Vapour Permeable Underlays

Vapour permeable or low-resistance (type LR) underlay is airtight, but allows water vapour to disperse into the atmosphere. Where used in a cold roof solution, this type of underlay should be used in conjunction with high-level ventilation through tile or ridge vents. Where the loft space is used as living space, this type of underlay offers an ideal solution, with no additional ventilation needed providing the ceiling is well-sealed and a vapour control layer is in place.