Influence of temperature on the sorption-desorption curves of earth-based materials and consequences on their hygrothermal behaviour

Abstract

There has been a rising interest by the building sector in using passive solutions to regulate the indoor relative humidity, since humidity levels can directly affect the health and comfort of the occupants. Earth based materials are known for their ability to regulate the relative humidity and improve indoor comfort. Another motivation is the potential to reduce the energy consumption of air conditioning systems. The assessment of the hygrothermal transfers within earthen walls/plasters has been the focus of many researchers, but the proper modelling and coupling of these characteristics for unconventional materials like earthen walls and plasters still is a major scientific and technical challenge. The main objective of this dissertation consists in first to check the validity of steady state material characteristics obtained through standard procedures. Furthermore, validate different assumptions and the reliability of the different methods to determine the precision of the experimental test results. The second objective is to analyse the influence of temperature on those characteristics and their consequences on the hygrothermal behaviour. For that purpose, two types of porous hygroscopic materials are studied: compressed earth samples and earth plasters with the addition of organic natural fibres. Results showed a high variability due to experimental set ups and conditions. However the influence of temperature on the sorption and transfer properties could be determined. An analysis of the results based on thermodynamics gave surface characteristics and the heat involved in the adsorption and condensation process of the materials used.