Tech companies are always battling each other for the title of the greenest organization out there and these so-called green roofs are the latest turf for these environmentalist wars. Both Facebook and Google have a green roof project in the works. In Facebook's just released plans, it outlines the design for the top of its brand new Frank Gehry designed headquarters, which will certainly be green in color, at least. The social network says it will "plant a ton of trees" on the rooftop garden, which will span the entire length of the 433,555 square foot building. In fact, both of these spaces will look more like parks than roofs, with cafes and kiosks, sprinkled alongside pathways with outdoor seating. But beyond that what makes a green roof green?
Minimizes Runoff: Normal roofs push rainwater onto city streets where it has the potential to flood, increase erosion, and push sewage into rivers. It can also pick up more "impurities"—like bacteria and pesticides—on the way down through storm sewers, which eventually end up in water. All those plants on top of Facebook's roof will help mitigate this run-off. Other buildings also find alternative uses for water, such as using it for flushing toilets. One study found that green roofs reduced runoff by more than 75 percent, according to the EPA. Another one found othe green building tops could remove up to 95 percent of the cadmium, copper, and lead from stormwater runoff alone.