Section C403.1/Mechanical Systems Scope
IECC C403 covers HVAC energy efficiency requirements including equipment efficiency, controls, economizers, and duct insulation.
Mechanical systems and equipment serving the building heating, cooling, and ventilation loads must comply with Section C403. This includes minimum equipment efficiency ratings (Table C403.3.2), HVAC system controls (thermostat setback, optimum start, demand control ventilation), economizer requirements in climate zones 2 through 8, duct sealing and insulation, and hydronic piping insulation. Equipment must meet or exceed the minimum efficiency in Table C403.3.2 at the time of installation.
Why this section exists
HVAC systems typically account for 40-60% of commercial building energy consumption. Equipment efficiency sets the baseline, but controls, economizers, and distribution system insulation determine how efficiently the equipment operates in practice. An efficient chiller connected to leaky, uninsulated ducts wastes much of its efficiency advantage. Section C403 addresses the full HVAC system, not just the equipment.
What plan reviewers look for
Plan reviewers check equipment schedules for efficiency ratings against Table C403.3.2. They verify that the control sequences include thermostat setback, economizer operation where required, and demand control ventilation for spaces with high occupant density. They check duct insulation R-values on the mechanical details and verify piping insulation on the specifications.
Common violations
Related IECC requirements
Section C402 covers the building envelope that determines the HVAC load. Section C403.3 covers specific equipment efficiency requirements. Section C403.7 covers duct and plenum insulation and sealing. ASHRAE 90.1 Section 6 provides equivalent mechanical system requirements.