Air barrier with variable vapour diffusion resistance
ProctorPassive SmartVap 100 (SmartVap) is a two layer AS4200.1 compliant light duty air barrier and variable vapour diffusion resistance retarder.
When installed as a continuous layer, SmartVap will form an air tight layer, improving the efficacy of ventilation systems and thermal efficiency of the building enclosure. The effective management of air and vapour passage through wall, ceiling and floor assemblies can help protect the building fabric and insulation from condensation and related problems such as mould, timber rot, corrosion and loss of thermal resistance.
SmartVap should not be used on the exterior side of insulation in cold and temperate climates as an alternative to a vapour permeable sarking, where there is a risk that condensation will form on the interior face of the retarder.
Variable vapour diffusion resistance
The functional layer of SmartVap is a polyamide film. Such films passively adjust vapour diffusion resistance depending on the humidity where located. The polyamide absorbs water vapour from the air, opening the molecular pores thus adjusting vapour diffusion resistance according to ambient humidity conditions.
SmartVap is not “smart” enough to tell what season it is, and it would be simplistic to claim vapour tight in winter and vapour open in summer. The vapour resistance of SmartVap is not seasonal, but is influenced by the relative humidity on both sides of the membrane where it is located, whatever the season.
When the ambient humidity is low the diffusion resistance is higher. When the ambient humidity is high, the diffusion resistance is lower. This functionality can assist the building fabric to dry towards the interior when relative humidity is higher, and vapour pressure is lower on the interior side of the membrane.