Paper Conference

Proceedings of eSim 2004: 3th Conference of IBPSA-Canada



Hartwig Künzel, Achilles Karagiozis

Abstract: The use of traditional vapor barriers or retarders to avoid interstitial condensation may have undesirable side-effects. Numerous moisture damage cases have been attributed to the fact that a vapor retarder is nearly impermeable in both directions, i.e. it does not allow any dry-out from either side. Some wall and roof assemblies are only durable if they are allowed to dry out towards the interior side as well. The current stateof-the-art experience with building enclosures exposed to transient temperature and moisture loads shows that the approach to create a durable hermetic sealing is almost impossible and should be replaced by a controlled moisture management approach. It is better to use moderate vapor retarding layers instead of vapor barriers in order to assure a sufficient drying potential. In this paper the transient temperature and moisture behavior of building enclosure assemblies is investigated for cold and northern coastal climates in the United Sates with the aid of a hygrothermal simulation model. By way of an example case, the consequences of choosing a moderate vapor retarder and a retarder that reacts to the ambient humidity are demonstrated.
Pages: 55 - 60