Text 1 The Concept of Green Building

Buildings have a profound effect on the environment, that’s why green building practices are so important to reduce and perhaps one day eliminate those impacts. In the United States alone, buildings account for: 39 % of total energy use, 12 % of total water consumption, 68 % of total electricity consumption, 38 % of total carbon dioxide emissions.

On the aesthetic side, green architecture or sustainable design (the two terms are often used interchangeably to relate to any building designed with environmental goals in mind) is the philosophy of designing a building that is in harmony with the natural features and resources surrounding the site. There are several key steps in designing sustainable buildings: specify 'green' building materials from local sources, reduce loads, optimize systems, and generate on-site renewable energy.

Building materials typically considered to be 'green' include rapidly renewable plant materials like bamboo and straw, lumber from forests, stone, recycled metal, and other products that are non-toxic, reusable, renewable, and/or recyclable. Building materials should be extracted and manufactured locally to the building site to minimize the energy embedded in their transportation.

Low-impact building materials are used wherever feasible: for example, insulation may be made from low VOC (volatile organic compound)-emitting materials such as recycled denim, rather than the insulation materials that may contain carcinogenic or toxic materials such as formaldehyde. When older buildings are demolished, frequently any good wood is reclaimed, renewed, and sold as flooring. Many other parts are reused as well, such as doors, windows, mantels, and hardware, thus reducing the consumption of new goods. When new materials are employed, green designers look for materials that are rapidly replenished, such as bamboo, which can be harvested for commercial use after only 6 years of growth, or cork oak, in which only the outer bark is removed for use, thus preserving the tree.

To minimize the energy loads within and on the structure, it is critical to orient the building to take advantage of cooling breezes and sunlight. Daylighting with ample windows will eliminate the need to turn on electric lights during the day (and provide great views outside too). Passive Solar can warm a building in the winter - but care needs to be taken to provide shade in the summer time to prevent overheating. Prevailing breezes and convection currents can passively cool the building in the summer. Thermal mass stores heat gained during the day and releases it at night minimizing the swings in temperature. Thermal mass can both heat the building in winter and cool it during the summer. Insulation is the final step to optimizing the structure. Well-insulated windows, doors, and walls help reduce energy loss, thereby reducing energy usage. These design features don't cost much money to construct and significantly reduce the energy needed to make the building comfortable.

Optimizing the heating and cooling systems through installing energy efficient machinery, commissioning, and heat recovery is the next step. Compared to optimizing the passive heating and cooling features through design, the gains made by engineering are relatively expensive and can add significantly to the projects cost. However, thoughtful integrated design can reduce costs, for example, once a building has been designed to be more energy-efficient, it may be possible to downsize heating, ventilation and air-conditioning (HVAC) equipment, leading to substantial savings.

Onsite generation of renewable energy through solar power, wind power, hydro power, or biomass can also significantly reduce the environmental impact of the building. Power generation is the most expensive feature to add to a building.

Good green architecture also reduces waste of energy, water and materials. "Greywater", wastewater from sources such as dishwashing or washing machines, can be used for non-potable purposes, e.g., to water lawns, wash cars, etc. Rainwater collectors are used for similar purposes, and some homes use specially designed rainwater collectors to gather rainwater for all water use, including drinking water.

Green building often emphasizes taking advantage of renewable resources, e.g., using sunlight through passive solar or active solar , and photovoltaic techniques. Passive solar technologies convert sunlight into usable heat, cause air-movement for ventilation or cooling, or store heat for future use, without the assistance of other energy sources. Technologies that use a significant amount of conventional energy to power pumps or fans are classified as active solar technologies. Passive solar technologies often yield high solar savings fractions, especially for space heating; when combined with active solar technologies or photovoltaics even higher conventional energy savings can be achieved. Photovoltaics, or PV for short, is a technology in which light is converted into electrical power. It is best known as a method for generating solar power by using solar cells which require protection from the environment and are packaged usually behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels (Fig. 4.1).

Figure 4.1 - Solar panels

 

A good example of sustainable architecture is K2 apartments in Windsor, Victoria, Australia designed by Hansen Yuncken in 2006 (Fig.4.2) which features passive solar design, recycled and sustainable materials, photovoltaic cells, wastewater treatment, rainwater collection and solar hot water.

 

Figure 4.2 – K2 sustainable apartments by Hansen Yuncken