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Derry Public Library

New Hampshire’s Derry Public Library Upgrades to LED Lighting to Improve the Lighting for Patrons and Reduce Energy and Maintenance Costs

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The Derry Public Library in Derry, New Hampshire, opened August 10, 1905, as a few furnished rooms in the Adams Memorial Building. In 1926 Henry F. MacGregor’s will instructed his widow to purchase land and build a new library. Paul Collette, Derry’s first mayor, became the driving force behind getting the appropriate funds for a 15,000-square foot library expansion in 1989. The new Derry Public Library opened March 8, 1990, with a total area of 22,771 square feet. Since then the library collection has nearly tripled and serves over 33,000 community members

A Board of Trustees oversees the library budget and operations and identified the need to address the lighting issues throughout the facility. Leading Edge Design Group (LEDG) was hired to perform a lighting assessment for the Derry Library, report back on lighting issues, and recommend long-term solutions to the Board.

The fixtures that were installed throughout the Library were direct/indirect decorative pendants with a 400W metal halide lamps and an acrylic opal bowl lens. The fixtures caused many issues that include:

  • A non-uniform color shifting to green and blue hues as the lamp life diminishes.
  • The bowl style lens collected dust and dirt, and the heat of the HID lamp caused debris to solidify causing a smoke tint on the acrylic lens.
  • As the lens degraded, the lighting output and distribution changed significantly. The brightness and usefulness of the direct lighting component of the fixture decreased month over month as more dirt gathered in the fixture. This caused visibly noticeable lighting challenges in important patron areas such as the book stacks, reading tables, and meeting rooms.
  • Since there is no lens for the indirect lighting component of this fixture, the indirect brightness remained the same, yet variable due to the lamp issues, as the indirect lighting output diminished.Compact fluorescent and metal halide recessed can lights were also installed in concentrated areas and also caused continuous maintenance challenges and inconsistent lighting output.The LEDG team sought out cost-effective LED lighting solutions that would greatly improve the lighting output and decrease maintenance and energy costs. To adhere to the Library’s budget and approval process, LEDG recommended a three-phase approach to their LED upgrade.


The three-phase approach created a way for the Derry Library to tackle the patron-centric areas first that included the entryway, lounge, and cafe’ followed by meeting and office spaces. The phased approach also enabled the Board to see the impact new lighting could have on the entire library.

For phase one, a new linear LED fixture with a specular clear lens replaced all hanging HID fixtures. The linear fixture provides a more uniform distribution of light throughout all the library spaces. The high-performance solution, at 98 lumens per watt, is more aesthetically pleasing and has an integrated sensor with daylight and occupancy sensor capabilities. LED downlights with dimming capabilities replaced all compact fluorescent and metal halide recessed cans. At 90 lumens per watt, the downlight lighting output is brighter and delivers a significant energy reduction.

To take advantage of today’s innovative LED lighting technologies, the Derry Library will also use handheld remotes to control the lighting using integrated sensor technology. The remote interacts with the fixture sensors to give the user the ability to turn the lights on and off, adjust light levels, and program occupied and unoccupied scenes. The ability to program energy saver scenes also provides a way for the library to lower costs during daylight hours as an example.

Phases two and three includes the installation of more fixtures in other sections to include the non-fiction, reference, and teen book areas, the installation of low-profile wall sconces, and downlight replacements. Phase three will include the installation of 2 x 4 LED troffer fixtures in the office areas and the LED replacement of other downlights. A troffer is a rectangular fixture that fits into a modular dropped ceiling grid and produces uniform light in smaller spaces.


The Board of Trustees is very pleased with the technology and lighting output delivered by LEDG recommendations. Patrons are noticing the modernization and the improved visibility on the library stacks.

For phase one, the Derry Library is expected to save approximately 15,000 kWh of energy annually resulting in a $2,166 reduction in energy costs, a $2,000 reduction in maintenance costs, and the elimination of 20,000 pounds of greenhouse gases. Phase two and three is expected to double these estimates and will be completed in 2017. At this time, the Derry Library did not apply for utility incentives. LEDG will help the Board review incentive options after all three phases of the project are complete.