Vapor Permeable Roof Membrane

It is also important to consider that some finish roof materials such as metal panels may require a high temperature underlayment membrane.

Vapor permeable roof membrane.

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. Regardless of your roofing underlayment choice your insulated roof assembly will not dry to the exterior unless the roofing is vapor permeable. 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. This seal can be accomplished with a strip of vapor permeable liquid applied flashing.

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. Designed to provide a decorative finished waterproof deck surfacing miraflex ii is ideally suited for either new construction or deck renovation. Other types of roofing including cedar shingles and concrete tile roofing are. 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.

A vapor permeable material permits the passage of moisture vapor 2. 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. The roof must be able to breathe i. Securock exoair 430 pre applied fluid applied synthetic permeable air water barrier membrane is a monolithic elastomeric membrane that is applied in a factory setting eliminating the inconsistencies and weather impact that can occur when applied in the field.

Miraflex ii is also available. Complete with an integrated tape system this underlay provides and effective wind barrier with unrestricted usage across all uk wind zones bs 5534. 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 roofing membrane must be permeable to water vapor.

Marley universal vapour permeable underlay is a high performance breathable roof membrane for use in a range of pitched roof constructions. Many types of roofing including epdm and standing seam steel roofing are virtually impermeable to water vapor.