A River Runs Through It
Dave Linamen knows the value of documentation. While attending an orientation meeting in the fall of 1998 for a design competition for the replacement of Pittsburgh's then-existing convention center, Linamen jotted down a number of items on the potential client's wish list: minimal environmental load, maximum natural ventilation, daylighting, and most importantly, the celebration of water.
Dave Linamen knows the value of documentation. While attending an orientation meeting in the fall of 1998 for a design competition for the replacement of Pittsburgh's then-existing convention center, Linamen jotted down a number of items on the potential client's wish list: minimal environmental load, maximum natural ventilation, daylighting, and most importantly, the celebration of water. Linamen, by the way, is a P.E. and director at Butler, Pa.-based Burt Hill Kosar Rittelmann Assocs. (BHKR).
His notes are important for a couple of reasons. First, they document the passion the M/E/P engineering team had for this project. "Green engineering was part of their vision from the start," recalls Vivian Loftness, head of the school of architecture at Carnegie Mellon University and a member of the convention center Request for Qualifications committee. "Dave was committed to the marriage of natural conditioning and high technology and never waffled on the viability and criticality of natural conditioning approaches," she says.
Second, Linamen's notebook is evidence of the humility and commitment he and BHKR had in making this project happen, as they would eventually partner with New York superstar architect Rafael Viñoly to deliver a building that would not only link the city architecturally to its Golden Triangle confluence of the Allegheny, Monongahela and Ohio Rivers, but would also literally pull the waterways into the structure itself.
Viñoly spoke of his inspirations at a recent symposium hosted by the Green Building Alliance. GBA, a Pittsburgh-based green organization, was a driving force in bringing the sustainable convention center to life. At his lecture, Viñoly communicated that it was his desire to connect the Allegheny andits "Three Sisters"—a trio of cable-stayed suspension bridges located in the foreground of the convention center site—to the building and city itself (see "Viñoly on Green," p. 44). He eventually came up with a dramatically curved roof that reflects the shape of the bridges, and alsoin theory, would allow water to run down its slope, returning the element to the river itself.
"I have a debate with Rafael as to whose idea it was to put water on the roof," says Linamen, who again points to his notebook. But, as Loftness observes, the best compliment one can receive is when somebody else thinks your idea is their own. Passions were so high, in fact, that the roof water element became a bit of a sore spot later when the engineering team informed the architect the idea would be too difficult to execute. "At that point Rafael turned to one of his associates and said, 'If he [Linamen] can't put water on the roof, he's no good to me.' So I said OK, we'll find a way," says the engineer.
Actually, the Uruguayan-born architect lavishes much praise on Linamen, pointing out that it was he and his team that made the majority of the sustainable elements work. Sadly, the hotly debated water element would never see the light of day due to value engineering decisions. Also derailed was the team's desire to fully exploit Pittsburgh's "fourth river," an aquifer that runs under the convention center. For the record, it was the engineering team's scheme to use aquifer water as a cooling source for air-conditioning coils, replacing the need for cooling towers. The heated water, says Linamen, would then trickle down the roof and channel to the Allegheny.
But as their investigation proceeded, roadblocks emerged. First, the team had to get a permit from the city to dump the water into the river. After some hard-won arguments, the team was set to proceed when ground contamination was discovered. "The concern was that we'd draw so much water from the aquifer on a regular basis that we would eventually start to pull that polluted water," says Linamen. As a result, the idea was shelved.
Aquifer water, however, is being used as make-up water for the building's 60,000-ton chiller plant, which was designed and built and is operated by an independent party. Linamen also holds hope that the aquifer might be further exploited in the future, in the form of a closed geothermal loop that could be used to help condition a future expansion in the heating season. "We can get about 55°F in the winter, but in the summer it's too warm at about 73°F," he says.
In the end, heat, like cooling, was also outsourced. Being local, BHKR was aware of an existing city steam utility, which was incorporated into the design, a decision that averted the need for boilers.
Speaks for itself
But enough about outsourcing and concepts that didn't work—the building is filled with examples of how sustainability and great design are not mutually exclusive. The exhibit hall itself best demonstrates this. An airy and dynamic room, it's mostly day-lit and naturally cooled—a far cry from the black boxes that typically house trade shows.
"For natural ventilation you need a chimney effect. So we were in good shape because the area along the river is very windy and Rafael's sloped design worked perfectly," says Linamen.
Vents in the north and south facades allow outside air to flow through the building without using fans. The system is operable for about a third of the year when temperatures are between 45°F and 65°F. It's also used to flush air from hall at night. Linamen estimates natural ventilation saves about 3.8 million kWh per year.
In contemplating a mechanical HVAC solution for other times of the year, Linamen did a quick calculation and figured 2.4 cfm per sq. ft. was necessary to provide a comfortable environment. That meant the space would likely be fan-intensive, something contrary to the team's goal of reducing as much energy-consuming equipment as possible. Instead, BHKR proposed the idea of introducing very low-temperature air—41°F. "That's about the lowest acceptable temperature, but we thought we could pull it off with the high ceilings," says Linamen.
After recalculation, the airflow requirement was reduced to 1.6 cfm.
How air is delivered to the hall itself is also interesting. "Rafael made it clear he didn't want big ugly ducts," says Linamen.
One of his BHKR associates pitched Linamen the idea of using fabric duct—a solution that provided multiple benefits. First was the product's aesthetic appeal. Second, it overcame the problem of the undulating roof, which again, is cable-stayed in homage to the bridges it was modeled after. In other words, undesired effects from the weight of traditional ductwork on the flexible roof were averted, as was the need for custom diffusers. Finally, and perhaps most importantly, in Linamen's mind, the fabric duct creates a microclimate that helps avoid condensation problems.
Lighting beams the way
Still, the team did have to come up with a custom hanger solution for the fabric duct, which in many ways behaves like helium-filled holiday lawn ornaments. In other words, without a steady airflow they go limp. But that problem led to another integrated innovation—a combination duct/luminaire.
According to Keith Yancey, a senior associate with Lam Partners, Cambridge, Mass., the project's lighting consultant, the firm really wanted to follow suit with what Viñoly started. "In our experience, lighting design is much easier in a well-designed building since the architecture itself suggests the solution," he says.
In this case, the exhibit hall features a lot of natural illumination from the skylights and giant triangular glass sidewalls that function as clerestory windows. As a result, their mission, says Yancey, was more about augmentation and creating evenness. For the exhibit hall, he notes the team settled on T5 high-output lamps instead of traditional metal-halides. "The T5HOs allowed us to pack a lot of light into a small package," says Yancey.
But more importantly, the illumination experts were able to combine the framework for the lamp hardware with the fabric duct itself to create a custom luminaire that helped baffle and redistribute the T5HO's bright light (see adjacent figure).
In fact, the mounting detail that supports the fixtures, according to Yancey, also supports the ductwork in a way that maintains the basic shape of the tube even under a no-airflow condition. "It's a great example of integration at it's best," says Linamen.
The lead engineer is also quick to hand out kudos to several other members of the team. "If it weren't for Vivian [Loftness] and Rebecca [Flora, the Green Building Alliance's executive director and chair of the RFQ committee], we never would have pulled this off. They're really the green champions," says Linamen.
For example, Loftness, he says, in her initial presentation, made reference to another naturally ventilated building as a case study. Linamen would eventually research that facility and later consult directly with its designer, who in turn, directed him to the the works of Brian Ford, a professor at Nottingham University in the U.K., whose theories he modeled his project on.
Briefly, BHKR employed air movement modeling software to develop the airflow scheme. Wireless sensors are used to open or close dampers depending on winds and seasonal conditions. But getting a handle on the whole natural-air dynamic is an art the firm is still learning, as Linamen says different directional winds produce different effects—good and bad. For example, some parts of the hall may experience cold spots due to vent locations—something, he says, show planners need to be sensitive to when locating exhibitors.
Change of plans
Alas, everything does not always work out rosy. "The mechanical spaces were radically altered midstream," says Linamen, regarding a problem concerning parking lots. An environmental study of the area during the project declared that the original convention center's parking lots—which were scheduled for reuse—were in a flood plain and therefore unusable. As a result, the level of the building had to be raised, which meant the mechanical rooms got "squashed."
Another alternative technology studied, but abandoned, was thermal ice storage, which was nixed because of payback concerns (see "Thermal Storage for Big Spaces," p. 48, for ways thermal storage is being used in convention centers). But one alternative technology that did make the cut was the "Dolphin" system. Instead of treating cooling towers with a chemical water treatment process, the facility employs an electromagnetic system by Clearwater Systems that imparts pulsed, high-frequency electromagnetic energy into flowing water by inducing varying electromagnetic fields 60 times per second. This, according to Linamen, causes the particulates in the water to coagulate, which in turn, allows for them to be blown out. In addition to its superior environmental nature, Linamen says the system is much safer for people working near cooling towers, and there's also a lower risk of Legionella.
A job not finished?
Commissioning was, and remains, a vital part of the project—something Linamen is glad to see. "Before [LEED], people were not interested in commissioning—or at least paying for it—but now there's interest in LEED and it's a requirement," he says.
Besides fine tuning systems, BHKR hopes to be involved in a pair of projects still on the drawing boards: first, a 500- to 1,000-room hotel, and second a duplicate west wing the city's Sports and Exposition Authority eventually hopes to build.
LEED will likely come to bear on those jobs, and CSE will delve more deeply into the process, continuing coverage of the Lawrence Center in future installments of Project Journal . Specifically, we'll go into greater detail on some of the systems noted here, as well as what's involved in making LEED work—which it certainly did on this job, as Flora, at the conclusion of the symposium, proudly announced the project officially received gold certification. This makes Linamen happy, as did working with Viñoly, despite their debate on whose idea it was to place water on the roof. In fact, Linamen says he and the architect were on the same page from the beginning as ideas from their initial brainstorming session produced many of the systems incorporated today—a testament to the impact an engineer can have on a job.
"I believe strongly in the integration of architecture and engineering," he says. "The engineer must be involved early, because most success occurs from the very earliest stages," a lesson that Linamen emphasizes other architects must learn.
ViÃ±oly on Green: Don't Think About it
"My thoughts from the very beginning were that the only way to make a green building was to try not to do one," says renowned architect Rafael Viñoly on creating the vision for what would become the nation's first LEED-certified convention center.
Fifty years ago, the architect notes, the major concern in the design world was how tall buildings could be. A whole series of codes and standards were developed to address this issue, and now, says Viñoly, no one thinks twice about whether a building will stand or not. Today, the architect notes, there is an equal concern about the sustainability of buildings, yet there are no standards whatsoever regulating green design.
His point is that designers do not question meeting established structural requirements in their high-rise buildings. In his opinion, that same sense of unquestioned responsibility should exist concerning sustainable systems.
Viñoly says he never thought twice about conforming to LEED requirements in establishing a vision for the project. "If a big, 200-ft. span of steel was needed to make the building work, I couldn't worry about how much energy we'd expend to get there."
Instead, he let that worry fall on the shoulders of his partners, M/E/P engineers Burt Hill Kosar Rittelmann Assocs., and the client itself. "Rebecca [Flora, executive director of the Green Building Alliance, and the chair of the project's design commission on behalf of the Sports and Exhibition Authority] was very firm and very forthcoming as to the sustainable elements she wanted. But the main idea that reverberated in my mind was that the convention center needed to be the mechanism to reconnect the city to the river," Viñoly says.
With that in mind, he studied the city and its rivers and bridges and came up with his sloped-roof structure. But most importantly, the lesson to be learned here, he says, is that good design should not take the LEED checklist as its guide. Instead, he says, those elements should emerge naturally in the course of proper due diligence.
"It's really about team integration," says Viñoly. "It was essential—including the city's participation. And it really wasn't about one person or agency. It has to be bigger."