Reflective Materials
Traditional construction materials contribute to the Urban Heat Island Effect by soaking up solar radiation, converting this to heat, and transmitting it to the air above them. The darker the material, the more dramatic the effect, and recent studies have shown that conventional rooftops and sidewalks can reach peak summertime temperatures of 49°C to 77°C. One answer is to use materials that have a higher Solar Reflectivity Index (SRI). In Phoenix, Arizona, a 8,400-square-metre car park recently "went green" when traditional black asphalt was swapped for Celadon Green, a new solar reflective coating that will reduce surface temperatures by up to 17°C. Recent research by Columbia University also showed that rooftop surface temperatures in Manhattan were reduced by as much as 24°C when tar and asphalt were replaced with a permanent white polymer coating.
Shade
Although it is yet to open, the new headquarters of the Abu Dhabi Investment Council has been recognised as one of the world's most innovative buildings and a project that will influence the design of skyscrapers the world over. The Al Bahr towers are protected from the kind of overheating experienced by normal, glass-clad high rises by a "dynamic mashrabiya", a robotic shade screen that will open and close in response to the sun. Not only does the mashrabiya reduce the amount of energy required to cool the building, its transparency reduces the need for artificial lighting during daytime, producing energy savings and a reduction in the building's carbon footprint of 20% to 50%.
Vegetation
Measuring a full hectare in area, the California Academy of Sciences in San Francisco has one of the largest living roofs in the world. Made of a tapestry of native plant species, the roof consists of 50,000 porous, biodegradable planting trays that are bound together, like a jigsaw, by the plant's roots. Not only does the roof helps to cool the building beneath by 6°C, it also recycles rainwater, converts carbon dioxide into oxygen, and reduces the amount of energy required for cooling and heating. Given that one sixth of all the electricity consumed in the USA is used for cooling buildings, vegetated roofs and walls have a considerable contribution to make in reducing carbon dioxide emissions and combating the Urban Heat Island Effect in temperate and tropical regions around the world.
* The National
