Albedo influence on the microclimate and thermal comfort of courtyards under Mediterranean hot summer climate conditions.

• ENVI-met is validated to analyze the effect of albedo on courtyard microclimate. • Albedo of surfaces is found to have little effect on courtyard air temperature. • Albedo has an important effect on surface temperature, MRT and comfort. • High albedo of the walls reduces surface temperature but increases MRT. • Medium-range albedo is recommended to balance positive and negative effects. The Urban Heat Island (UHI) effect represents a threat to the well-being of cities. Cities must adapt to this phenomenon, prioritizing the improvement of outdoor environment quality. Urban materials have a great impact on outdoor environment quality, energy demand, and citizens' well-being. Based on the literature, it can be stated that changing the albedo of on-site materials (pavements, facades) is a relevant strategy. The environmental impact of reflective materials from buildings to urban microclimate has been widely discussed in the literature. However, few publications assess the role of albedo in inner courtyards. This work uses simulation results to evaluate the impact of different surface albedo on the thermal performance and comfort of a courtyard in Seville. To do so, the simulation tool ENVI-met, one of the most widely used for outdoor spaces, is validated through a comparison with monitoring results. In conclusion, high reflectance compromises user comfort up to 5 °C of PET despite the fact that the use of high albedo on surfaces reduces surface temperature up to 25 °C in comparison with low albedo as it accumulates less heat by reflecting more solar radiation. Some of the recommendations given include the use of medium albedo (around 0.4) on walls to balance positive and negative effects, and high albedo on the pavements (above 0.7). [ABSTRACT FROM AUTHOR]