Commercial Ventilation Requirements Under Title 24

The rate follows expected occupancy

For spaces designed for an expected number of occupants, or with fixed seating, Section 120.1 determines the zone outdoor airflow rate by equation from the expected occupant count stated by the building designer. That figure is a design input with consequences: it sets the ventilation obligation for the life of the building.

It is also why a classroom or a restaurant dining room carries far more outdoor air than an office of the same size. The area is the same; the people are not.

Demand control ventilation, and its sensor rules

Section 120.1(d)3 requires demand control ventilation in a space with a design occupant density, or a maximum egress occupant load factor, of 25 people per 1,000 square feet or more (40 square feet or less per person) when the ventilation system serving it has an air economizer, modulating outside air control or a design outdoor airflow rate above 3,000 cfm. Spaces under 150 square feet or with a design occupancy under 10 people are excepted, and so are spaces whose processes generate dusts, fumes, mists, vapors or gases without local exhaust ventilation.

Under Section 120.1(d)4, CO2 sensors are then installed in each room that meets the Section 120.1(d)3 criteria, at no less than one sensor per 10,000 square feet of floor space, between 3 feet and 6 feet above the floor.

The sensors themselves are specified in Section 120.1(d)4F, not left to the installer. Each must be certified by the manufacturer as accurate to within plus or minus 75 ppm at 600 and 1000 ppm concentration, measured at sea level and 25 degrees Celsius, factory calibrated, and certified to require recalibration no more often than once every five years.

The control target

The controls must maintain CO2 at or below 600 ppm plus the outdoor air CO2 concentration in every room carrying a sensor. Note the form of that: it is a figure above ambient, not an absolute ceiling, so the target moves with the outdoor air rather than being fixed.

It is acceptance tested

Demand control ventilation is functionally tested on site and documented on NRCA-MCH-06-A by a technician certified for mechanical acceptance testing. Sensor accuracy and calibration certification are part of what has to hold up, which is why specifying a compliant sensor matters more than it looks on a schedule.

Where this decides a project

On any occupancy with dense or variable occupancy — classrooms, dining, assembly, conference. Those are the buildings where the ventilation load is large enough that modulating it is worth the sensors, and where the acceptance test is most likely to be in scope.

Common Title 24 Questions

1. Does replacing commercial HVAC trigger Title 24?
2. Does a rooftop unit replacement require Title 24?
3. Do heat pumps affect commercial Title 24 compliance?
4. Does adding air conditioning trigger Title 24?
5. What are Title 24 lighting controls?
6. Title 24 economizer requirements

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