Tuesday, April 21, 2009


Green Roofs - A new approach to building sustainable urban environments are buildings built with green roofs. Actually, this is an approach that might have been utilized to help cool one of the first cities in ancient times -- i.e. the hanging gardens of Babylon. Unfortunately, most modern cities with all of their concrete consist of 85 percent nonpermeable surfaces. Such nonpermeable surfaces both reflect heat and result in stormwater runoff that catches pollutants before it runs into our streams, rivers, and estuaries. Green buildings help to catch rainwater and reduce stormwater runoff. Green buildings also help to absorb heat and thus reduce the "heat island effect" created by all the concrete of our urban areas that cause cities to be hotter than the surrounding area. This, in return, reduces the need for air-conditioning and energy usage. Green roofs also can help to absorb carbon dioxide from the air. Both can help reduce global warming. In recognition of this, on Earth Day 2009, the City of New York announced incentives and regulations to require the conversion of all buildings in New York City to green roofs where there can be shown to be an economic benefit. Chicago is another city that is aggressively promoting the conversion of buildings to green roofs. The Chicago City Hall was one of the first public buildings in the U.S. to install a green roof. Chicago also has turned an old industrial building into the Chicago Center for Green Technology to demonstrate green technologies and to provide green advice to individuals, including help on how to build a green roof. What makes green roofs attractive today are new plastic membranes that are laid on the roof to collect the rain water run-off. A special soil is then put on top of the membrane in which plants are grown. The plants in turn absorb much of the rain water, thus reducing the stormwater runoff produced from the building. Also, the temperatures on a green roof are typically only one tenth that of a regular roof. Above is an example of a green building built recently in Fukuoda, Japan. Another exciting example of the use of a green roof is a gas station in Eugene, Oregon that sells biodiesel, uses solar panels on the roofs of the pump islands to produce electricity, and has a green roof on the station's convenience store.