Vapor Permeable Roof Membrane

This helps to reduce the amount of condensation build up within the roof or wall and insulation which can lead to long term problems such as mould and damp which can lead to serious structural issues.

Vapor permeable roof membrane.

Marley universal vapour permeable underlay is a high performance breathable roof membrane for use in a range of pitched roof constructions. The roofing membrane must be permeable to water vapor. So the open nature of air permeable membranes therefore allows air movement through the membrane and that in turn boosts the rate at which vapour can escape a roof and what that does is significantly reduces the risk of condensation occurring in the roof. The 2009 international residential code irc defi nes a vapor permeable membrane as a material or covering having a permeance rating of 5 perms or greater when tested in accordance with the desiccant method with procedure a of astm e 96.

Newer roof underlays made of calendered spunbonded or so called flashspunvlies show just enough water resistance more than 100 cm water column tight by far not the water vapor permeability that is desirable would. The vapor permeable ab can be used in high temperature roofing applications with acceptable service temperatures up to 225 degrees fahrenheit. Vapour permeable breather membranes allow water vapour to pass through the membrane out of the roofing system or walls. Regardless of your roofing underlayment choice your insulated roof assembly will not dry to the exterior unless the roofing is vapor permeable.

Complete with an integrated tape system this underlay provides and effective wind barrier with unrestricted usage across all uk wind zones bs 5534. Miraflex ii is also available. A roof to parapet transition is shown in detail 12. Miraflex vapor permeable membranes and waterproofing miracote miraflex ii decking system is a multi layered promenade deck coating consisting of formulated resins cementitious underlayment and waterproof membrane.

The roof must be able to breathe i. Other types of roofing including cedar shingles and concrete tile roofing are. It is also important to consider that some finish roof materials such as metal panels may require a high temperature underlayment membrane. This seal can be accomplished with a strip of vapor permeable liquid applied flashing.

Many types of roofing including epdm and standing seam steel roofing are virtually impermeable to water vapor. When using a roof underlayment as a temporary moisture protection membrane over the clt roof panel the perimeter is sealed at the parapet to close off this joint to water ingress.