Hygro-thermal analysis of a flat roof structure integrating a variable vapor-diffusivity membrane

The work presented hereby aims at verifying the hygro-thermal performances of a non-ventilated timber frame flat roof structure integrating a variable vapor-diffusivity membrane. However, it is not a common approach to use this kind of membranes in roof structures since, in order to avoid condensation issues in the outer layer of the structure during cold season, vapor barriers or retarders are usually installed. Actually, this approach does not consider eventual criticalities occurring on the building site while installing these membranes, since the posing procedure may cause dangerous leakages for vapor within the structure. The variable vapor-diffusivity membrane can solve this issue behaving as a vapour retarder within typical relative humidity ranges, while becoming more vapor-open when surrounded by higher humidity values.