One of the advancing technologies in American urban spaces over the past few decades is the green rooftop terrace. These urban green spaces create a symbiotic relationship between the building, its users and the environment. Green roofs provide unique opportunities for gardening, relaxation and enjoyment in urban areas where open land may be minimal. In terms of the building, green roofs have significant insulation benefits, resulting in reduced air conditioning output in summer and lower heating costs in winter. When planning for reduced human impact on the environment we generally strive for the zero sum game of adding none and taking none away. Rainwater which would otherwise be redirected to city sewers is retained on site, absorbed into the roof planting medium and ultimately into the plants. On sunny days, ultraviolet rays are gathered by plants and converted to energy which helps the plants produce clean oxygen. Without the green roof, this sunlight would be radiated off hard surfaces, back into the atmosphere where it contributes to urban heat islands.
