ASHRAE Journal - March 2014 - 65

2014 ASHRAE TE c H nology AwAR d cASE STudi ES
TE
AwAR
ARd
STudiES

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.

Design
From the outset of the design
process, the team set a goal of
Figure 1 High performance SIP envelope cross section.
making the most energy-efficient
building possible. Acknowledging
that a design fee typical of small buildings would not
calculations and measured peak loads, the peak cooling
be sufficient to exhaustively explore possibilities with
load is 25% to 30% lower than a standard building of
complex energy models, the design team developed an similar size.
energy efficiency strategy from a basis of team experiTo further minimize loads, the design team made
ence and best practices, running simple energy models conscientious use of glazing. GTTEC is fully daylit with
as needed.
a 26% window-to-wall ratio, which provides occupants
The design team brought significant previous expewith good views of the outside, and minimizes glare
rience to bear on the project, most notably from the
and usage of artificial light. Many modern buildings are
U.S. Department of Energy's Solar Decathlon, where
heavily glazed, resulting in high cooling loads and sighigh-efficiency envelopes, radiant heating and cooling
nificant glare challenges in addition to the cost of glass
systems, natural ventilation, and dedicated outdoor air
being relatively high compared to opaque walls.
systems are common strategies. These approaches and
Lighting loads were substantially reduced using both
technologies were investigated and found to meet the
controls and daylighting. Key spaces were modeled in
intent and budget of GTTEC.
Radiance, optimizing window locations to verify that
The project site allowed for optimal orientation and
glare was not a nuisance by maintaining a maximum
massing, facing the building south. While the south
daylight autonomy (DAmax) below 5%. Users typically
façade has the highest solar load, it's also easiest to shade complain or permanently draw shades under condicompared to east or west façades. The roof overhang
tions where simulated DAmax values are greater than
enables substantial reduction of peak cooling loads dur- 5%, eliminating the load reduction associated with
ing the summer, but is sized for solar gain to provide
daylighting. The Radiance model revealed potential
passive heating in the winter.
glare on the north side of the workshop area during
To make radiant heating and cooling with natural ven- midday in December and January, as the low winter
tilation work in the demanding Wisconsin climate, the
sun entered just below the shade of the south clereenvelope had to reduce loads substantially. Radiant slabs story (Figure 2a). The window location was raised 14
react relatively slowly to changing loads as compared to
in. (356 mm), and this change substantially reduced
VAV systems, therefore, the changes in the environment the potential for glare (Figure 2b). In addition to active
must be dampened.
daylight harvesting, occupancy sensors are deployed
The high performance envelope primarily consists of
throughout the building to ensure that lights stay off
structural insulated panels (SIPs), offering high insulawhile spaces are unoccupied, further reducing the
tion values with relatively few seams, thereby reducbuilding cooling load.
ing infiltration. Recouping cost of installation through
With the loads reduced, there is a significant period
reduced heating and cooling loads and subsequent
of the year during which natural ventilation can play
sizing of the mechanical system, made a greater investa role in ventilating and cooling the building. Based
ment in insulation feasible. Based on comparative load
on a bin analysis, and the ASHRAE Standard 55-2010
March 2014

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