Light-saving solutions help an army hangar surpass its goal of a LEED Silver certification
By Katie Nale
It’s not easy being green—especially when you’re the first of your kind. Case in point: Fort Carson. Named a Net-Zero Pilot Installation for Energy, Water and Waste, the U.S. Army installation in Colorado is gearing up to reach its energy goals by 2020. When the 4th Infantry Division of the Army was relocated to Fort Carson in 2009, the need emerged for several new facilities on the property, including an Aviation Support Battalion (ASB) Hangar. Acting as an aircraft maintenance facility, the hangar required energy-efficient measures to help Fort Carson reach its net-zero goals.
Numerous lighting design strategies and an overall focus on maximizing energy conservation helped the 136,377-sq ft ASB hangar achieve a LEED v3.0 Platinum rating, making it the first Platinum-certified hangar the Army has ever done.
The project, managed by the U.S. Army Corps of Engineers, Omaha District, was not all smooth sailing, however. Lighting power density goals, as well as first-generation LEDs and high mounting heights provided obstacles for the design team. “Each luminaire selected needed to encompass all of our sustainability goals. Our lighting calculations needed to include all aspects of the space that might affect our energy modeling, including finishes and obstructions such as bridge cranes, bird netting and translucent panels for daylighting,” says lighting design lead Kimberly Smith of Jacobs, Fort Worth, TX. A mindset of “thinking outside of the lighting design box” helped the team overcome challenges and create a facility that surpassed its original LEED Silver goals with no additional cost to the owner.
Strategy and Application
The hangar includes administrative and operations space, maintenance and repair shops, parts and tool storage, more than 86,500 sq ft of aircraft maintenance bays, and two exterior rotary wing wash racks. A mixed bag of lighting design strategies were used to meet energy and financial goals of the large space including:
- An intelligent lighting control system with monitoring and addressable fixtures
- LED fixtures with dimming drivers
- Occupancy sensors
- Lighting groups with graduated zones for daylighting in each hangar bay
- Task lighting for individuals
- Dimming for group areas
LED high-bay fixtures are used in the high and low hangar bays. “The wattage of each fixture is approximately half of a 400-W metal halide and one-fourth the wattage of a 1,000-W metal halide typically used in a hangar,” says Smith. “This energy savings from the LEDs usually result in a payback of less than two years.” Dimming configurations based on ambient light levels save energy while the building’s overall lighting control system turns off during nonoperational hours with a local override switch.
In the administration and workshop areas, shielded, high-efficiency LED recessed fixtures are used in lay-in ceilings. A full-range dimming driver offers reduced light levels based on an overall building lighting control system. Occupancy sensors and daylight sensors are used in administration spaces to turn lights off or dim lights automatically based on ambient light levels from natural daylight. Workshops are lit with T5 industrial fluorescents. “At the time [the project lasted from 2012-2015], the cost was less and LPW was about the same as LED so we chose to stick with T5 for these areas,” says Smith.
One of the project’s biggest challenges included lighting the hangar floor at a level of 50 footcandles from a mounting height of 36 ft-6 in. with the first-generation LEDs. “We were unfamiliar with how LEDs performed at the time and lumen packages and efficacy were limited,” says Smith. After specifying directional LEDs, the team concluded that the lack of spread resulted in light averages that were lower than expected and additional fixtures were necessary. Despite the extra fixtures, the combination of energy-saving design strategies yielded a lighting power density 62% below the ASHRAE IES 90.1-2007 baseline.
Meeting lighting power density goals also led Smith to make use of the finishes within the space. “I didn’t want to throw in a design that meets these goals, but is not beneficial to the end-user,” says Smith, who factored the light reflectance value of the floor into the design—an admittedly risky move, but one that paid off. Smith praises the lighter finishes as helpful in achieving a uniformly lit space. “Considering the hangars were lit with first-generation LEDs, it is amazing that we could achieve a lighting power density of 0.38 watts per sq ft.”
The hangar’s energy-saving features have not gone unnoticed by the design and construction community. It earned a 2017 IES Illumination Award of Merit, a USACE Building the Future Sustainability Award and an Award for Construction Excellence (ACE). Upon completion, the hangar achieved a reduction in energy usage of 56% without renewable systems and an additional 49% with renewable energy systems. LEED credits SSc8 Light Pollution Reduction and IEQc6.1 Controllability of Systems-Lighting were both achieved.