PROGRAM NEWS
Page 8: Tim Greenway; this page: Robert Benson Photography
the center selected Bensonwood builders because of their experience constructing custom high-performance structures with a panelized system. The builders worked with the project team to focus on the energy efficiency of the building first and “have it in harmony with building aesthetics,”
transparent feel. Windows connect the entryway and classroom with the gardens behind the building, and skylights and windows allow natural light into all upstairs offices. “Daylighting is just lovely in the classroom spaces,” says Andy Shapiro of Energy Balance, the project’s energy
per square foot of exterior surface area. A Mitsubishi air-source heat pump efficiently heats and cools the space, solar panels generate hot water, and daylight dimming and cutoff controls adjust the high-efficiency lighting throughout the building. To offset electrical use for heating, cooling, and
The building offers a welcoming gateway to the center's classroom space and the botanical gardens beyond, while achieving the zero net energy and LEED Platinum goals set by the major donors.
On one wall of the inviting entrance, an educational display showcases the building’s energy features.
according to Hans Porschitz of Bensonwood. Site work began in October. Over the winter, Bensonwood designed and built most of the panelized structures at their indoor manufacturing facility, including support structures, flooring systems, interior partitions, and insulated exterior walls and roof panels. They arrived at the site with these completed structures in mid-January. With lightning speed, they had enclosed the building by the end of February, applying an approach that they refer to as “montage building.” This assembly technique, more common in Germany, Austria, and Sweden, made it possible to build in midwinter, saved significant construction time, and limited the project’s impact on the gardens. The center achieved excellent energy efficiency in Maine’s cold climate despite extensive fenestration that gives the building an almost
lighting, there are 135 rooftop and 102 ground-mounted PV panels. In the year that the center tracked the system for the ZNEBA application, the building exported just shy of 8,000 kilowatt hours (kWh) more than it imported. The ZNEBA judges chose the project not only for its energy performance, but also for its impact on the public. Every summer, tens of thousands visit the gardens and interact with a beautiful building. They may be surprised to learn that it generates more energy than it consumes. A truth wall reveals the dense-packed cellulose in the walls, and signage on an education wall and throughout the building explains the green features. The education wall’s touchscreen computer display shows the modest energy draw and substantial electric production. Also important, the design and high-performance montage building technique can be replicated by other
consultant. “Lighting is what people interact with on a daily basis.” With so much glass, how does the center use so little energy and even generate significantly more than it consumes? To start with, heat loss is limited by triple-pane, argon-filled windows with U-factors as impressive as 0.16, and the skylights, 0.27 and 0.154 (the lower the U-factor, the more energy efficient the window). It’s also a very tight building (see the cutaway diagram on page 50). The panelized system’s dense-packed cellulose insulates the roof cavity to an R-value of 60 and the walls to R-40 (nearly 12 inches of cellulose). The slab perimeter, edge joint, and subslab were insulated to R-20 with expanded polystyrene (EPS). Tight sealing on assembly left the building with a modest air leakage rate of 0.115 CFM50 (cubic feet per minute of airflow with a building pressurized to 50 pascals of pressure with a blower door)
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