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Green building is the practice of
increasing the efficiency with which buildings use resources — energy, water,
and materials — while reducing building impacts on human health and the
environment during the building's lifecycle, through better siting, design,
construction, operation, maintenance, and removal.
Green buildings are
designed to reduce the overall impact of the built environment on human health
and the natural environment by:
- Efficiently using energy, water,
and other resources
- Protecting occupant health and
improving employee productivity
- Reducing waste, pollution and
environmental degradation
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Environmental impact
Green building practices
aim to reduce the environmental impact of buildings. Buildings account for a
large amount of land use, energy and water consumption, and air and atmosphere
alteration. In the United States, more than 2,000,000 acres of open space,
wildlife habitat, and wetlands are developed each year.
As of 2006, buildings used 40 percent
of the total energy consumed in both the US and European Union. In the US,
54 percent of that percentage was consumed by residential buildings and
46 percent by commercial buildings. In 2002, buildings used approximately
68 percent of the total electricity consumed in the United States with
51 percent for residential use and 49 percent for commercial use. 38 percent of
the total amount of carbon dioxide in the United States can be attributed to
buildings, 21 percent from homes and 17.5 percent from commercial uses.
Buildings account for 12.2 percent of the total amount of water consumed per day
in the United States.
Considering these statistics, reducing
the amount of natural resources buildings consume and the amount of pollution
given off is seen as crucial for future sustainability, according to EPA.
The environmental impact of buildings
is often underestimated, while the perceived costs of green buildings are
overestimated. A recent survey by the World Business Council for Sustainable
Development finds that green costs are overestimated by 300 percent, as key
players in real estate and construction estimate the additional cost at
17 percent above conventional construction, more than triple the true average
cost difference of about 5 percent.
Green
building practices
Green building brings
together a vast array of practices and techniques to reduce and ultimately
eliminate the impacts of buildings on the environment and human health. It often
emphasizes taking advantage of renewable resources, e.g., using sunlight through
passive solar, active solar, and photovoltaic techniques and using plants and
trees through green roofs, rain gardens, and for reduction of rainwater run-off.
Many other techniques, such as using packed gravel for parking lots instead of
concrete or asphalt to enhance replenishment of ground water, are used as well.
Effective green buildings are more than just a random collection of
environmental friendly technologies, however. They require careful, systemic
attention to the full life cycle impacts of the resources embodied in the
building and to the resource consumption and pollution emissions over the
building's complete life cycle.
On the aesthetic side of green
architecture or sustainable design 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.
Green building materials
Building materials typically considered to be 'green' include rapidly renewable
plant materials like bamboo and straw, lumber from forests certified to be
sustainably managed, dimension stone, recycled stone, recycled metal, and other
products that are non-toxic, reusable, renewable, and/or recyclable (eg Trass, Linoleum, sheep
wool, panels made from paper flakes, compressed earth block, adobe, baked earth,
rammed earth, clay, vermiculite, flax linen, sisal, seagrass, cork, expanded
clay grains, coconut, wood fiber plates, calcium sand stone...) The EPA
(Environmental Protection Agency) also suggests using recycled industrial goods,
such as coal combustion products, foundry sand, and demolition debris in
construction projects. Building materials should be extracted and manufactured
locally to the building site to minimize the energy embedded in their
transportation.
Reduced Energy Use
Green buildings often include measures to reduce energy
use. To increase the efficiency of the building envelope, (the barrier between
conditioned and unconditioned space), they may use high-efficiency windows and
insulation in walls, ceilings, and floors. Another strategy, passive solar
building design, is often implemented in low-energy homes. Designers orient
windows and walls and place awnings, porches, and trees to shade windows and
roofs during the summer while maximizing solar gain in the winter. In addition,
effective window placement (daylighting)
can provide more natural light and lessen the need for electric lighting during
the day. Solar water heating further reduces energy loads.
Finally, onsite generation of renewable
energy through solar power, wind power, hydro power, or biomass can
significantly reduce the environmental impact of the building. Power generation
is generally the most expensive feature to add to a building.
Reduced
Waste
Green architecture also
seeks to reduce waste of energy, water and materials used during construction.
For example, in California nearly 60% of the state's waste comes from commercial
buildings. During the construction phase, one goal should be to reduce the
amount of material going to landfills. Well-designed buildings also help reduce
the amount of waste generated by the occupants as well, by providing on-site
solutions such as compost bins to reduce matter going to landfills.
To reduce the impact on wells or
water treatment plants, several options exist. "Greywater",
wastewater from sources such as dishwashing or washing machines, can be used for
subsurface irrigation, or if treated, for non-potable purposes, e.g., to flush
toilets and wash cars. Rainwater collectors are used for similar purposes.
Centralized wastewater treatment
systems can be costly and use a lot of energy. An alternative to this process is
converting waste and wastewater into fertilizer, which avoids these costs and
shows other benefits. By collecting human waste at the source and running it to
a semi-centralized biogas plant with other biological waste, liquid fertilizer
can be produced. This concept was demonstrated by a settlement in Lubeck Germany
in the late 1990s. Practices like these provide soil with organic nutrients and
create carbon sinks that remove carbon dioxide from the atmosphere, offsetting
greenhouse gas emission. Producing artificial fertilizer is also more costly in
energy than this process.
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source: Wikipedia |