Various writers have stated that spatial redesign of the landscape and built-environment may be the single most effective means of achieving new levels of efficiency and sustainability (Lyle, 1994; Mollison, 1983; Alexander, 1977; Van der Ryn & Cowan, 1996). Building materials are also quite important. They have been estimated that building materials make up forty percent of material through-put of entire economy (Milani, 2001).
In the book “Green Building: Project Planning and Cost Estimating”, Keenan and Georges (2002) identified some key characteristics of green building materials. As regards green building materials, they should be healthy for the internal environment, healthy for the natural environment, minimize building energy use, have low embodied energy, be reusable, recyclable and/or biodegradable, and be locally obtained. Embodied energy is a concept that takes into account several factors to determine the energy needed to produce a product and can be used as a comparison between different materials.
There is some controversy surrounding embodied energy as there is no internationally agreed method for calculating this value and many times it is not known what has been accounted for (Woolley and Kimmins, 2005). For example, cement has an embodied energy of 7. 8 MJ/kg, while virgin steel is 32. 0, and recycled steel is 10. 1 MJ/kg (Keenan and Georges, 2002). In these values however, consideration is not given to transportation, durability, reuse and recycling. These factors could significantly alter the original values.
Building materials are also the stuff of our personal environments. They are all around us, and literally part of the air we breathe. They can damage the biosphere: VOCs from paints alone are responsible for perhaps 9 percent of the damage to the ozone layer. They can also damage us: the US Environmental Protection Agency (EPA), for example, estimates that indoor pollution—caused by materials like paints, plastics and particleboards—is responsible for more than 11,000 deaths each year from cancer, kidney failure, and respiratory collapse (Ligon, 2001).
The fact that buildings are all around us means not only that they immediately impact us, but that we can potentially affect them. The building industry is a decentralized one that exists in virtually every community. Not surprisingly, the built-environment is a major venue for ecological and community development alternatives, with materials being an increasing focus of concern over the past decade.
The first is the section on Materials and Resources. This section consists of one prerequisite and eight credits. The eight credits focus on reuse and management of construction and demolition waste; using refurbished or reused materials and materials with a recycled content; using regional and rapidly renewing materials; and lastly if new wood must be used, using products certified accordance with the Forest Stewardship Councils principles and criteria The second section which pertains to building materials is Indoor Environmental Quality.
The important credit is number four: Low Emitting Materials. For this credit, the Volatile Organic Carbon (VOC) content of adhesives and sealants must be less than the VOC content limits of the State of California South Coast Air Quality Management District’s (SCAQMD) rule number 1168 from October 2003. For paints, the VOC content must be less than the VOC and chemical component limits of the Green Seals Standard GS-11 from January 1997. Composite wood and laminate adhesives must contain no added urea formaldehyde resins.
Concrete is a strong and durable material with a high heat storage capacity (Keenan and Georges, 2002). It is good from an indoor air quality standpoint as it is inert. The problems associated with concrete are washout water at concrete plants which can have a high pH, and the use of cement as a binding agent in concrete. Cement is very energy intensive and is a major contributor of greenhouse gases. To counteract this, up to 70% of cement in concrete can be replaced with fly ash. Fly ash is a waste product from coal fired plants.
Brick, block and stone have a low embodied energy and are therefore environmentally friendly materials (Keenan and Georges, 2002). To avoid added impacts of transportation, local masonry should be used where available. STRUCTURAL FRAMING An ongoing environmental debate is wood versus steel as components for framing. Both materials have been destructive to the environment and both have advantages and disadvantages. One of the advantages of wood is that it is a natural insulator while steel is a conductor. Steel is 400 times more conductive than wood (Keenan and Georges, 2002).
One of the disadvantages of wood is that it needs to be treated with preservatives which can be toxic and render the wood non-biodegradable. Steel on the other hand offers resistance to insects and water rot. Steel is also recyclable. The choice between steel and wood should depend on the application they are being used for. Wood may be more environmentally friendly if you can use non-treated and certified wood. The production process is less energy intensive than for steel, and creates less pollution and environmental degradation than the mining and processing of steel (Keenan, A. , and Georges, D. , 2002). INSULATION
Some of the considerations which need to be taken in account when choosing an insulation material are: 1) does it retard airflow, 2) which type will provide the best Rvalue within a reasonable thickness, 3) does it pose health risks, and 4) does it contain ozone depleting chemicals (Keenan and Georges, 2002). In the Green Building Handbook, the authors offered their choices for “best buys”. Their top three choices were wool, cellulose fiber, and cork. These choices are thermally as good as conventional insulators (Woolley and Kimmins, 2005). Cellulose Fiber is made from processed waste paper, with added borates for fire and pest resistance.
It is made into a fluff that can either be placed by hand or sprayed (Woolley and Kimmins, 2005). Insulation corkboard is produced by cooking cork granules at high temperature and pressure. The granules bond themselves together with their own resins (Woolley and Kimmins, 2005). ROOFING For materials used in roofing, durability is critical. One option for materials is metals, such as copper, steel and aluminium. Metal roofs are good because they can be made of recycled material and can be recycled at the end of their life cycle. They also last longer than asphalt (Frej, 2005).
Cool roofs are an option that can be useful in both mild and hot climates. The roof material is covered with a reflective coating. This coating prevents the building from getting hot, reduces heat island effects and prolongs the life of a roof (Keenan and Georges, 2002). A non-petroleum based coating should be used. Living “green” roofs are another option. Green roofs are roofs that are partially or completely covered with soil and vegetation. These roofs provide environmental cooling, habitat, added insulation, storm water management, natural beauty, cleaner air and can extend the life of a roof (Keenan and Georges, 2002).
One source suggested two to three times longer than a conventional roof (Frej, 2005) while another suggested they can extend the life up to 100% (Keenan and Georges, 2002). Planted roofs can require more maintenance and require a system to prevent root penetration and water seepage.