The Design Energy Code is an input in the Extended Project Info section. For whole building projects that are not energy modeled, the Design Energy Code selection determines the savings for the project. The savings percent is a code equivalent percent savings of the selected code to the code basis for the 2030 Challenge (CBECS 2003).
The Design Energy Code Equivalent Percentage Savings values are based on a collaboration with New Buildings Institute, which utilizes the code determination analysis by Pacific Northwest National Laboratory (PNNL) for each new version of ASHRAE Standard 90.1 to establish zEPI scores that ultimately become the code equivalent savings (100 - zEPI).
The DDx Design Energy Code Equivalent Percentage Savings can vary over time, due to one or more of the following reasons:
- Significant new research has been made available; for example, when ASHRAE started using 90.1-2004 as the baseline for their calculations to assist making new versions and versions of other codes comparable to a single version. Leading up to this shift, additional research and analysis were completed to assess what the percentage savings between 90.1-2004 and CBECS 2003 (baseline for 2030 Challenge) should be. The resulting adjustment had a ripple effect across a number of design energy codes, and the update has now been incorporated into the DDx.
- There could be a difference between the pre-publication and final determination of percent savings. The timing of the PNNL final determination can vary, but they tend to issue a pre-publication notice near the release of a new ASHRAE version. The pre-publication value will be associated with the design energy code initially, and it will be updated as needed after the final determination has been published.
- Additional research and analysis has been provided to AIA for regional and/or international codes that warrant an update of the value. Changes to the code equivalencies will only be updated at the point of saving and will not get updated across projects unless the projects are re-saved.
Design Energy Code Percent Reduction vs. Modeled pEUI Percent Reduction
- If the percent savings pEUI reduction for modeled projects is less than the design code percent saving equivalent, consider adjusting the baseline to meet the design code equivalent percent savings.
- If using code equivalent savings, the selected design energy code will drive the percent savings.
- If a project has an energy model, the percent savings is derived from the pEUI and the baseline EUI.
- If a project has an energy model, check to make sure the percent savings is a reasonable number – comparing to the code equivalent percent savings is a helpful benchmark.
- If the percent savings value is unexpected, reevaluate and consider adjusting the baseline EUI.
The table below details the approximate percent reduction based on the selected design energy codes.