ProctorPassive SmartVap is a two layer AS/NZS 4200.1 compliant light duty air barrier and variable vapour diffusion resistance retarder. 

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.