a b s t r a c tIn this paper, the results of static and dynamic hygric tests on 114 unfired clay masonry samples are presented. Samples were prepared as Compressed Earth Blocks (CEB) or plasters. The variability of soils, the soil density and the preparation methods were investigated to determine their influence on the moisture buffering capacity, water vapour permeability and sorption isotherms. The Moisture buffering Value (MBV) was measured according to the Nordtest protocol and the results could therefore be compared to conventional materials. The results indicate unfired clay masonry has a much higher potential to regulate the indoor humidity than conventional construction materials previously reported in the literature. Because of the benefits of humidity buffering, using unfired clay masonry could reduce health risk for inhabitants, reduce mould growth, reduce energy consumption of air conditioning and ventilation systems and increase the durability of building materials. The presented results show that the soil selection (mineralogy and particle size distribution) is more important for humidity buffering than changes than can be made to a particular soil (density, preparation methods or stabilisation) and the information presented will therefore allow designers to maximise the buffering capacity of buildings.

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Unfired clay building materials are recognised for their ability to regulate indoor humidity levels through their moisture buffering capacity. Research is being conducted on the moisture buffering capacity of a variety of building materials with natural materials, such as clay, and organic materials, such as hemp or straw, presenting a greater potential to regulate indoor humidity than industrial building materials. Due to their high affinity to water, which is usually regarded as detrimental, clay materials present complex hygrothermal coupling phenomena, which are still under investigation. This paper summarises some recent investigations into the dynamic water adsorption process within clay materials in relation to their ability to regulate indoor air humidity levels. First, a review of the experimental methods to characterise this behaviour is provided. A review of experimentally measured results on the material scale using compressed earth block, rammed earth or plaster samples is then provided, followed by some larger and whole building measurements.