Hygroscopic Materials

A hygroscopic material has the ability to adsorb and store moisture from the surrounding air. When the RH changes, a difference in the vapour partial pressure results in the material absorbing or desorbing moisture in order to reach equilibrium. Most materials have a hygroscopic potential which is too low to have any impact on indoor humidity, however this ability can vary to a great extent in building materials and is related to the available surface area/porosity and the nature of the material. A small number of studies have demonstrated that interior moisture buffering by the building fabric can beneficially affect energy consumption, component durability, thermal comfort and air quality (Janssen, H and Roels, S., 2009). Padfield (1998) demonstrated the enhanced moisture buffering potential of clay based materials compared to many other conventional materials. However, there is still a need for wider recognition of these effects, scientific characterisation of materials and development of a rigorous design model or tool to support implementation by industry.

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About Helen Cornwell

Helen Cornwell is the Project Manager for the EU funded project ISOBIO (Development and Demonstration of Highly Insulating, Construction Materials from Bio-derived Aggregates) and Networking Coordinator for the ECO-SEE project (ECO-innovative, Safe and Energy Efficient wall panels and materials for a healthier indoor environment).

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