The Hidden Life of Green


Sustainable Features In Buildings Don't Have To Be Front And Center To Have A Meaningful Impact On Performance

04/2007

This article appeared in the April 2007 print issue of GreenSource Magazine.

Click here to view a slide show; Photo Courtesy Bruner Cott

We all have images in our minds of what it means to be sustainable. For many, the term “green” connotes double facades, solar arrays, or wind turbines. But as the sustainable movement matures, eco-friendly designers have come to learn that high-performance buildings do not have to dress for the part: “Buildings do not have to wear sustainability on their sleeves,” says Graham Wyatt, AIA, a partner at Robert A.M. Stern Architects (RAMSA) in New York City. In fact, some of the most ecologically effective strategies can be imperceptible to the casual viewer.

Sustainable design is not a style, but an approach in which the various inputs and outputs of the building are considered and optimized for the long-term health and well being of people and the environment around them. To accomplish this, many factors need to be considered simultaneously and early in the design process so that the most eco-efficient patterns become intrinsic characteristics of the initial concept. Once these qualities have been woven—or integrated—into the preliminary design, they offer the architect elements that can be articulated if desired, much the same way an architect can decide to express or conceal the building structure.

“We have some clients that come to us with a notion of what a green building looks like or needs, such as photovoltaic panels or double-facade envelopes,” says Nico Kienzl, a director of the New York City office of Atelier Ten, which specializes in environmental and building services engineering. “We try to take a step back and show them the bigger picture—what they and we are really trying to achieve—and how to get there.” Kienzl finds that once he presents the data, clients don’t have a hard time reconsidering their initial assumptions and reprioritizing. It’s much easier, for example, to make the case for a ground-source heat pump, which could potentially have a payback of about 5 to 10 years, than for photovoltaic panels, which currently take 20 to 30 years to recoup their initial investment, even though photovoltaics seem to have more “green” cachet. Kienzl doesn’t discount the more visible and, therefore, more attention-getting solar collectors, but argues that the more mundane strategies must take priority: “If you really want to reduce energy consumption, first insulate and provide shading.”

Buildings that are highly sustainable but do not look particularly “green” have become standard for universities that retain and manage their properties for the long term.

For many projects, says Wyatt, his firm applies what he calls “stealth” sustainability. “We have standard specifications, such as nontoxic paints and carpets that don’t off-gas, which we use as a matter of course for any design.”  The firm doesn’t necessarily discuss the sustainable nature of these items with the client but simply selects them as part of its basic business practices.

And now that the U.S. Green Building Council’s LEED rating system has become widely known and accepted, more and more clients do not need much prodding to undertake the basic testing, or commissioning, of building systems to ensure that equipment has been installed properly and is therefore functioning optimally. “Commissioning has become an easy sell,” says Kienzl, “because LEED requires it as a prerequisite for certification.” In addition, the practice has become standard for many public and institutional clients, who often have commissioning requirements that are more stringent than those required for LEED. Kienzl notes, however, that it can be more difficult to convince commercial clients to undertake the quality assurance procedures on their first project because they perceive it as an extra cost that they would rather avoid. But clients who have built more than once quickly learn that “the cost of commissioning is nothing compared to the cost of fixing things once the building opens,” he observes.

Highly sustainable buildings that don’t look particularly “green” have become more standard for acadmic institutions that retain and manage their properties for the long term. In large part, due to their sense of permanence and past experiences, these clients have taken the lead in recognizing and taking advantage of the operational benefits of high-performance construction. After all, explains Robert Simmons, AIA, senior associate at Bruner/Cott & Associates in Cambridge, Massachusetts, “It saves money in the long run.” At the same time, however, these institutions must carefully consider how new facilities will fit visually into their existing campuses, be they modern or traditional in style.

Robert A.M. Stern Architects, working with Atelier Ten and the New York City engineering firm Flack and Kurtz, recently designed the School of Business at Ithaca College in New York with no overtly green attributes (although the team is aiming for a LEED Platinum rating, the highest level offered by LEED). Philosophically, explains Wyatt, his firm believes that a new building should be appropriate to its particular campus. In this case, the existing style is post-World War II modern.

The building site is on the north side of the campus and its best views are due north, as the terrain slopes away to Lake Cayuga. Keeping to a Modernist vocabulary to help stitch the new building into its existing fabric, the architects—led by RAMSA Associate Partner Kevin Smith, AIA—developed a panel-cladded rain-screen wall system with horizontal windows on the north facade to maximize the panoramic view while minimizing energy loss, and a glass wall on the south to maximize daylighting. The glass wall begins at a vertical angle at grade and then curves at top to obtain the preferred solar angle for this latitude, thereby increasing the amount of light penetrating the south-facing rooms and courtyard during winter. Its high-performance glazing transmits a high percentage of visible sunlight, minimizes solar heat gain, and exhibits good color rendition. The base of the building—constructed with a six-inch metal-stud backup wall that is heavily insulated and air-sealed—is clad with ashlar stone from a local quarry, reflecting the surrounding landscape.

Wyatt explains that, at the beginning of design, the project team kept in mind a broad selection of potential sustainable technologies—including photovoltaics and hydronic solar heating on the south facade—because a LEED Platinum rating was one of the project goals. Both types of panels, however, were nixed as the design progressed because further testing and analysis indicated that there were more cost-effective ways to achieve the desired performance level in the locale at the time. The architects did specify a vegetated roof for part of the building because it provides more insulation, captures storm water, and has a longer service life than a conventional roof, but it will not be visible to onlookers.

Wyatt credits basic massing strategies—such as the building’s central atrium and south-facing second-floor garden terrace, both of which are consistent with a Modernist design vocabulary—with much of the building’s expected energy savings. Both the atrium and terrace will bring daylight further into the interior of the building. In addition, the atrium will encourage thermal stratification, which will help the ventilation system achieve greater comfort and more efficient cooling in summer. And, the warm air that rises to the top of the atrium in winter will be recirculated, thereby helping to reduce the building’s heating load. 

Through daylight harvesting strategies, electrical systems also play an important role in energy conservation: all offices and classrooms will be equipped with both occupancy and daylight photosensors. The office sensors will turn electric lights on and off as needed while the classroom sensors will be linked to dimming system controls to provide a more graduated response to available natural light. Another unobtrusive strategy in the building is displacement ventilation. Here, conditioned air is provided at relatively low velocity in the lower portion of a room, instead of the more conventional high-velocity airflow from registers located near the ceiling. Displacement ventilation requires less energy, is quiet, and easy to control. Wyatt reports that initial energy modeling of the design predicts that the building will use 47.5 percent less energy than the standard set by ASHRAE 90.1-1999, all with technology that is fairly tried. true, and inconspicuous. He doesn’t believe that people entering the building, which is expected to be completed by the end of this year, will immediately think “green.”

Meanwhile, Bruner/Cott & Associates was asked by Vanderbilt University in Nashville, Tennessee, to design a high-performance dining facility that would fit into the school’s Peabody campus, which was originally built in the Georgian style in 1914 and was designated a National Historic Landmark in 1966. Recalls Simmons, “Everyone felt that the LEED buildings didn’t have to look different to get certified. Just doing a smart building with sensible features could get you there.” The university set out hoping for a LEED-certified rating for the Commons Dining Center, but Simmons thinks they will achieve Silver. Group Six Consulting in Atlanta served as environmental consultants on the project, which will be completed this spring.

The elevations present classic visages: symmetric facades clad with red brick on a limestone base; limestone pilasters, sills, and headers; cornices of glass-fiber-reinforced concrete; traditional glazing proportions; and painted steel standing seam roofs on corner towers. Site conditions and program required the building to have a compact massing. To increase natural light penetration into the large floor plate, the architects created a central atrium, which may not be traditional Georgian but reads on the exterior like a clerestory base of a classical dome.
 
The building’s most sustainable feature is a special exhaust system in the kitchen. In a standard commercial kitchen, fresh air that has been heated up to 55 degrees and blasted out of the multiple ventilation hoods is subsequently exhausted in large quantities. “This wastes a huge amount of energy,” he continues. At Vanderbilt, the mechanical system uses 30 to 40 percent less make-up air than the standard, because part of the make-up air is ducted into special jets that induce currents within the hood that capture a much greater percentage of smoke and grease-laden vapors from the cooking equipment, reducing the necessary volume of exhaust air normally required by code. The jet hoods also remove the convection heat generated by the cooking equipment below. Simmons estimates that this technology alone will reduce the total HVAC energy load by as much as 5 percent.

Simmons explains that although the exhaust system is a little more expensive than conventional models, the reduction in air requirements allowed them to downsize the overall HVAC system, so the total cost for the mechanical system was less than if they had specified a less expensive exhaust system up front. Although the technology is clearly high-tech, it is not very visible. “The outside viewer would never notice it,” adds Simmons. “Even the chefs may not notice, except it’s more quiet.”

- by Nancy B.Solomon, AIA

Contributing editor Nancy B. Solomon, AIA, writes about sustainability, computer technology, building science, and other topics of interest to the building design profession.