The German Institute for Building Technology has approved the use of BASF's Styrodur 3035 CS, 4000 CS and 5000 CS insulation materials in double-layer installation for inverted roofs.
Double-layer installation of Styrodur C in inverted roofs
Styrodur C is an extruded polystyrene rigid foam insulation material that is water-repellent, rot-proof and pressure-resistant. It can prolong the life of homes and buildings.
The inverted roof, which is a type of flat-roof construction, has several advantages. The waterproofing layer lies below the insulation material, which produces a layered structure to provide long-term structural protection and energy-efficient thermal insulation. The Styrodur C material has foam skin on both of its sides and a closed-cell foam structure, which prevents water absorption. It has been approved for applications in inverted roofs since 1978, but only for single-layer installations.
BASF has proved the feasibility of Styrodur C double-layer installations in inverted roof with respect to construction physics. The material can also meet stringent insulation requirements. In double-layer installations, the insulation panels have to be enclosed with a permeable separating and water-repellent layer, so that the rainwater permanently runs off the surface. Existing inverted roofs that have a single-layer of insulation can be upgraded by adding a separating layer and a second Styrodur C insulating layer.
The insulating layer protects the waterproofing against mechanical and thermal stress and prolongs the life of the inverted roof. This would also help comply with modern insulation and energy consumption standards.
Source: http://www.basf.com/