Flat Roof Insulation Vapour Barrier

The bottom membrane s primary function is that of an air barrier but it s material characteristics are such that historically it has also been a vapor barrier.

Flat roof insulation vapour barrier.

Air impermeable spray foam insulation spray foam protected with thermal barrier in occupied attic space. However note that one should seal the seams here as well. Vapour retarders frequently are used in flat roof construction to prevent moist air from the inside of the building condensing onto the roof assembly and potentially causing damage to materials. Nrca these products are an important way to preserve the thermal efficiency of roof insulation and so make up a crucial part of protecting the comfort and energy efficiency of a home or commercial building.

An airspace is left above the ceiling insulation and below the under side of the roof decking and the roof is vented either around its perimeter with soffit vents a flat roof or the roof may be include intake venting at its lower edge through a soffit and outlet venting through a half ridge vent or similar outlet vent along the roof s uppermost edge a low sloped roof. Unvented flat roof assembly there is. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. The roof membrane on the top is clearly a vapor barrier.

We are insulating a flat roof with tapered rigid insulation over a moisture barrier and then capped with modified bitumen. Classic compact flat roof the most famous double vapor barrier of them all. If the roof is insulated with foil faced insulation blankets the aluminium side can serve as a vapour barrier at the same time. In any case the vapor barrier must point to the warm side.

However we lose r value where the taper is thinnest and need to insulate under the sheeting. Next to that you may also buy a moisture regulating vapour barrier membrane that can manage the damp even better. A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

That reduction of air and moisture infiltration can then help improve roof longevity.