LED Lighting The Best Solution

Approaches for lighting designers
This is a synopsis of lighting design methods recommended by key organizations, sources and leading authorities. Note: For full information sources and links, go to Boca web page: California Title 24 and ASHREA

Performance approach
Calculate the energy budget according to Section 141, then ensure that the building uses no more time-dependent valuation energy than the calculated budget. Time-dependent valuation of energy is a significant change for the Code, replacing the term “source energy” throughout this section. Traditional valuation of energy as a basis for energy standards centers on a flat energy value. With a flat energy value, a kW saved is valued the same for every hour of the day. Time-dependent valuation of energy takes into account the life-cycle value of energy as it varies by time of day, day of week, time of year, climate zone and other factors. This results in an hour-by-hour factor that is applied to energy savings to account for a more realistic value. For example, this method values on-peak energy savings higher than off-peak energy savings. The use of time-dependent valuation as a basis of efficiency standards will encourage building design and equipment that use less on-peak energy.

Prescriptive approach
The prescriptive approach is largely the same as a process. Follow all applicable requirements in Sections 142-146. Prescriptive requirements for indoor lighting are covered in Section 146. Additionally, outdoor lighting is covered in Section 147, and signage is covered in a new Section 148, which are entirely new Code sections. Lighting system designers can calculate allowed indoor lighting power density using one of three methods, listed below in order of flexibility, from least to most:

The Complete Building Method, which can only be used for projects/permits involving entire buildings with one type of use occupancy or mixed occupancy buildings where one type of occupancy makes up 90% of the entire building. A single lighting power value governs the entire building. Hotels/Motels cannot use this method. Retail buildings can under specified conditions.

The Area Category Method, in which the total allowed lighting power for the building is the sum of all allowed lighting powers for all areas in the building. Lighting power values are assigned to each of the building’s major function areas.

The Tailored Method, in which allowed lighting power is calculated according to primary function type. Lighting power values are determined room-by-room and task by task for areas. The Tailored Method part of the Code has been entirely rewritten. The Tailored Method generally can be applied to up to 30% of the building that is otherwise using the Area Category Method (with no trade-offs between them), and all of the building area of retail sales and museum buildings. A number of restrictions and exceptions apply; consult the Code for more information. Notably, there is no longer an exemption for unconditioned spaces. Prior to 2005, Title 24 did not regulate lighting of unconditioned buildings. The new standards have requirements for efficient electric lighting and controls that apply to unconditioned buildings such as warehouses and parking garages. Conditioned and unconditioned spaces must be calculated separately, with no trade-offs between them.

Synopsis of requirements for lighting systems and equipment in commercial buildings
See California Title 24 compliance manual for specific details, exceptions, etc.

Indoor lighting – automatic shut-off
Indoor lighting systems shall be equipped with a separate automatic control to shut off the lighting for every floor. This automatic control may be an occupant sensor, automatic time switch, or other device capable of automatically shutting of the lighting. It shall have a readily accessible manual override switch located where the person using the override can see the lights. Various exceptions for areas requiring continuous 24 hour/365 day lighting. Also, up to .5 Watts/sq. ft. of lighting for any area that must be lit for security for emergency egress.

Exterior Lighting
Besides various exceptions, permanently installed lighting shall be controlled by a photocontrol or time switch that automatically turns off the outdoor lighting when daylight is available. For building facades, parking lots, garages, canopies, and all outdoor sales areas, where 2 or more luminaires are used, there shall be an automatic time switch. It should reduce the lighting power by at least 50% but not exceeding 80% or provide continuous dimming through a range that includes 50% through 80% reduction.

Daylighting
Besides various exceptions, daylit areas in enclosed spaces greater than 250 sq. ft. must have a light control that controls at least 50% of the power in the daylit areas separately from other lighting in the space and controls luminaires in vertically daylit areas separately from horizontally daylit areas. Daylit areas in enclosed spaces under skylights larger than 2,500 sq. ft. must use a CEC approved multi-level daylighting control or a CEC approved time switch with override capability.

Further requirements
Display lighting must be separately switched on circuits that are 20 amps or less. Building lighting controls shall be certified as meeting the Acceptable Requirements for Code Compliance. A Certificate of Acceptance shall be submitted to the building department that certifies that the lighting systems and controls comply with Title 24 requirements.