Klober air-open underlay tops performance ratings

Variable performance of vapour permeable underlays ultimately prompted the BSI to require supporting high level ventilation for such products.

For roofs needing the highest standard of ventilation performance, Klober Permo® air, which is classified as air-open, offers not just an exceptional level of breathability, with a water vapour transmission sd-Value of 2736g/m²/day, but a water vapour resistance which has been independently confirmed to be as low as 0.03 MNs/g. It has been used to upgrade countless historic buildings and to provide unparalleled performance during the critical drying out period on new builds.