The air and windtight building envelope can be compared with the clothing of people. In cold and damp weather several layers of clothes proved their value ("onion principle").

On the skin you wear functional underwear to carry sweat away from the skin. This corresponds to the airtight building envelope formed by the base plaster on the masonry and the vapour control layer in the roof. It is required by Part L of the Building Regulation from July 2008 (IRL, UK) and § 6 of the German energy saving regulation (EnEV) and can be easily tested by a blower-door test.

A woolly sweater protects from cold (= insulation). But in cold, windy weather this sweater is not sufficient; you additionally need a windtight jacket (= facade membrane or breathable membrane). When this jacket is open, cold wind and moist air enter the sweater and you feel cold. If it is, however, closed, which corresponds to the windtight building envelope, wind and weather are kept out and the body remains comfortably warm. This layer is formed by the roofing tiles and the permanently sealed breathable membranes.

More than one third of the warm air escapes through leaking areas in the building envelope. Consequently an air and windtight layer is the most reliable protection against energy and heating cost loss! Regular, controlled ventilation or a ventilation system provide for healthy indoor air.

In addition, the air and windtight building envelope fulfills further important functions:

SIGA high-performance adhesives offer first-class quality. With the easy to apply SIGA system you create an air and windtight layer which offers you the best reliability and comfort throughout the entire life of your house. Our word for it!