The sustainable-design movement is driving demand for more sophisticated lighting and control systems as a means of maximizing energy savings and flexibility in commercial buildings. Increased sophistication, however, imposes greater risks of design and installation errors that can jeopardize energy savings and user acceptance.
These risks can be mitigated through building commissioning as it is defined by ASHRAE Guideline 0–2005, The Commissioning Process. The guideline recommends documentation that reveals how the design will satisfy the owner’s project requirements. This documentation is also required for LEED certification, where basic building commissioning is a prerequisite and points are offered for advanced commissioning. For lighting-control systems, a number of tools are available to help express design intent—control zoning, one-line wiring diagrams, specifications and cut sheets, panel schedules, device settings, and performance-testing criteria—but arguably, the most important tool is the written lighting-control narrative.
As a simple document developed by the party primarily responsible for lighting-control design in a project, the written lighting-control narrative should inform everything else. It describes the lighting controls, including a detailed sequence of operations—a description of responses by the control system to various inputs such as occupancy levels, time and schedule, or daylight levels—that will be installed in the project whether it is a new building or an existing structure. The narrative goes beyond what drawings can communicate. In the long run, the written narrative supports the implementation of controls that are intended to save energy, and it helps support user acceptance.
Unfortunately, a lighting-controls narrative is often omitted in many projects that do not have a commissioning process. It is skipped due to time pressures or the lack of awareness of its usefulness. But within the next two years, the inclusion of this document will become standard practice in building construction in most of the United States. In October 2011, the Department of Energy recognized ASHRAE Standard 90.1–2010 as the national reference standard for commercial building energy codes, requiring all states to enact a code at least as stringent as 90.1–2010 by Oct. 18, 2013. Standard 90.1–2010 requires that a lighting-controls narrative showing “how each lighting-control system is intended to operate, including recommended settings” be given to a building’s owner within 90 days of control system acceptance. The standard is written for new construction and major renovations.
Beyond the simple definition shown above, there is no standard about what constitutes a lighting-controls narrative or how its information should be presented. Obviously, the more detailed the information—which is then vetted to satisfy owner requirements—the more accurately the design will meet the owner’s needs. At a minimum, a written narrative should include a general description of the project requirements and control strategies employed to satisfy them, followed by a description of the control system, its intended functionality, and a sequence of operations for each space type or individual space. It might also include performance-testing procedures and criteria, as well as references to other documentation such as wiring diagrams, control zoning, and equipment specifications and cut sheets. The information should be expected to evolve as the project design moves from the conceptual phase to completed installation.
Formatting of the narrative is another matter that is open to debate. The document may be a simple written description for each space or space type in a consistent format. For larger projects with many space types and control systems, a matrix approach can help organize the information into an easily readable view for each space type or individual space (with room numbers pulled from the drawings). Along with the lighting-control matrix (see slide show), the sequence of operations would be accompanied by a written description for the given control-system type. Here’s a brief example for a space type “open office” in an office building:
On–Off control of the general lighting in each open office area will be controlled by a combination of manual wall switches and time-clock schedule functionality residing in a low-voltage, relay panel-based control system. Users entering the space at the start of business hours will turn the general lighting on by control zone, with each zone being within 2,500 square feet in area or per the local energy codes. At 6 p.m., the control system will blink several times, warning users that the lights will turn off in five minutes. At 6:05 p.m., the control system will turn the general lighting off. Users working after hours turn the lights back on by toggling the manual wall switches, which function as a 120-minute override for the time-clock automatic shut-off system. After 120 minutes, the system will blink the lights again, and sweep them off five minutes later, unless the override is again activated.
The lighting-controls narrative can reduce design risks, provide contractors and manufacturers clear direction for bidding and installation, enable the commissioning authority to test the system to expressed criteria, and increase the likelihood of the owner receiving a quality installation that will achieve its requirements and satisfy users.
More in-depth information on building commissioning can be found in the full text of ASHRAE Guideline 0–2005. More information specifically focused on commissioning as applied to lighting is available in the Illuminating Engineering Society’s Design Guide 29, The Commissioning Process Applied to Lighting and Control Systems.
ECO-STRUCTURE contributing editor Craig DiLouie is a lighting specialist and principal of Zing Communications. He is the former editor and publisher of Architectural Lighting magazine. This is the first of a three-part series focusing on lighting. The next installment will appear in July/August.