Daylighting controls, such as the ones used in the gold-rated capitol east end complex block 225 project, complement fundamental sustainability practices like architectural daylighting design.

With the surging popularity of the Leadership in Energy and Environmental Design (LEED) rating system and sustainable building practices, the importance of lighting controls is more significant than ever. Since lighting accounts for nearly half the energy usage in commercial buildings, controlling and reducing unnecessary lighting makes an invaluable contribution toward achieving LEED certification.

In the first place, the use of lighting controls enables compliance with energy code provisions, a prerequisite for seeking LEED certification. Furthermore, exceeding these provisions enables credits or points that can increase the LEED certification level. In addition, control technologies, such as daylighting, complement fundamental sustainability practices such as architectural daylighting design. Finally, the use of lighting controls can interface with other building systems, such as HVAC, to optimize building energy performance. It all adds up to a unique opportunity to enhance sustainability practices through the use of lighting controls.

In the context of lighting and lighting control systems, green design means ensuring that the right amount of light exists when it's needed and where it's needed. Doing this in the context of a LEED project means identifying and seizing opportunities for implementing the appropriate control strategy in terms of the current LEED program structure.

satisfying basic leed requirements in lighting control

Daylighting controls reduce unnecessary lighting, making an invaluable contribution toward achieving LEED points.

Developed by the U.S. Green Buildings Council (USBGC), the LEED-NC (specific to new construction) rating system enables commercial and institutional buildings to obtain independent certification as a sustainable project. Currently, LEED defines four levels of certification, including Certified, Silver, Gold and Platinum. A 69-point scale determines the certification level a specific project may be awarded.

To qualify for certification at all, a project must satisfy specified standard prerequisites and accrue at least 26 points. Then, to achieve higher levels of certification, the project must earn additional points through implementing energy saving measures within any combination of LEED's five environmental categories (Energy & Atmosphere, Indoor Environmental Quality, Sustainable Sites, Water Efficiency, Materials & Resources) and one design category (Innovation & Design Process).

One of the basic prerequisites relevant to lighting and controls demanded by the LEED criteria is compliance with an energy efficiency threshold as defined by ASHRAE/IESNA 90.1-1999, or local energy codes (whichever is more stringent). Another basic prerequisite is the fundamental building systems commissioning prerequisite. To satisfy the former, buildings larger than 5,000 square feet must employ some method of automatic lighting shut-off.

In addition, individual spaces must utilize independent controls. For automatic shut-off, lighting controls such as occupancy sensors, time scheduling devices such as time clocks, or signals from building automation systems can be used.

Additional requirements include time limitations on manual overrides and occupancy sensors as well as the physical location of space controls. (For the detailed requirements and exceptions of 90.1-1999, refer to IES LEM-99, or Standard 90.1.) To satisfy the building-commissioning requirement, projects must utilize an independent commissioning agent, develop and use a commissioning plan throughout the project, and produce a commissioning report upon project completion.

lighting control strategies for earning additional leed points

Once the prerequisites have been satisfied, implementing lighting controls can boost LEED certification levels by garnering points in specific categories. Two specific categories of the LEED program structure offer the greatest opportunities: the Energy & Atmosphere (EA) category; and the Indoor Environmental Quality (EQ) category. Additional points can be earned in the Innovation & Design category as well.

To earn points in the EA category, a project must demonstrate efficient technologies that improve building energy performance. The designer must document and establish the increment of energy savings above the 90.1-1999 baseline model that have been realized. Each 10 percent increment in energy savings earns two additional LEED points. Lighting control strategies that will help earn more points in this category include using occupancy sensors for control functions beyond the automatic-off prerequisite such as controlling lighting during occupied times, bi-level switching, and using control devices to signal other mechanical or building automation systems to operate at lower levels.

Another strategy used effectively by some designers involves the max level set feature available in various control devices. This feature enables designers to set the output of lighting fixtures at a level below full output; for instance, at 85 percent or 90 percent of full output. This reduces the watts/square foot lighting usage and contributes to optimizing a building's energy performance, which in turn, will increase the points earned.

While a variety of lighting control strategies can be used to earn points, in many cases, the use of daylighting controls offers a unique opportunity to maximize the number of LEED points earned. This is due to the fact that architectural daylighting design is at the heart of sustainable building design. Furthermore, the LEED program structure strongly encourages using daylight as a primary light source by providing opportunities to earn points for the use of daylight and views. Commonly used architectural daylighting design features, such as skylights, clerestories and light shelves, offer enhanced opportunities for using controls that automatically dim or turn off electric lighting in those areas when daylight levels are adequate.

In fact, implementing daylighting control strategies alone can increase energy savings by 10 to 30 percent. The experience in various LEED-certified projects illustrates the value of daylighting control. (See related projects sidebar).

In the EQ category, a project can earn LEED points by providing a high level of occupant control in perimeter and interior spaces. For perimeter spaces, designers can achieve this result by implementing low-voltage or standard switching strategies, or by implementing automatic strategies using daylighting controls or occupancy sensors. At a minimum, this involves designing one lighting control zone per 200 square feet for all occupied areas within 15 feet of the perimeter wall. For interior spaces, the minimum requirements include providing individual control of the lighting for each occupant for half of the regularly occupied non-perimeter areas. This requirement is met by implementing simple manual switching or dimming strategies. If occupancy sensing is used to comply with 90.1-1999, a manual switch or dimmer can be used for providing the occupant the ability to override lights off.

The Innovation & Design Process category also offers some opportunities for earning additional points by adding controls. This category serves as an impetus for innovative sustainable practices that are not specifically addressed in the LEED framework. For instance, controlling desktop loads, such as task lighting via occupancy-based plug load controls, has been recognized by LEED as a creditable innovation.

Other designers have earned points for innovation by selecting cutting-edge controls. For instance, a project that implemented newly developed DALI-based controls, which utilize a lighting-specific, open communication protocol known as Digital Addressable Lighting Interface to provide ballast-level control, was awarded a point in this category for its innovative use.

Unquestionably, as LEED standards continue to evolve and mature [the USGBC is rolling out pilot versions of standards for existing building (LEED-EB), commercial interior (LEED-CI), and core and shell (LEED-CS) projects], green opportunities through lighting controls are sure to be plentiful.

Daylighting boosts LEED ratings

In Sacramento, Calif., Annapolis, Md., and Clackamas, Ore., highly rated LEED projects employed daylighting controls to achieve these prestigious certifications.

A state project, the capitol east end complex block 225 in Sacramento not only satisfied the rigorous requirements of that state's energy code, title 24, but exceeded it by 30 percent, earning a gold LEED (version 2) rating. Contributing to this rating was a battery of stand-alone photocell controllers positioned around building perimeters where daylight was more abundant. In those spaces, configured primarily as open office areas, the controls operate in conjunction with dimming ballasts to dim artificial lighting during daytime hours.

In Maryland, the Chesapeake Bay foundation project utilized an architectural passive solar design for open office areas in its headquarters. Then, by installing dimming photocells to control lighting in these areas, the electric lighting is automatically reduced when adequate daylight is present. Completed in 2000, the building uses 50 percent less energy than a comparable office building. As a result, CBF earned the first-ever platinum rating awarded by LEED (version 1).

The experience in Clackamas, involved the widespread use of daylighting controls to maximize the architectural daylighting design of a large high school campus. The complex controls system includes hundreds of photocells and control software to achieve the right mix of daylight and artificial lighting. A silver LEED (version 2) rating was awarded in December 2003. (for more information on Clackamas high school, see ED+C's March/April 2003 issue, "lighting controls pose challenges," by Jerry Yudelson.)

In practice, the use of daylighting controls seems to enhance the likelihood a project will earn a higher-level LEED rating. Because daylighting control can boost energy savings, the achievable potential points in the ea category increase as well with the implementation of these controls. Many design professionals feel that obtaining the maximum number of points available in the ea category is virtually essential for achieving a higher level LEED rating and the prestige that accompanies it.