The mechanical portion of the energy code, IECC C403, sets minimum equipment efficiencies and mandates several energy-saving features. Heating and cooling equipment must meet listed minimum efficiencies; larger systems require economizers (to use outside air for "free" cooling), demand-controlled ventilation in high-occupancy spaces, and specific control provisions like setback and optimum-start. Duct and pipe insulation minimums also live here.
The common mistake is equipment selected without confirming it meets the C403 efficiency minimums, or a system that skips a required economizer or demand-controlled ventilation for its size and type — again surfacing in the COMcheck mechanical compliance.
Reviewers check the mechanical schedule efficiencies against C403, confirm economizers and DCV where required by capacity and space type, and look for the control provisions. This is the mechanical leg of the three-part COMcheck (envelope, mechanical, lighting), so it has to reconcile with the equipment schedule — a natural tie-in to the equipment-schedule tooling most projects already prepare.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.