Thermal analysis of roofs with thermal insulation layer and reflective coatings in subtropical and equatorial climate regions in Brazil

• An ideal cool roof exists for temperature and solar radiation combination.
• Ideal cool roof designs save cooling energy and mitigate urban heat island.
• Thermal insulation saves cooling energy, but contributes to urban heat island.
• White paints/selective coatings save cooling energy and mitigate urban heat island.

This article presents a comparative analysis of the thermal performance of large metal roofs like those found on exhibition halls, airports, and malls located in subtropical and equatorial climates regions in Brazil. The focus of the investigation was the suitability of the use of white paints, selective coatings, and thermal insulation layers in those regions. The survey was based on a model of heat transfer through a roof where solar radiation and ambient air-temperature were studied as functions of time. The results showed that in cities with an equatorial climate, the roof with the thermal insulation layer and selective coating is the best option because it saves more energy and reduces the effects of urban heat island (UHI). Otherwise, in cities with a subtropical climate, the application of white paint on a roof without a thermal insulation layer is the best solution for both a reduction in energy consumption and a decrease in the formation of UHI.