An integrated empirical and modeling methodology for analyzing solar reflective roof technologies on commercial buildings

Buildings impact the environment in many ways as a result of both their energy use and material consumption. In urban areas, the emission of greenhouse gases and the creation of microclimates are among their most prominent impacts so the adoption of building design strategies and materials that address both these issues will lead to significant reductions in a building's overall environmental impact. This report documents the energy savings and surface temperature reduction achieved by replacing an existing commercial building's flat roof with a more reflective 'cool roof surface material. The research methodology gathered data on-site (surface temperatures and reflectivity) and used this in conjunction with the as-built drawings to construct a building energy simulation model. A 20-year cost benefit analysis (CBA) was conducted to determine the return on investment (ROI) for the new cool roof construction based on the energy simulation results. The results of the EnergyPlus (TM) simulation modeling revealed that reductions of 1.3-1.9% and 2.6-3.8% of the total monthly electricity consumption can be achieved from the 50% cool roof replacement already implemented and a future 100% roof replacement, respectively. This corresponds to a saving of approximately $22,000 per year in energy costs at current prices and a consequent 9-year payback period for the added cost of installing the 100% cool roof. The environmental benefits associated with these electricity savings, particularly the reductions in environmental damage and peak-time electricity demand, represent the indirect benefits of the cool roof system. (C) 2009 Elsevier Ltd. All rights reserved.