In many cities around the globe, a skyscraper building boom threatens to diminish the amount of sunlight that reaches street level. Sydney and Melbourne share top honors for skyscrapers in Australia, both claiming 31 structures over 150 metres.
Brisbane tallies 13 skyscrapers, the Gold Coast comes in with seven, Perth has five, and Chatswood has two. Approximately 50 more are under construction, approved, or proposed. Will the residents of tomorrow's cities be starved of sunlight?
Manhattan is currently home to 41 towers of 700 feet and taller, with 34 more underway or proposed. London takes it even further, with more than 230 new towers planned and under construction.
While this may be welcome news for architects, developers, and apartment owners in those towers, what’s the effect at street level? Will sunlight be restricted for everyone but the wealthy?
No, that won’t be the case, but there will certainly be districts where dense blocks of towers will block much of the sunlight from reaching the street level. However, it’s not just condominium projects for millionaires and billionaires that are creating more shade.
Many dense cities are facing intense demand for affordable housing, which must compete with market-rate projects for buildable land, leading to calls for taller buildings. According to The Washington Post, New York Mayor Bill de Blasio has proposed 88,000 affordable housing units to be built over the next 10 years. Toronto has built more than 67,000 units in the last five years. With a limited supply of land, municipalities will change zoning laws, and many of these projects will be built taller than would have been considered a decade ago.
As zoning rules now stand, skyscrapers are not permitted everywhere, so zoning remains a bulwark against over-densification through excess building heights. Air rights, not commonly used in Australia, are another tool for both limiting and increasing building heights. Air rights are the legal right to use the space above a building. Developers can purchase air rights from adjoining structures in order to increase the size of their projects.
Australia’s dense urban areas are facing the same problems, and in need of solutions for both the practical and social issues associated with taller buildings and loss of sunlight. In addition to zoning rules, technological solutions might also play a role. By using software to track sunshine, architects and planners can manipulate the shape, orientation, and spacing of towers to reflect light into the plaza spaces at street level.
Alex Washburn of architecture firm NBBJ, and formerly the chief urban designer for New York City under Mayor Michael Bloomberg, tackled the challenge with design he calls “heliostatic massing.” While working on a large-scale project in 2008, he wrote that his team struggled to fit in all the required building area on the site while also making way for sunlight in the central park area. Washburn and his team wondered about reflecting sunlight with the towers themselves, and tested the idea.
“We looked for property that was adjacent to a shaded public space (in the northern hemisphere,)” he wrote, “typically to the north of that space, where a building would be ideally positioned to bounce sunlight all day), and where the surrounding lots would not allow future development to block the sunlight.”
Architect Christian Coop, also with NBBJ, explains the “No Shadow Tower” here:
“Unlike other reflective towers,” he wrote, “which have concave surfaces that focus the sun’s rays like a magnifying glass, No Shadow Towers reflect pane by pane. This creates pools of sunlight and a moving light show on the ground, reducing shade up to 50%.”
Though this type of design is not part of zoning requirements yet, it offers the potential to mitigate some of the objectionable facets of skyscrapers, making them more hospitable for all users of a city. As capital concentrates in cities around the world and cities further densify, Washburn noted that “regulations such as these could improve the quality of life for all city residents, not just the occupants of a particular building.”