In recent years, insulating materials made from renewable natural materials have gained in importancemainly due to advantages in sustainability and carbon footprint. However, the moisture content limits specified in standards and guidelines for such materials are mostly quite low, which considerably restricts their range of application. In order to enable reliable and broader use in the various areas of the building envelope, robust limits are required that relate not only to the combination of temperature and humidity but also to the duration of their exposure. After all, microbial growth in the exterior climate is possible in most regions, at least temporarily. Therefore, a transient assessment can best evaluate how a construction must be designed to safely avoid damage. In this contribution both new limit curves and a transient decay prediction model, based on durability tests of natural fibre materials in the laboratory are proposed. First evaluations by field tests have already been performed.Peer-review under the responsibility of the organizing committee of the ICMB23.

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