There’s money in the air, especially above Union Station’s train tracks.

In a growing metropolis like Toronto, every speck of space comes with a dollar sign, from the ground beneath our feet to the air above our heads.

And increasingly, cities around the world are using that “air” — or more specifically, the rights to it — to transform skylines. Should Toronto be doing the same?

Air rights are used “to either preserve a historical building of a lower density, or the character of a neighbourhood,” said David Lieberman, an associate professor at the University of Toronto who teaches architecture and urban design.

Say, for example, a historic theatre house needs funds. If the plot of land it is located on allows for higher density/more storeys than the theatre’s status quo, the rights to that “air” can be sold to another property. The density of that property can then be increased.

Air rights can also help facilitate massive development projects, like Hudson Yards, the so-called “floating city” being built above an active train yard in New York. It’s the largest private development in U.S. history, and includes a 99-year lease with the Metropolitan Transportation Authority to the air rights above the tracks.

As Lieberman noted, the tracks that divide Toronto’s downtown, as well as the rail yards in the city’s outskirts, are cumbersome to navigate and build around. Selling air rights could offer a way to better integrate these spaces: Just imagine a new neighbourhood springing up above the tracks leading to and from Union Station.

For David Amborski, director of Ryerson University’s Centre for Urban Research and Land Development, transit air rights hold lots of potential.

“You could lease air rights above significant transit sites and transit locations, and that’d be a way to capture revenue to fund transit investment,” he said, adding he doesn’t know if building above Union Station’s train tracks is technically feasible.

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As for air rights in general, Amborski said they’re an idea Toronto has barely explored, and that comes with some risk.

“They have to be used appropriately and studied very carefully,” he said.

For example, a poorly planned air rights development could lead to conflict between lower infrastructure, like a train station, and upper infrastructure, like an apartment building or school. When the lower infrastructure was originally designed, engineers may not have considered that something might be built on top of it somewhere down the line.

Lieberman said if Toronto properly co-ordinates air rights, it can lead to much smarter urban planning based on neighbourhoods as a whole.

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“So much of our zoning here and in most jurisdictions is done on an individual property-by-property basis, and doesn’t necessarily make for an intelligent texture of the city,” he said.

Ultimately, Lieberman said, air rights should be part of a conversation about how Toronto becomes a more sustainable and enjoyable place to live.

“But you have to accept a different density of city, and is Toronto ready for that? Maybe not yet,” he said, citing the backlash against the Mirvish Towers proposal for three 80-plus-storey buildings. City council has agreed to convene a panel on the future of the proposal.

Lieberman noted New York is one of the most sustainable cities in the world because of how it consolidates infrastructure — transportation, water, power and so forth. Part of that process is the city’s longstanding history with air rights, and how residents navigate competing demands to maintain neighbourhood character and get the most out of every inch of space.

“The dispersed building of a city, such as we have — not only in the downtown core, but in Toronto as a whole — has been disastrous,” he said.

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