Council on Tall Buildings and Urban Habitat
 

Fourth Building Tall Lecture Series Installment Focuses on “Greening” High-Rise Cities

February 01, 2018

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The movement to incorporate full-height planted walls in tall buildings around the world, as well as green roofs, is gathering pace, alongside the greater “green” movement to reduce the carbon footprint and energy consumption of the built environment. A panel of experts convened on Feb. 1 at the Chicago Architecture Foundation (CAF) to discuss the potential and challenges for “Greening Tall” in the near future. This, the fourth and final installment of the CTBUH / CAF joint lecture series, “Building Tall,” continued the format of the original three, by beginning with a short Pecha Kucha (20 slides in seven minutes) presentation, followed by a panel discussion.

First to present was Yibo Xu, Co-founder of the Chinese branch of Stefano Boeri Architetti, which has become well-known for its “vertical forest” projects, first in Milan, Italy  with the Bosco Verticale and now around the world. The firm is now designing more than 10 such projects. These include a twin-tower project in Nanjing, China, an 80-meter hotel near the Bund promenade in Shanghai, as well as Paris; Eindhoven, Netherlands; and Lausanne, Switzerland. In describing the projects, which will bring more than 500,000 square meters of new planted area to China alone, Xu described the steep education curve needed to make the projects viable.

The event included presentations (from left to right) by Luke Leung, Director of MEP / Sustainability, Skidmore, Owings & Merrill; Sara Beardsley, Senior Architect, Adrian Smith + Gordon Gill Architecture; Reed Kroloff, Partner, jones/kroloff (moderator); Molly Meyer, CEO & Founder, Omni Ecosystems; Yibo Xu, Co-founder, Stefano Boeri Architetti China.
Xu’s team needed to persuade the government that balcony-planted trees would withstand typhoons, and ultimately had to travel to RWDI’s wind lab in Canada in order to model the conditions correctly. Other adjustments had to be made to standard nursery practices in China, so that the trees would predominantly grow vertically and limit their horizontal span. In the end, tree selection at the Nanjing project – with one tower going up to 200 meters – was limited to 14 species.

The second presentation, by Sara Beardsley, Senior Architect, Adrian Smith + Gordon Gill (AS+GG) Architecture, was less literal in its interpretation of “greening tall” but just as diverse. Beardsley noted the success of using tilted glass facades along the height of Seoul’s FKI Tower, so that optimal solar angles for photovoltaics and views were both achieved.

“We thought of the façade as not an extrusion, but as a 3D opportunity to make energy as well as cut the energy load,” Beardsley said.
The audience packed into the Chicago Architecture Foundation's lecture hall to listen to presentations by an impressive selection of experts. Yibo Xu, Co-founder, Stefano Boeri Architetti China, described the steep education curve needed to make the projects viable.
Façade manipulation was also a key strategy in another major project shown, the Wuhan Greenland Center in China. The tapering, ovoid tower has several multi-story notches cut into its broad face to admit the wind. This reduces wind pressure on the façade and allows for a thinner and less embodied-energy-consumptive structure, which also has the benefit of being cheaper. Solar shading is attached to the façade at key locations.

Luke Leung, Director of MEP/Sustainability, Skidmore, Owings & Merrill, took a holistic, humanistic approach to the question of how to get “greener.” Referring to his work on the CTBUH 2016 International Research Seed Funding Project, “Vertical Variations in Indoor Exposures to Outdoor Pollutants in Tall Buildings,” Leung noted that the higher temperatures and particulate matter levels at the street could be mediated by not only more people inhabiting tall buildings, but by designing the buildings to alleviate these conditions on the ground.

“If we allow the wind to flush through the bubble that forms at street level, it can create a comfortable condition,” he said. At a broad regional scale, cities have much more work to do in densifying to a level that will truly profit the environment. Even in a city such as Chicago, with many tall buildings, the average height of all buildings is only 4.8 meters – about the height of a London double-decker bus, Leung said.
Sara Beardsley, Senior Architect, Adrian Smith + Gordon Gill Architecture, noted the success of using tilted glass facades along the height of Seoul’s FKI Tower. Luke Leung, Director of MEP/Sustainability, Skidmore, Owings & Merrill, took a holistic, humanistic approach to the question of how to get “greener.”

More than any one design solution, Leung said, the key to a better future lies in cultivating a culture that is in close contact with, and thus values nature – an increasing challenge in a world with so many distracting electronic devices and the night skies blotted out by city lights. Bringing nature into daily city life is one way to counteract that.

Building on this theme, Molly Meyer, CEO & Founder, Omni Ecosystems, explained how her approach to greening tall was taking a requirement for green roofs on certain types of developments in Chicago and turning it into an opportunity to gain social as well as financial value from rooftop gardening. By arrangement with its sister company, Roof Crop, Omni Ecosystems designs and sells planted, harvestable rooftops, and Roof Crop harvests and maintains them at no charge to the building owner. The food is sold to local restaurants. The partnership has led to a commercial farm some 46 meters above grade, and a field atop the offices of Studio Gang Architects that produced 27 kilograms of wheat in one growing season. Joint research with Perkins + Will has determined that, if every arable rooftop in Chicago were actually planted, it would yield more than 4.5 million kilograms of wheat – enough to make bread for the entire city for one month, each year.

Molly Meyer, CEO & Founder, Omni Ecosystems, explained how her approach to greening tall capitalized on Chicago’s requirement for green roofs on certain types of developments.
Luke Leung answers an audience question as the panel looks on.
After their presentations, the panelists answered audience questions about the cost-effectiveness and broad applicability of green design strategies.

Referring to a project in which AS+GG proposed a full-building retrofit of Chicago’s Willis Tower, which would have resulted in an 80% reduction of energy use, Beardsley explained why only portions of the plan was adopted – the 25-year payback was too long for the owner to justify.

“Energy is very cheap in the US, so there is not much incentive to green existing buildings,” she said. “The owners would have had to increase leasing rates and recoup the costs in other ways.”

On the other hand, if green buildings and lifestyle continue to be the subject of major marketing campaigns, some owner/developers see the financial value of “greening tall.”
Following the event, guests were given the opportunity to mingle and engage in deeper discussions with the panelists.

“A green roof is an upcharge,” Meyer said. “But the sales process is trying to understand what the building owner envisions in the long term. Is green space part of the brand identity? We find that lease upgrades happen faster for buildings that have outdoor space. It has to be presented in metrics that matter to developers.”

Referring to his earlier comments about the potential for cities to go higher and denser, Leung clarified, “We don’t need to be Manhattan in order to get benefits from increases in density. If you look at Paris, that is a very efficient and dense city. Intrinsically, that model has been supportable for centuries. And in terms of money, if you think carefully, you can minimize green strategies’ cost impact. If you position a tree well, you can lower the cooling load on the building. People at the higher levels do breathe cleaner air – and if you look at the holistic costs and benefits , for instance, if your health-care costs are lower due to better air quality – that has a value.”

At the end of the program, the audience milled about for some time, eager to engage the panelists further about the potential for city dwellers to get closer to nature, while still enjoying all the cultural benefits of city life.


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