In this study, we examined the effect of cool roofs on commercial and residential buildings in each climate zone, by looking at monitored case studies and DOE-2 simulations from various sources of literature; and using an online tool - the Cool Roof Calculator and a simple COP ratio model to validate the results of the case studies. It was found that the Cool Roof Calculator does not take building form into account, hence a sensitivity analysis was first conducted to rank the importance of various building parameters against one another. The analysis was conducted on the EPC normative building energy model. Results indicated that roof absorptance coefficient, aspect ratio and number of floors were the three parameters that either ranked highest or were important parameters, and were chosen for further parametric analysis to evaluate the impact of these building parameters on total building loads. A simple COP ratio model was also developed to validate the results from the literature review and Cool Roof Calculator, and it was found that in terms of cost, for a prototype medium-sized commercial building, it is always beneficial to use a white roof, but cities in northern climates may have little advantage, and insulation may be a better choice.