6.4.9 Energy Modeling and Modeling Software

A. Modeling or simulation of expected building performance is a common technique for estimating and comparing utility use results achievable with alternative designs or construction methods. Certifications that allow performance-based options require modeling to verify expected results. Many green building certifications allow the designer a choice of a “prescriptive” option for meeting certification requirements or a “performance” option. Prescriptive in this context means a fixed “recipe” of building parts and components each with an individual qualitative metric or specification, e.g., fiberglass batt insulation rated R-30. By contrast a performance standard allows the design professional flexibility to create a unique “recipe” provided the whole building design is modeled to estimate overall performance. Prescriptive options do not require modeling. The energy professional and the Project Architect are responsible for selection and proper use of appropriate, industry recognized energy modeling software. In general, selected modeling software must simulate the actual buildings, common spaces, accessory structures and site improvements proposed (See Section 6.4.8 above). For buildings over three stories or containing common spaces, the modeling must be completed in accordance with the requirements of ASHRAE 90.1 Appendix G. For buildings up to three stories with no common space, the HERS Resnet rating system may be used, provided that other specialized modeling software or methods, (e.g., for site lighting, clubhouse and pool, etc) are used to document all energy use apart from the residential buildings. In a property with buildings of both kinds, the energy professional may use ASHRAE 90.1 Appendix G or a combination of both methodologies provided that all energy use for the entire property is included in results. Plans and specifications for construction should be at least 80% complete and include all design elements that impact energy use. All factors other than design variations must be held constant from one modeled iteration to the next. Modeling for an existing property must incorporate as-built design as modified by proposed repairs and alterations, and for any buildings, units or spaces unchanged, the model should incorporate benchmarked consumption. Recognized software and modeling standards are described in Appendix 6.