Commercial Daylight Control Requirements Under Title 24
Daylight responsive control is required where an enclosed space has 75 watts or more of general lighting in one daylit zone type, but a long exception list removes it from many rooms: small glazing, shaded glazing, low secondary-zone wattage and retail sales floors. On an alteration, only the full Section 140.6 compliance route brings it in.
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The exceptions that settle most projects
- Rooms with under 24 square feet of total glazing, or garage areas with under 36 square feet of glazing or opening.
- Luminaires in sidelit zones of retail merchandise sales and wholesale showroom areas.
- A secondary sidelit zone with under 85 watts of general lighting, where the primary zone needs no control.
- Areas under skylights where obstructions block direct sun for more than 1,500 daytime hours a year between 8 a.m. and 4 p.m.
- Glazing under an overhang covering its full width, with a projection to rise ratio above 1.5 on south, east and west, or above 1 on north.
The thresholds are on daylighting controls.
When an alteration adds them
Table 141.0-F requires daylight responsive controls only on the full Section 140.6 compliance route. The 80 percent and one-for-one routes do not. Where skylights are added to an existing building and the lighting is not recircuited, the control need not meet the multilevel requirement (141.0(b)2G). Large enclosed spaces have their own rule in Section 140.3(c); see daylighting in large spaces.
How the test samples
Every photocontrol serving more than 5,000 square feet of daylit area is tested. Smaller ones are all tested up to five, then one per group of up to five more with similar sensors and glazing orientation; a failed first sample sends its group to full testing. Primary and secondary sidelit zones are tested separately.
What the test measures
The tester picks a reference location, either the darkest task point or the point farthest from daylight, and records the electric-only illuminance. At daylight above 150 percent of that value, controlled power must drop by at least 90 percent, or 100 percent in garages. In the partial test, with daylight at 60 to 95 percent of the reference, combined light must be at least the reference and no more than 150 percent of it, without flicker. Results go on NRCA-LTI-03-A, described under lighting acceptance testing. Quotes start from the commercial page.
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
Luminaires in sidelit zones of retail merchandise sales and wholesale showroom areas are excepted by Exception 7 to Section 130.1(d). Skylit zones are not covered by that exception.
Only on the full compliance route in Table 141.0-F. The 80 percent and one-for-one routes do not require them.
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