Breathable membranes allow the roof to breathe, negating the requirement for traditional ventilation. They are suitable for use as a full supported or unsupported underlay beneath tiled or slated pitched roofs, in warm or cold non-ventilated and cold ventilated roofs.
Breathable membranes are very popular and are increasingly used on a wide range of projects.  Their adaptable, multi-purpose use is seen by specifiers, merchants and installers as the optimum solution to underslating requirements.
The IKO pitched roof breathable underlay range is designed to:
  • Transport any moisture resulting from any ingress through the primary roof covering in to the roof drainage system
  • Provide a barrier to minimize the wind uplift load acting on the slates or tiles
  • Provide a secondary barrier to the ingress of wind driven rain, snow and dust
  • Provide temporary weather protection before the installation of the primary roof covering.

Why ventilate cold or warm roof constructions?

Building regulations have encouraged the development of more energy efficient building construction techniques. Therefore buildings are becoming more air tight via improved draught proofing, double glazing and the use of central heating. The result is an increase in the water vapour content within the building and this combined with better insulated buildings can create a colder loft space and the risk of condensation forming. Condensation, be it surface or interstitial, can damage the roof construction.
People and their normal activities within the building can produce 5-15 litres of water vapour per day. Of this up to 60% can diffuse through gaps in the ceiling, light fittings and loft hatches and enter the roof space. To counteract this, it has been  recommended to ventilate the loft space to allow water vapour to disperse before it is possible to condense and cause damage.
Note: Investigations by the BBA, through consultation with a wide cross-section of the building industry, indicate that the possibility of roof-space condensation is highest during the first heating season after building works, and can affect any roof. This is due to the volume of retained water following wet trades used during the building work.  For further information refer to BBA Bulletin 1.