Rooftop Unit Replacement: Title 24 Requirements
Replacing a commercial rooftop unit, or its air handler, outdoor section or coil, is an alteration under Section 141.0(b)2. A packaged unit below 65,000 Btu/hr must follow Table 141.0-E-1, which sets the allowed unit type by building use and climate zone. Larger units follow the Section 140.4 rules for the equipment replaced.
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What counts as the replacement
Section 141.0(b)2E names the triggers: a new or replaced air handler, the outdoor condensing unit of a split system, or a heating or cooling coil. A whole packaged rooftop unit contains all three. The nonresidential compliance manual (NRCM) calls filter and belt changes maintenance. Each trigger also brings a demand responsive thermostat where the old one is not, plus duct sealing unless an exception applies. Economizer and duct detail are on our rooftop unit replacement page.
Below 65,000 Btu/hr, a table picks the unit type
A new or replacement single-zone packaged rooftop system with direct-expansion cooling below 65,000 Btu/hr must meet Table 141.0-E-1 or the alteration performance approach in Section 141.0(b)3. Each cell gives one answer: a single-zone heat pump with economizer, an air conditioner with furnace plus variable speed fan plus economizer (a dual-fuel heat pump with that fan qualifies too), or no requirement. Schools have a requirement in Climate Zones 1 to 15. Retail, grocery, office and financial-institution spaces have none in Zones 1, 2, 14 and 16.
The variable speed fan needs two stages at least, and at 50 percent speed it may draw no more than 30 percent of full-speed fan power. The table does not apply when the alteration exceeds existing service panel or transformer capacity, shown by an Article 220 load calculation from an engineer.
Curb adapters and the fan budget
Table 141.0-D adds allowance to a replacement's fan power budget, but its adapter-curb rows add allowance only for multi-zone VAV systems. They read 0.000 for other fan systems, so a curb adapter on a single-zone unit adds no fan power.
What goes to the building department
The permit application carries NRCC-MCH-E, and the installing contractor completes NRCI-MCH-E. The acceptance forms match what was installed: NRCA-MCH-03-A for unit controls, NRCA-MCH-05-A for an economizer, NRCA-MCH-04-A where ducts are tested, each signed by a certified mechanical acceptance test technician. A factory-certified economizer skips only the functional-testing step. See also small commercial replacements and heat pump replacements. Commercial reports are quoted per project.
Common Title 24 Questions
- When does a commercial project need Title 24?
- Does an office tenant improvement need Title 24?
- Does a restaurant remodel need Title 24?
- Does a retail tenant improvement need Title 24?
- What plans are needed for a commercial Title 24 report?
- What is an NRCC certificate of compliance?
Frequently Asked Questions
No. The table applies to any new or replacement single-zone packaged rooftop system below 65,000 Btu/hr, whether or not the new unit matches the old one. The cell for the building type and climate zone decides, and a no-requirement cell leaves the type open. The office row prints Zone 11 as SZAC2, a code the footnotes do not define, so confirm that cell with the department.
Yes. At 65,000 Btu/hr and above the table stops applying and the Section 140.4 requirements for the equipment replaced apply, including the economizer rules when design cooling capacity is over 33,000 Btu/hr.
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