Hygrothermal behavior of façade with thermal mortar in Porto Alegre and Lisbon

Abstract

This study evaluated the hygrothermal performance of façades coated with thermal mortar containing expanded cork aggregates. The façades were exposed to the climatic conditions of Porto Alegre (Brazil) and Lisbon (Portugal). Thermal mortars have lower thermal conductivity than conventional ones. This property offers potential for improved thermal comfort, enhanced energy efficiency, and greater sustainability when produced with bio-based materials such as cork. Numerical simulations with WUFI Pro 7.1 quantified heat and moisture transport in a double ceramic wall with an unventilated air layer. Results showed higher moisture contents in Lisbon. The north façade in Lisbon performed similarly to the south façade of Porto Alegre, mainly due to wind-driven rain. No risks of mold growth were identified on the interior surface. External condensation was assessed by hours at 100% relative humidity on exterior surfaces. The south façades recorded more hours, three to four times more frequent in Lisbon. Monthly thermal transmittance coefficients met local standards except in some summer months. Thermal mortars were viable under these conditions. Further optimization is recommended by considering water absorption of finishes, temperature- and moisture-dependent thermal conductivity and vapor permeability, real interior conditions, and ventilation within the air layer.