Pakistan is facing sever energy crises which has adversely affected its economy. Retrofitting of existing buildings though energy efficient building material can possibly help reduce the energy consumption. This study involves analysis of energy consumption pattern of an existing commercial building in Lahore and its retrofitting. A computer programme named Ecotect has been used to simulate and determine the heating and cooling load of the building and testing the efficacy of retrofitting measures in terms of energy saving. Our results suggests that significant amount of energy can be saved by making slight modifications in the building using energy efficient material available in the market. The cost of retrofitting can be recovered within a few years. The findings of this study also serve as a guide for owners/tenants of other existing commercial buildings on how to move towards sustainable practices and gain enormous amount of energy savings.