With all the focus on the role of architects and engineers in creating sustainable designs, it's easy to overlook the vital role played by the construction team in green building achievements. Contractors have the expertise to translate designs into finished buildings; often, they are instrumental in suggesting better ways to accomplish a goal that the design team didn't consider. Early involvement of general contractors is vital to integrated design efforts; they can offer early pricing of design alternatives and consult on the constructability of new approaches.
In green building, contractors are specifically tasked with pollution prevention, eliminating runoff of sediment from construction sites through such practices as silt fencing (the black plastic or cloth mesh you see at most well-run construction sites), seeding and mulching, sediment traps and basins, along with earthen dikes. LEED awards points for five major influences of construction on environmental quality:
• Reduction of site impacts from construction staging by keeping all equipment and soil disturbance within specified limits to avoid soil compaction.
• Construction waste recycling of at least 50% of materials, with extra points awarded for 75% and 95% waste diversion. This not only keeps materials out of landfills but recovers valuable products for recycling. In most urban areas, contractors are discovering they can recycle or recover more than 90% of construction waste and that this is economically beneficial for them, given the high costs of landfilling. Recycling such items as cardboard, metal, brick, acoustic ceiling tile, concrete, plastic, clean wood, glass, gypsum wallboard (sheet rock), carpet and insulation is surprisingly simple. On tight construction sites, in some cities, wastes can be co-mingled in a single dumpster and sorted offsite at a local recycling center.
• Indoor air-quality maintenance during construction through best practices such as keeping ductwork, carpets and other absorptive surfaces covered and out of the weather and dust-free.
• Indoor air-quality assurance before occupancy by conducting a two-week building flush-out with 100% outside air and changing all filters before occupancy, or by conducting a test of key indoor air-quality contaminants to make sure they are below threshold levels for health effects.
• Monitoring the activities of subcontractors to make sure that specified low-VOC paints and coatings, adhesives and sealants are actually used on the project without substitution.
Contractors document their best practices as part of the LEED certification process. Without their active and often creative cooperation, LEED projects would not be successful. Turner Construction, the largest commercial builder in the US, expects to achieve a goal of 50% waste diversion in 100% of their projects by the end of 2007, despite the difficulties of working in many cities without active recycling programs or financial incentives such as high landfill fees.26
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