If one had to devise a scientific experiment to determine the insulating qualities of a material, what better than a suspended hollow cube of the material, fitted with a known wattage electrical heater inside, with thermometers inside and out. A bit of simple math would quickly establish an R value, based on the heat loss. And if you visit a box store, the R [or U ] values are printed on all the insulating products. Except on the foil where no such values are ever quoted! The reason? The 'experiment' to determine the wild claims often made for foil insulation is this. An infra red lamp is set up pointing at a screen of the foil. Temperatures measured each side of the screen are compared to various thicknesses of other insulation. "Hey presto!", they cry, "Our product is the same as 10" of Rockwool!" - failing to point out that it's also equivalent to a sheet of newspaper.
