CORRELATION BETWEEN SOLAR ABSORPTANCE AND PAINT COLOR PARAMETERS

Abstract

The surface characteristics of the materials of the building envelope have a great impact on the transmission of heat to the internal environment, which suggests the importance of knowing the properties of the envelope and understanding the relationships between them. Among the properties of the paints that can be applied to the facades of buildings are solar absorptance and the parameters that characterize the colors. It is known that in general, lighter paints tend to absorb less solar radiation, and darker paints tend to absorb a greater amount of this radiation. This paper intends to analyze, for six different colors of paints with matte finish, the correlation between solar absorptance and their color parameters. The solar absorptance was calculated from the solar reflectance, which in turn was measured in a spectrophotometer with an integrating sphere and adjusted to the standard solar spectrum. For the color parameters, a colorimeter that takes measurements considering the CIELab color space was used. The correlations of the data were performed by regression analysis. Among the solar absorptance values, it was noticed that the lighter colors presented lower solar absorptances, followed by the red and blue colors, which presented similar absorptances, and finally the black color was the one with the highest absorptance among all. For the correlation between solar absorptance and the L* parameter, an R² of 0.93 was found, with a standard error of 0.08. Considering all color parameters (L*, a*, b*, C and h) together and correlating them with the absorbance, the R² was even higher, 0.99, with a lower standard error of 0.03. Thus, the correlation of all parameters is more reliable than using only the luminosity (L*) for the samples evaluated here.