Why this Ontario engineering firm is the go-to for starchitects designing the world’s supertall towers

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Walking into the headquarters of engineering consultancy RWDI is like stepping into a museum of architectural marvels and engineering feats. From the lobby to the lunchroom to the shop floor—especially the shop floor—are models of the world’s tallest buildings. There’s the Burj Khalifa in Dubai, which in real life will soon be surpassed by Saudi Arabia’s Jeddah Tower, rendered here in red. You’ll see Manhattan’s 432 Park Avenue, the loftiest residential skyscraper in the northern hemisphere, and One Bloor West, which will be Canada’s first supertall structure when it’s finished in 2022. These buildings represent the high life, and they would be impossible to erect without the wind engineering chops of RWDI. Though judging by its own unassuming home—a low-slung box that rubs concrete shoulders with Sleeman Breweries and Ontario Pork on a swath of industrial land in Guelph, Ontario—you’d never guess at the big things happening inside.

“See, models everywhere!” exclaims Michael Soligo, RWDI’s CEO, as he opens the door to the shop floor. The hangar-like facility is redolent with the smell of wood, and there’s a whir from circular saws being used to build streetscapes that replicate Chicago, Shanghai and Toronto. “These are our large models—towers and stadiums over here, bridges over there,” says Soligo, hinting at the firm’s broad repertoire.

Despite its relative obscurity to the general public, RWDI (the name is derived from the first letters of the four co-founders' last names) has become a household name among starchitects globally since its launch in 1986. That's in large part thanks to its expertise in wind-tunnel testing, which enables engineers to design skinny but stable supertall structures (defined by the Council on Tall Buildings and Urban Habitat, a.k.a. CTBUH, as 300 metres or more).

“RWDI is one of only four or five firms with such specialized knowledge,” says Daniel Safarik, the CTBUH's editor. “That expertise has made it a go-to, with contracts on some of the biggest developments around the globe.” Indeed, of the nearly 300 supertall buildings already standing or under construction globally, RWDI has been involved in one-fifth.

Wind engineering accounts for about half of RWDI's $80 million or so in revenue (the private company, which is owned by 50 of its 500 employees, is reluctant to disclose financial information). But the firm, which has 17 offices worldwide, has its hands in an expanding list of areas, with a staff that includes mechanical, structural, environmental and aerospace engineers; scientists with expertise in meteorology and climate; and carpenters. (Most of its employees have been with the company for a decade.) It has consulted on adding safety nets to the Golden Gate Bridge (which has seen 1,700 suicides since 1937), contributed to the design of the housing for the Giant Magellan Telescope and helped elite road-bike maker Cervélo design more aerodynamic rides. It even did forensic work on the World Trade Center after Sept. 11, 2001, to help sort through insurance implications.

Perhaps its fastest-growing line of business is related to climate change and the extreme weather events that come with it: helping clients design smarter buildings or retrofit existing ones, and projecting what the climate will be like 50 years from now. “We've always looked at climate, but now we see more dramatic aspects of it,” says Soligo. “Building science is going to remain our growth area because it's so vast.”

For now, though, the most prominent niche RWDI has carved out for itself is how to turn wind into windfall.

By the time it’s completed in 2020, the Jeddah Tower—now under construction in Saudi Arabia’s second-largest city—will stretch more than a kilometre skyward, from its flared base to its needle-like tip. (The tower will be at least 170 metres taller than the reigning Burj Khalifa, which stands at 830 metres.) At that height, winds can be two to four times their speed at ground level, causing buildings to sway up to two feet from side to side on a blustery day, or as much as two metres during a 50-year storm. But visitors to the tower’s upper floors—say, the penthouse earmarked for billionaire Saudi Prince Alwaleed bin Talal, one of the project’s backers—won’t need to pop a Gravol.

RWDI co-founder Anton Davies is talking about the Jeddah project while scribbling diagrams to show the impact wind has on buildings. “The taller a skyscraper, the greater the force of the wind, especially higher up, where it bounces off the structure as vortices that create turbulence,” says Davies, a mechanical engineer. It's these vortices that make a structure sway. Wind also puts pressure on the cladding and windows, and on such features as observation decks and helipads, both of which form part of the Jeddah megalith. So architects and structural engineers depend on wind engineering, where a scale model of a structure—be it a skyscraper, a bridge or an oil rig—is subjected to wind force in what's called a boundary-layer wind tunnel. Data captured during this process helps them craft a final design that slows down wind and minimizes turbulence long before hoardings go up around a construction site.

Look up from RWDI’s shop floor, and you’ll see the underbellies of these tunnels overhead. Wood-panelled rectangles, they look more like modernist cabins than engineering tools. The Irwin tunnel (named for co-founder Peter Irwin) measures 24 feet wide, while the smaller Davies tunnel clocks in at 12 feet. “You want as big a tunnel as possible, especially for one-offs and experimental tests, and for bridges, whose models are longer,” says RWDI technical director Will Yakimyk as he steps inside the eight-foot-tall Davies tunnel. It’s empty at the moment, a gaping hole revealing the concrete shop floor below.

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The first step in the process is building a scale model. Most of the towers are created from liquid resin in a stereolithography 3D printer based on drawings from the architect’s office. (Bridges tend to be handcrafted onsite by model builders.) Then the miniature structure is installed on a disc that features a model of the surrounding streetscape. Think of it as Google Street View in 3D styrofoam. When fully kitted out, the disc is placed on the turntable, which is raised through the wind-tunnel floor. “Models with cities can take days to build,” says Yakimyk, “and then it can take up to eight hours to install the turntable.” Once it’s in place, though, the pressure is on. Wind is blown in at 15 kilometres an hour from one end of the tunnel, but speeds of up to 70 kilometres an hour are used to test weather extremes. “At that click, you’d be knocked over,” Yakimyk says.

The disc is then rotated 10 degrees at a time, to test wind from every possible direction, sending data through a Medusa's head of cables spilling out of the tunnel floor. “For the Jeddah Tower, there were more than 1,000 cables,” says Yakimyk, with each one corresponding to a pressure point along the façade. This data is added to weather data from the past 50 years (temperature, precipitation, wind speed and direction) to extrapolate the loads the structure will be under in the real world. RWDI's input helped architect Adrian Smith, who also worked with RWDI on the Burj Khalifa, develop a tapering tripod design that makes the Jeddah Tower behave nicely on windy days. Since the spire above the occupied floors sways more, two dampers—weighing 870 and 260 tonnes—were added to help reduce displacement (and make it more comfortable for any workers who might need to enter the spire).

“RWDI has been the leader in identifying issues relating to wind interaction on buildings that had previously been unknown or misunderstood,” says Smith, adding that its work has led to significant breakthroughs in tower design, particularly on supertalls. For Smith's 7 South Dearborn Tower in Chicago, for instance, RWDI recommended including venting or notches at intervals on the facade to let the wind through, reducing both turbulence and costs, since Smith would be able to create a slimmer building using less material.

RWDI’s wind tunnel has also become legend in the industry, leading some of the biggest players in architecture—Frank Gehry, Rafael Viñoly, Sir Norman Foster—to RWDI’s modest head office (it also operates tunnels in India and the United Kingdom). “RWDI’s expertise and accuracy in tall-building testing and reporting is unequalled,” says Robert Sinn, a principal with New York—based structural engineering firm Thornton Tomasetti, which has worked with RWDI on 20 projects over two decades, including Jeddah. “We can’t do our structural engineering work, especially on tall buildings, without it.”

Being Canada, all this wind business started with snow. Back in the 1970s, the roofs on a couple of arenas in rural Ontario collapsed under the weight of the white stuff, which wasn’t properly addressed in Canada’s building code, according to co-founder Bill Rowan. Spotting a potential niche, RWDI’s predecessor company began using physical models to predict how snow would pile up and to recommend features to prevent collapse. Its engineers used a water flume, like a huge aquarium, to mimic drifting snow, a method RWDI still uses today. Silica sand simulates snow; when the water is set in motion, it pushes the “snow” around, creating drifts along model facades or piles on roofs. The company’s landmark project was the SkyDome, whose retractable roof RWDI helped design—work that eventually changed the building code.

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The physical modelling using the water flume soon expanded to wind, when Davies was hired to develop the company's first boundary-layer wind tunnel in 1977 (it sits unused on the shop floor—"we keep it for sentimental reasons,” says Soligo). While early contracts put mostly bridge designs to the test, Asia's rapidly expanding skylines in the 1990s laid the groundwork for RWDI's growth as the go-to wind engineering firm.

Now RWDI is expanding from wind-tunnel testing to urban planning with climate change in mind. “Climate and microclimate is becoming a point of differentiation for us,” says Mike Williams, head of RWDI's sustainability group, which ramped up after RWDI bought Williams's sustainable-building consultancy in 2015. “Snow-load studies and wind testing of towers are still a big part of what we do,” says Williams, the son of Colin Williams, the late engineer and founding partner of RWDI. “But we're responding to new requirements and opportunities that come with climate change.”

Since buildings account for nearly 40% of global energy consumption, RWDI is working with the University of Toronto to reduce energy consumption and CO2 emissions by retrofitting more than 100 buildings, including its heritage properties. For Enwave, RWDI provided data that helped the energy company develop a deep-lake cooling system using water from Lake Ontario, reducing CO2 emissions in the process.

But RWDI's climate engineering goes beyond individual projects. It may not be as sexy as its work on the world's mine-is-bigger-than-yours skyscrapers, but there's nothing hot about power grids failing because of too much demand for cool air during a prolonged heat wave. The science and data the company gathers and applies, even on a local level, have global implications, because when the carbon footprint for a Toronto or Vancouver building is reduced, the planet benefits. RWDI also has an ongoing contract with the National Research Council to update the current building code to include predictions and prescriptions for building on a warming planet.

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For Williams, that notion of influencing government policy is what’s most exciting. “Meteorological records going back 50 years and current climate data show there will be more demand for cooling in the future,” says Williams from behind the wheel of his Volvo. Toronto will pass from Climate Zone 5 to Zone 4—the same bracket as Washington, D.C.—in the next 20 years, he says as he wheels through a constantly changing cityscape where RWDI has been involved in more than 1,000 projects. One of its latest is a first-ever climate-resiliency assessment of 150 City of Toronto buildings. “We’re looking at how the buildings will be stressed by climate change and what those stresses are, so we can find ways to design for adaptability—buildings that work today and tomorrow,” Williams says, adding that the work has led to more climate consulting in other parts of the world, designing buildings that require less cooling in summer and less heating in winter.

Williams pulls over at the SickKids research tower, which features a high-performance curtain wall rather than floor to-ceiling windows. “Laboratories, with a ton of equipment and refrigerators, are energy hogs,” says Williams, “so you don’t need the added pressure of cooling and heating a glass cube.” The design dramatically cut the building’s energy expenditures, along with its CO2 emissions. Williams is also proud of the seemingly smaller touches: For the 2,000 scientists working, there are only 200 parking spots—"to encourage active transportation and public transit use,” he says.

Reducing car use might seem minor, but every bit counts, says Williams—not only for the environment, but also for RWDI’s growth. Because by helping organizations adapt to a warming planet, RWDI is safeguarding its own sustainability.