Title 24 Requirements for Office Buildings in California

The zoning rule that fails open-plan designs

Occupant sensing is required in offices of every size, and the rule changes at 250 square feet. Under Section 130.1(c)5, an office of 250 square feet or smaller needs occupant sensing controls that shut off all of the lighting in 20 minutes or less after the room is empty.

In an office greater than 250 square feet, Section 130.1(c)6D requires occupant sensing control zones of no more than 600 square feet, shown on the plans. An unoccupied zone must reduce its lighting to no more than 20 percent of full power within 20 minutes (switching it completely off qualifies), and once the whole office is unoccupied, all zones must turn off in 20 minutes or less.

A single sensor covering a large open floor therefore fails on zoning even when the sensor works perfectly. It is the most common reason an office lighting scheme does not pass acceptance testing.

Power follows the room schedule

Allowed lighting power comes from Table 140.6-C by space category, and an office building is rarely one category. Open office, private offices, meeting rooms, lobby, corridors and storage each carry their own density, and the permitted total is the sum. A plan that labels rooms by number rather than by use has to be interpreted before it can be calculated.

Corridors and stairwells are in scope too

Both appear on the occupant-sensing list in their own right. They are circulation rather than occupied space and are the element most often left off a controls scope, which then surfaces at test rather than at design.

Mechanical, when the fit-out touches it

Many office fit-outs leave the base building services alone, which keeps them to a lighting submittal. Where they add a supplementary unit for a server or conference room, rework zoning, or relocate ductwork, the mechanical requirements come in, and an economizer is required on a cooling air handler over 33,000 Btu/hr of design cooling capacity unless an exception in Section 140.4(e)1 or Section 141.0(b)2C applies.

Both disciplines are acceptance tested

Lighting controls and mechanical systems are the two disciplines requiring functional testing on site by a certified technician. An office project touching both needs both certifications represented, which may mean two technicians.

Where to go deeper

Two sections bite hardest on an office fit-out. Controlled receptacles are required in offices, lobbies, conference rooms, kitchens and copy rooms — the section names those rooms specifically. And a perimeter office with glazing will usually engage automatic daylighting controls, which trigger at only 75 watts inside a daylit zone.

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