Polysicocyanurate PIR is an alveolar insulation material, composed of small cells containing a gaz with low thermal conductivity. It is often used for construction and industry purposes. The result is a thermal insulation material with a good report between thermal and physical characteristics. Because of its performances the material has a limited thickness with equal thermal resistance. It also provides considerable gains in weight in comparison to mineral wool, and a better resistance to compression which enables the use under ballast.