March 1, 2004
How Buildings Breathe
A savvy mix of high technology and age-old wisdom is delivering healthier air to indoor spaces from office complexes to concert halls.
Modernist architects viewed the advent of air-conditioning as a liberation. The dissemination of the International Style relied in part upon the ability to design a building without too much regard for regional climate variations—and that only became possible when you could control the climate inside. But later architecture has often taken this reliance on climate control too far, resulting in buildings that show no regard to energy costs or to the effects of working and living all day in an environment without fresh air or natural light.
Fortunately some architects have begun to redress this situation and look for ways to ventilate buildings naturally without sacrificing aesthetics. In fact, many of the pleasing forms in the buildings examined here came about because they aided natural ventilation. These four buildings marry modern materials and techniques with the ancient architectural understanding of air and heat circulation to create healthy, energy-efficient, and beautiful “breathing buildings.”
When Arup Associates decided to consolidate their Coventry and Birmingham offices, they picked a site midway between the two cities to average out commute times. This bit of ecological efficiency and concern for employees is well matched in the natural ventilation system employed in the campus buildings, which opened in January 2001.
Daniel Jang Wong, an Australian project architect with Arup, used a canny mix of daylighting and user flexibility to greatly expand the typical size of a naturally ventilated building. “We defied the conventional wisdom that a naturally ventilated building’s depth should be no greater than fifteen meters,” he says. These buildings are 24 meters (79 feet) deep, and the roofs are crowned with distinctive “pods,” which increase the floor-to-ceiling heights of the rooms while allowing cross-ventilation and natural lighting. As wind passes over the back side of the pods, it helps to draw out the hot air that has been gathering at the top of the building, much like a pop-up vent on the hood of a hot rod draws out engine heat.
But what makes the ventilation system especially noteworthy is the degree of control employees have over it. “The main parts of the windows are operated by the occupants and are designed to allow draft-free ventilation by opening sashes at both high and low levels,” Wong says. “This gives the occupants intuitive control over their own local environments and contributes to the overall environmental quality of the space, but also to a feeling of well-being.”
Though the building was severely tested by an uncharacteristically hot summer in 2003, it has proven to be economically efficient in some unexpected ways. Wong notes that employee absentee rates are down by at least 5 percent, and estimates show that the campus has saved approximately $147,000 a year in energy costs and $130,000 a year in maintenance. “We used pretty much standard components and fabric to achieve our aims,” he says. “The final result gives us living proof that designing an innovative building doesn’t necessarily mean increasing the up-front capital expenditure.”
Roof pods (above and below) serve as chimneys for light and ventilation and also provide a defining aesthetic component to the building.
Experimental Media and Performing Arts Center
Rensselaer Polytechnic Institute,
Troy, New York
Nicholas Grimshaw & Partners
How does a 1,300-seat concert hall breathe? Located on the campus of Rensselaer Polytechnic Institute, the Experimental Media and Performing Arts Center (EMPAC) will use a displacement ventilation system. “The way it works is you deliver air from a low level,” says Denzil Gallagher, an associate at Buro Happold, the project’s consulting engineer. “It can either be from a wall or from the floor.”
To ventilate EMPAC, the engineers place a large volume of space underneath the seating areas—a plenum where air is stored before it is dispersed through the audience. “The air comes out of this big duct and gets circulated through grills under each seat in the house,” Gallagher says. “It comes out very slowly so that it’s equalized across the concert hall, creating a blanket of air along the entire floor.”
As the cooler ankle-high air meets and intermingles with the audience, it picks up heat and rises, moving slowly out of the occupied space toward vents in the ceiling. The stage area has a separate but similar system—except the air traveling toward the ceiling vent moves much faster because of intense heat from the stage lights.
The system has two major advantages. Air quality is greatly improved because the rising air carries particulates off of audience members, up with the warming air, and out of the auditorium. Second, it is more energy efficient than traditional overhead ventilation systems. “With an overhead system, when you finally get the air from the top of the concert hall down to where the audience is sitting,” Gallagher says, “you’ve got to make it pretty cold to make it drop through that heat layer created by the audience.” Displacement ventilation, in contrast, uses the natural tendencies of hot and cold air. The building, designed by Nicholas Grimshaw & Partners, broke ground in September and is scheduled for completion in 2006.
Rinker Hall, School of Building Construction
University of Florida,
Croxton Collaborative/Gould Evans
The challenge here was to cool—efficiently—a 48,000-square-foot classroom building located in a tropical climate. “Our first choice is always natural ventilation,” says Randolph Croxton, of Croxton Collaborative Architects, one of the firms responsible for Rinker Hall, which was completed in 2002. “But if a building requires some level of air-conditioning, then we adjust the system to take full advantage of the precise profile of the available air at the site.”
This was accomplished in hot-and-humid Gainesville by using an enthalpy wheel, which preconditions air prior to its entry into the HVAC system. The Rinker Hall wheel is roughly eight feet in diameter. Acting as a kind of ventilating sponge, it is positioned so that supply and exhaust air-streams travel through it in separate but adjacent compartments.
As the wheel rotates it absorbs heat and moisture from the warmer incoming air. Meanwhile, air being vented out of the building cools and dries the wheel, making it more absorbent. (In colder climates the enthalpy wheel reverses functions, using the warm exhaust supply to heat the chilly air being brought into the building.)
“Once that incoming air gets past the wheel, it has been preconditioned,” says Croxton, whose firm has used enthalpy wheels in a number of projects. “It has not been cooled adequately to be comfortable for people in the classrooms, but now when you send that air to your air-conditioning unit, you’ve got a much smaller load to deal with, so you can really downsize the system.”
David L. Lawrence Convention Center
Rafael Vi–oly Architects
Fresh air and sunshine are not usually associated with a convention center, but these are exactly the surprising qualities that David Rolland, project manager at Rafael Vi–oly Architects, managed to bring to the exhibition hall of the David L. Lawrence Convention Center, the largest building to receive a Gold LEED rating from the U.S. Green Building Council. Strips of skylights, two vertical glass curtain walls, and a Teflon-coated fiberglass membrane allow sunlight and heat to filter into the enormous space. The curved shape of the center’s cable-stayed roof—which looks from a distance like an improbably elegant snow plow—facilitates the natural circulation of air in the enormous space.
“From a material standpoint, using a cable-stayed structure was the most efficient,” Rolland says, “but the shape of the roof also allowed for improved convection of air.” As the air warms up in the 16,000-occupancy exhibition hall on the top floor, it travels up the curve of the ceiling to dampers at the top of the building. “As that hot air is released,” Rolland explains, “it pulls in fresh air through ducts on the other side of the hall that face out over the Allegheny River. It naturally draws in cooler air from the riverfront.”
Though it’s embodied here at a massive scale, the system is remarkably simple—in many ways a return to the basic roots of architecture. “The more mechanization we have, the better we can model the air circulation,” Rolland says. “But like most sustainable-design initiatives, the convention center’s ventilation system harks back to things that people used to do before buildings became large and automated. If you look at the kivas of the Navajos—the small underground spaces they use for ceremonial and religious purposes—they have a fire in the center and a hole in the top, and off to the side there’s a little hole that draws in air from below as the hot air goes up. It’s the same exact principle.”