Impact of using cool paints on energy demand and thermal comfort of a residential building

Abstract

This work studies the impact of using cool paints and/or thermal insulation on the thermal behavior and energy demand of a residential building. Buildings with thermal characteristics representing both old and new constructions are considered. The results were obtained using the dynamic computer simulator ESP-r. Recommendations for designers and/or house-owners in terms of deciding the best thermal comfort solution are withdrawn. For a case-study building in Portugal, in the summer, it was found that an increase in roof and façade value of total solar reflectance (TSR) from 50% to 92% reduced the maximum indoor free-float temperature between 2.0 C and 4.7 C in old construction (without thermal insulation), and between 1.2 C and 3.0 C in new construction (with thermal insulation). This had as a trade-off effect the decrease of the minimum indoor temperature of up to 1.5 C. The results of annual energy demand for heating showed a maximum penalty of about 30% when using cool paints. However, it was demonstrated that the cooling demand almost vanishes, eliminating the need to install air-conditioning devices. The analysis of specific real hot weather time periods showed that the maximum altitude of the sun, which is related to the month of the year, determines the solution that originates the highest temperature reduction. As the maximum sun altitude decreases the cool paints show comparatively better results.