Some people may be surprised that the use of rapidly renewable materials is included in the LEED rating system. But if you think about it for a minute, it's not so surprising. After all, why shouldn't we be looking for substitutes both for old-growth timber, tree-farmed wood and chemical substances such as vinyl composition tile (VCT). Each of these substances has some environmental issues associated with its production, harvest and use. In the LEED system, the category of rapidly renewable materials in-
cludes anything that can be grown and harvested in less than ten years, such as agricultural panel boards from wheat, rice straw, sunflower seeds and sorghum stalks and used for cabinetry and wainscoting, interior doors, subflooring and even plywood; cork (cork typically has an ten-year regeneration cycle and comes from harvested tree bark in Spain and Portugal) and bamboo for flooring, linoleum floor covering and wool rugs.
Note that not all rapidly renewable materials meet other environmental criteria such as locally sourced (most bamboo flooring is from China, for example, and most linoleum from Europe), so it's sometimes necessary to make decisions about which values are more important to a project. Of all the rapidly renewable materials, bamboo seems to have penetrated farthest into the mainstream green building market. Growing up to 2 feet in a day and 60 to 80 feet in a year, bamboo can harden in 5 years to be equal in strength to a 50-year-old tree.126
Bamboo flooring is often chosen for its distinctive appearance and such desired qualities as hardness, resiliency and stability. Cork flooring is valuable for its sound and thermal absorption as well as its resilience. Linoleum is made from linseed oil, cork dust, natural fiber and wood powder — rapidly renewable and recycled ingredients. Project designers and product specifiers are critical components of the new green building "ecosystem," and they often have to consider issues other than the environmental attributes of a product, including performance, cleanability (especially for flooring) and durability. As they acquire more experience with new types of green products, many of these concerns gradually disappear.
To get a LEED point for using rapidly renewable materials, 2.5% of the total value of materials in a project need to be from this category. In a $10 million (construction cost) project, with $4.5 million devoted to cost of materials, this represents about $113,000 worth of such materials, about 1.1% of the total construction cost. These materials can be specified later in the design process, particularly where their aesthetics and provenance might prove valuable to the project's goals.
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