The flat roof structure is a complete system. It typically consists of a supporting structure, a vapour barrier, insulation, waterproofing and effective ventilation. The supporting structure is usually double-T slab, corrugated steel sheet, reinforced concrete slab or hollow core slab.
Upward directed heat losses are the greatest. Prevent air from flowing through the building envelope and causing negative effects on the structure by placing a vapour barrier on the inner side of the roof. In practice, an air infiltration barrier (e.g., plastic foil) provides sufficient air tightness.