Thermal efficiency of roof tiles

Abstract The correct specification of roofing materials can contribute both to the improvement of energy efficiency in buildings and to the mitigation of the urban heat island effect. However, the lack of characterisation of the thermal properties of these materials is still the rule. This research study investigates solar reflectance in three different types of roof tiles: enamelled ceramic tiles, rustic tiles and concrete tiles, with samples in different colours. The solar reflectance of the samples was measured using the ALTA II portable spectrometer, and, subsequently, the solar reflectance index (SRI), based on the ASTM E1980 standard was calculated. The results showed that colour variability had a direct impact on the tiles' performance regarding solar reflectance (enamelled ceramics from 0.11 to 0.67, concrete 0.1 to 0.37, rustic ceramics from 0.25 to 0.47). The concrete tiles presented a lower solar reflectance index (39%). The lighter colours showed to be more efficient, presenting higher solar reflectance values. However, the diversity of light tones led to variations in solar reflectance (0.67, 0.37, 0.47, enamelled, concrete and rustic, respectively). The results of this study point to the importance of analysing the solar reflectance of roofing materials and the need for their correct specification in buildings.