The residential buildings consume almost 50% of the total energy producing about 30% of the world's CO2 emissions. As the building envelope is the one that is responsible for the whole thermal performance of the building, the thickness, and characteristics of its material play an important role in improving the thermal performance and minimizing the cooling and heating loads to achieve thermal comfort inside the spaces.

The main aim of this research is to study the effect of the wall's thickness and material on the energy consumption in a residential unit located in Janna Residential Project, New Cairo.

The methodology of this research starts with reviewing the literature and the methods related to the effect of the building envelope on energy consumption. Then, the practical study using the Design-Builder Plug-in which is in the Revit Program to study the effect of the wall thickness and material on the heating and cooling loads.

The results show that using the indirect green façade without an air gap and with an air gap in the west and south orientation with WWR 30% reduced the energy consumption by 8.9% in case of no air gap and the wall's R-value increased from 0.6 to 0.88m2k/w and in case of 60 cm air-gap the energy consumption reduced by 14.48% and R-value increased to be 0.91m2k/w. and that means that the thickness and material of the wall as a part of the building envelope have a great effect on the total energy consumption of the building.