Green roof

©  2009  Rose George

Hurrah for the US’s General Services Administration, which owns and manages more than 1500 federal buildings in the country, and for the Pentagon. Both plan to use some of their stimulus money ($4.5 billion for the GSA; $7.4 billion for the Pentagon) to green their roofs. At the Interior Department headquarters in Washington D.C., a 5000 square foot roof garden is already in place. In this Federal Times report, Interior Department official Michael Cyr, calls a green roof a good investment because “it can double or even triple the life of a roof, reduce the heat island effect that warms buildings during the summer months, and mitigate the effects of carbon emissions in the atmosphere — all the while saving the government energy and maintenance costs” But the biggest benefit is that it helps out overloaded sewers. “During heavy rains, water that hits impervious surfaces such as buildings, roads and parking lots flows into city drains. The city’s sewer system is unable to handle the excess water and ends up overflowing, releasing more than 1 billion gallons of raw sewage into surrounding rivers each year, [Cyr] said.” The Department of the Interior’s roof cost $228,000 and, according to the piece, will “retain up to seven-tenths of an inch of rainfall, enough to retain 93 percent of water from all storm events in Washington.” 93 percent? Really? If that’s true, it’s extraordinary. And extraordinary that everyone doesn’t immediately lay turf on their roof-tiles.