In another study, Li et al. [20] used EnergyPlus simulation software to estimate the energy consumption index of a typical office building in Hong Kong. They developed linear and nonlinear regression models to assess the energy performance of different building envelope designs with daylighting controls. Most of the previous researches seldom focused on the relationship between energy consumption of office buildings and the variations of building envelop influencing factors in different climate regions in the United States. To surmount these hurdles, present study developed regression equations to predict energy savings in different climate regions in the United States. This study considers seventeen influencing factors including building construction materials and their thickness, building orientation, glass type, etc. Of particular interestin this article is the application of the parametric study in order to understand and determine the most dominant set of input parameters affecting total energy consumption in commercial buildings