Insulated radiator foil

As it turns out, the Wikipedia article itself actually points to some (albeit Radflex funded) reports. The second report BRE shows ~45% reduction in heat lost to the wall behind the radiator.

Tables 4 to 11 of the BRE report show a range of figures to do with efficiency and energy saving. Table 4 shows the amount of energy you could save on an annual basis, broken down by the energy loss (insulation efficiency) of the wall:

Assuming an area of 1 meter per radiator and 10¢ per kWh (rough average of US price), you this will save $2-$9/year for each radiator. However, these are all back-of-the-envelope calculations based on a study paid for by Radflek and they don't even have full distribution across the EU (let alone the US)5. AFAIK, the heating hours are calculations done for climate emissions ratings, so it's a big average of heating of UK(?) homes. Will a competitor be as efficient? Is your wall going to leak heat the same as an averaging of a bunch of houses in another area? Who knows!

So is it worth the $29 (£18) price for the minimum order of 6 reflectors to UK address? I am personally placing a ~50% penalty on evaluating cost effectiveness (note that I even work on pro-climate change policy research). So I would start to recoup the material losses after ~2 years.

I had a radiator in one of my old houses that didn't heat up. I thought it was a valve, but it turned out that it just needed bleeding. There was a lot of air in the radiator, and the water couldn't get into where it needed. If you haven't already, bleed it.