Nov 6, 2009

Vegetal steel: bamboo as eco-friendly building material

Forget steel and concrete. The building material of choice for the 21st century might just be bamboo.

This hollow-stemmed grass isn't just for flimsy tropical huts any more - it's getting outsized attention in the world of serious architecture. From Hawaii to Vietnam, it's used to build everything from luxury homes and holiday resorts to churches and bridges.

Boosters call it "vegetal steel," with clear environmental appeal. Lighter than steel but five times stronger than concrete, bamboo is native to every continent except Europe and Antarctica.

And unlike slow-to-harvest timber, bamboo's woody stalks can shoot up several feet a day, absorbing four times as much world-warming carbon dioxide.

"The relationship to weight and resistance is the best in the world. Anything built with steel, I can do in bamboo faster and just as cheaply," said Colombian architect Simon Velez, who almost single-handedly thrust to the vanguard of design a material previously associated with woven mats and Andean pan pipes.

Velez created the largest bamboo structure ever built: the 55,200-square-foot (5,128 sq. meter) Nomadic Museum, a temporary building that recently debuted in Mexico City and takes up half of the Zocalo, Latin America's largest plaza.

The museum, open until May, is the brainchild of Canadian artist Gregory Colbert, who wanted a monumental structure built entirely of renewable resources to house his tapestry-sized photos of humans interacting in dreamlike sequence with animals.

He turned to Velez, who two decades ago made a simple discovery.

By using small amounts of bolted mortar at the joints - instead of traditional lashing methods with vines or rope - he was able for the first time to fully leverage the natural strength and flexibility of guadua, a thick Colombian bamboo, to build cathedrallike vaults and 28-foot (8.5-meter) cantilever roofs capable of supporting 11 tons.

Curing the stalks with a borax-based solution deterred termites.

He perfected his technique on hundreds of projects, mostly in Colombia but also in Brazil, India and Germany with structures as graceful as they are muscular.

In steamy Girardot, a two-hour drive from his bamboo home in Bogota, the 58-year-old Velez has just completed a prototype of an energy-saving store for French retail giant Carrefour.

The 21,500-square-feet (2,000 sq. meters) structure has a domed roof made of guadua - instead of sun-absorbing metal - that will cut down on air conditioning costs. In Bali, German Joerg Stamm applied the same technique - learned as an apprentice to Velez - in constructing a 160-foot (50-meter) bridge strong enough to hold a truck.

But Velez, the son and grandson of architects who grew up in a Bauhaus-inspired glass house in western Colombia, has little patience for environmentalists now drawn to his work for its planet-saving possibilities.

"I hate environmentalists. Like all fundamentalists, they just want to save the world," he says.

For this iconoclast who designs exclusively in freehand, bamboo is foremost a high-tech material.

Seismic testing of bamboo seems to back his claim. After years developing construction codes for bamboo in his lab in the Netherlands, Jules Janssen was in Costa Rica in 1991 when a deadly 7.7 magnitude earthquake struck. Touring the epicenter hours later, he found every brick and concrete building had collapsed.

"But 20 bamboo structures built there by coincidence held up marvelously. There wasn't a single crack," said Janssen, a civil engineer and expert on bamboo's physical properties.

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