ΞΥΛΙΝΟΙ ΟΥΡΑΝΟΞΥΣΤΕΣ - ΤΟ ΜΕΛΛΟΝ ΤΗΣ ΠΕΡΙΒΑΛΛΟΝΤΙΚΑ ΦΙΛΙΚΗΣ ΔΟΜΗΣΗΣ ΣΤΙΣ ΜΕΓΑ-ΠΟΛΕΙΣ ΤΟΥ ΚΟΣΜΟΥ;

Ήδη η αρχή έγινε στη Ν. Ζηλανδία, υπάρχουν σχέδια για το Βανκούβερ και η Κίνα περιμένει στη σειρά.

Προφανώς η ξυλεία είναι ανανεώσιμο υλικό σε σχέση με τα ορυκτά αλλά ως πιο σημείο η αύξηση της ζήτησης θα μπορεί να καλυφθεί από φυτείες;

Σχέδια για 30 ουρανοξύστες από ξύλο στο Βανκούβερ του αρχιτέκτονα Michael Green



Το άρθρο από την Guardian  

Wooden skyscrapers could be the future of flat-pack cities around the world
The development of engineered timber could herald a new era of eco-friendly ‘plyscrapers’. Christchurch welcomed its first multistorey timber structure this year, there are plans for Vancouver, and the talk is China could follow.
When American engineer William Le Baron Jenney designed the world’s first skyscraper in Chicago in 1884, no one believed in his unconventional technologies. His lightweight steel frame relieved a structure of its heavy masonry shackles, enabling it to soar to new heights. Perplexed by this trade-in of solid brick for a spindly steel skeleton, Chicago inspectors paused the construction of the Home Insurance Building until they were certain it was structurally sound.

Of course, Jenney’s revolutionary edifice provided a blueprint for city skylines across the world. By 2011, China was reckoned to be topping off a new skyscraper (500ft or taller) every five days, reaching a total of 800 by 2016. Toronto, now North America’s fourth largest city, currently has 130 high-rise construction projects under way.

Chicago's Home Insurance Building, widely considered to be the world's first modern skyscraper. Chicago’s Home Insurance Building, widely considered to be the world’s first modern skyscraper. Photograph: Chicago History Museum/Getty Images
As a result, buildings are slowly choking the atmosphere. In Britain, where the construction industry accounts for almost 7% of the economy (including 10% of total employment), 47% of greenhouse gas emissions are generated from buildings, while 10% of CO2 emissions come from construction materials. Furthermore, 20% of the materials used on the average building site end up in a skip.

So just as Jenney’s steel-frame solved the issue of the dense, stunted buildings in the 19th century, architects and engineers are now seeking new ways of building taller and faster without having such a drastic impact on the environment. And that has seen them revisit the most basic building material of them all: wood.

Although wood in its raw form could not compete with Jenney’s steel-frame wonder, a type of super-plywood has been developed to step up to the challenge. By gluing layers of low-grade softwood together to create timber panels, today’s “engineered timber” is more akin to Ikea flat-packed furniture than traditional sawn lumber, and offers the prospect of a new era of eco-friendly “plyscrapers”.

For Vancouver-based architect Michael Green, the sky is the limit for wooden buildings. While nearing completion of the University of Northern British Columbia’s Wood Innovation and Design Centre in Prince George, Green’s practice, MGA, has also drawn up plans for a 30-storey, sun-grown tower for downtown Vancouver.

If built, Green’s vision would be easily the world’s tallest wooden building, soaring past the current contenders – London’s Stadthaus at nine storeys, and the 10-storey Forte Building in Melbourne. But that’s not the main motivation, according to MGA associate Carla Smith. “To be honest, it’s not like we really care about being the tallest,” she says. “We really do see a wooden future for cities, and our aim is to get others to jump on board too.”

Arts & Media Building in Christchurch, New Zealand.
 The Nelson Marlborough Institute of Technology arts and media building under construction in Nelson, New Zealand
Green is giving away his hefty, 200-page instruction manual, The Case for Tall Wood Buildings, free of charge. He hopes it will inspire architects and engineers to branch out beyond their concrete and steel confinements, and embrace a material that sequesters carbon dioxide from the atmosphere, holding it captive during its growth and lifetime in a structure – one tonne of CO2 per cubic metre of wood. To put that in context, while a 20-storey wooden building sequesters about 3,100 tonnes of carbon, the equivalent-sized concrete building pumps out 1,200 tonnes. That net difference of 4,300 tonnes is the equivalent of removing 900 cars from the city for a year.

But while timber advocates such as Green hope to to sow the seeds of change in the minds of policymakers worldwide, building regulations still put a low-rise lid on the height of timber buildings. This is based on wood’s historic reputation as kindling for a great city fire: in London, Chicago and San Francisco (to name just a few), roaring fires have ravaged city streets, wiping out great swathes of grand architecture and razing urban history to the ground. But while the classic timber-framed city of 1870s Chicago was gone in an instant, today’s engineered timber develops a protective charring layer that maintains structural integrity and burns very predictably – unlike steel, which warps under the intense heat.

The rigidity of mass timber panels has tended to restrict architects to a “house of cards” design, whereby panels are slotted together and stacked on top of one another in repetitive patterns. But new innovations are coming thick and fast: the USDA recently announced a $2m investment for wood innovation, and in the previously scorched city of Chicago, mega-firm Skidmore, Owings and Merrill published a study that re-imagines the 42-storey Dewitt Chestnut apartment block as a timber tower. In Europe, a 14-storey wooden building is currently under construction in Bergen, Norway, with another eight-storey structure on its way up in Dornbirn, Austria – the prototype for a 20-storey plyscraper designed by the global engineering firm Arup.

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