The shading coefficient shows the amount of solar energy which ends up behind the arrangement, most often in the form of secondary radiation. The lower the value, the more effective the reflective arrangement. Still, a high-coefficient foil can be used to good effect if heat absorbed in the foil is ventilated away, which is the case if the foil is fitted to a self-ventilated window.
All values are based on ASHRAE-testing methods. This means, among other things, that the foil is fitted to the inside of 4-millimetre thick neutral glass.