Sustainable Building Technical Manual - Etn-presco.net

others, not themselves toxic, require toxic processes in their manufacture. Site materialextraction (like logging or mining) can also have environmental consequences byincreasing erosion and contaminating water bodies.Site materials face severe conditions, such as exposure to water, freezing, and ultravioletrays. 10 When site materials fail, resources are wasted and soil or water may be contaminated.Materials must also be physically and psychologically comfortable for outdooruse: for example, metal seating is uncomfortable except in moderate temperatures.No single rule or practice can guarantee materials that are both environmentally appropriateand suitable to their construction purpose. Materials should be compared notonly against other materials, but against the baseline of a “no-build” option. Considereach material’s “embodied energy,” the known amount of energy expended in itsextraction, transportation, production, recycling, and disposal. Selecting products manufacturedlocally can reduce embodied energy by decreasing transportation. Also importantis the product’s life cycle. Life-cycle cost (LCC) analysis takes into accountpurchase, operation, maintenance, replacement, and disposal costs over the expectedservice life of the product, thus revealing cost/benefits more clearly than conventionalcost analysis. 1 1 Life-cycle assessment (LCA) is a related analysis method that helps comparethe environmental consequences of material choices. (See the American Society forTesting and Materials (ASTM) Standards E 917-93 and E-50.06 (Draft); and Chapter 2,“Selecting Environmentally and Economically Balanced Building Materials,” for moreinformation on LCC and LCA.). ☛ SUGGESTED PRACTICES AND CHECKLISTI❑ Reduce material use, reuse, and recycle—in that order of priority.– Reduce material requirements through effective site layout. For example, re-routinga walkway or rotating a building can eliminate a costly retaining wall and site grading.Structures designed and sited without careful regard to site-specific conditionscreate structural, maintenance, and ecological problems.– Specify reused materials where possible. With the exception of railroad timbers,reuse is rare in landscape materials. In some regions, used brick is a popular commodity,and other durable items like flagstones are reused.– Specify recycled-content materials for site use, based on life-cycle performancerequirements. Wood substitutes made of recycled plastic are now available as lumberand in site furniture. Concrete and asphalt can also be recycled.❑ Use new materials thoughtfully; consume the minimum for the purpose;avoid waste.Support manufacturers whose product literature includes environmental data.Consider renewability (can the material be grown or naturally replenished?), sustainableproduction (will resources be used up too fast?), and recyclability. For example,wood is renewable and recyclable, but production of some timber species is not sustainableat current rates of consumption. Several natural ecological timber organizationsprovide useful information about these issues.❑ Perform an environmental-impact and cost analysis of all materials based on lifecycleprinciples.(See Chapter 2, “Selecting Environmentally and Economically Balanced BuildingMaterials,” and Chapter 17, “Specifications.”)