Non-Residential Lighting and Title 24

Indoor lighting is one of the single largest consumers of energy (kilowatt-hours) in a commercial building, representing about a third of electricity use. The objective of the Title 24 non-residential lighting standards is the effective reduction of this energy use, without compromising the quality of lighting or task work. The Title 24 non-residential lighting standards are the result of the involvement of many representatives of the lighting design and manufacturing community, and of enforcement agencies across the state. A great deal of effort has been devoted to making the lighting requirements practical and realistic.

 

The primary mechanism for regulating indoor lighting energy under the standards is to limit the allowed lighting power in watts installed in the building. Other mechanisms require basic equipment efficiency, and require that the lighting is controlled to permit efficient operation.

Mandatory Lighting Controls

The simplest way to improve lighting efficiency is to turn off the lights when they are not in use. All lighting systems must have switching or control capabilities to allow lights to be turned off when they are not needed. In addition, it is desirable to reduce light output and power consumption when full light output is not needed. These mandatory requirements apply to all nonresidential, high-rise residential and hotel/motel buildings for both conditioned and unconditioned interior spaces. The Title 24 non-residential mandatory lighting control requirements can be summarized as follows:

  • Light switches (or other control) in each room
  • Multi-level control for lighting systems > 0.8 W/ft² in rooms > than 100 sq. ft.
  • Daylighting controls
  • Separate switches when skylit or primary sidelit zone > 250 sq. ft.
  • Automatic multi-level daylighting controls when skylit or primary sidelit zone > 2,500 sq. ft.
  • Controls calibrated so that space always meets or exceeds design footcandles and electric lighting is fully dimmed when daylight is 150 percent of design illuminance
  • Automatic shut-off controls – a time sweep with an override switch or occupancy sensor to assure lights are off after business hours
  • Display lighting is separately switched
  • When the tailored lighting method is used to show compliance, general lighting must be on a separate shut-off control from display lighting
  • Stores larger than 50,000 ft² must have 15 percent of the lighting load connected to a demand responsive lighting control system

Detailed descriptions of each of these mandatory control requirements can be found in the CEC Non-Residential Compliance Manual.

 

Lighting Trade-offs

The Title 24 non-residential lighting standards restrict the overall installed lighting power in the building, regardless of the compliance approach. However, there is no general restriction regarding where or how general lighting power is used. This means that installed lighting may be greater in some areas of the building and lower in others, as long as the total does not exceed the allowed lighting power. Trade-offs cannot be made between conditioned and unconditioned space.

 

There is another type of lighting trade-off available under the Title 24 standards. This is the ability to make trade-offs under the performance approach between the lighting system and the envelope or mechanical systems. Trade-offs can only be made when permit applications are sought for those systems involved. For example, under the performance approach, a building with an envelope or mechanical system that is more efficient than the prescriptive efficiency requirements may be able to meet the standard design energy budget with a bit more lighting power than allowed under the prescriptive approach. When a lighting power allowance is calculated using the performance approach, the allowance is treated exactly the same as an allowance determined using one of the other compliance methods. No trade-offs are allowed between indoor lighting and outdoor lighting or with lighting that is in unconditioned spaces.

 

(Excerpted form the CEC Title 24 Non-Residential Compliance Manual)