Sallan Looks Back. London's a leader in urban sustainability, which makes PlaNYC 2030 news in London. Nancy provides the back story on where buildings fit into the mix.

Great to see what Mayor Bloomberg's PlaNYC look like from "across the pond". I'd like to add some thoughts from a New Yorker's perspective. The key to success for NYC, and I suspect for London too, is greening its building stock.

With any luck, a building constructed today can last 50, 80 or a 100 years and its lifespan will literally embody today's money, materials, and norms. Less fortunately, this building also will create a decades-long carbon footprint whose final size will be determined by the structure's energy consumption and resulting greenhouse gas emissions. To cut 16.7 million tons of greenhouse gas emissions per year, PlaNYC 2030 calls both for improving energy efficiency in existing buildings as well as requiring that new construction be energy efficient. Shrinking our carbon footprint by 16.7 million tons translates into meeting fully half of the City's entire carbon reduction goal.

Because the stakes are so high, let's see where we are now. Looking only at existing buildings, PlaNYC predicts that 85% of New York City's current building stock will be standing in 2030. Since concerns over carbon footprints and climate change are of recent vintage, a walk down any NYC street offers a glimpse of the carbon challenge embedded in our 950,00 standing structures. And it is a challenge because we cannot get anywhere near the City's 30% target for reducing the size of our carbon footprint by the year 2030 if these existing buildings aren't altered or "retrofitted" to become high performance green machines.

Of all New York's older buildings, exactly one has achieved a United States Green Building Council LEED rating. Although overlooked by the New York Times, the New York Mercantile Exchange achieved a LEED for Existing Buildings certification in 2007. Additionally, twenty-three existing buildings have earned Energy Star labels. This adds up to twenty-four high performance retrofits. That's a starting point.

Consider these 24 buildings as the "cream of the crop". The entire number of energy-improved buildings is certainly larger, but there is no aggregating, authoritative record keeper to cite. "Without publication there is no discovery" is the rule-of-thumb here.

London, how do you do keep score?