Increased urbanization have many negative effects on human well-being, city infrastructure, electricity usage and the increase of indoor temperatures. A solution may be to retrofit existing buildings, with implementing a vegetated layer to roofs and walls, this may enhance building performance, reduce consumption and improve indoor comfort. Cities with tall buildings may be more adequate to implement a green-wall as it have more area to make impact. This paper examines the energy reduction advantages of adding greenery on buildings in the hot arid climate of Egypt by considering three typical types of residential buildings in the city of Cairo as a case study. Designbuilder software was selected to stimulate the buildings chosen in this research. The results shows that an extensive soil thickness of 15cm performs better in the arid climates. electricity consumption for the base case is 52 kWh/m2 annually when used a traditional external envelop and dropped to 43 kWh/m2 when a vegetated layer added to the whole building (roof & wall), annual electricity consumption reduced by 17% to 25% per annum when added a vegetated layer. In addition to enhancing the indoor thermal comfort by 3 PMV values and indoor air temperature by 5°C.

Green-roofs are becoming a popular breathing roofing alternative to traditional roofing systems. Green-roofs were mentioned as an ecological-economical solution; however, limited work has been carried out on the potential life cycle cost savings of green roofs in arid climates. This paper present costs savings by green roofs in arid climates. The model accounts for energy savings, structural considerations as well as other variables. Detailed thermal simulations for various configurations of green roofs are performed to assess energy savings using DesignBuilder. Experiments are performed for a two story residential building in Egypt with a base case control that uses a traditional roof meeting standard model energy codes. One local sub-climatic zone was simulated while changing the thickness of the green-roof soil, the conductivity of the green roof and building aspect ratio. Costs for green-roof saving potentials were estimated according to Egyptian electricity consumption calculator, other parameters as retrofit potential and structure allowances to withhold the required layers with different thicknesses. The results demonstrate the economic benefits of using green-roofs under different design situations and provide guidance for the selection and design of green-roofs systems in similar climates. Savings varied from 15-32% compared to traditional and un-isolated roofs. It was also found that reducing soil thickness to 15 cm results in 15% annual savings, Moreover, conductivity of soil has significant impact on amount of savings. The research shows that the most energy saving realized when the aspect ratio of the building is 1:1.5.