©2018 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 60, no. 9, September 2018.
By Stet Sanborn, AIA, Member ASHRAE; Dawn Pillsbury
About the Authors
Stet Sanborn, AIA CPHC, is a principal and engineering discipline lead at SmithGroup’s San Francisco office. He was an associate principal at Integral Group in Oakland, Calif., when he received the Technology Award and wrote this article. Dawn Pillsbury is a journalist turned energy efficiency activist.
What’s a university to do with a quickly failing barn that holds historic significance and a prominent location near the entry to campus? In this case, they transformed it into a state-of-the-art campus and community center featuring elegant and easy-to maintain systems and an ultra-low energy use intensity (EUI).
The University of Santa Cruz sought to retrofit the 150-year-old Cowell Ranch Hay Barn in 2014 and make it the headquarters for the university’s Center for Agroecology and Sustainable Food Systems (CASFS) and its faculty. For a half century the CASFS Farm and Garden has been shaping the organic food movement through teaching, research, and policy innovation. In keeping with the group’s mission, the project aimed to maintain the historic nature of the building while dramatically increasing its comfort and energy efficiency. The 4,910 ft2 (456 m2) retrofit also had to meet the strict regulations of a historic renovation.
The Hay Barn now serves both the campus and community as a gathering place for classes, workshops, and other programming, as well as offices and a reception site for CASFS. The LEED v2009 Certified Gold facility is available to both the campus and the general public for conferences, seminars, weddings, parties, and other gatherings and is the distribution point for the Community Supported Agricultural program.
Energy Efficiency
The design goal was to transform the 150-year-old barn into an ultra-low EUI building. The energy use would be offset with a new central campus photovoltaic (PV) array. The University requested aggressive energy conservation measures to help reduce the PV array size required to achieve net zero energy. These goals were attained by reducing energy loads through use of an exceptionally tight envelope with high R-values, skylights and windows placed for 90% daylight autonomy, natural ventilation and a highly-efficient heating only HVAC system. After two years of operation, the building is currently at an EUI of 10.5 kBtu/ft2·yr (119 249 kJ/m2·yr) (significantly lower than the average EUI of around 50 for university buildings in California.
Significant energy savings can be mostly attributed to the passive natural ventilation cooling strategy, allowing the project to use one-third the energy of the modeled building, which includes cooling by default (Figure 1).
An in-slab hydronic radiant heating system provides heat for the building. Hot water for the hydronic radiant system is provided by a central residential sized 3 ton (11 kW) air-source heat pump. All electric and more than three times as efficient as gas, the heat pump reduces the EUI and carbon footprint of the building dramatically. Highly insulated roofs, walls, and windows all help to lower this heating loss. The renovation included R-24 walls, an R-40 roof with continuous insulation, and avoiding thermal bridges throughout the building enclosure. Double pane windows and skylights were added to optimize daylighting while minimizing unwanted thermal gains and losses. Radiant heat with no compressor cooling and natural ventilation takes advantage of the area’s mild climate.
Daylighting was optimized in the building through distributed skylights, and deliberately placed windows. The low W/ft2 (W/m2) LED lighting design is controlled by daylight and occupancy sensors, further reducing energy use.
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Figure 1
