DIAlux false color rendering of lighting simulation

UC Santa Cruz McHenry Library Lighting Retrofit and Optimization

Over several years now, energy managers at UC Santa Cruz have demonstrated significant in-house proficiency for managing lighting upgrades by using advanced lighting simulation tools, monitoring occupancy, and by thoughtfully considering the needs of building users. The most recent demonstration of this methodology involved the McHenry Library, an important campus facility at the center of campus built in 1968 and renovated and expanded in 2011. Although many lights were upgraded during the 2011 renovation, the building offered additional savings opportunities due to its long hours of operation and high lighting base load.

This project benefited from the team’s detailed investigation of occupancy patterns and the adoption of newly available technologies.

During the initial planning, the team considered several options including a comprehensive “deep” retrofit as well as more focused strategies. The final design was a compromise, with LED upgrades in offices, study areas and hallways; new occupancy sensors and controls in the book stack areas; and reprogramming of the existing controls throughout building. This set of options was selected based on cost constraints and concerns for potential disruption impacts on library users.

Project team members

Project team members from left: Rudy Martinez, Sarah Gilchrist, Elizabeth Cowell and Marcus Thayer.

The work involved three levels of lamp and fixture upgrades. The simplest level was replacing lamps only with compatible LED lamps, and this was completed in approximately 2000 fixtures. The next level was more extensive retrofitting, by replacing the lamps and ballasts or other hardware, as done in 200 fixtures. Lastly, the project included full replacements of entire fixtures, which was done for approximately 1300 lights.

The project team paid special attention to the bookstack areas, which were unique in terms of illumination requirements and usage patterns. As part of this investigation, the team used freely available DIALux lighting simulation software to test and evaluate various bookstack lighting options. As they had done in previous projects, they also monitored occupancy in multiple locations using “data loggers” that record occupancy and lighting status, providing insights into the potential savings from better control strategies. From this exercise they learned that aisles are occupied on average only 550 hours per year, and many aisles are occupied even less.

Project leaders use lighting interface

Project leaders reviewing energy savings using a web based interface.

However simple on-off controls were not acceptable to the library staff, as minimum lighting levels are required to make the bookstack areas appear inviting and safe. The selected control solution assigned a minimum light level to each aisle based on the expected usage and layout. During hours of operation, a minimum light level is always maintained, and occupancy triggers brighter illumination. The smaller interior aisles are set to maintain an unoccupied level of 9 percent of full power, while a set of larger pathway aisles have a minimum bightness of 15 to 18 percent. After regular library hours lights are turned off, but turn on to the usual occupied brightness when triggered by users. Each occupancy sensor was connected to two fixtures to provide a sufficient level of granularity while controlling project costs.


Lighting in public spaces and offices was adressed through fixture and lamp upgrades, and improvements to controls.

In the bookstack areas the project team is piloting a control system by Enlighted, one of several systems being evaluated by energy managers in an effort to identify products that may eventually be adopted throughout campus. The system includes a smartphone app, for which the project team plans to provide training for library staff (once the operation of the system is fully resolved.)

In other areas, the project team reprogrammed switches and lighting schedules using the existing control system. The lighting shut off “sweep” was re-scheduled to match building hours, and switches were re-programmed with a manual override available for library staff and custodians. Although many areas in the building do not yet have the web and mobile app functionality as in the bookstacks, the project team is planning to later expand the newer control system, to provide the newer capabilities throughout the building.

In the first year, annual energy savings of over 350,000 kWh were measured in the bookstack areas, and approximately 200,000 kWh in the rest of the building. Sarah Gilchrist, UCSC’s energy analyst and coordinator for this project, explains that understanding occupancy and use patterns are key to making informed decisions about lighting upgrades. “There are many more lights in the rest of the building than there are in the stacks, so a good take-away would be that you can only get so far by just converting to LEDs,” she says. Also, in high-use spaces with that are occupied constantly or frequently, advanced control strategies are not likely to provide savings.

Images 1-3 courtesy of UCSC; Library image © Chad Ziemendorf.

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Green Features
  • Custom controls for bookstack areas tuned to individual aisles
  • LED upgrades in offices, corridors and study areas
  • Design based on DIALux simulation and measured occupancy data
  • Updated control strategy using existing hardware and software
  • Monitoring of occupancy with data loggers to inform control strategies
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