Hygrothermal performance of Brazilian gypsum walls

The aim of this article is to evaluate the hygrothermal behaviour of gypsum walls in the climatic diversity of Brazil, based on the action and interaction between external climatic variables and the facade element. First, a laboratory characterization of material properties for the gypsum was carried out to determine their hygrothermal behaviour, particularly water vapour permeability, capillary absorption, retention curve and thermal conductivity. Second, the wall system performance was also evaluated in terms of its watertightness. It was concluded that the addition of a silicone water-repellent, typically used by the local industry, could lead to a classification of preventive against water. It was also concluded that a content of water-repellent above 0.5% would not result in additional benefits regarding watertightness. The second part of this work was focused on the evaluation of the hygrothermal behaviour of the standard and the water-resistant gypsum walls by means of hygrothermal numerical simulation. This analysis was intended to assess the influence of various factors such as the wall components (namely, wall coatings), the climatic conditions by geographical location and also the interior conditions, the orientation of the facades and the driving rain. The results demonstrated that the Brazilian climatic diversity can lead to very different exposure conditions. The locations in Interior Northeast Brazil, which are especially dry, corresponded to the ones with lower moisture content results. The results showed that gypsum masonry application on facades, with unfavourable climatic contexts, high precipitation and low solar exposure, would result in low durability. Only future works, including in situ studies may support the justification for applying the studied solutions in facades in favourable climatic conditions.