Thursday, January 29, 2015

How tall could a wooden building rise? Experts say the sky is the limit and talk skyscrapers

A nice wooden cottage with a lake view; a wooden chalet in the mountains where you could sit in front of the fireplace with a good book and watch the snow fall on the window; or a small log cabin in the woods, where you could enjoy your breakfast on the porch every morning, listening to lovely bird songs, these are the types of buildings that you most probably imagine whenever you think of wood buildings. But could you envisage working in a wooden skyscraper? Hardly.

130 years after the world’s first skyscraper- the Home Insurance Building- was built in Chicago by American engineer, William Le Baron Jenney, the construction methods and by-products associated with such large scale infrastructure has inevitably led architects and engineers to seek 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.

Not any wood is suitable for such a concept though. A type of super-plywood, called cross-laminated timber (CTL) has been created to maintain the strength of high-rise constructions. This effect is achieved by gluing the layers of low-grade softwood together to create stronger timber panels. Softwood panels are usually made of cedar, Douglas fir, pine, or redwood.

Reducing the environmental impact of architecture

In his book, “The Case for Tall Wood Buildings”, Vancouver- based architect, Michael Green explains how wood will be able to absorb carbon dioxide from the atmosphere.  Unlike conventional materials like concrete, wood can be used as it is. Natural resources like coal and gas don't need to be burnt to produce it, so less carbon ends up in the air. Since it is healthier for us, and for the planet, why not make the best of it?

Timber stores 0.8t of carbon dioxide within 1 cubic meter. In comparison, the production of both concrete and steel are one-way energy intensive processes that release large amounts of carbon dioxide into the atmosphere.  A 10-storey building could absorb as much as 1,600 ton of carbon, in comparison to a concrete building’s comparatively low 600 tons, according to the Canadian architect.
Michael Green proposed 20-storey (60-metre) structures made from cross-laminated timber (CLT) panels. CLT is a durable and solid-wood material developed European technology, to replace all structural elements above ground level.

Untreated timber has the potential to rot when exposed to moisture and air over extended periods of time, but CTL buildings are designed with a rain screen façade to effectively manage moisture exposure.

Stadthaus Building- London
How long will a CTL building last for? Apparently it can last as long as a concrete or steel building. CTL has been certified for a minimum 60 year lifespan by Building Research Establishment in the UK, which is the equivalent of concrete or steel.

Moreover, wood is natural, warm (intrinsic thermal properties means lower heating and cooling costs), compatible with other materials, non allergic and healthy to inhabit and has attractive natural colors.

Stop cutting trees and beware of fire!

The benefits of wooden skyscrapers are clear for all to see.  Criticisms regarding cutting even more trees down to aid the trend have also been refuted, with there now being a use for trees already damaged. Similarly, trees can also be grown in nurseries.

But while timber advocates such as Green hope 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.

Roaring fires have ravaged city streets, in London, Chicago or San Francisco, to only mention a few cities, wiping out great examples of grand architecture and razing urban history to the ground. But 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.

Europe leads the way in the concept’s innovation

Until now, America’s conservative building regulations and a lack of interest from developers and their customers have meant few interesting wooden buildings have been built there. In contrast, Europe, Australia and especially Canada are embracing the emerging technologies.

Forte Building- Melbourne
So far two high- rise buildings made of wood have been erected in the world: nine-storey Stadthaus in London and the 10-storey Forte Building in Melbourne.  Also in Bergen (Norway), a 14-storey wooden building is currently under construction.

Forté, the world's tallest timber apartment building, raising 10 floors above the ground only includes 23 apartments and was built in 16 weeks.

With so much controversy around this subject we are obviously not going to see the first wooden high-rise building city in the near future. Until then you might just want to have a look at Michael Green’s video “Why we should build wooden skyscrapers”.

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