Section C407.1/Total Building Performance
IECC C407 provides the performance compliance path allowing trade-offs between systems using energy modeling.
The total building performance method allows compliance by demonstrating that the proposed building's annual energy cost does not exceed the annual energy cost of a baseline building designed to meet the prescriptive requirements of Sections C402 through C405. Both buildings must be modeled using approved energy simulation software following Appendix G of ASHRAE 90.1 or the simulation requirements of Section C407. The proposed design must include all building systems: envelope, HVAC, lighting, service water heating, and process loads.
Why this section exists
The prescriptive path (Sections C402-C405) is straightforward but does not allow trade-offs between systems. A building with an exceptionally efficient HVAC system might not need as much envelope insulation, but the prescriptive path requires both. The performance path allows these trade-offs by comparing the total building energy to a baseline, giving designers flexibility to optimize the overall design. This is the preferred compliance path for complex buildings with high window-to-wall ratios, unusual geometries, or advanced systems.
What plan reviewers look for
Plan reviewers check the energy model report for the proposed and baseline building energy costs. They verify that the modeling assumptions match the construction documents (envelope values, HVAC equipment, lighting power, schedules). They check that the baseline building is modeled per the prescribed rules (Appendix G or C407). They also verify that the energy modeler is qualified and the software is approved.
Common violations
Related IECC requirements
Sections C402 through C405 provide the prescriptive requirements that define the baseline building. Section C406 covers additional efficiency requirements that apply to both paths. ASHRAE 90.1 Appendix G provides the detailed modeling rules referenced by C407.