.
Steel vs Plastic vs Wood as a Conductor
Thermal conductivity is defined as "the quantity of heat transmitted through a unit thickness of a material - in a direction normal to a surface of unit area - due to a unit temperature gradient under steady state conditions." Thermal conductivity units are expressed as the amount of energy in Watts per meter Kelvin.
Most species of wood: 0.15 W/(m K)
Polymer plastics: 0.25 W/(m K)
Carbon Steel (iron): 43.0 W/(m K)
The values above make a clear case for using steel or any other material with significant thermal conductivity attributes. It also demonstrates why the big old cast iron radiators have always been made the way they were. That iron holds heat!
Of course there are other reasons why insulating materials like wood and plastic should be avoided for baseboard heater covers. In the case of wood, it is a natural product that contains moisture. Any wood that is exposed to constant heat (as a wood baseboard heater cover would be) will eventually crack as the water content evaporates. This includes man-made fiberboard.
Plastic baseboard heater covers, assuming they don't melt, will offer a low retail price point - but be careful. When you use an insulating material like plastic or wood over an emitter, you might experience a change in the efficiency of the heating system when compared to using a heat conducting material. That low-cost purchase might actually cost you a few extra dollars in day-to-day use in the long run.
Wood Baseboard Heater Covers Over Metal
It's common to see finely crafted wood radiator enclosures that dress up the old style radiators. These wood enclosures are installed purely for aesthetics. With baseboard heating, the wafer-thin aluminum fins cool down very quickly so a steel baseboard heater cover will act as the heating element for a period of time after the boiler turns off, the same way the cast iron structure of the upright radiator holds heat.
Baseboarders have been designed around the traditional role of using significant amounts of heat-hungry steel around finned tube element. We use heavy duty steel between 18 and 24 gauge thickness. This generous amount of material offers the right combination of durability, structural integrity, heat retention and aesthetic beauty.