Each company producing thermal insulation materials has its own surface insulation system. Such material is very expensive, purchase 1 m2 is an expense of the order 40-45 zloty. The price is influenced by a number of additional requirements. Wool must not only insulate well, but it should be sufficiently hard and meet the physical and chemical parameters.
We can achieve similar effects by creating a thermal insulation system from elements purchased separately, corresponding to the requirements specified in the building design.
Place the vapor-permeable foil between the actual covering (for example, a tile, trapezoidal metal sheet) and a heat-insulating layer, arranging it in stripes with an overlap – from the bottom of the roof upwards. Its task is to discharge water vapor to the outside and prevent the wool from getting wet. Each foil is characterized by a so-called water vapor basis weight 1 m2 discharged within 24 hours. Inferior foils, light weight (50 g/1 m2/24 h) they are cheaper (price approx 2 PLN for 1 m2) and we use them, when the distance between the covering and the thermal insulation layer is large (5-10 cm), which increases ventilation and reduces the risk of dampness. With less free space, we have to use a foil with a high grammage – above 3000 g/1 m2/ /24 h. The price of a square meter of such foil exceeds five zlotys.
The use of bituminous felt instead of foil is unacceptable, because these materials differ fundamentally in their properties.