Tin foil behind radiators that are against outside walls helps conserve energy.
The foil reflects heat back into the room.
You can use normal kitchen foil or buy special foil from a DIY shop.
Place the foil behind the radiator with the shiny side facing outwards and the dull side attached to the wall.
You can use double-sided sticky pads to attach the foil or certain types of wallpaper paste will also work.
If you want to watch a video on how to put it up here is an idiot’s guide:
Shelves above your radiators also deflects heat into your rooms.
The shelf should be slightly above the radiator.
Also avoid putting furniture in front of radiators.