27, Sep 2020 -

London’s soaring timber tower could be a game changer for CLT

London’s soaring timber tower could be a game changer for CLT


The world might not be quite ready for soaring timber skyscrapers but one architectural firm is getting headlines for a proposed wood tower that would be the tallest building in London, England.

The conceptual 80-storey building called Oakwood Timber Tower "is the largest use of cross-laminated timber (CLT) in the U.K. and in Europe," Kevin Flanagan said at the recent Green Building Festival in Toronto.

Flanagan is a partner at London's PLP Architecture which is behind the tower that would have as many as 1,000 residential units in about one million square feet in the heart of London. PLP has partnered with engineering firm Smith and Wallwork and Cambridge University's Centre for Natural Material Innovation on the project.

The tower is engineered in a series of quadrants or bundled columns, much like Chicago's 1,450-foot-tall Willis Tower, formerly the Sears Tower, Flanagan said.

As big city cores such as Toronto's are pressured to intensify, CLT could prove to be a prime building material for residential towers, he said.

"Rather than create CO2, by harvesting the renewable timber you can reduce CO2 (emissions) and actually go negative," he explained.

Flanagan said wood towers could create a building industry comprised of "new types of contractors" assembling buildings from modular prefabricated panels.

Interest in CLT for housing is growing in Europe, Flanagan reported to the designers and builders in attendance and that "there is enough material in Canada to house a billion people, according to Cambridge University."

Flanagan said the energy required to produce timber building materials is substantially lower than steel or concrete — about 90 per cent of the energy is in the drying and seasoning process.

Timber is comparable in strength to steel and stronger than concrete by weight, he claimed.

Another benefit of CLT is it requires fewer site deliveries than concrete — a big plus in dense urban settings where construction disruptions can significantly impact surrounding businesses, he added.

Flanagan explained that CLT could prove ideal for structures proposed on top of existing masonry or steel buildings.

Because it is light, it would require little if any reinforcing to existing concrete foundations, he said.

"This is what is happening in Europe and in London. People are realizing they can build high (on top of buildings) if they can build light," he said.

Among the challenges to building tall with wood is how to face or cover exterior timber to prevent weather damage such as moisture that will cause it to expand.

"Every material has its downside but to date there are no show-stoppers," Flanagan told delegates.

He said in Toronto "quite astonishingly" about 80 per cent of construction material specified for towers is concrete.

"They don't even use that much in New York," he stated. "It (CLT) can create a new industry and it can broaden the use of different materials."

Flanagan's architecture firm is no stranger to innovation. It designed The Edge, an office building in Amsterdam that was awarded the Building Research Establishment Environmental Assessment Method's (BREEAM) greenest office building in the world last year. A world standard, BREEAM rates and certifies the sustainability of buildings.

Through the use of 30,000 monitors to review occupant activity in the building, it was discovered that staff worked in entirely different ways than was expected. As a result, office workers in the building aren't assigned one desk or office but are offered a variety of workplace options throughout the building.

"It re-envisions how the office is intended to work," Flanagan said.

The Green Building Festival was hosted by Sustainable Buildings Canada in downtown Toronto.

Source: Journal of commerce

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