New Building Codes Change Energy Efficiency Criteria
Traditionally, government examined building codes by using checklist requirements. The Pacific Northwest National Laboratory (PNNL) is working with New York City to take a different approach, one which could pave the way for more energy-efficient city buildings.
Buildings use 75% of the country’s power. Energy codes are a subset of building codes, which establish minimum requirements that govern building construction. The codes encompass requirements for the energy performance of a building, including its systems and related components.
Embracing a Performance Based Approach
A performance-based code determines compliance based on projected energy performance of a whole building or its systems. These estimates rely on energy modeling and simulation tools to account for interactions between systems and components. Conversely, a prescriptive approach, which has been the standard in building energy codes to this point, considers a building compliant only if a set of requirements for individual components is completed, like a checklist.
The pilot removes the prescriptive approach that has always been used in energy codes Why? There is no extra credit for doing more, and if one item is not done exactly, the whole building is considered non-code compliant.
So, prescriptive codes typically limit the amount of light and solar gain allowed in by windows to reduce cooling energy. But well-planned designs take advantage of passive heating, or those that automatically reduce the electric light required during the day benefit from increased solar gain. Performance-based codes recognize these benefits; prescriptive codes cannot.
Testing a New Approach for Energy Codes
For the pilot, PNNL developed a 100 percent performance-based energy code. Within this new framework, there are two different ways to show compliance. One way is to assess whole-building performance, which mirrors the current national energy code standard for commercial buildings but reflects NYC’s own policy goals and energy code requirements.
A second option evaluates energy performance at the building systems level, such as HVAC, lighting, and envelope. A building’s envelope system includes items that separate its interior and exterior, like the foundation, walls, roof, windows, and doors.
System-based performance approaches address one of the main criticisms of whole-building performance approaches. Here, an improved system with a shorter lifespan, such as an HVAC system, could make up for a less efficient system with longer-term impacts, such as the building envelope. By encouraging tradeoffs within a system, that concern is mitigated.
The work is in an early stage. NYC has to determine how to incorporate results of the study. The state plans to examine the new approach in 2023. Other cities and states may follow. If so, how government evaluates buildings may change, and the new approach result in improved energy efficient designs.