Effects of natural weathering on the solar reflectance, color parameters and surface temperature of roof tiles in a tropical climate

This study investigated how three years of natural weathering affected the solar reflectance, color parameters, and surface temperature of 25 roof tiles in São Carlos, SP, Brazil. Initially, light-colored tiles lost reflectance due to particulate deposition, which was partially offset by rainfall. Meanwhile, darker tiles showed slight increases due to pigment fading. Light glazed ceramic tiles exhibited the greatest loss in reflectance in the visible spectrum, while concrete tiles showed broader degradation into the infrared spectrum. This indicates that optical degradation is influenced by color change and alterations to the surface microstructure. Highly reflective tiles were most sensitive to surface soiling. The largest reductions in solar reflectance occurred in the samples with the highest initial reflectance. Although these samples experienced the greatest impact from weathering, they maintained the highest solar reflectance after three years. Color measurements showed a consistent darkening trend (ΔL∗), which was strongly correlated with reflectance loss; meanwhile, hue changes (Δa∗, Δb∗) were weakly related. Lighter tiles experienced greater overall color change, which was strongly associated with larger reductions in solar reflectance. Surface temperature remained closely tied to solar reflectance before and after aging (R 2 0 = 0.89; R 2 3 = 0.88), highlighting reflectance role in heat retention. A comparison with the Brazilian NBR 15575-1 standard revealed strong agreement (R 2 = 0.96), which validates the experimental setup and confirms the standard accuracy. These findings shed light on the effects of natural weathering on solar reflectance, color stability, and surface temperature. This information is useful for selecting durable roofing materials in tropical climates.