Some of the heat from a radiator will heat up the wall on which it is mounted. If that wall is an outside wall, a lot of this heat will be conducted to the outside of the building and lost. Luckily, it is very cheap and simple to prevent this from happening, by placing reflective foil on the wall behind the radiator. Research in the UK has shown that almost any kind of reflective foil (even ordinary aluminium kitchen foil) can reduce this heat loss by 5%. Properly designed reflective panels, which combine reflective foil with a thin layer of insulation, can reduce the heat lost through walls by up to 18%.
Test was done in a house in North-east England using a thermal camera. There is a radiator mounted on the wall below the window. Without any reflecting layer behind the radiator, heat loss is significant. With a reflective (and insulating) panel fitted heat loss is lower. In this particular example, the panel used was a ‘Reflecta’ panel, manufactured by Pan Manufacturing Ltd., and costing approximately £6 per radiator. However, if custom-made panels are not available, it is possible to achieve significant energy savings by using ordinary household materials such as kitchen foil glued to a sheet of corrugated cardboard.
Thermostatic radiator valves
In many heating systems, all the radiators are controlled by a single thermostat or, in the worst cases, there may be no thermostat at all. This makes it very difficult or even impossible to achieve an adequate level of control over the heating system. It is very likely that some rooms will end up being over-heated while others are under-heated, resulting in discomfort and / or excessive heat wastage.
Thermostatic radiator valves (TRVs) allow the output of individual radiators to be automatically regulated to an appropriate level for the room. They are not particularly cheap (approximately £30 per radiator) but in many cases they will repay their cost in energy savings in about four to five years. TRVs are fairly simple to fit, although most people would probably prefer to let a trained plumber do the installation. Also, depending on the type of heating system, it may not be possible to use them at all. It’s therefore important to seek guidance from an expert before spending any money.
Location of radiators
Clearly, if a heating system is already installed, then moving radiators is not a practical proposition. However, if a heating system is being planned, then its effectiveness can be maximised by paying attention to the location of radiators. If a room is heated with portable heaters, the same criteria for location apply.
The optimum location for a radiator or a portable heater is beneath a window. If a radiator is located on the far side of a room from the window, there is a tendency for convection currents to be set up. This can result in all the hot air from the radiator rising to the ceiling, while the room occupants are surrounded by cold air from the window. The room occupants may then be tempted to turn up the thermostat (if there is one) to try to achieve comfortable conditions.
By locating the radiator beneath the window, the hot air from the radiator mixes with the cold air from the window, resulting in warm air which is propelled into the room. The effect is enhanced further if there is a shelf or window-sill projecting out above the radiator. But remember that if the radiator is on an outside wall, you should consider placing a reflective layer on the wall behind the radiator to reduce the amount of heat lost through the wall (see ‘Reflective foil behind radiators’ above).
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