Building controls drive smart lighting, HVAC design
Driven by market demand to reduce operating costs, the combination of efficient lighting technology, versatile controls, and sophisticated modeling tools offers new opportunities to improve overall building performance.
- Know the codes and standards that define lighting design and HVAC design, plus their integration.
- Understand the new technologies driving the lighting market.
- Explain the various modeling tools to help calculate and design energy-efficient integrated systems.
The use of solid-state lighting (SSL) products—specifically light-emitting diodes (LEDs)—in commercial lighting design represents one of the fastest technology-adoption trends in recent history (see Figure 1). With luminous efficacy reducing overall energy costs, and projected life reducing maintenance costs, codes and standards, such as ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings, ASHRAE Standard 189.1: Standard for the Design of High-Performance Green Buildings, and California Title 24, now hold SSL products as the baseline efficiency for commercial lighting design in new construction and major renovation.
These electronic boards that provide light have introduced a host of new opportunities for advanced lighting control and integration with building systems. While previous designs consisted of luminaires separated from the lighting control systems that operated them, new technology is bringing those worlds closer together, making them one and the same.
In the same way that lighting specifications have changed, lighting control technology has changed as well. Distributed controllers and gateways now allow lighting and HVAC technologies to communicate without the cost, complexity, incompatibility, and physical limitations of previous designs, and allow the same sensor to actuate both systems. Furthermore, smarter devices allow smaller control zones, resulting in greater energy and cost savings.
Today’s building management systems (BMS), the necessary technology backbone for the simultaneous modulation of lighting and HVAC systems, have further developed to support deeper integration of building systems. Well-informed design, supported by the degree of verification made possible by today’s suite of modeling tools, can leverage these advances to realize the functional performance, occupant comfort, and operational efficiency represented by the best of lighting and HVAC technologies.
LEDs, fixtures, sensors, and control technologies
LEDs differ from fluorescent lamps in how they operate: Electrical energy is directly converted into light without the intermediate step of excitation in a gas discharge. As a result, they are able to turn on instantly and last longer, even with frequent switching. Their inherently dimmable operation makes them a “no questions asked” alternative to fluorescent. Where fluorescent dimming was previously a significant additional cost, there is no additional fixture cost associated with the standard dimming of LEDs. These factors, along with their continuing drop in cost, make them prime candidates for use with advanced lighting control systems.
Sensors are getting smarter. Until recently, photocells had to be specified separately from occupancy sensors, and occupancy-sensor technologies—such as passive infrared, ultrasonic, and microphonic—had to be determined and specified depending on the obstructions in the space and use of adjacent spaces. In addition, auto-on/auto-off or manual-on/auto-off and vacancy time-out/delay settings had to be programmed during installation via dipswitch or push button. Because those adjustments often require a facilities person on a ladder and some disruption to occupants, sensor settings were rarely changed or fine-tuned once the space was in use. Smart sensors now incorporate a wide variety of sensing technologies, and in most network control systems have the capability to be addressed remotely via desktop or phone apps.
With the adoption of LEDs, many new lighting controls products have emerged in the market that use wired, wireless, or hybrid devices. Most systems work with standard, nonproprietary 0 to 10 V dimming drivers, so no customization of luminaires is required. While some companies offer control within the driver of the luminaire, others offer control devices that attach to each luminaire.
In addition, many luminaires are now available with built-in occupancy sensors and photocells. To address the need to provide emergency lighting, products meeting UL 924: Standard for Emergency Lighting and Power Equipment can be added to individual luminaires located in the path of egress or provided at the controller for zoned control. The relays force the luminaire to be turned on at full output during loss of power, but it is controlled based on preferred settings during normal use. This range of devices, all integrated at the luminaire level, allows the luminaires to operate independently or in easily reconfigured zones with more intricate control commands, resulting in greater energy savings.
When deciding on the sensor and controls approach, the design team must fully understand not only the energy goals of the building, but also the level of technology awareness of the people within it. By creating a list of detailed questions with which to engage the owner, building users, and building operators, the energy goals for the building can be better understood. If this information is obtained at the beginning of the design process, the building energy model can be fine-tuned to better reflect the proposed energy usage of the building.
For instance, what are the building’s hours of operation? Should all operation be fully automated, or will there be occupant overrides available? How long should lights stay on after no occupancy is detected? What minimum light levels are required during daylight-harvesting hours? What is each size of a control zone? Will areas be reconfigured after initial occupancy? Are shading devices also to be controlled?
With the adoption of networked control systems, facility-driven layered control strategies can be used. Advanced control strategies include lumen maintenance and task tuning. Lumen maintenance reduces LED output at the beginning of rated life and increases output over time to maintain a specified illuminance level as the source output depreciates. This strategy can save 30% in initial installation, averaging 15% savings over the course of the luminaire’s rated life. Task tuning (also referred to as high-end trim or institutional tuning) reduces output and consequent energy use by tailoring the illuminance levels to the specific needs of the space.
However, while energy savings is a primary motive, there needs to be a balance between saving as much energy as possible and not creating annoyances that will affect occupant comfort and productivity—or create the desire to override the systems in place. For instance, the application of small lighting control zones with more intricate control commands in applications, such as open-plan offices, can invite nuisance issues if range and cutoff angles of various sensors are ignored. Daylight harvesting has long been a way to save energy, but systems must be calibrated so that footcandle levels and time delays for shades and automated dimming are appropriate for the use of the space. A short time delay may save energy, but possibly at that expense of adversely affecting building occupants.
Whether a wired, wireless, or hybrid system is selected, the BMS architecture is now able to directly tie zone sensors, switches, relays, and actuators straight to multipurpose digital controllers, completely eliminating the need for individual system gateways for individual HVAC, lighting, and other building systems. Digital control systems are now able to interface directly with the BMS for simple on, off, airflow-modulation, and light-dimming commands. The rapid change and development of these separate, but codependent systems, has not only been fueled by the need to make our buildings increasingly more efficient to meet new code requirements, but by building owners wanting to streamline building operations.
Previously, lighting control systems were often kept simple and separate to operate on their own, because most building operators only knew how to operate the BMS set before them. Now that lighting control can be simply integrated into the BMS and controlled via a variety of different apps or from remote locations, the advantages to the overall building operation are significant—and owners are taking notice (see Figure 2). As always, their successful implementation is dependent on a thoroughly considered, well-documented design.