Roadmap for the Future of Commercial Energy Codes

Abstract

Building energy codes have significantly increased building efficiency over the last 38 years, since the first national energy code was published in 1975. The most commonly used path in energy codes, the prescriptive path, appears to be reaching a point of diminishing returns. The current focus on prescriptive codes has limitations including significant variation in actual energy performance depending on which prescriptive options are chosen, a lack of flexibility for designers and developers, the inability to handle optimization that is specific to building type and use, the inability to account for project-specific energy costs, and the lack of follow-through or accountability after a certificate of occupancy is granted. It is likely that an approach that considers the building as an integrated system will be necessary to achieve the next real gains in building efficiency. This report provides a high-level review of different formats for commercial building energy codes, including prescriptive, prescriptive packages, capacity constrained, outcome based, and predictive performance approaches. This report also explores a next generation commercial energy code approach that places a greater emphasis on performance-based criteria. For commercial building energy codes to continue to progress as they have over the last 40 years, the next generation of more » building codes will need to provide a path that is led by energy performance, ensuring a measurable trajectory toward net zero energy buildings. This report outlines a vision to serve as a roadmap for future commercial code development. That vision is based on code development being led by a specific approach to predictive energy performance combined with building-specific prescriptive packages that are designed both to be cost-effective and to achieve a desired level of performance. Compliance with this new approach can be achieved by either meeting the performance target, as demonstrated by whole building energy modeling, or by choosing one of the prescriptive packages. This review of the possible code formats (further described in Section 2.1) arrives at the following conclusions: • Predictive performance with energy use index (EUI) targets falls short as a code mechanism, since it is difficult to match individual building use to broad EUI targets. • Outcome-based codes–while an essential approach that should be applied to all buildings–are not a substitute for design and construction energy codes that focus on compliance at occupancy. • For a design and construction code, a differential predictive performance method with a stable and independent baseline provides the best accuracy and potential for a highly automated approach that could eventually be applied to most buildings. • Current performance codes that have a dependent and time-variable baseline should be replaced by a differential predictive performance method with a stable and independent baseline. • At some point in the future, tools that demonstrate predictive performance compliance may become so simple that there will no longer be a need for any prescriptive path. • As a bridge, prescriptive packages can provide a transition from the current component prescriptive approach to a performance only code, while providing flexibility and improved energy equivalency. « less