Natural weathering rack to assess solar absorptance degradation of tiles and surface temperature measurements

Abstract

The use of materials with low solar absorptance on the building envelope has shown to be an effective strategy to optimise the thermal and energy performance of buildings located in climates with incidence of high solar energy. However, the ability of coatings to reflect solar energy changes over time, mainly due to degradation caused by natural weathering and dust or soot deposition, leading to loss of building thermal performance. Therefore, assessing the effects of solar absorptance degradation is crucial to predict the ability to maintain the reflective properties of coatings over time. With the aim of contributing with research on this subject, this paper presents the design, construction, and operation of a natural aging rack to evaluate tiles and coatings exposed to natural weathering conditions, with simultaneous and continuous surface temperature measurements with thermocouples. The results obtained for 28 tiles exposed for 2 years indicate a strong correlation (R² = 0,81) between surface temperatures and solar absorptance over time, as well as the usability of the natural weathering rack to assess solar absorptance degradation of tiles and surface temperature measurements.

Keywords:
Solar absorptance; Degradation; Natural wathering; Tile