Hunt Library lighting energy consumption

In response to several questions and comments about impact of the new exterior lighting at Hunt Library on CMU energy consumption, an engineer for the project writes:

“The Hunt Library exterior lighting project sought to create an aesthetically pleasing effect on the exterior of the building, while maintaining an energy-efficient and sustainable design. The façade lighting utilizes 50-watt, long-life LED fixtures. By installing high output, energy-efficient fixtures, the design passed the state energy codes for façade lighting by 58%. Although the design only consumes 40% of the energy permitted for façade lighting, the project scope also included the replacement of several site fixtures to offset the increased wattage from these light fixtures. The existing security lighting for the sidewalks adjacent to the Library was previously provided by three 1000-watt flood lights and six 210-watt pole mounted lantern-style fixtures. These fixtures were replaced by six 71-watt LED site fixtures, which are energy-efficient, long-life, and dark-sky compliant. This replacement resulted in a net decrease of about 3800 watts. Overall, the only wattage increase for the addition of façade lighting on Hunt Library, as well as three site fixtures for security lighting along the sidewalk adjacent to the peace garden, was about 800 watts – which is approximately equal to the energy consumption of a coffee maker.”

Amy L. Ford, P.E.
LEED AP BD+C
Electrical Engineer

CJL Engineering logo

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5 responses to “Hunt Library lighting energy consumption

  1. The article mentions that the replaced sidewalk lighting is dark-sky compliant, but does not say whether the new lighting on the Hunt exterior walls is also dark-sky compliant. Where are the wall lights located? Are they at ground level and pointing upward, sending rays into the sky?

    • Hi, Duane
      Thank you for the good questions. The sidewalk lighting is inherently dark-sky compliant since all the light output is directed down, which is why they were specifically listed in the article as being dark-sky compliant. Although the new lighting fixtures for the exterior façade are considered to be “uplight” fixtures, the fixtures were located and aimed so that the light is directed back down by the overhang of the building. This project was not actually submitted for LEED compliance. However, this method of directing the light back down by an overhang has been acceptable to demonstrate dark-sky compliance on past projects. Thus, although the façade lighting is not inherently dark-sky compliant, the aiming of the fixtures allows them to be considered dark-sky compliant for this application.

      Thanks,
      Amy

      Amy L. Ford, P.E.
      LEED AP BD+C
      Electrical Engineer
      CJL Engineering

  2. Duane Williams

    I take it that your answer is “yes,” because you didn’t say that the lights are so narrowly focussed that all the rays strike the overhang and bounce back to the ground. Can someone stand near the facade lights, but not under the overhang, and have rays from the lights enter their eyes?

    • Cindy Limauro’s reply: No light rays enter anyone’s eyes standing near the facade.

      Professor Cindy Limauro and Christopher Popowich, design partners in C & C Lighting designed the new exterior lighting for the Hunt Library.

  3. Pingback: Hunt Library lighting energy consumption | The Library Giving Times

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