Influence of human behavior on cool roof effect for summer cooling

Abstract

Cool roofs represent an acknowledged solution for cooling energy saving. However, the efficacy of such physical intervention can be affected by occupants' attitudes. Human behavior, in fact, is often neglected or underestimated at the design stage, e.g. while assessing the effect of physical retrofits. Accordingly, the purpose of this study is the assessment of cool roof effect with varying those occupants' attitudes having some effect on energy need for cooling and indoor Thermal Deviation Index (TDI). The analysis has been performed through calibrated dynamic simulation of a continuously monitored historic building. Innovative cool roof clay tiles, suitable for application in historic buildings, have been selected as physical retrofit. Main findings show that occupants' role can dominate the thermal-energy effect of the selected physical retrofit. For instance, cool roof tiles contribute to save 50% of primary energy for attic cooling in the hottest month, from 782 kWh to 398 kWh. If occupants’ adaptation availability in adjusting temperature setups is taken into account in combination of the cool roof effect, the energy need for cooling becomes less than 100 kWh. Also, the same cool tile is able to reduce the TDI from 0.87 to 0.54. If occupants are able to implement effective natural ventilation programs, TDI decreases to 0.29. These results show the necessity to consider neither only the effect of physical retrofits, nor only the effect of human attitudes, but the combination of both of them, in order to perform reliable energy need estimation, in both ante and post-occupancy assessment.