Vegetal steel: bamboo as eco-friendly building material

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Vegetal steel: bamboo as eco-friendly building material

Post autor: Sobal » 05 cze 2008 11:42

Vegetal steel: bamboo as eco-friendly building material

GIRARDOT, Colombia (AP) - 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.

In an age of diminishing resources and burgeoning populations, bamboo's
environmental and social benefits are its biggest selling point as
construction material.

Unlike steel, which is produced in only a handful of industrialized nations,
more than 1,100 bamboo species - a few dozen of them suitable for building -
proliferate in the tropics. Culms, or stalks, shoot up almost anywhere,
easing carbon dioxide's choke on the planet while absorbing water as
efficiently as a desert cactus.

But building with bamboo is labor intensive and can be costly in parts of
the world, depending on local supply.

Velez estimates that 80 percent of his costs on any project go to paying the
300 specialized craftsmen who follow him around the world, most recently to
Guangdong province, China, where he built the country's first commercial
bamboo project, the award-winning Crosswaters Ecolodge for tourism.

Bamboo's abundance is, ironically, an obstacle to wider acceptance. Its most
visible use is as rickety, makeshift housing - feeding the stereotype that
it is poor man's lumber.

That hasn't stopped David Sands. The Hawaii-based architect creates Robinson
Crusoe revival homes in Vietnam then ships them in panels around the world
for quick assembly.

After building a hundred homes in Hawaii and a resort in Bali, his Bamboo
Technologies company is aiming for the U.S. mainland, where its challenges
include insulating against colder temperatures and coping with uninformed
building inspectors.

But in a sure sign that bamboo's time may have come, Sands says he's had to
turn down a $20 million (euro13.5 million) unsolicited offer for his company
from potential investors.

"It came as a total shock. We're not ready for the kind of scale they were
proposing,'' Sands said, laughing.

The world's bamboo crops may not be ready either - there are few commercial
bamboo farms to meet a growing demand, and the United Nations in 2004 warned
that as many as half of all wild species may be in danger of extinction due
to forest loss.

For the Nomadic Museum, Velez had to ship 9,000 pieces of guadua to Mexico,
undercutting much of the material's "grow your own house'' mystique.

But shortages may also be filled as bamboo plywood - already a major
industry in China - gains acceptance in the United States and Europe, and
growers rush to meet the demand.

"The rate at which it grows is amazing,'' says Raul de Villafranca,
consultant for Agromod, a Mexican company that is planting 9,880 acres
(4,000 hectares) in the southern state of Chiapas. "In one year, you can
harvest stalks 15 meters (50 feet) tall, and unlike hardwood, it never needs
to be replanted.''

San Francisco architect Darrel DeBoer, who specializes in sustainable
materials, says bamboo-framed structures buttressed by earth or straw bale
are viable in any climate, once isolated from the elements with a proper
foundation.

But he says bamboo has the potential to make its greatest impact where its
already found.

"If you can afford the high price of land in the states, you're not going to
worry about using low-cost building materials,'' says DeBoer, who has hosted
several workshops with Velez. "In contrast, the developing countries around
the tropics need affordable housing, and the jobs that building with bamboo
can generate.''-AP
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