Lighting control requirements: What's current and what to expect
Controls for natural side-lighting
ASHRAE 90.1 requires and IECC has the option of automatic daylighting controls for primary side lighted areas. (IECC has the option for manual controls in lieu of automatic.) When the combined primary side-lighted area in an enclosed space is equal or greater than 250 sq ft, the lamps for general lighting in the primary side-lighted (daylit) area must be separately controlled by at least one multilevel photocontrol and be remotely controlled and readily accessible. The artificial lighting must be continuously dimmable or step dimmed. Both require a minimum of one step no greater than 35%, and ASHRAE requires a second step at between 50% and 70%.
There are many fluorescent ballast and LED drivers that can provide either required continuous diming or stepped dimming. For the daylighting controls, the light fixtures can have integral light sensors or one light sensor for a zone (group) of light fixtures.
ASHRAE exceptions to 188.8.131.52 are:
- Primary (daylighted) side-lighted areas where the tops of the existing adjacent structures are twice as high above the windows as their distance away from the windows
- Primary side-lighted areas where the side-lighting effective aperture is less than 10% percent
- Retail areas.
Specific application controls
The following areas require special controls above and beyond other requirements in ASHRAE 90.1 and IECC:
1. These types are controlled by dedicated, independent control
a. Display and accent lighting
b. Display case lighting
c. Non-visual applications (i.e., plant growth and food warming)
d. Lighting equipment for sale or demonstration in lighting education
2. Hotel and motel sleeping units and guest suites
a. Master control device at main room entry
i. Controls all permanently installed luminaries and switched receptacles
3. Supplemental task lighting, including permanently installed
4. Under-shelf or under-cabinet lighting
a. Have control device integral to luminaries or
b. Be controlled by a readily accessible, wall-mounted control device
5. Stairwell lighting (ASHRAE 90.1 specific)
a. Have one or more control devices to automatically reduce lighting power in any one controlled zone by at least 50% within 30 minutes of all occupants leaving that controlled zone.
Parking garage lighting controls
ASHRAE 90.1 has specific requirements when it comes to parking garage lighting. It is important to note the following requirements:
1. Lighting is to be controlled by one or more devices to reduce the lighting power to each fixture by 30% when no activity is detected within a zone for no more than 30 minutes. This can be accomplished with occupancy sensors. Due to deep structures in garages, the line of sight for occupancy sensors is challenging. A practical way to accomplish this is to provide integral occupancy sensors in the parking garage fixture and link them together in the lighting zone. This will provide good coverage.
2. Daylight transition zone lighting is to be controlled separately by a device that would automatically turn on the lighting during daylight hours and off at sunset. This helps the eye accommodate from high levels of daylight to lower artificial daylighting levels.
3. For light fixtures within 20 ft of any perimeter wall structure that has a net opening to wall ratio of at least 40% and no exterior obstructions within 20 ft, the power shall be automatically reduced in response to the natural daylighting.
Daylighting transition zones and ramps without parking are exempt from the first two items above. Applications using high-intensity discharge (HID) of 150 W or less or induction lamps are exempt from the first item above.
Exterior lighting controls
IECC requires exterior lighting to be controlled by a photocell and/or astronomical time switch. Lighting control systems and BAS are typically used for astronomical time switches, and photocells can be an input to the system. Dusk to dawn operation can be accomplished with a photocell controlling all of the fixtures, or lighting fixtures can have integral photocells or a combination of the two approaches. Photocell and astronomical time switches can be used for fixtures that are not dusk to dawn and that can be turned off 2 hours after the last event and then turned on 2 hours before the first event. This reduces total energy consumption and is recommended by Illuminating Engineering Society (IES) as a control strategy for security (dark campus).
ASHRAE is similar to IECC, except the code requires building façade and landscape lighting to shut off between business closing or midnight, and business opening or 6 a.m. In addition, all other exterior lighting, such as area parking lot lighting, wall packs, and canopy fixtures shall reduce 30% for energy savings for at least one of the following conditions:
- From midnight or within 1 hour of the end of business operations, whichever is later, until 6 a.m. or business opening, whichever is earlier
- During any period when no activity has been detected for a time of no longer than 15 minutes. This can be accomplished with an integral occupancy sensor and stepped/continuous dimming ballast/driver.
Exception to ASHRAE 90.1 Section 184.108.40.206: Lighting for covered vehicle entrances or exits from buildings or parking structures where required for safety, security, or eye adaptation.
Functional testing (commissioning) is required for both ASHRAE 90.1 and IECC to verify that all control hardware and software are performing as designed. It assures the controls are located, adjusted, aimed, calibrated, and programmed per construction documents and manufacturer’s installation instructions and recommendations. The construction documents must list the person and/or company that will perform the functional testing. The authority having jurisdiction (AHJ) can reserve the right to have an approved party independent of the design or construction perform the functional test. When occupant sensors, time switches, programmable schedule controls, and photosensor daylighting controls are installed, the following procedures shall be performed:
- Placement, sensitivity, and time-out adjustments for occupant sensors yield acceptable performance.
- Time switches and programmable schedule controls are programmed to turn the lights off.
- Placement and sensitivity adjustments for photosensor controls reduce electric light based on the amount of usable daylight in the space as specified.
As-built drawings and operation and maintenance manuals must be turned over to the building owner within 90 days of the date of receipt of the certificate of occupancy. This requirement is for both ASHRAE 90.1 and IECC. Drawings are to include the location and performance data on each piece of equipment.
The U.S. Dept. of Energy’s (DOE) COMcheck is required in most states and local jurisdictions to show compliance not only for lighting power densities, but also for lighting controls. COMcheck verifies state code compliance for interior lighting, exterior lighting, HVAC, and building envelope. Engineers are required to verify if automatic controls meet or exceed code requirements as discussed above. COMcheck was developed by the DOE to make compliance easier for engineers, architects, and contractors to determine whether applicable projects meet ASHRAE 90.1, IECC, and state-specific codes. Building officials, plan checkers, and inspectors can review a completed COMcheck, allowing them to quickly determine if a building project meets code.
Energy codes are becoming more complex and stringent to meet. Understanding the requirements and what technology is available is imperative for the lighting engineer. Automatic lighting controls are required to provide additional energy savings over the prescribed power densities.
While this is a comprehensive overview of lighting control requirements, it is not an all-encompassing look at lighting control requirements for commercial buildings. State and local codes and amendments along with local land development codes can be stricter than the requirements discussed in this article. Controls are necessary and, with careful selection and thoughtfulness with the owner in mind, can be a successfully engineered system.
Many owners and building managers express frustration when lighting controls fail, become uncalibrated, or experience other issues. Changes in season affecting the daylighting zone controls or software updates are two of the many issues building owners deal with daily. When designing the lighting control system for a building, consider involving the owner during design to understand complexity and trade-offs that will impact operation.
Brian K. Baumgartle is partner and electrical engineer at CMTA Consulting Engineers. He has presented at Lightfair International and the Green Schools National Conference on the subject of integrating daylight harvesting into lighting controls. He designed the lighting and lighting control systems for Richardsville Elementary, the first net-zero energy public school in the United States, and many other projects effectively implementing lighting controls for energy efficiency.