Eco-buildings take on many forms; they can be schools, offices, community halls or places of worship. These buildings are also known as green construction or sustainable building. When building these structures the materials are environmentally friendly and efficiently resourced right from the beginning of its lifecycle from design through to construction, operation and maintenance.
Although new technologies in relation to eco-buildings are being discovered all the time, the main aims of these buildings are to efficiently use water, protect the health of employees, and improve productivity and to protect all users of these buildings. They also aim to reduce waste and pollution to reduce their impact on the local environment. However green construction does not address the issue of refitting existing homes, corporate and public buildings.
The idea of environmentally friendly construction first came to light in the 1970s during the fossil fuel crisis and pollution concerns. The eco-building movement originated in the US, with the need for more energy efficient and environmentally friendly construction practices which would benefit all, economically, socially and environmentally.
Environmentally friendly construction uses a range of practices which will hopefully eliminate the impact of new buildings on human health and the environment. It often uses renewable resources ie using sunlight for solar heating and hot water, and using plants and trees for green roofs and rain gardens to reduce rain water run off. Cracked gravel or permeable concrete is used in place of conventional concrete. This enhances replenishment of ground water.
The essence of green building is applying one or more of the following principles:-
- Siting and Structure Design Efficiency
- Energy Efficiency
- Water Efficiency
- Materials Efficiency
- Indoor Environmental Quality Enhancement
- Waste and Toxics Reduction
The practices or technologies used in eco-building are constantly changing and may indeed differ from place to place, but the above principles are applied in some form and with proper design individual eco-building technologies can work together to greater effect.
The philosophy of designing an eco-building is that it is built in harmony with the natural environment surrounding it. There are several steps in designing eco-buildings that specify “green” building materials from local sources, reduction of loads and generate on-site renewable energy.
The concept stage is one of the major steps in the life cycle of the building project, as it has biggest impact on the cost and performance of the eco-building. The objective in designing eco-buildings is that the total impact on the environment is minimal at all stages of building. The building process varies from site to site never repeating itself identically as every piece of land is different and has different needs. Eco-buildings are more complex and any variation in design may affect the surrounding environment during the building’s particular life-cycle stage.
Eco-building nearly always includes measures to reduce energy use. The building envelope (“the barrier between conditioned and unconditioned space”), high efficiency windows and insulation in walls, ceilings and floors are often used. Passive solar building is often used in environmentally friendly homes. The designer may place, windows, walls, porches and trees to shade windows and roofs in the summer but this will also maximise solar gain in the winter. Daylighting also known as effective window placement provides more natural light during the day which lessens the need for using electric lights during the day. Water heated by solar power also reduces the energy used. Generating power is usually the most expensive part of an eco-building.
Water consumption and water quality are the key objectives used in eco-building. A major issue surrounding water consumption is that in some areas the demands on the local water supply exceed the possibility of replenishment. To overcome this problem, the protection and conservation of water can be achieved by designing a dual plumbing system that recycles water when the toilet is flushed. Water wastage can be reduced by fitting water saving fixtures such as ultra-low flush toilets and low flow showers. Bidets can help eliminate the use of toilet paper and increase the possibilities of re-using the water on site. Treating water at the point of use improves both the quality of the water and increases energy efficiency whilst reducing the amount of water circulating around the site. Using non-sewage waste water on site for irrigation will minimise the impact on the local water supply.
Examples of environmentally friendly building materials are expanded polystyrene, rapidly renewable plant materials such as bamboo as this grows very quickly. Straw, wood from sustainably managed forests, insulated concrete, recycled stone and metal and other non-toxic materials that are renewable, reusable or recyclable such as linoleum, sheep wool, paper flake panels, compressed earth, baked earth, clay, flax linen, coconut and calcium sand stone are yet more examples of environmentally friendly building materials. The EPA (Environmental Protection Agency) also recommends using recycled industrial goods such as coal, foundry sand and demolition debris in eco-building. It also recommends that building materials should be extracted and manufactured locally to the building site to minimise the energy used in transporting them. This will minimise waste, maximise recycling and create less noise and dust.
During the construction of eco-buildings construction materials and paints that have zero or low emissions will improve indoor air quality. Many conventional building materials and cleaning products give off toxic gases such as formaldehyde. These gases can affect human health and productivity and can also cause physical symptoms such as skin rashes and headaches.
Proper temperature and airflow control together with a good designed building envelope will also help in increasing heat in the building. With careful use of natural and artificial light sources, the need for using electric lighting can be reduced.
An eco-building can only continue to be environmentally friendly if it is maintained properly. Often operations and maintenance (O&M) staff are employed to ensure all the objectives of an eco-building are adhered to. The development of new eco technologies is also the responsibility of the O&M personnel. Waste reduction may be a goal that is applied during the design and construction of an eco-building, but it is the ongoing O&M that ensures it takes place.
During the construction of eco-buildings, designers also aim to reduce waste produced from energy, water and materials. For example in California nearly 60% of their waste is obtained from commercial buildings. An important goal in the construction phase is to reduce the amount of waste material transported to landfill sites. Eco-buildings that are well designed can also reduce the amount of waste generated by providing on-site recycling solutions such as compost bins. Again this reduces the amount of waste matter going to landfill sites.
Several options also exist that can reduce the environmental impact on local water supplies and treatment plants. “Greywater” which is dirty water that comes from dishwashing or washing machines can be irrigated. If the water is treated it can also be used to flush toilets and wash cars.
Centralised water treatment systems can be very costly and use high amounts of energy. The alternative to this is converting waste and waste water into fertiliser. Collecting human waste and transporting it to a biogas plant with other biological waste can produce liquid fertiliser. This system also puts nutrients into the soil and creates what is known as a carbon sink that removes CO2 from the atmosphere, thereby reducing greenhouse gases in the atmosphere. Making artificial fertiliser costs more and uses more energy.
