that stuff that looks a bit like foil with fibreglass wool inside, same as spacecraft insulation. you can get it at b&q, altho it will be cheaper at your local place. it reflects almost all heat.Under our stairs is where the gas/electric meters live. There is a rad on the wall of the hall which divides the hall and under stair area. Its thin panelling. I dont need to the cupboard under the stairs heated, so what is the best thing to put on that panelling to bounce the heat back?