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By Erik Olsen, Andrew Gilles, and Jessica Wojtas, OWP/P, Chicago, IL
View the pdf of this article
A schematic of the proposed addition
A multidisciplinary team of architects and engineers applied
Airpak airflow modeling software to develop their award-winning
entry in the first annual U.S. Green Building
Council (USGBC) Design Competition. The team from Chicago-based
OWP/P was the third-place winner in this competition
for emerging green builders.
Temperature contours on selected planes in the proposed addition show the range
of temperatures that can be expected with natural ventilation
Velocity vectors show the airflow through the building, driven by natural convection
A section view of the proposed addition, showing the original building at left, the
glass tower in the middle, and the proposed addition at right
Entrants designed a theoretical addition to the existing
facility for The Pittsburgh Project, an urban, neighborhood-based,
Christian community development organization serving
the north side of Pittsburgh. Submissions were required
to meet the stringent requirements needed to earn a Platinum
rating under the USGBC’s LEED (Leadership in Energy and
Environmental Design) green building rating system, while
also meeting the aggressive target budget of $100 per square
foot. To enhance occupant comfort, minimize the building’s
energy use, and keep the project cost low, the team designed
a naturally ventilated building with no mechanical ventilation
or cooling.
The design concept relied on buoyancy-driven flow developing
within a solar-heated cavity created between the brick
exterior of the existing building and a new, three-story plane
of glass located at one end of the new building. This solar
tower pulls air through the operable windows of each individual
room, down the corridors, and out of an exhaust stack
at the top of the building. The thermal mass of the brick
wall maintains warm temperatures in the solar tower through
the night, driving cool night air through the building to remove
heat built up during the day.
The team used Airpak to verify and develop the design
concept. The Airpak model was developed from very early
hand sketches and computer-based architectural models in
order to confirm that sufficient ventilation would be provided
by this design. Early models showed that openings
between the three levels outside of the solar tower allowed
too much air to rise from floor to floor, bypassing the tower
and creating uneven temperatures and air quality in the building.
These openings were closed off from airflow with suspended
pieces of glass, allowing light transmission and visual
communication between levels. The final model shows large
amounts of air flowing in through all windows and out through
the solar tower, in keeping with the design intent.
This type of early design stage modeling exercise allows
concepts that might be considered unrealizable to be explored
and tested. Unviable concepts can be rejected, while promising
concepts can be refined.
More Information:
www.usgbc.org
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