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4/2006 |
Bamboo in Construction: Is the Grass Always Greener? |
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by Nadav Malin and
Jessica Boehland
The most common use of bamboo in North American construction has, by far, been as a flooring material. In 1997 Environmental Building News found only eight companies supplying the North American market. In contrast, about 200 companies imported about 45 million square feet of bamboo flooring into the U.S. in 2005, estimates David Knight, president and CEO of Teragren, LLC (formerly Timbergrass), in Bainbridge Island, Wash. That represents about 2 to 3 percent of the market for wood floors, according to Knight. One of the largest North American bamboo distributors, Teragren, has achieved its distribution scale by selling through retail flooring outlets—it has product in 1,700 stores in the U.S. and Canada and hopes to be in 3,000 by the end of 2006, he says. Like many of the other reputable importers, Teragren has an exclusive relationship with a producer in China—that producer now has three factories and more than 500 employees, and Teragren handles two-thirds of its production (the rest goes to France and various outlets in Asia). Varieties. Bamboo flooring comes in several varieties. First, it can be solid or engineered. Solid bamboo is not solid planks of bamboo, as the name implies, but rather strips made up of distinct layers of bamboo. Engineered flooring is made of a bamboo top layer glued to one of a variety of materials. For the “solid” products, the surface bamboo can be oriented either vertically or horizontally. Horizontal-grain (aka, flat-grain) flooring is the more traditional look and features bamboo’s characteristic nodes, or “knuckles.” Vertical-grain (edge-grain) flooring, on the other hand, has the bamboo strips lined up on edge, resulting in a more uniform look and reducing the knuckle appearance.
Within the last few years, several bamboo flooring companies have introduced strand products, made by separating the bamboo into individual fibers and then binding them under heat and pressure with a phenol-formaldehyde resin. Smith & Fong calls its version Plyboo® Strand™ flooring, and Sustainable Flooring, LLC, calls it Strandwoven bamboo. Teragren offers its Synergy strand product. Hardness. One factor that differentiates high-quality bamboo flooring and plywood from lower-quality products is the age at which the culms were harvested. Moso bamboo culms emerge from the ground at their full dimension of up to eight inches. They spend the next several years “hardening their arteries,” whereby the capillaries thicken toward the inside, but the diameter never changes. What begins as almost entirely sugar and water lignifies into hard cellulose. Although three-year-old culms can be made into flooring, some companies claim to harvest only after five years. According to Knight, “We can see that younger than five or six years, the fibers aren’t as long. The longer the fiber, the better the stability.” Dan Smith, founder of Smith & Fong, agrees, noting, “I interpret the six-year point as the maximum apex for strength and for keeping the resource healthy.” Others, including Doug Lewis, founder of Bamboo Hardwoods, believe bamboo reaches its peak hardness at about three years and doubt whether there is any benefit to letting it age further. Lewis also questions whether it’s possible to ensure that only older culms are used. “I couldn’t tell if a pole is much beyond three years,” he told EBN. Smith admits that ensuring the use of older culms is difficult. “I don’t think there’s any way to control, to say ‘I want six-year growth’,” he says. Trevor Gilmore, of Bamboo Mountain, Inc., agrees, noting, “The purchasers have to have a really good relationship with the manufacturers they work with.” Although it is hard to tell a pole’s age by looking at it, most bamboo farmers actually track their plants carefully. Culms are often marked with a name and date after their first year, when they’ve reached full size. Some companies even use electronic tagging systems. “We go to the farmer and purchase it from him after the first year. We put our name and ID chips into it and know it’s ours,” says David Kurland, of Mill Valley Bamboo Associates.
Various manufacturing processes also affect the hardness of the finished product. Notably, heating bamboo to caramelize it softens the fibers. Teragren’s vertical-grain caramelized flooring is rated at 1,470 newtons on the Janka hardness test, compared with 1,850 for the same product in the natural color. (Red oak scores about 1,360 on the same test.) The difference is less dramatic in the flat-grain configurations, but caramelizing still reduces the hardness by about 10 percent. Strand bamboo, on the other hand, is much harder than conventional bamboo flooring and generally considered appropriate for commercial and other high-traffic areas. Smith & Fong and Teragren both claim their strand flooring is twice as hard as red oak, and Sustainable Flooring describes it as “bomb-proof.” Manufacturing and transportation considerations
The fossil fuels required to move bamboo products halfway around the world constitute an environmental strike against the product, although oceangoing freighters move material more efficiently than trucks. No North American companies are currently growing bamboo for building uses, and, due primarily to the high cost of labor in North America relative to the parts of the world where bamboo is currently grown for building uses, this situation is unlikely to change. Copyright 2006 BuildingGreen Inc. Copyright 2006 The American Institute of Architects.
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This article is excerpted from Environmental Building News, a publication of BuildingGreen Inc. (AIA members get a 30% discount on Building Green Suite subscriptions.) The full-text article, including a more detailed analysis of the environmental pros and cons of bamboo, is available on the BuildingGreen Web site. |
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