Green City

Green City

Green Construction

Buildings are responsible for more than half the world's energy use, thus thinking sustainably requires attention to how buildings can be designed, constructed, and operated to use less energy and fewer material resources (Susan and Kira, 2008).

Two central objectives in green design are to reduce energy use, especially the use of fossil fuels, and to minimize the wasteful use of resources. The aim of designing green buildings is to produce zero net energy; this is achieved through conservation measures and by using the building or site to produce energy with renewable sources, such as geothermal, solar, or wind power. Any surplus may be sold back to the local energy grid. The latter goal, minimizing use of resources, may be achieved by using smaller amounts of materials, using recycled or salvaged materials, using materials that are produced in a sustainable way or without harmful chemicals, or by some combination of these.

Reducing Energy Use

Before modern (usually fossil-fuel generated) methods of heating, cooling, and lighting became standard in the Western world, builders designed their structures to respect and work with climate and site conditions. In northern climates, for example, buildings were designed to minimize exposure on the northerly side through use of berms and limitations on the size and amount of windows. Exposure was maximized on the south-facing sides, allowing buildings to take advantage of passive solar gain. Southern overhangs were calculated using sun angles to allow low angled winter sun to penetrate windows, yet block solar radiation during the warmer months (Maria, 2004).

Deciduous trees were planted to shade buildings in the summer and allow sun to reach roofs and walls during the winter. Evergreen hedges provided windbreaks on the northern sides. Windows and doors were situated to maximize natural ventilation and natural lighting where most needed during the daylight hours. In colonial America, a large masonry chimney absorbed heat from fireplaces and radiated it into adjacent spaces. In climates with moderate to heavy precipitation, roofs were sloped to prevent water or snow from collecting and leaking into interior spaces. Natural, renewable materials, such as wood, sod, and straw were the building materials of necessity.

Many of these techniques and materials began to receive renewed attention in the 1970s, when oil shortages and spiking prices refocused design attention on energy conservation. In particular, this period focused attention on efficient building envelope designs and materials that would conserve energy, such as new forms of insulation with greatly increased insulation capacity (Charles, 2008).

More recently, concerns about global climate change through increases in atmospheric concentrations of greenhouse gases, coupled with geopolitical and technical limitations on mining petroleum reserves, have renewed interest in green building. Green-oriented websites and magazines provide a wealth of information for the do-it-yourself renovator or small contractor, while architectural and engineering firms working on large industrial and office buildings have also accepted the challenge of designing buildings with zero or low net energy loads.

Designers have adapted techniques used in smaller buildings, like shading and natural ventilation; they have ...