When Oxford Properties upgraded its Waterpark Place I and II towers from LEED Gold to Platinum, it marked the first time existing North American buildings were re-certified as such. (Talk about following through on a New Year's resolution.) It also helped Oxford secure top ranking in a global sustainability survey released today.

This is the second year in a row Oxford has scored No. 1 spot in the Global Real Estate Sustainability Benchmark (GRESB) survey in the North American Diversified-Office and Retail category. SVP Andrew MacAllan (above) tells us his firm earned the accolade by increasing the LEED-certified buildings in its portfolio to 60% in 2014, up from 40% a year before. And Oxford’s retail portfolio achieved 87% BOMA BESt certification in 2014, versus 77% a year earlier. Plus all Oxford-owned hotels are certified Green Keys, “the hotel version of LEED,” says Andrew, who’s also chair of the Canada Green Building Council.

The upgrade of Waterpark Place I and II (built in 1986 and 1990 respectively) was a huge effort, Andrew says. It was spurred by the fact that the project's third phase (below, it opens next month)—a 1M SF tower with RBC as its anchor tenant—is targeting LEED Platinum with an array of innovative sustainability features, including individual-workspace climate and lighting controls and fresh-air supply on every floor. Oxford couldn’t let the older buildings seem like “poor cousins,” says Andrew.

The WaterPark I/II upgrade was ”the right thing to do,” Andrew says, but it was a business decision above all else. Greener offices are top of mind for most companies these days as they seek to attract young talent. And Andrew says he's had significant tenants tell him they’ll only renew their leases if the workplaces are LEED certified.