Warm roofs with vapour permeable underlays and well-sealed ceilings
All warm roofs require a continuous vapour control layer (VCL) to be installed on the warm side of the insulation. The VCL should be lapped and sealed and all penetrations of the VCL, e.g. pipes, wires, etc., should be sealed to prevent moisture transfer into the insulation and the fabric of the roof structure. If a well-sealed ceiling is provided and the integrity of the VCL can be maintained, then, no ventilation is required with a vapour permeable underlay provided that the roof type is simple and does not contain any cold / warm hybrid elements.
For the simple warm roofs illustrated in this example no ventilation is required.
