Energy, environmental and economic performance of an external roof for a sustainable building

Abstract

ABSTRACT The external roof is considered to be a key component in building energy consumption; this is why special attention is addressed to improving its thermal performance. This paper starts with numerical modeling of a multilayered roof exposed to the real climate of Morocco. The model is validated through our experimental results in the case of a reduced scale cavity. The numerical model is used to compute the annual loads of cooling to compare different configurations using two types of insulation (Rock wool and Expanded polystyrene).The results start with the determination of the optimum thickness of thermal insulation using an economic model based on life-cycle cost analysis, and this is for three different climate regions. The distribution of this optimum thickness between the roof layers is studied according to the annual cooling loads. Then, the four configurations were studied to evaluate the most suitable location of the insulation in the roof using the optimal thickness. The results show that the optimum insulation thickness varies between 0.03 and 0.07 m, with an energy gain between 63 and 75%, depending on the region and the type of insulation. Moreover, the integration of insulation in the roof demonstrates its environmental effectiveness by reducing GHG emissions by an average factor of three. The results also show that insulation location is beneficial to reduce the energy need, especially that of cooling. It is seen that the minimum temperature swings and peak load occur in the case that insulation is placed inside, outside, and in the middle of the roof, with a significant energy saving of about 92% for Fez, 90% for Marrakech and 89% for Ouarzazate.