The energy model for the prescriptive path takes all of these factors into account to demonstrate that the proposed building will perform as well or better than the code minimum building. In the past many teams used a "prescriptive" path within these standards to demonstrate compliance (e.g., limit window area, use a certain level of insulation, select an air conditioning unit with a certain efficiency or better), but with performance requirements trending higher for code, many are forced to use a "performance" path to demonstrate compliance.Įnergy modeling is used to support the performance path, allowing project teams to make trade-offs (e.g., perhaps the window area and fan horsepower don’t comply with code requirements, but improved glass and more efficient HVAC system types can provide counterbalance). It also has placed a challenging requirement on project teams to demonstrate compliance. (See Figure 1.) This reflects the importance being placed on energy and energy performance in buildings and has in part been driven by federal legislation advancing the energy codes on a more regular basis. While some states were still using the 1989 version of ASHRAE Standard 90.1 as recently as 5 years ago, today most states have adopted recent versions of ASHRAE 90.1 (2013, 2010, or 2007) or the International Energy Conservation Code (IECC) (2012 or 2009). The University of California, the University of Michigan, and the State of North Carolina are such entities. One example is the decision by many organizations to require that all new projects achieve particular energy savings targets as compared to code because their LEED projects were not necessarily achieving high scores in the energy savings credit. Indirect impacts are largely the result of heightened awareness of energy issues attributable to the USGBC’s efforts, manifested in the form of institutional policy or legislation. The direct impact, attributable to the need or preference of many projects to complete modeling, has led to development of energy modeling talent within architecture, engineering, and construction (AEC) firms and has created a large contingent of firms that provide LEED, energy modeling, and related consulting services. The rapid growth of the LEED rating system and other certification programs that require energy performance improvements over energy code has had a significant impact on the role of energy modeling in design, both directly and indirectly. Compared to today, there were very few modeling practitioners, the budget for such activity was often limited, and many of the tools were not nearly as user-friendly. Green Building Council’s (USGBC) LEED rating system, or possibly a few lifecycle cost scenarios. Ten years ago, energy modeling executed during the design phases of projects was generally still relegated to the role of documentation, whether for code compliance, the U.S.