Built envelope (external wall and roof) significantly influences the environment during construction as well as operational phase of the building. The present study examines environmental impact reduction of a building in tropical climate through low-impact materials and green roof. Ecological footprint (EF) is a globally recognized assessment tool that assesses the environmental impact of the human activities. EF tool was used in this study on two different design models: conventional design (Model I) and modified design (Model II). It was observed that modified design reduces the EF of the built envelope significantly. By taking the built envelope as the research object, this study experimentally examines the thermal characteristics of the external wall/roof structure and analyzes the materials used in Indian buildings for a modified design. For external wall surface area, the constructional EF of the Model I and Model II is 0.0091 and 0.0049 gha/m2, respectively. For roof surface area, the constructional EF of the Model I and Model II is 0.0064 and 0.0071 gha/m2, respectively. The monthly operational EF reduction potential of external wall and roof of the Model II as compared to Model I is in the range of 25–30.1% and 61.9–67.1%, respectively. The constructional cost per unit external wall surface area of the Model II is 10% higher than the cost of conventional external wall (Model I), while the constructional cost per unit green roof surface area of the Model II is 15.6% higher than conventional roof of the Model I.