July 01, 2006
Appeared in Building Operating Management/FacilitiesNet
The bad news is that high energy prices are here to stay. The good news: The rapid growth and evolution of lighting technology has allowed lighting designers and facility executives to improve energy efficiency without sacrificing occupant comfort.
In a typical office building, lighting and HVAC account for the majority of the utility budget. So it makes good sense to look at existing lighting design and ascertain if the long-term utility savings could offset the up-front investment required for a redesign or retrofit.
When it comes to new construction and major remodels, tighter state energy codes already will effectively mandate the implementation of fairly sophisticated lighting design — and subsequently the use of some of the latest technology — to achieve compliance and maintain the lighting levels that will enable occupants to perform their tasks. The days where every nook and cranny of an existing space could be lit at the same high levels are definitely over.
Meeting Code in the Age of Energy Efficiency
When it comes to code-compliant lighting design, technology has clearly upped the ante. To create a well-lit office environment that meets code, facility executives will have to spend more on technology and design. Organizations like ASHRAE or the Illuminating Engineering Society of North America review their guidelines every three years. Aware of technological advances that reduce wattage without affecting lighting levels, these organizations have tightened their requirements to encourage the use of the most energy-efficient equipment available.
In 2001, for example, the lighting requirement table of ASHRAE/IESNA standard 90.1 listed 1.3 watts per square foot for open plan offices. In 2004, this amount was reduced to 1.1 watts per square foot.
In practice, lighting designers will determine the maximum energy use permitted for the entire building and design individual spaces to meet occupant needs for each space. One way to stretch the overall energy allotment is to introduce lighting control systems such as occupancy sensors. In fact, occupancy sensors or time scheduling have just been made mandatory for new office construction larger than 5,000 square feet by the Energy Policy Act of 2005, which requires compliance with ASHRAE/IESNA 90.1.
Occupancy sensors can be installed in place of light switches at the door or on the ceiling. In larger spaces, ceiling-mounted sensors are preferable. Where local codes require dual switching, sensors are now available offering dual switching and sensor capabilities within a single gang device. These dual-technology sensors tend to be more reliable in sensing smaller ranges of motion. In all cases, it is important to carefully follow manufacturers’ recommendations for spacing and coverage. If lighting sensors interfere with day-to-day activities, users are likely to disable them.
For the most part, however, achieving the right balance between user-friendly conditions and code-driven energy guidelines will mean investing in more sophisticated hardware in the hope that lower maintenance and energy costs and possibly a reduction of the total number of luminaires throughout the space will make up for the increased material cost.
The introduction of the T-5 fluorescent lamp has allowed for a significant reduction in the physical luminaire size. The high output version of this lamp provides almost twice the lumen output of a similar T-8 lamp and the 5/8-inch diameter permits smaller reflector design and improved optical efficiencies. The improved efficiencies can allow luminaires to be spaced farther apart for the same lighting levels and thus reduce watts per square foot.
The T-8 product line has also seen a number of improvements. New high-lumen output systems have increased lumen output from 2,850 to 3,100 lumens for the same energy input. At the same time, lamp life has been extended from 20,000 to 30,000 hours, allowing facility executives to recoup some of their investment through lower maintenance and replacement costs.
The combination of high-output T-8 lamps with reduced ballast-factor ballasts that operate the lamps under their lumen rating can achieve the same lighting levels for less wattage. The combination provides more lumens per watt at a lower output and the net effect is the same lighting levels at a lower energy than standard lamps and ballasts.
Consider the retrofit of the library of a major West Coast university. Because the original position of the lights could not be changed, the challenge was to choose a suitable lamp and ballast combination that would reduce energy use without significantly cutting lighting levels. Because the existing system used T-12 lamps, the library achieved a 30 percent reduction in overall energy use with low wattage T-8 lamps and ballasts. Mock-ups were done to involve the users and maintenance staff and the project results were successful.
Energy Efficiency and EPACT
In addition to the payback of a lower utility bill, facility executives may be able to benefit from the incentives in EPAct 2005 to increase energy efficiency beyond current code-mandated levels. New construction after Dec. 31, 2005, is eligible for a tax deduction of $1.80 per square foot, if annual energy and power costs of interior lighting systems, heating, cooling, ventilation, and hot water systems are 50 percent or more below ASHRAE 90.1-2001. Interior lighting systems are eligible for up to $0.60 per square foot depending on the reduction of consumption below the standard. Currently, the deductions only apply to buildings or systems placed in service in 2006 or 2007.
LEDs and Daylighting
Beyond installing more sophisticated luminaires, fixtures and fixture optics, the use of LEDs may help achieve these additional energy savings. Historically limited to use in electronic equipment and exit signs, LEDs are now available for use in wall sconces, step lights, exit signs, wall washers and strip lights. LEDs provide many advantages over more conventional light sources, including 100,000-hour life, low energy consumption, low heat generation and miniature size. Currently, the common commercially available LED lamp is 1 watt. Five-watt LED lamps will be introduced which will significantly expand the application opportunities.
Undoubtedly the most effective way of saving energy is to maximize the use of daylighting. According to the Environmental Protection Agency, automatic daylighting controls can achieve energy savings of up to 40 percent. Daylighting control employs ceiling-mounted sensors that actively measure available daylight and are calibrated to maintain light levels within a predetermined range.
Selecting a daylighting approach
When designing for maximum daylight use, correct placement of the sensing photocell is of utmost importance. In open loop dimming systems, the photocell will be placed to look out through the glass, sensing how much sunlight is available and adjusting dimming levels inside accordingly. However, such a system will not account for any lighting level differences that exist within the space. In a closed loop system, the photocell will be placed within the room.
While this approach allows for greater flexibility, the challenge is orienting the sensor in such a way that it measures the daylight reflected on the task surface in correct proportion to the incoming daylight. The ideal placement of the photosensor will allow for a high level of daylight illumination while shielding it from any exterior glare sources.
A dimming, daylighting control system was recently installed in a college library. Skylights were angled to face south and baffles added to block any direct exposure to the space. Dimmable fluorescent coves were installed around the perimeter of each skylight with a photocell sensor within. The fluorescent luminaires were used to balance daylighting contribution and maintain the desired lighting levels on the floor below. Although actual energy savings have not been measured, the users of the library are pleased with the results.
Advances in lighting technology have allowed lighting designers to make significant contributions to help facility executives combat increasing utility costs. In addition to maximizing energy efficiency, effective and innovative lighting designs can also improve the functionality of a space and improve occupant comfort. While tighter code requirements will require the use of more sophisticated equipment, it is up to facility executives to analyze existing buildings to identify economically viable retrofits.
Paul Ericson is vice president of Syska Hennessy Group. He has more than 32 years of experience as a lighting designer for new and renovation projects, including commercial, government and institutional projects. He also regularly teaches lighting design and electrical engineering at the University of California, San Diego He is located in the company’s San Diego, Calif., office.