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Nonresidential Indoor Lighting

Measure Description

This CASE Report for nonresidential indoor lighting consists of two submeasures: multi-zone occupancy sensing in open plan offices and updating lighting power densities.

Multi-zone Occupancy Sensing in Large Offices

2019 Title 24, Part 6 currently mandates shut-off controls for large offices, allowing a single occupancy sensor controlling areas between 1,000 to 2,000 ft2, with multiple occupancy sensors jointly controlling an area as large as 5,000 ft2. However, occupants in large offices are away from their desks frequently for meetings or other tasks, leaving significant portions of the office area unoccupied. Occupants staying after hours may need to walk over to a manual control switch to enable an override control. Using separate occupancy controls can reduce lighting energy consumption in unoccupied parts of large workspaces where there is often partial vacancy.

However, occupant sensing control requirements for office spaces greater than 250 square feet (ft2) are not currently mandatory. Shut-off options include time-switch controls and an occupancy sensor without coverage area limits. The Power Adjustment Factors (PAFs) from the 2013 Title 24, Part 6 code cycle enable a pathway for utilizing occupancy controls with varying control zone sizes. Most occupancy sensors control the lights digitally through either a room controller or a networked lighting control system. The occupancy sensors are configurable in terms of their associations with the luminaires and/or control zones. By using software, and occasionally hardware, different sensors can be configured to monitor and work with different control zones and control zone sizes. As such, control zones can be easily programmed, added, and rearranged at the control panel or remotely through computer, and even mobile phone applications, rather than requiring rewiring and use of ladders to access systems.

Another popular control implementation is luminaire level lighting control (LLLC), where sensors are an integral part of the luminaires, so each luminaire has its own sensor. This luminaire and sensor configuration can increase the granularity of the control area as each on-board sensor controls an individual luminaire independently. With LLLCs, the luminaires may also be networked together to coordinate with each other and act as a single, larger zone if that would be the desired lighting design.

This proposal aligns with the 2018 International Energy Conservation Code (IECC) C405.2.1.3 Open Plan Office Control which mandates similar requirements. Industry stakeholders highlighted the challenge of needing to comply with multiple standards simultaneously, and shared that increased coordination across standards would benefit the industry.

The multi-zone occupancy sensing in large offices measure proposes two major changes:

  • A mandatory control requirement for nonresidential indoor lighting systems in “large” offices, defined as enclosed offices greater than 250 ft2. The term “open plan office” is undefined in Title 24, Part 6, and this proposal would remove all mentions of “open plan office.”
  • Since the general lighting in large offices would be required to have occupancy sensors and large offices can have ventilation rates set to zero during occupied standby mode, large office spaces would be required to have HVAC occupied standby controls and enable HVAC occupied standby mode.

The proposed code change would mandate a maximum 600 ft2 control zone size and specify that all control zones shall be switched separately, controls shall automatically turn off all lighting in control zones within 20 minutes of all occupants leaving the space, and that each control zone must reduce lighting by at least 80 percent power, or switch off, within 20 minutes of occupants leaving a control zone.

The proposed code change applies to general lighting, with an exception for under shelf or furniture-mounted supplemental task lighting. It impacts all new construction and certain additions and alterations.

In response to comments from stakeholders, this proposal includes clarifications to the occupancy sensing HVAC zone control requirements.

Technology to implement this code change is already readily available in the market. This measure would save energy through two main mechanisms: (1) reducing the full load hours of operation on the lighting system in large offices, and (2) enabling HVAC occupied standby mode in large office spaces, and therefore, reducing energy usage from HVAC systems. HVAC occupied standby resets thermostat setpoints and shuts off ventilation air to a zone when the entire space is unoccupied. The energy savings calculations, as found in Section 2.3, estimate 1.025 kWh/ft2/yr in per-unit savings.

Lighting Power Densities

Over the past 30 years, lighting efficacy has continued to improve. As a result, the allowed indoor lighting power density (LPD) values in Title 24, Part 6 have been updated every cycle. During the 2019 update of the LPDs, the basis of standards shifted from the legacy lighting technologies (such as fluorescent, metal halide, and infrared reflecting halogen light) to light emitting diode (LED) light sources. The Statewide CASE Team updated LPD values during the 2019 Title 24, Part 6 code cycle to represent an all LED (light emitting diode) baseline.

The savings associated with this proposal are relatively modest compared to the 2019 code cycle since the proposal is comparing LEDs available 3 years ago to LEDs available now. Though this proposal’s statewide lighting energy savings are only 5.6 percent of the baseline energy consumption, this small fraction is multiplied by a large value (the total lighting power installed in all new and retrofitted buildings) and results in approximately 100 GWh/yr savings for each year’s new construction. These savings are realized while increasing the flexibility of how additional lighting power allowances are calculated which should reduce compliance burden.

During this code cycle, the Statewide CASE Team refined this previous work by updating the calculation method and models to more accurately account for technology advancements and to better reflect lighting industry standards. LEDs are typically dimmable and the distribution of light is more controllable, allowing for higher optical efficiencies. Over the last three years, the Statewide CASE Team documented efficacy increases for luminaires with high color rendering index (CRI) LED sources, color tuning, and dim-to-warm controllability.

The LPD measure proposes to:

  • Update the allowable lighting power density (LPD) values (watts of lighting per square foot of room floor area) based on a re-analysis of LPDs with improved tools and changes to the products available in the market.
  • Update the definitions, mandatory, and prescriptive sections of Title 24, Part 6 to improve clarity and readability, offer design flexibility and simplify documenting compliance.

The Statewide CASE Team has updated models based on revisiting Illuminating Engineering Society (IES) Recommended Practice (RP) and IES Standards. The Inverse Lumen Method lighting power density model has been improved to provide a more accurate estimate of required lighting power. This allows the Statewide CASE Team to use proposed LPDs that more closely match the results of the model as there is less error in the calculations. Improvements include:

  • Detailed documentation of the target illuminance values used for the general, task, supplemental and wall wash systems, and references to the various IES RPs.
  • Direct use of the zonal lumens extracted from the IES-LM-63 formatted photometric files of luminaires to calculate the coefficients of utilization for the luminaires for any combination of room reflectance and rectangular room geometry.
  • Direct use of manufacturer lamp lumen depreciation values.
  • Implementation of the luminaire dirt depreciation model (i.e., cleanliness) from IES RP-36 specific to luminaire type and primary function area.

The proposed LPD updates do not prevent light levels that are compliant with the IES RPs from being achieved. In addition to general lighting LPDs, there are several additional power allowances that all contribute to providing sufficient lighting power to ensure proper light levels are achievable for task work, display, and ornamental lighting. There are also additional wattage allowances for several special scenarios, such as additional lighting wattage for providing extra light to areas occupied by the elderly or visually impaired. Compliance options have been simplified for the additional power allowances in the area category method using the combined “Display/Decorative” qualifying allowances. Of the 71 primary function areas for the Area Category Method LPDs, 10 increase, 30 decrease, and 31 of the combined general lighting and additional lighting allowances stay the same.

The LPDs for the Complete Building Method have been updated. The Tailored Method LPDs have updated to account for the increased efficacy of high CRI lighting sources. Many LPDs in both the Complete Building Method and Tailored Method decrease slightly; in most cases there is a 0.05 decrease.

This proposal also updates requirements in Section 130.0(c)2 for downlights with a line voltage socket. Specifically, downlights with a line voltage socket would be based on installed wattage on luminaire labeling alone and would no longer use the higher of the luminaire labeled wattage and 50 watt per socket (except if the lamps in the luminaire are JA8 rated). In the prescriptive section, code language for calculation of adjusted indoor lighting power and luminaire classification and power adjustment has been updated for clarification and to reflect updated LPD values. Likewise, the LPD values in the tables for the Complete Building Method, Area Category Method, and Tailored Method have all been updated. These updates affect new construction, additions, and alterations. Not every building type is affected by the updates, but many have minor to moderate updates.

Submeasures Moved to Future Code Cycles

The Statewide CASE Team is no longer pursuing the proposed changes listed below as it was determined that they did not meet the Energy Commission’s requirements for market readiness, technical feasibility, cost-effectiveness, or enforceability at the time they were considered.

Networked Lighting Controls

This submeasure would provide power adjustment factors or allow a tradeoff to mandatory or prescriptive requirements to encourage the deployment of networked lighting controls. The Statewide CASE Team is not pursuing this measure due to a lack of information needed to estimate incremental energy savings and calculate the power adjustment factors.

To support ongoing research and future code cycle consideration, additional information on nonresidential networked lighting controls can be submitted to the Statewide CASE Team through info@title24stakeholders.com. This measure may be pursued through CalGreen (Title 24, Part 11).

Materials that the Statewide CASE Team developed when investigating this code change for the 2022 code cycle will be moved to the Future Code Cycles section of this website. Follow this link to find materials on nonresidential networked lighting controls.

Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.

CASE Reports

Round Two Utility-Sponsored Stakeholder Meeting Materials

Round One Utility-Sponsored Stakeholder Meeting Materials

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Final CASE Report Now Available

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email info@title24stakeholders.com. Include the measure name in the subject line.

 

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The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

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