Skip to content
BPindex — The Largest Building Products Directory in the UK

Underlay

Klober air-open underlay tops performance ratings

Building Products Index Ltd Roofing, Underlay Leave a Comment

View the Klober BPi entry

Visit the Klober website

image descriptionThe variable performance of vapour permeable underlays ultimately led to the decision by the NHBC and the BSI that only air-open membranes could be used without supporting high level ventilation. Klober Permo® air offers an exceptional level of breathability, with a water vapour transmission sd-Value of 2736 g/m2/day and a water OLYMPUS DIGITAL CAMERAvapour resistance which has been tested by the BBA and confirmed to be as low as 0.03 MNs/g. As a result, it has been specified for roofing upgrades of many high profile and historic buildings. For new builds, particularly those with complex roof designs, underlay performance is put under greatest strain during the critical drying out period. Permo air’s use on both cold Permo air installed for BBA certificate 25-6-07and warm roof installations avoids the additional cost of supporting ventilation and offers the additional benefit of having been tested for wind uplift resistance by the BRE. It found the membrane to be suitable for use up to Zone 5 on the recently introduced BS5534 wind speed map (with laps taped or battened in zones 4 and 5).

Klober Permo® roofing underlays for the most complex roofing designs

Building Products Index Ltd Roofing, Underlay Leave a Comment

View the Klober entry on BPi

Visit the Klober website

rogbis6When it comes to choice of roofing membranes, Klober Permo® underlays and vapour control layers offer the widest range of application and performance. From the ‘air-open’ Permo air to the low pitch Permo extreme RS SK2 and Wallint® solar air barrier all enjoy specifications on projects of considerable diversity and complexity. Such high performance is backed by fully independent testing of aspects such as wind uplift to support BBA and LABC certificates, some of which are among the longest standing in the industry.

Klober’s provision of detailed technical advice on aspects such as SAP and control of condensation has resulted in the widespread use of products such as Permo® air, which remains the most breathable air-open underlay currently available. It enjoys NHBC approval for use without supporting high level ventilation and has been used on many historic buildings as well as new builds.

klober-permo-forte-r-bisby-19-sept-10The 4-layer Permo® forte offers high vapour permeability and the benefit of a mesh reinforcement which provides added safety for the roofer. Permo forte SK2 also has integral edge tapes to seal the product at laps, abutments and junctions.

Permo® extreme RS SK2 is still the only product of its type currently available for use on monopitch extensions at pitches as low as 15⁰. Its tear-resistant PEF fleece and self-permo-products_packaging_rolls_19895-copyadhesive edge tapes seal laps and enable double lap tiles such as clay and concrete plain tiles to be laid significantly below their normal recommended pitch.

Permo® sec provides a separating layer between copper, zinc, aluminium and stainless steel roofs, while Permo light is a strong 3-layer underlay for traditional warm and cold roof applications.

In terms of air barriers and vapour control layers, Wallint® solar has a vapour resistance of over 500 MNsg, far exceeding the requirements of BS9250 (Code of Practice for design of the airtightness of ceilings in pitched roofs). Its reflective surface also helps to retain heat within the building.