Effect of Different Types of Paint on the Hygrothermal Behavior of Facade-Rendering Mortars in Brazil

Abstract

Facade-rendering mortars and their painting layers are constantly exposed to weather and, therefore, influence the hygrothermal behavior of buildings. The characterization and assessment of coating materials is fundamental, seeking adequacy in their selection, especially regarding moisture and temperature. Considering the exposure conditions of the facades, risks of damages, such as mold development, may be avoided by an assertive evaluation and selection among different types of paints. In this context, this paper experimentally determined essential properties related to the hygrothermal behavior of painted mortars and simulated their resulting performance when applied on exposed facades in three Brazilian cities in distinct bioclimatic zones. Hygrothermal simulations were carried out using the software WUFI Pro 6.6. Six different types of paints were studied, among which satin acrylic paint (SAP) led to the lowest water vapor permeability and matte polyvinyl acetate (PVA), silicate (SIL), lime (LP), and hydrated lime with white glue (HLG) paints led to the highest. Matte acrylic paint (MAP), PVA, SIL, LP, and HLG had similar impacts on the vapor transmission of mortar renderings. In the simulations, reference (REF) and LP specimens generally resulted in the highest water contents throughout the year, followed by SIL and HLG. SAP led to the lowest water content and a more homogeneous curve than the other paints. Among the studied cities, Macapá, which has the highest annual normal rainfall sum and mean relative humidity, also had the highest mean total water content values over time, followed by Porto Alegre and Petrolina. In general, no probable mold development is expected. However, caution should be taken when extrapolating the results for climate or construction conditions different than the simulated ones.