YBS Essentials Multi Purpose Bubble Insulation roll 600mm x 10m, 3.5mm Thickness - DIY 3-in-1 Thermal Reflective Insulation - Roofs, Walls, Floors, motorhomes, Boats, cellars & More. Made in Britain

I haven't used this to put behind my radiators (not in a heatwave) but what I have done is stick it over the windows (with double sided tape at each corner) so the heat from the sun is reflected away. I have a lung problem and find it difficult to breathe when its as hot as it is so product has fitted the bill nicely and does keep the rooms nice and cool. It's easy to cut and will probably reuse behind the radiators in the winter.

So easy to use and instantly effective great value

My home warms up twice as quick

bought this to make window covers for the inside of my RV. I covered cardboard and used stick on velcro pads to fit to windows. Works well with the silver tape also purchased, will keep heat inside in cold and sun off on hot days, much cheaper than buying ready made window covers

Very foil. Great value for money .