©2019 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 61, no. 7, July 2019.
About the Author
Sarah Berseth is a mechanical engineer and associate vice president at HGA in Minneapolis, Minn.
Ramsey County Library set ambitious energy goals for its new branch library in suburban Shoreview, Minnesota, northeast of Minneapolis-St. Paul. As with many newer libraries, Ramsey County Library Shoreview provides multiple resources for a growing community—an educational resource for children, teens and adults; and a community gathering place for diverse groups and interests. The civic leader in sustainability and environmental stewardship uses 70% less energy compared to the Minnesota energy standard.
Opened in January 2017 on a civic campus that includes the City Hall, community center, school district offices and other public agencies, the 32,565 ft2 (3025 m2), single-story library consists of three architecturally distinctive, brick-clad volumes with expansive windows overlooking the campus. Inside, an open plan subdivides library and community spaces into varying scales to meet multi-functional programming, which includes:
- 22,000 ft2 (2044 m2) of library space for book stacks, a computer area, teen and children’s sections, multiple study rooms, a marketplace, community room; and
- 11,600 ft2 (1078 m2) of administrative space for system-wide Ramsey County Library and Ramsey County technology services.
With this newest branch, the library recognized the opportunity to set ambitious energy-efficiency goals that would serve the community long-term, including:
- Meet Minnesota B3 Guidelines for site, water, energy, indoor environment, materials and waste.
- Achieve 70% reduction in energy use compared to a baseline building in Minnesota’s energy standard, SB 2030.
- Design for flexibility to adapt to changing programming and energy needs.
The engineering and architecture team exceeded goals through integrated solutions that included underfloor air distribution, high-efficiency air-cooled chillers, controls tailored to occupant use in concert with the building envelope, passive solar control and 100% LED lighting. Energy-efficient planning resulted in 70% reduction in energy use, 41% reduction in water use, and 44% reduction in carbon output.
Mechanical System
The mechanical system integrates several key components to achieve maximum efficiency, including:
Underfloor Air System. This was pivotal in meeting the client’s desire for future flexibility. In addition, it proved to be extremely energy efficient.
Zone Controls. Motorized dampers in underfloor ductwork provide zonal control. The dampers open and close based on space thermostat setpoints. The variable volume air-handling unit ramps up and down as motorized dampers change position. A mixture of fixed, adjustable, and motorized floor diffusers was used to meet the varied levels of control required throughout the building.
Perimeter Underfloor Fan Powered Terminals. Perimeter underfloor fan powered terminals were used to decouple the building envelope load from the primarily cooling dominant interior spaces. Separating the envelope load was especially advantageous on the large expanses of glazing on the south and west façades. The underfloor fan powered terminals feed linear bar grilles at the perimeter. Reheat at the terminals is from a loop of hot water supply and return piping routed below the floor.
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