Commercial Demand Control Ventilation: Title 24 Requirements
Demand control ventilation is required in a space designed for 25 or more people per 1,000 square feet when its system has an air economizer, modulating outside air control or a design outdoor airflow above 3,000 cfm. CO2 sensors hold the room to 600 ppm above outdoor air, and NRCA-MCH-06-A tests it.
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Does the space cross the density line
Section 120.1(d)3 looks at design occupant density, or the egress occupant load factor in the California Building Code, of 25 people per 1,000 square feet (40 square feet per person) or more. Table 120.1-A lists default densities: 25 for classrooms, 33 for conference rooms and restaurant dining, 71 for lecture halls and auditoriums, and only 5 for office space. A conference room trips the line where an open office does not.
Exceptions: it is skipped where space exhaust exceeds the design ventilation rate minus 0.2 cfm per square foot, and where the space is under 150 square feet or designed for fewer than 10 people. It is barred in spaces with unexhausted dusts or fumes, such as unvented food preparation, daycare sickrooms, science labs, barber shops and nail salons.
Sensors and setpoint
- One CO2 sensor per qualifying room, at least one per 10,000 square feet, placed 3 to 6 feet above the floor.
- The controls hold CO2 at or below 600 ppm plus the outdoor concentration. Outdoor CO2 is assumed at 400 ppm or measured by a sensor within 4 feet of the intake.
- Sensors are accurate to within 75 ppm at 600 and 1000 ppm, factory calibrated, and need recalibration no more often than every 5 years. A failed sensor drives the zone to its minimum outdoor air.
What the test looks like
The technician checks sensor calibration and placement, then disables the economizer. A signal at or just above the setpoint must open the outdoor air damper (single zone) or the zone damper (multiple zone) to the full ventilation requirement. A signal well below must reduce it. With controls restored, calibration gas slightly above the setpoint is applied to the sensor, and the damper must open.
The 2022 manual, which the 2025 manual points to here, asks for one NRCA-MCH-06-A per CO2 sensor and the outdoor air test before or alongside it. General rules are on the commercial ventilation page. Dense uses such as schools and restaurants meet it most often. Commercial projects are quoted individually.
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
Only if its design outdoor airflow exceeds 3,000 cfm or it has modulating outside air control, and the space is at 25 people per 1,000 square feet or more. The density test applies first.
Yes. Section 120.1(d)4D allows 400 ppm without direct measurement, or a sensor within 4 feet of the outdoor air intake.
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