Abstract
Green roofs improve building energy performance and constitute an alternative to sustainable buildings. A green roof model is dynamically coupled with a building thermal model to assess its energy performance that takes into account the indoor air temperature dynamic changes. Under the climate conditions in Antananarivo, we compared green and conventional roofs. The present study shows that green roofs protect the roof structure under extreme temperature and large temperature fluctuations. For the case of Antananarivo, the amplitude of the temperature fluctuations at the top face of the support is reduced by 28 °C when using green roof. The impact of the green roof on indoor air temperature and energy demand is investigated. The vegetation decreases the maximum indoor air temperature and improves the building thermal comfort during summer days. It has no effect on the minimum indoor air temperature, but additional soil thickness can increase it. In addition, a global sensitivity analysis, which is carried out on the proposed model without considering any specific weather data, allows us to identify the most influential parameters on the energy demand. It has been found that green roofs have almost insignificant thermal impact in insulated buildings; however, their potential prevails over the building envelope and weather characteristics in the case of non-insulated building.
Highlights
Rooftop greening is a practice that has been used since ancient civilizations
We mainly focus on the results that highlight and compare the thermal performance of the green roofs
In the sunny winter, a large fluctuation amplitude (FA) of Tst* is observed; in that day, Tst* varies between 9 °C and 41 °C, but Tst remains between 19 °C and 23 °C
Summary
Its utilization had been rare for centuries, until the Swiss architect Le Corbusier included them in his “Five Points of a New Architecture” in the twentieth century [1,2] This technique is considered to be an effective solution to improve the internal and external environments at the building and urban levels. Green roofs improve storm water management [3,4] and reduce air [5,6] and noise [7] pollution They increase both plant and animal biodiversities in the cities [8,9] and reduce a city’s carbon footprint by converting carbon dioxide to oxygen through photosynthesis [6,10]. They improve the thermal insulation of a building so that solar heat gain and heat loss are reduced by approximately 70%–90% in the summer and 10%–30% in the winter, respectively [11]
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