Where insulation is used under roofs that are studded with nails, the tiles are made of slate, ceramic or concrete and are fixed with nails onto a sloping frame that forms the slope of the roof with the corresponding struts. Between the roof tiles and the insulation, a ventilated air chamber avoids condensation forming in the roof tiles and helps to reduce overheating of the roof due to sun's rays. This type of roof also enables the space beneath the roof to be inhabited. The right product in this case is XPS SL.
There are other types of sloping roofs where the spacing struts are fitted between the sheets (II)*. In this case, where the insulation material does not support the tile weight, XPS CR is used.