External blinds for windows, when properly adjusted, can significantly reduce the bills we pay for heating. They are able to reduce heat loss. People professionally involved in their production and assembly emphasize that this reduction can be up to 15 percent in the case of passive windows. When in our houses there are still windows of the old type, the profits can be even greater. The roller shutter armor itself is able to inhibit the flow of heat, becoming an impenetrable barrier. The lowered roller blind behaves like a cushion in which there is still air. It is it that is an extremely effective insulator.