Most polystyrene panels for DakaTherm XPS products are with a groove (L-cut). The boards are usually installed in a single layer. A two-layer application is desirable for panels with square edges (L), thus preventing the formation of thermal bridges in the joints. DAKA XPS thermal insulation in panels should be installed on flat inverted roofs in a single layer. DakaTherm XPS thermal insulation boards are resistant to cold, rain and snow, but not to long-term exposure to ultraviolet radiation, such as that caused by direct sunlight. Therefore, the panels should be handled with care and the protective packaging should only be removed shortly before installation.