Radiator foil efficiency depends on wall insulation type

Using radiator foil can reduce heat loss through external walls or windows, though the financial benefits vary significantly based on the type of wall insulation present.

According to calculations from Milieu Centraal, the potential gas savings per square meter of foil depend on the specific structure. An uninsulated solid wall can see a saving of approximately 11 cubic meters of gas per year, while an uninsulated cavity wall offers about 7 cubic meters. In contrast, an already insulated external wall provides minimal benefit, estimated at only 1 cubic meter of gas per year. For windows, the savings are notably higher, with single glazing potentially saving 50 cubic meters and double glazing saving 25 cubic meters per square meter.

Foil can be applied either directly to the wall or to the back of the radiator. Applying it to the wall reflects radiant heat back into the room, while applying it to the radiator reduces the amount of heat directed toward the wall. For a single radiator, placing foil on the wall may be preferable to avoid restricting heat output to the room. In a typical corner house with uninsulated external walls, the total annual savings could reach approximately 50 euros.