An exploration of green roofs for indoor and exterior temperature regulation in the South African interior

Abstract

Green roofs have been shown to improve comfort levels of rooms directly below them, since they act as insulators; however, global research suggests that the performance of green roofs in attenuating temperature extremes is dependent on local climatic conditions. This study is located in Johannesburg in the South African interior, in a climate that has not previously been researched. Using heat sensors on the exterior and interior, it explores the thermal performance of a scale model of a vegetated roof in comparison with a soil roof devoid of planting and a tile roof during the dry winter season. Four different methods of enclosure were used to simulate various walling conditions. The maximum, minimum and mean temperatures for the upper and under sides of each roof were compared with the ambient temperature. Exterior temperatures for the green roof closely matched ambient temperatures, suggesting that this roof type would help in minimising the urban heat island effect. The soil roof returned the highest minimum temperatures, thereby achieving the best thermal comfort levels at night; however, this roofing solution is not recommended since the exterior maximum temperatures were considerably higher than the ambient temperature. However, the interior under the green roof has a minimal improvement on ambient temperatures and well below the recommended minimum interior temperature of 19 °C promoted by SANS10400-XA. This study forms part of a broader research initiative into energy-efficient low-cost housing solutions.

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Correspondence to Anne Fitchett.

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Fitchett, A., Govender, P. & Vallabh, P. An exploration of green roofs for indoor and exterior temperature regulation in the South African interior. Environ Dev Sustain 22, 5025–5044 (2020). https://doi.org/10.1007/s10668-019-00413-5

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Keywords

  • Vegetated roof
  • Thermal regulation
  • Johannesburg
  • Indoor climate