A recent survey found that Washington D.C. led the charge in installing green roofs in North America, vastly outperforming all other cities and taking the lead spot for the third straight year.

Green Roofs for Healthy Cities’ 2013 Annual Green Roof Survey found that Washington D.C. installed more than 2 million square feet of green roof space in the year. In comparison, runner-up Chicago managed to install less than 800,000 square feet.

Three Canadian cities made the top 10 list, with Toronto, Montreal and Calgary placing number eight, nine and ten respectively.

The survey found that North America’s green roof industry grew by 10 per cent in 2013. Nearly 6.5 million square feet of green roof space across 950 projects was installed in 2013. The year prior saw the installation of just over 5.5 million square feet.

It also noted that a “significant development” in 2013 was that more square feet of green roof space were installed on public buildings compared to private ones. That said, the actual number of green roofs installed on private buildings far exceeded those created in the public sector.