The Mayor's office in NYC recently announced a $106 million plan to plant trees and carry out other activities to reduce the "heat island" effect in New York, concentrating mainly on Northern Manhattan, the South Bronx and Central Brooklyn.
As someone who lived in Tokyo for around 8 years, I'm very familiar with the heat island effect of a large concrete-covered city. In Japan at least, there has been some effort to combat this. One policy, for example, requires that 20% of all new flat roof surfaces are covered with plants on public buildings exceeding 250 square meters, and 10% of all flat roofs on private buildings exceeding 1,000 square meters.
But why green roofs? Green roofs can help reduce the flow of heat into and out of the surfaces they cover - meaning that the summer sun heats up our buildings less. But additionally, they can reduce wear and tear on an actual roof surface, reduce stormwater runoff, reduce winter heating costs, and even dampen noise. Greenery is obviously also more appealing than concrete.
The IGRN Case Study has a good summary of Tokyo's Green Roof policy, which includes some of the following facets:
- Building, landscape, energy, or other code or policy (e.g. land-use plan, green roof bylaw, zoning code, green factor, design regulations, etc.)
- Reduced stormwater fees
- Financial Incentives & Tax Credits
- Favorable Credit Terms
- Density Bonuses
- Demonstration Projects
- Ecological Labels
- Education and Information (e.g. seminars, conferences, green roof tours, etc.)
- Local Green Roof Guidelines
- Consultancy offer for constructors, investors, building owner
In addition to mandatory green roofs, there are also some architecturally-striking examples of green roof design across Japan that are more about inspiration than eco credentials.
Above, BAKOKO's concept for Doshisha University's campus in Kyoto.
It's early days, but we strongly support initiatives to increase greenery in cities, whether that's on roofs, in parks, or even small plantings by roadsides. Fellow Farming.NYC member Urbanstrong consults on, and builds green roofs, living walls and other installations in New York. More details on the NYC funding plan in The Gothamist.