Super tall skyscrapers are popping up in cities around the world, and it’s never been more important to understand how to design a super tall green building.
Here in the Seattle area, Amazon is preparing to build its tallest office tower yet in Bellevue Washington, called Bellevue 600 while several developments around the world are preparing to surpass the height of One World Trade Center. The Council of Tall Buildings and Urban Habitat (CTBUH) observed that the past decade has witnessed the completion of more skyscrapers than any previous decade in history.
Getting air, water, and energy 800 feet up requires a specialized approach to building engineering. Third-party certifications like LEED, WELL, and Living Building Challenge provide a common language for sustainability that can be applied to a sustainable skyscraper or super tall building, but the rating systems don’t provide guidance for designers, developers, and builders of super tall structures about how to navigate the unique design challenges of these projects.
Wind and Air’s impact on super tall green buildings
Wind changes from season to season and city to city and is the biggest challenge faced by tall building engineers. In fact, the interplay between super tall buildings and the wind is so strong that super tall buildings can have adverse effects on microclimate due to wind funneling and turbulence that impacts the people and wildlife outside the building. Further, building facades are home to bats, birds, insects, windblown seeds, microbes, and spores – all heavily impacted by a super tall façade and its influence on the wind.
Today’s supertall buildings are designed to bend, not break. Complex systems of counterweights, dampers, and devices to mitigate movement, and these systems often account for the added costs required to engineer and build a super tall building.
When it comes to fresh air, the project needs to balance ventilation schemes with fire safety. Will a double façade create a chimney? How will natural ventilation impact smoke movement? Outside ventilation is often introduced into technical floors via outdoor air louvers and distributed within the building’s core. There may be vertical shafts. Operable windows, balcony doors, vestibules, and rooftop amenities are precarious in super tall buildings unless designed to meet the basic principles of isolation and control.
Water in a super tall green building
Speaking of wind, super tall buildings sway in heavy winds, which can impact the plumbing system. While the mild jostling caused by extreme winds at 800 feet up might unsettle an occupant, it can be much more influential on the sloshing of water within the structure.
Inside the building, a critical issue in a super tall building is water pressure. If the municipal water supply can’t meet the needs of the building, engineers may need to include a pressure-boosting system.
A super tall building can’t operate with a single pump because the amount of pressure needed to force the water up the height of the skyscraper is dangerous. Engineers need to consider a series of tanks and pumps distributed throughout the height of the building. Because there are multiple pumps throughout the building, there are also multiple opportunities for greywater and rainwater treatment to serve the landscaping and operational needs throughout the height of the building.
Of course, the system also needs to include fixtures that can deliver the desired water pressure under the desired conditions. When it comes to sustainability strategies and water, low flow fixtures create an opportunity simply because of the scale of the project and the number of fixtures to be impacted.
Energy in a super tall green building
Because high-density urban projects have been prioritized for energy benchmarking efforts, skyscrapers and super tall buildings are typically a leading building typology in terms of sustainable energy performance. While the assessment is complex, research indicates that overall, tall buildings save energy relative to an equivalent floor area of low-rise buildings. (source) Their carbon impact is a different story (see below.)
Super tall buildings can function like vertical cities, so there are diverse needs for heating/cooling and power. The surface area presents an opportunity to deploy solar panels, photovoltaic cells, and wind turbines. And as vertical cities, they can be ideal for the installation of an integrated energy plant, serving the tenants and occupants in the building through a combined and highly efficient heating/cooling and power distribution plant. Additional descriptions of systems and technologies that are proven globally for super talls can be found here.
Large utility networks often offer utility frequency modulation programs, where private owners of battery storage systems supply on-demand capacity back to the grid, so utility companies can avoid operating expensive standby natural gas-fired peaker plants. (source)
It’s just as important to operate a super tall building sustainably as it is to design it sustainably. Uniformity of systems will make it easier for future facilities teams to properly operate the building. Design and engineering teams should standardize air handling units, heat exchangers, pumps, storage tanks, electrical switchboards, transformers, and systems risers whenever possible.
Carbon in a super tall green building
The creation, operation, and maintenance of buildings accounts for more than 50% of greenhouse gas emissions. With the increase in building height, the amount of carbon dioxide discharged by a building increases significantly during its life cycle. The carbon emissions are composed of embodied carbon, operating carbon, and demolition and disposal carbon. While super tall skyscrapers tend to perform well on energy, they are less successful in minimizing carbon emissions.
In a study of 40 super tall buildings in Hong Kong, it was found that embodied carbon of steel and aluminum in Hong Kong buildings was more than that in concrete buildings. This research explores a comparison of carbon impact on three buildings of similar size with different building materials and is a worthy read.
Density is one strategy to mitigate the carbon impact by housing more people on a smaller footprint. But the systems, materials, and foundations needed to support a super tall building cut back the environmental advantages achieved through its density. Buildings at increased scales allow for greater investment in design, technology, and systems that support the building and allow help to be provided easily by delivering goods and services to fewer locations.
One of the best ways to reduce carbon emission is to build compact places where people accomplish more with less driving – tall and super tall buildings support that recommendation. Studies illustrate that cities like Hong Kong and Singapore, where clustering of tall buildings is the norm, are among the world’s most transport-energy efficient. Tall buildings in a compact urban core can reduce the per capita carbon footprint of a city compared to a suburban project. (source) Consider the Abeno Harukas in Osaka Japan, which houses a hospital, art museum, retail, office, hotel, and railway station, all within one building.
Sky gardens present an opportunity to mitigate carbon. The Abeno Harukas also brings green space in the program, with numerous atria, rooftop parks, and circulation spaces.
Where vertical forests were once an aspirational concept, they are increasingly normalized, with developments such as Bosco Verticale designed by Stefano Boeri Architects, which contains more than 800 trees and 14,000 plants housed on steel-reinforced balconies going 116 meters up.
The 545 foot Tower at PNC Plaza also includes a five-story indoor “park in the sky” on a top floor, which helps to offer a low energy and seasonal space and is ventilated with fresh air.
Super Tall Buildings Must Be Green
Engineering makes the impossible possible. Consider the Empire State Building, which is a symbol for skyscrapers in the early 20th century – it is 424 feet across at its widest point. This contrasts with 432 Park Avenue, which is 100 feet taller and has a base that is only 90 feet at its widest point. (source)
Is it possible for skyscrapers, so separate from nature with all their glass, concrete, steel, and engineering, to be part of the environmental solution? In dense cities where wild spaces are scarce, is being in the sky going to give the same biophilic rush as being at the shore?
As we have worked on tall and super tall buildings such as the World Trade Center and The Tower at PNC Plaza, we’ve seen first-hand that the rating systems provide structure but not a roadmap to achieve the sustainability goals for skyscrapers. The complexity of super tall buildings means that there is an abundance of opportunities to streamline, optimize, and integrate the various systems to achieve maximum benefit for minimum environmental impact.
- Ten Tallest Buildings under construction or in development around the world