A warm flat roof is a roofing system in which the thermal insulation is installed below the waterproofing membrane. Unlike an inverted roof, the insulation therefore remains protected from direct exposure to rainwater by the waterproofing system above it.
Warm roofs can be constructed with different waterproofing systems, including bituminous and synthetic membranes, provided that the insulation, membrane and installation method are compatible with each other.
The insulation used in this type of roof must provide appropriate thermal and mechanical performance and must be suitable for the temperatures and installation conditions associated with the selected waterproofing system.
Rigid polyisocyanurate (PIR) insulation is particularly suited to warm flat roofs because it combines high thermal performance with good compressive strength and can be supplied with facings specifically developed for different waterproofing systems.
For warm roofs with bituminous membranes, POLIISO® SB provides a dedicated solution. The PIR panel features a bituminised glass-fibre upper facing and a saturated mineralised glass-fibre lower facing, with a declared thermal conductivity λD from 0.025 to 0.028 W/mK depending on thickness, compressive strength of ≥ 150 kPa and a maximum operating temperature of 110 °C.
The specific facing configuration makes POLIISO® SB suitable for use beneath bituminous waterproofing membranes, including applications involving torch-applied membranes where the specified system permits this installation method.
