An Integrated Ecoroof Energy Analysis Model

Vegetated roofs (ecoroofs) offer diverse benefits, including energy savings and stormwater runoff reductions. Installation of ecoroofs in both new and existing buildings has expanded significantly during the past 5 years, with several local jurisdictions providing incentives for their installation and the Leadership in Energy and Environmental Design green building rating system offering multiple credits for them. Decisions to install ecoroofs now largely rely on anecdotal evidence or overly simplified models of benefits. Inadequate models can lead to the underutilization of ecoroofs and the potentially large number of benefits that could result. On the other hand, uneconomic applications of ecoroofs result in less significant benefits than are estimated for the use of currently available methods. This Phase I project will complete initial development of an analysis tool to estimate the energy usage impacts of ecoroofs on commercial buildings. The tool will build on past research conducted by members of our project team by bringing together the U.S. Department of Energy’s EnergyPlus building energy simulation engine and an ecoroof analysis module. The integrated model augments EnergyPlus to allow for the physically based representation of the complex effects of rooftop vegetation and soil on the building envelope’s energy budget. Our team members already have started to incorporate the classic Penman-Monteith representation of vegetation heat transfer characteristics in a building energy simulation module. During Phase I, the integration with EnergyPlus will be completed, tested, and verified. Once the functionality of the integrated model is demonstrated, Quantec will conduct a limited series of runs using the model to examine the energy consumption impacts of a range of ecoroof characteristics, given diverse climate and building characteristics. During Phase II, the integrated model will be refined and used to conduct an extensive set of runs providing inputs for a Web-based tool with a user-friendly graphical user interface that accesses, interpolates, and extrapolates simulation results for evaluating alternative ecoroof options. Phase II will include laboratory experiments to provide accurate estimates of the parameter associated with ecoroofs, and these will be used in the integrated model runs. The Web-based decision support tool will be made available to the public and will immediately find a large national and international market. The detailed improvement to the building energy simulation code, the specific knowledge developed as part of the experimental portion of this project, and the exposure provided by the widespread decision support tool uniquely will position Quantec to address the more sophisticated modeling and analysis needs of select customers.