They're not the sort of architects you go to when you want just another pretty building. They don't design walk-in sculptures that swirl like ocean waves. A plain skyscraper would bore them to tears.

Instead, they dream of making buildings that can go up in weeks instead of months, that are manufactured rather than constructed, that penny-pinch on energy, and that can be tossed into the recycling bin when the world grows tired of them.

Meet the Philadelphia Four, a group of rising design firms that see architecture as a weapon in the battle to stave off environmental ruin.

Unlike many of the celebrity architects of the last decade, who pursued innovation with exotic shapes and gravity-defying constructions, these architects focus on process rather than looks. They want to use their creativity to invent cheaper, greener ways to build.

All share a conviction that conventional building methods have become as obsolete as hunting and gathering. Construction, they argue, takes too long, wastes too much of our resources, and spews out way too much carbon dioxide. Rather than attempting to make our system greener, these architects are bent on overthrowing it.

The Philadelphia Four include the internationally recognized KieranTimberlake, which the American Institute of Architects named its top U.S. firm in 2008; the up-and-coming Erdy McHenry and Onion Flats; and the still-emerging Interface Studio Architects.

"These are architects who do not blush in saying that what they're doing is socially important work," said David Brownlee, who teaches architectural history at the University of Pennsylvania. "All of them are committed to architecture as an intellectual project."

Like the Philadelphia School radicals, who emerged in the 1960s with the ascent of Louis Kahn and Robert Venturi, these firms are starting to attract notice beyond the city, winning national awards and the attention of prestigious architecture journals. Their designs are showing up from New Orleans to Ithaca, N.Y.

At first glance, their buildings might not appear to have much in common. Erdy McHenry's swaggering style, vividly on display in its twisting new dormitory tower at Drexel University, is clearly at odds with KieranTimberlake's more sober approach and its devotion to craft, a trait that won it accolades for green projects at Yale University and Sidwell Friends School in Washington, D.C.

The family resemblance between Onion Flats and Interface is stronger, especially in the syncopated facades for their housing designs. But what really links the Four is their efforts to change how we build.

Their aim is to reduce costs by doing more construction off-site with the help of digital software. Three of the firms have already experimented with assembling buildings in factories, while the fourth, Erdy McHenry, is achieving dramatic savings by making contractors part of the design team.

They envision a day, not long off, when they can e-mail digital models of entire buildings to a factory. Whole rooms will be built under controlled conditions, with finished floors, walls, wiring, plumbing, and ventilation. Workers will just snap the sections together.

If this sounds a bit like the old modernist dream of mass-produced, prefabricated housing, well, it is. And the same challenges remain.

Architects have been struggling for well over a century to perfect factory construction, yet prefab designs still often end up being more expensive and less attractive than conventional buildings. Architecture stubbornly remains an artisanal product, built by hand, one piece at a time, Onion Flats' Tim McDonald acknowledged.

"You say 'modular' to people, and they think tract homes," he said.

But he argues that prefab's time has come because of the opportunities opened by software technology. McDonald said the savings from designing digitally would free up money for quality architecture. The future involves "transforming the building industry into the manufacturing industry."

The Four still have a long way to go before they produce all their buildings on an assembly line. But they have already accomplished a lot in a few years, mostly around their home base of Northern Liberties: The Piazza at Schmidts by Erdy McHenry, Thin Flats by Onion Flats, and the $100K House by Interface Studio allowed them to experiment with new building methods. At Penn, KieranTimberlake's Levine Hall made its shimmering glass facade do double duty as a ventilation chamber, saving money and space.

These tough, unsentimental designs take their inspiration from Philadelphia's practical, glitz-averse, manufacturing past.

The Four see themselves as the successors to Philadelphia's great industrial innovators, companies like Baldwin locomotive and Disston saws. Rather than coming up with new inventions, those companies made their names by pioneering cost-effective production methods. The Four also hope to make architecture more efficient by improving the construction process.

Architects don't generally make the act of building the central focus on their work. The process is not, as McDonald put it, "the sexy part" of architecture. Design aesthetics are - or have been.

During the last decade, the projects that drew the biggest raves were the ones with the most dramatic forms, such as Frank Gehry's Walt Disney Concert Hall in Los Angeles.

But a cycle developed in which architects came to design increasingly for the cameras. They paid less attention to how their buildings functioned or meshed with their surroundings. To get attention, architects were obliged to come up with stranger, more idiosyncratic shapes and materials.

The world's financial meltdown appears to have put a halt to that. The architectural journals are now full of articles repenting the excessive boom days, when condos soared without clients, museums debuted without collections, and the flamboyance of the design was seen as an end in itself.

These days, indulgence is out, relevance in.

Barry Bergdoll, chief curator of architecture and design at New York's Museum of Modern Art, has been watching the global shift in design priorities. "I think there is a kind of generation emerging that is more interested in process than form," he said. "They're interested in how architecture is made, how it builds cities."

For a change, Philadelphia architecture is on the cutting edge of the next movement.

KieranTimberlake

Vanguard of prefab movement

Stephen Kieran and James Timberlake, now in their mid-50s, are the elders of the Philadelphia Four. They were the first in this group to make the connection between the construction process and architecture's impact on the environment.

Their thinking began to develop in 1984 after they left Venturi, Scott Brown & Associates to start their practice. They were eager to differentiate their work from Venturi's jokey, postmodernist style. They focused on craftsmanship, and craft led them to think about how buildings are made.

They soon came to realize that buildings are triple polluters: first when they're going up, again during their operation, and finally when their useful life has expired and they are hauled off to a landfill.

Long before green and sustainable became buzzwords, they sought out recyclable materials. Because so few products were available, they did their own research. They made a habit of installing monitors inside walls to see how much energy their buildings consumed. They argued that architects had an obligation to plan for the building's disposal after it became obsolete.

And, increasingly, performance became their mantra.

"We never begin a project with a specific image in mind - never," insisted Kieran. "We begin with deep research. It goes on for quite some time."

And sometimes, he admitted, "it frustrates our clients. The outside appearance is almost the last thing we do."

Their innovations won notice, commissions, and, eventually, a fellowship that allowed them to write the manifesto of the prefab movement, Refabricating Architecture.

Published in late 2003, the book argues that buildings should be constructed like airplanes or cars. No one starts by welding together the metal plates of a plane's fuselage. Instead the plane is built virtually, on a computer, before it is built physically. The design is broken up into discrete chunks, such as the cockpit's dashboard or the toilets, and farmed out to different factories to be assembled.

The work on the chunks, as they call them, takes place simultaneously. When all the chunks are ready, they're sent to a central facility to be pieced together.

That's a lot different from conventional construction: Buildings are assembled in sequence, piece by piece. First the frame goes up, then the outer walls.

Because the digital model is so complete, hundreds of steps in the construction process can be eliminated. The streamlined process would mean that almost nothing is wasted during construction.

It hasn't been easy to find guinea pigs to test their theories. So, in 2006, Kieran offered to assume the role by building a vacation home according to the book's methods.

After searching out a manufacturer willing to participate, the architects built a digital model of the house, which would be near the Chesapeake Bay. They worked out every last detail, from the way the aluminum frame locked together to the pattern of the Japanese river stones on the bathroom floor.

They also broke down the model into chunks, fully finished rooms that could be popped into place. Once the parts were delivered to the site, it took just six weeks to put everything together. Getting the living-room floors stained just right turned out to be the most time-consuming task, Kieran recalled.

The house, named Loblolly after the local pine trees, was covered with a rhythmic wooden screen inspired by hunters' duck blinds. It was unusually beautiful for a prefab house, but typically expensive, although the exact cost was never disclosed.

The architects were not deterred. They saw Loblolly as a prototype. What they needed was volume. Since then, they've completed two more high-profile prototypes, both with the same mixed results.

The first was Cellophane House, a four-story townhouse built on a parking lot next door to the Museum of Modern Art for a 2008 exhibit on prefab design. It featured clear walls made from recycled soda bottles that allowed the architects to show off the embedded wiring and solar cells. The dazzling, see-through house became the star of the show.

Besides cutting Loblolly's assembly time by half, to three weeks, Cellophane House demonstrated another of the architects' theories: the power of mass customization. They believe that prefab construction will enable a designer to tailor each building to its buyer's taste, just as cars are customized.

But like Loblolly, Cellophane was not cheap, and cost as much as a million dollars, according to some estimates.

Kieran and Timberlake acknowledged that it wouldn't be possible to bring down the costs of such houses until they established a factory for production.

They thought they had their chance when they were selected to design a prototype for actor Brad Pitt's Make It Right project in New Orleans, which is rebuilding the ravaged Lower Ninth Ward. But Pitt's project was overwhelmed with start-up problems, and KieranTimberlake's dreams of setting up a local production factory fell by the wayside.

The architects remain determined. They're designing more Make It Right houses, and hope to set up a production facility in New Orleans.

It's not just about making housing cheap, Timberlake pointed out. "If we create jobs locally in a factory, and employ those people in long-term jobs, they're going to be a lot better off."

Interface Studio

A dream that's sustainable

What KieranTimberlake hasn't been able to pull off yet in the Ninth Ward, Interface's Brian Phillips was able to realize on a gutted street in Kensington using a simpler form of prefabrication.

At 38, Phillips, who studied at the University of Oklahoma and Penn, is the youngest and least known of the Four. He spent seven years as an architect at WRT, a Philadelphia landscape and planning firm, before setting up his own office in a stark corner of the Crane Arts Building, a vestige of North Philadelphia's manufacturing heyday.

His break came when his design for a group of energy-efficient, low-income houses won AIA honors in 2006. The houses, planned for a desolate North Philadelphia block, incorporated a prefabricated wall system and used solar panels as a deck awning. They have yet to be built, but the experience wasn't wasted.

Soon after, developer Chad Ludeman, who had just bought a weedy lot in Kensington, contacted Phillips to build four green rowhouses that would be highly energy-efficient and very cheap. Ludeman even had a name for his product: the $100K House.

Would Phillips accept the challenge?

"We gulped a bit," Phillips recalled. Even with the experience in North Philadelphia, it was going to be a push. To save money, Phillips used a factory-made wall system that came insulated and wired.

Unlike in a typical house, no wooden frame is required. When the panels are bolted together, they become the supporting structure. The interiors were constructed in much the same way as a traditional house's, using low-cost materials.

The result was a tight bandbox of a house that Ludeman calculated could subsist on $1,200 worth of energy a year.

Yet Ludeman's houses weren't quite the bargain he first envisioned. The $100K House, it turned out, cost $200K to construct. Even at that price, the houses could claim to be affordable compared with other new Philadelphia rowhouses. All four sold immediately.

Phillips, however, wasn't satisfied with his foray into prefab housing.

"Of course, the $100K House is modular, but now I'm not so sure it was the greenest thing we could have done," he reflected. "Is it really green to truck all these boxes in from Scranton?" He "began to see sustainability as a much more holistic issue."

"Just a small piece of construction is about construction," he said. "The other pieces are about politics and labor and money and environmental concerns."

Like KieranTimberlake, he dreams of starting a house factory in Philadelphia that would employ local workers.

Phillips may soon get to try out that approach. He's been talking to Temple University about building a dormitory using locally produced, modular components. This time, he hopes to partner with Onion Flats, a firm that has its own ideas about sustainability.

Onion Flats

Advancing the prefab cause

Garth Rockcastle, architecture dean at the University of Maryland, considers Onion Flats the most subversive and important of the Philadelphia Four. The firm shares KieranTimberlake's ideas, "but they've built a whole community around it," he said.

Onion Flats is no typical architecture firm. It was started by the three McDonald brothers and their childhood friend Howard Steinberg, 45. Only Steinberg and Tim McDonald, 45, trained as architects. Pat McDonald, 47, is a master plumber. John, 37, is a Realtor.

They've pooled their skills to create a very modern hybrid: designer-developer-builder. The combination enables Onion Flats to control production from the first doodle through the final walk-through inspection.

Like a modern version of the medieval guild, Onion Flats hires local fabricators and craftspeople. The atmosphere at its construction sites often feels like an old-fashioned barn-raising, with family and friends pitching in.

To qualify for a standard green rating, architects are expected to purchase materials within 500 miles; Onion Flats often buys materials from within a few blocks. Tim McDonald's wife, Liz Kinder, a ceramist, makes the sinks.

Their most ambitious project so far was an eight-unit condo building in Northern Liberties called Thin Flats, completed in 2008. The duplex units, initially listed for more than $500,000, have a single facade composed of glass, metal, and weatherproof panels. The composition is a jazz burst on a street of redbrick rowhouses.

Thin Flats won the U.S. Green Building Council's highest rating for its extreme energy efficiency. The designers included plug-in outlets in the yards for charging electric cars - a bonus with every purchase. But despite being lauded for sustainability, Tim McDonald felt, much like Phillips, that the project didn't do enough to advance the cause of prefab design.

For future projects, Onion Flats is working with Pottstown's Landmark Building Systems to produce modular units that can be fitted together into complex, multistory structures. Landmark has a long record of making prefab modules for light manufacturing and warehouses. What Onion Flats wants to do is turn those functional boxes into architecture.

Like KieranTimberlake's chunks and Phillips' integrated wall panels, the Onion Flats modules will be completely finished rooms. But they won't be mass-customized in the same way as Cellophane House.

McDonald takes issue with the notion that customization and factory production are compatible. "It's unbelievably crazy. You wonder why prefab hasn't taken off. Designers are using building typologies that are unsustainable. Why build one-off buildings in a factory?"

Warming to his theme, he went even further: "Why would you use prefab to build a single-family house? Single-family housing is not sustainable as a prototype," he argued. That's why it's rarely cost-effective.

Onion Flats already has lined up several modular ventures, including multistory buildings in New York and a small SEPTA station. These will be the biggest projects the family design collective has undertaken, and the test of its ideas.

Erdy McHenry

Architect as master builder

Erdy McHenry, which built the Piazza, is the only one of the Four that doesn't see the future dominated by factory construction. Like Onion Flats, founders Scott Erdy, 46, and David McHenry, 49, are trying to streamline construction by resetting the relationship between the architect and the builder. They may have a better chance of achieving their goals than their more utopian counterparts.

They argue that the lack of communication between the professions is the real reason for the high cost of construction. Erdy McHenry believes it can save money and speed up the process simply by engaging in a collegial back-and-forth with the craft trades - steelworkers, carpenters, electricians - before construction.

Those conversations would help fuse architecture and building so that the architects and contractors designed as a team. The goal, McHenry explained, "is for architects to become the master builder again."

Rather than wait until a design is finished, he and Erdy start sharing computer models with contractors as they're developed. The builders, they argue, can spot mistakes early and suggest a more efficient way of accomplishing the same task.

The architects recalled their first meeting with the Piazza's developer, Bart Blatstein. At first, he seemed uninterested in their design, which featured an interlocking arrangement of duplex apartments. They explained that the layout's advantage was that it reduced the space required for external corridors. Blatstein saw the savings potential immediately. That's when they got the job, the architects said.

"What they've been able to do on a shoestring is incredibly inventive," marveled Annette Fierro, a Penn architecture professor. "They're not looking at construction as a philosophy, the way KieranTimberlake does. They're not putting up a polemic like Onion Flats. They're good at being deft, at operating nimbly."

That nimbleness won the 10-year-old firm some of the most visible projects in Philadelphia. It has completed dorms at the city's three big universities, along with Independence Mall's best building, a small cafe along Fifth Street.

While the pair's designs tend to be more stylish than those by others in the Four, they pride themselves most on the low cost. "We built the new dorm at Drexel for $65,000 a bed, when the industry standard is $70,000," McHenry boasted.

Millennium Hall, which cost $40.5 million, doesn't look like a bargain building. Its rotating, elliptical concrete form is one of the city's most complex recent engineering feats.

But like the Piazza, it saved money by working out structural innovations, because of the architects' partnership with contractors. Erdy McHenry grouped the dorm rooms around the perimeter of the elliptical tower, while concentrating all the plumbing in an efficient core. The tapered shape wasted little space on corners or corridors. The elliptical form works because efficiency and aesthetics are inseparable. It's the essence of green design.

"The reaction from the old guard is always, 'How do you get away with this?' " Erdy said.

After piling up so many commissions in Philadelphia, the firm has been looking to broaden its reach. It's working on a dairy barn for Cornell University's agriculture school that will keep the cows cool with a green roof. McHenry and Erdy are not opposed to factory construction, but Erdy doesn't see it being cost effective for larger buildings.

And the firm was one of seven finalists in a Syracuse University competition to develop a prototype for a low-cost green home. Onion Flats, another finalist, was selected to build the prototype.

Marilyn Jordan Taylor, dean of Penn's School of Design, sees the Philadelphia Four as an extension of the city's great manufacturing tradition. "This wasn't New York, where they made money off the intangibles of finance," she said. "Philadelphia has always made things you can touch and hold in your hand."

Erdy echoed the sentiment.

"A lot of people forget that Philadelphia is based on ingenuity, all the way back to Franklin," he said. "There is a history of industrial invention."

That legacy seems likely to continue as the Philadelphia Four explore new ways of making buildings.

To view a photo gallery of the architects' work, go to http://go.philly.com/architectsEndText

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Profiles of the firms, and examples of their work. A18-19.

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