This piece was originally published in the August 2018 issue of electroindustry.
Peter Lafreniere, Cable Product Manager for AFC Cable Systems, Inc., a part of Atkore International
Mr. Lafreniere leads product strategy for the Cable Solutions business unit’s cable product line and is responsible for its strategic innovation initiative.
According to the United States Department of Energy (DOE) Building Energy Codes Program: National Benefits Assessment, commercial and residential buildings account for approximately 41 percent of all energy consumption and 72 percent of electricity usage in the United States.
Because of this, the DOE has a vested interest in developing national codes to support the improvement of energy efficiency in buildings. When properly followed, these codes reduce energy use and greenhouse gas emissions over the life of buildings.
The DOE implemented the Energy Policy Act of 1992 (EPACT92) to outline various measures designed to lessen the nation’s dependence on imported energy, provide incentives for clean and renewable energy, and promote energy conservation in buildings. EPACT92 gave rise to the Building Energy Codes Program, providing a comprehensive collection of resources, model adoption policies, compliance software and tools, and training modules based on best practices related to energy codes.
Now, nearly every state in the U.S. requires some form of energy efficiency in commercial spaces. Builders must comply with energy codes as stringently as they comply with codes for health and safety. The benchmark for commercial building energy codes in the U.S. is ANSI/ASHRAE/IES Standard 90.1-2013, which sets the minimum requirements for energy-efficient design and construction of new buildings as well as new systems in existing buildings.
Lighting energy consumption accounts for a disproportionate amount of a commercial building’s energy use. Whether through behavioral practices (e.g., lights left on when there are no occupants in the room), lighting design, or lighting controls that are set beyond a comfort level, there are various reasons lighting is the culprit of many energy-efficiency issues.
To account for this, Standard 90.1 requires some method of automatic lighting shutoff based on power allowance calculations. One of the mandatory lighting control requirements states that automatic lighting controls must be able to dim the fixtures closest to windows in the primary zone depending on how much daylight is hitting task surfaces. Controls must also respond separately for the secondary zone, thereby necessitating multiple zone controls.
Zones are established based on a combination of factors. The challenge is to minimize the number of control zones (as each control zone adds to cost) while ensuring maximum response of the control system to daylight availability to save the most amount of energy while providing appropriate lighting.
Daylight Harvesting Critical
Daylight harvesting is an energy-efficient lighting design that reduces energy consumption by adjusting the amount of artificial lighting used to illuminate a space based on the amount of daylight coming in. It also meets Standard 90.1 requirements when implemented properly. Lighting control systems are used to dim or adjust electric lighting in response to changing daylight availability, so when daylight penetrates into spaces, the amount of artificial lighting is reduced automatically.
Daylight harvesting systems automate this process, removing the human element of control by using a light sensor equipped with a light-sensitive photocell to measure light levels. This information is sent to a controller that is connected to the lighting control system that will dim or switch lights in response to the measured level.
Depending on a facility’s need and application, daylight harvesting controls may be implemented through open-loop or closed-loop systems. Both can impact businesses’ people, productivity, and energy savings.
Open-loop systems measure only the natural light coming in and do not measure the interior electric lighting. The light sensor is typically mounted outside of the building or near a window facing away from controlled light fixtures. In an open-loop system, lighting is adjusted based solely on natural light. It is often preferred for applications that are not dependent on accuracy or in outdoor environments such as a hallway or atrium, parking lot, or garage.
Closed-loop systems, which are generally considered more accurate, measure the combined contribution from both natural and electric lighting. The light sensor measures real-time light levels and control is typically limited to a single zone per sensor. Closed-loop is common in applications where a specific target light level is configured and will be closely maintained. It is also used for precise task-based lighting levels and where people remain in the space, like in small offices, classrooms, museums, and studios.
Daylight harvesting reduces energy consumption and saves money on lighting costs by using natural resources in place of electric lights. The combination of natural and artificial light also offers the best of both worlds—the productivity boost of natural light combined with the predictability of an artificial lighting system.
Moving Toward Sustainability
The estimated cumulative benefits from the Building Energy Codes Program through 2040 are significant. The cumulative energy savings attributed to the program will total nearly 46 quads of full–fuel cycle energy in 2040, or 44 quads of primary energy, equivalent to almost an entire year’s worth of primary energy consumption from the U.S. residential and commercial sectors at current consumption rates. Cumulative carbon savings by 2040 are estimated at 3,478 million tons.
Lighting manufacturers are moving toward sustainability through the proliferation of efficient light-emitting diode (LED)–based products. This adaptation is also driving the use of dimmable fixtures. LEDs may be finely adjusted, operating in a continuously dimmable range from 10 to 100 percent.
Electrical manufacturers are also developing products that provide an economical method to wire controlled lighting, such as a cable that contains power and control conductors under one armor. Another technology allows control for up to three dimming zones, combining electric lighting and control circuits within a single interlocked armor, which can replace up to six individual cable runs, increasing productivity and reducing costs, and providing the building owner with a secure lighting system.
As technology advances and buildings become smarter and more connected, building energy codes have responded by becoming stricter. As a result, the ASHRAE Board of Directors voted to place Standard 90.1 on continuous maintenance. As new limits appear in ASHRAE 90.1 and the International Energy Conservation Code®, manufacturers are implementing new controls to meet the limits.
Future Is Bright
Conserving lighting use and adopting more efficient technologies can yield substantial energy savings. Some of these technologies and practices have no upfront cost while others pay for themselves over time in the form of reduced building costs.
Design principles like daylight harvesting are becoming common practice, not only to provide better working environments and higher levels of worker satisfaction and productivity but also to increase energy efficiency. Because manufacturers are taking note and continuously adapting to more progressive and enhanced technologies, the future of responsive lighting systems is bright.
“National Benefits Assessment, 1992-2040,” Building Energy Codes Program, March 2014, https://www.energycodes.gov/building-energy-codes-program-national-benefits-assessment-1992-2040-0
DOE Energy Efficiency & Renewable Energy, “Codes Fact Sheet,” April 2015, https://www.energy.gov/sites/prod/files/2015/07/f24/Codes%20Fact%20Sheet%207-10-15.pdf