In the past decade, there has been considerable growth in the retrofit of existing roofs for energy and sustainability improvements. Although the study of roof systems (from coverings to structure) is of great significance to energy efficiency and sustainable development, design and construction of new roofs on top of existing roofs in buildings has not received sufficient attention. This work attempts to present a case study of an innovative and energy efficient design for dealing with challenges of integrating the new components with the existing deteriorated roof of a building in New Kensington, PA to prevent water leakage and harvest solar energy. The study uses green retrofit and sustainability-inspired initiatives such as designing and testing a conceptual model for a new roofing composite that will sit on top of the existing roof not only to improve the aesthetic qualities and thermal insulation but also to add renewable energy production capability. There is considerable potential to improve energy efficiency of existing buildings by replacing or retrofitting an existing roof. For example, a roof energy audit can provide an effective contribution to building energy efficiency retrofits. In this work, an energy assessment of the proposed prototype is used to assess the extent to which thermal insulation materials can contribute to sustainable energy retrofitting strategies for the existing roofs.