©2014 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 56, no. 3, March 2014.
By Fred Betz, Ph.D.; Jimmy Yoshida P.E., Life Member ASHRAE; and Scott Easton, P.E.
About the Authors
Fred Betz, Ph.D., is a senior sustainable systems analyst, Jimmy Yoshida P.E., is a mechanical engineer, and Scott Easton, P.E., is a principal at Affiliated Engineers, Inc.
A major flood in central Wisconsin on June 9, 2008 caused widespread damage including the spectacular breech of Lake Delton that drained the 267-acre (108 ha) lake into the Wisconsin River. While the village of Plain was not directly impacted, the presence of federal relief authorities in the region brought the village to the attention of the Department of Commerce’s Economic Development Authority. Fewer than 800 people live in Plain, where the predominant local industry is construction.
Plain received economic development assistance funds directed toward building a green technology training center that was focused on light commercial and residential construction.
With this use in mind, the design team worked to make the 11,000 ft2 (1022 m2) Green Technology Training and Enterprise Center (GTTEC) both a demonstration facility and a high performing incubator of teaching in sustainable construction and building operations.
From the outset of the design process, the team set a goal of making the most energy-efficient building possible. Acknowledging that a design fee typical of small buildings would not be sufficient to exhaustively explore possibilities with complex energy models, the design team developed an energy efficiency strategy from a basis of team experience and best practices, running simple energy models as needed.
The design team brought significant previous experience to bear on the project, most notably from the U.S. Department of Energy’s Solar Decathlon, where high-efficiency envelopes, radiant heating and cooling systems, natural ventilation, and dedicated outdoor air systems are common strategies. These approaches and technologies were investigated and found to meet the intent and budget of GTTEC.
The project site allowed for optimal orientation and massing, facing the building south. While the south façade has the highest solar load, it’s also easiest to shade compared to east or west façades. The roof overhang enables substantial reduction of peak cooling loads during the summer, but is sized for solar gain to provide passive heating in the winter.
To make radiant heating and cooling with natural ventilation work in the demanding Wisconsin climate, the envelope had to reduce loads substantially. Radiant slabs react relatively slowly to changing loads as compared to VAV systems, therefore, the changes in the environment must be dampened.
The high performance envelope primarily consists of structural insulated panels (SIPs), offering high insulation values with relatively few seams, thereby reducing infiltration (Figure 1). Recouping cost of installation through reduced heating and cooling loads and subsequent sizing of the mechanical system, made a greater investment in insulation feasible. Based on comparative load calculations and measured peak loads, the peak cooling load is 25% to 30% lower than a standard building of similar size.
To further minimize loads, the design team made conscientious use of glazing. GTTEC is fully daylit with a 26% window-to-wall ratio, which provides occupants with good views of the outside, and minimizes glare and usage of artificial light. Many modern buildings are heavily glazed, resulting in high cooling loads and significant glare challenges in addition to the cost of glass being relatively high compared to opaque walls.
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