Flexible Vapor Control Solves Moisture Problems of Building Assemblies—Smart Retarder to Replace the Conventional PE-Film

Abstract

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.