Insulated building assemblies require a vapor retarder at the warm side to avoid interstitial condensation during the heating season in cold and mixed climates. However, the low permeability of a traditional vapor retarder can be a severe drawback concerning the drying potential of the assembly in summer time. Because moisture is more harmful to the structure when temperatures are high, the evaporation of moisture from the assembly must be as effective as possible. Flexible vapor control means that the retarder is tight enough to avoid critical condensation in winter while being sufficiently vapor permeable in summer to guarantee a fast drying process by adapting its performance to the seasonal changes in environmental conditions. In this paper the principle of the smart retarder is explained and experiences from field tests are reported.

• smart vapor retarder
• vapor barrier, vapor retarder

1. Calculation of heat and moisture transfer in exposed building components
2. Combined effect of temperature and humidity of the detoriation process of insulation materials in ETICS
3. Moisture buffering effects of interior linings made from wood or wood based products
4. Mold growth prediction by computational simulation
5. Simulation of indoor temperature and humidity conditions including hygrothermal interactions with the building envelope
6. Simultaneous heat and moisture transport in building components. one- and two-dimensional calculation using simple parameters
7. Two-dimensional transient heat and moisture simulations of rising damp with WUFI 2D
8. Uncertainty of hygrothermal calculations
9. WUFI-ORNL/IBP - A North American Hygrothermal Mode