Exposed steel and expanses of glass are strong, stylish and cost-effective building materials, which is why so many new building designs use them extensively. Unfortunately, they can also turn a space into a greenhouse, cooking occupants inside-and nobody cares how good a building looks when they’re sweltering.
At the University of Texas at Dallas, the rotunda at the entrance of its Visitor Center and University Bookstore could easily have turned into an oven. The rotunda, a 35-foot-tall structure made of steel and glass, covered at the top and open at the base, was unconditioned. Even though the steel pipe sunshades spiraling around the exterior helped shade the space, the interior had the potential to quickly become stifling in the Texas heat.
An uncomfortably hot rotunda wasn’t an option; the space was designed as a doorway to the campus where tours would meet and students could congregate. The rotunda was also meant to function as a vestibule, to provide shelter from the elements and protect the entrance to the building. It wouldn’t do to have the interior of the rotunda be less comfortable than the outdoors.
To prevent that from happening, architects at Page Southerland Page, Austin, Texas, incorporated a massive fan into the design. The fan, a Powerfoil X by Big Ass Fans, Lexington, Ky., falls into the category of high volume, low speed
(HVLS) fans; these provide massive, energy-efficient air movement by rotating large airfoils at relatively low speeds. The fan installed in the space featured a 20-foot-diameter wingspan and fi t perfectly within the slightly larger diameter of the rotunda.
Cooling without Conditioning
The fan, hanging approximately halfway between the ceiling and the ground, creates a column of moving air that fills the space below it. While the fan doesn’t actually make the air colder, it lowers perceived air temperatures, providing a cooling effect to students, visitors and staff within the rotunda. The breezes created by HVLS fans like the Powerfoil X can create a cooling effect up to 10 degrees, which can make a significant difference in occupant comfort.
Since the bottom 10 feet of the walls is open, air conditioning wasn’t an option in the space. Instead, the structure was designed to be naturally cooled through stack ventilation. Stack ventilation involves air being driven through a structure by temperature differences at the top and bottom of a space. Due to its size and shape, the rotunda was a prime candidate. The fan helps accelerate that ventilation through air movement. Combined with the exterior sunshades and openings just below the roof, the fan keeps the rotunda temperate and comfortable. Even in the sweltering Texas summer, when temperatures can crest over the 100 degree mark, temperatures inside the breezy and shady rotunda stay comfortable, around 80 degrees.
Seen and Felt
In addition to providing comfort, the fan also adds to the aesthetics of the rotunda. “The fan provides a means to draw the eye and draw movement into the building,” says Lindsey Brigati, AIA, with Page Southerland Page, who acted as second designer on the project. “It definitely adds to the overall ambience of the rotunda.”
The fan was painted white to match the white structural steel members of the rotunda, and the sleek industrial look of the fan fits in well with the rest of the design, which emphasizes “crisp, clean lines and strong geometries,” according to Larry Speck, FAIA, the primary architect on the project. By adding an element of motion to the otherwise static space, the fan becomes a functional sculpture.
A Comfortable Welcome
With the fan in place, the rotunda becomes a cool, comfortable doorway to the UT Dallas campus. By introducing air movement on a massive scale, the rotunda creates a welcome haven from the heat and humidity that can come with Dallas summers. The award-winning space is proof that even in Texas you don’t need to rely on air conditioning to create a comfortable space.
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Kathy Martinolich is a writer for Big Ass Fans, Lexington, Ky. To learn more, visit www.bigassfans.com.