The effect of solar radiation on thermochromic building coatings: Testing the performance and proposing methods for their improvement

The improvement of the urban microclimate combined with the reduction of the energy loads is a highly important target that requires the research and development of innovative solutions with advanced thermal and optical properties. Color changing thermochromic coatings being reflective in summertime and absorptive in wintertime can address to the demand of lower surface temperatures and lower cooling loads. The interaction though with the solar radiation results in the breaking of the chemical bonds and the degradation of their performance.
The present work aims to investigate various methods and techniques for the improvement of the coatings performance. Towards this direction an important step is to identify the factors that affect thermochromism. Combinations of UV and optical filters were used on thermochromic coatings applied on concrete tiles under accelerated ageing conditions of one month period in order to isolate the parts of solar spectrum that cause the photodegradation. Covering the sample with red filter which cuts off wavelengths below 600nm protects most efficiently the reversible color change of the thermochromic coating as the solar reflectance at the dark phase remains unaffected during the whole experimental period.
The promising results of this research in addition to the advantages from the color changing properties concerning energy efficiency in buildings, indoor air environment and urban microclimate, encourages further investigation of the materials and the techniques.