Effects of compositional and textural characteristics of clay based plasters on the control of indoor relative humidity

Air humidity in contained spaces has a significant impact on health of inhabitants. The control capability of indoor relative humidity (RH) of clay-based plasters was tested on a series of commercially available products specifically designed for wall undercoating and on a natural earth collected in the surrounding area of Palermo. The innovative practice of ‘‘green building’’, since several years, led the interest of research to recyclable and reusable traditional materials that, in several cases, are a sustainable alternative to concrete and lime mortars. Earthen plasters, in general, have the ability to balance indoor humidity like no other classic building materials. The studied samples have been previously characterized in plastic behaviour, mineralogical and chemical composition, grain-size and pore-size distribution through a multi-analytical approach (Montana et al., 2014). This study was aimed to understand how compositional and textural characteristics of clay-based plasters may influence their end performances. Tests for determining Equilibrium Moisture Content (EMC) were performed in agreement with the norm UNI 11086:2003. Clay based plasters seem to combine the advantages of internal drywall construction with the properties of the clayey binder which is an healthy and versatile material. Specific performances seem to vary mainly depending on textural characteristics (i.e. aggregate/binder ratio and grain-size distribution, total open porosity, etc.). The results could be also useful in directing the selection of local raw materials for developing regional manufacture of clay-based plasters.