CREJ - Building Dialogue - March 2015
In 2008, we were chosen as the electrical design-build partner for the National Renewable Energy Laboratory Research Support Facility. The Department of Energy and NREL wanted this building to be the most energy-efficient office building in the world, and wanted the building to be net zero, if possible. The term “net zero” in this case is defined as a building that achieves zero net energy consumption; the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy created on the site. NREL wanted the Research Support Facility to achieve net zero energy consumption through the use of renewable energy sources mounted within the building footprint. As the electrical design contractor, our job was to provide the most energy-efficient electrical solution possible. The design team of RNL Design and Haselden Construction led the effort by designing a building 60 feet deep with an east-west orientation, which would maximize the opportunity for harvesting daylight and provide for an open office design, which allowed the daylight to be cast deep into the building. Exploring Innovative Lighting System Options Our primary focus during the design of the RSF was the building lighting system. Typically, the building lighting system consumes 30 percent to 40 percent of the energy used by the building. Our goal during the design phase was to achieve a level of energy efficiency never before realized. We did not assign an energy goal because we did not want to limit our thinking as we approached this project. Our first step was to consider the LED fixtures. LED was just beginning to be considered for commercial projects similar to the RSF and, in my opinion, was the lighting “rage” at that time. The problem was that in 2008, LED fixtures were only capable of producing 80 lumens per watt. Fluorescent lamps produced 90 or 95 lumens per watt at that time and, from an energy use only standpoint, were the only choice for the lighting system in the RSF. Having decided on a fluorescent solution, we examined T5 versus T8 lamps and discovered – to our surprise – that the T8 lamp ballast combination was the most energy-efficient solution. The primary lighting source in the RSF is a 25-watt, T8 direct-indirect linear fixture. Engineering Lighting Controls to Maximize Efficiency The next system we examined was the lighting control system. We designed an elaborate lighting control scheme that maximized the amount of harvested daylight and created micro occupancy zones to assure the most energy-efficient lighting control system possible. The lighting system in the RSF consumes less than 0.2 watts per square foot and accounts for 6 percent of the total energy used by the building. Rachel Fitzgerald of RNL was the lighting designer of record for the RSF, and Juliana Ruffalo of Illumination Systems teamed with Weifield to successfully implement this design. Setting the Course for the Future Fast forward to 2014: Weifield is currently designing a 120,000-sf office building that will use an all-LED solution. This new office building will easily achieve a watt density of 0.3 watts per sf. The new office building is not designed to maximize daylight harvesting and we do not have an elaborate lighting control scheme – yet, we are achieving watt densities very close to the watt density of the RSF. For another project, we are considering a foot-wide LED fabric to light the building corridors. LED fixtures capable of producing 120 lumens per watt are commercially available right now. According to colleagues in the industry, LED light sources in research facilities are achieving 300 to 700 lumens per watt. The speed of the LED evolution is breathtaking and, apparently, has just begun. Our vision and understanding of how a light fixture looks and operates is changing. This is a wonderfully exciting time to be part of building lighting design. I can hardly wait to see how lighting will evolve in the next 10 years!