Absortância solar e desempenho térmico de tintas frias para uso no envelope construtivo

Abstract

Materials with low absorptance and high emittance are known as cool materials. When used on the building envelope these materials decrease building surface temperatures, reducing energy demand in conditioned buildings and making more comfortable non conditioned buildings. In this work, cool and standard paints for exterior walls and roofs were comparatively evaluated through their absorptance and emittance properties, as well as the thermal performance evaluation with surface temperature measurements. Cool paints were selected from available products in the Brazilian and international market, as well as standard paints with the same color, totaling 15 samples. Results indicated that cool paints with low near-infrared absorption, but with the same color of standard ones have lower solar absorptance. Surface temperature measurements for samples exposed to the sun confirmed that coatings solar absorptance directly affects the thermal performance of painted surfaces, which corroborates that as lower is the surface solar absorptance, lower is the building envelope temperature. It was observed that the potential to use cool paints on buildings results from the decrease in the near-infrared solar absorptance, with the possibility to use paints with darker colors, but with better thermal performance when compared with standard paints with the same color.