By Kristine Barenholdt Bruun, March 2016
The world is in the midst of a tall building boom where skyscrapers are defining the prosperity of modern cities.
These towers come in all kind of forms with facades in all kinds of glazed material. But scratch below the surface, and you will find the same steel or concrete structure that supported the first skyscrapers in 19th century New York and Chicago.
However, this could be changed by one of our oldest construction materials – timber.
The ancient material possesses a multitude of qualities in regard to both building projects and environment. Ramboll Structural Engineering Director Gavin White, who has pioneered the use of timber and Cross Laminated Timber (CLT) over the last decade, explains:
- Timber construction can lead to shorter construction programmes due to offsite prefabrication. It has good thermal and fire performance properties and results in lighter buildings’ requiring smaller foundations. The sustainability benefits often make it possible to create a carbon neutral structure”.
Saving huge amounts of CO2
Currently, Gavin White is working on the tallest and largest CLT project globally. The name of the project is Dalston Lane - a 121 unit residential development in London that will use more timber than any other scheme in the world and stand at 33m tall.
Especially in regard to the climate, this is a very positive record to hold. Gavin White explains why:
- CLT boasts many material benefits, not least its sustainability. In total, Dalston Lane will save 2,400 tonnes of carbon, compared to an equivalent block with a concrete frame.
By using a CLT construction in the Dalston Lane project, the embodied carbon is 2.5 times less than that of an equivalent concrete frame. Taking into account that timber stores carbon by absorbing carbon dioxide (CO2) from the atmosphere, also known as sequestered carbon, the Dalston Lane structure can be considered as ‘carbon negative’. Its 3,852 cubic metres of CLT will form the external, party and core walls, floors and stairs.
- In a world where sustainability is ever critical, this truly viable construction material is one we need to embrace, Gavin White says.
Timber helps making room for a denser city
With an increasing number of the world’s population moving to central locations in capitals and cities, there is a growing need for densification as space becomes increasingly limited. But in the world’s developed cities, increased densification can pose significant challenges as these cities boast a myriad of underground infrastructure that supports the mobility of the city. This is where the weight of timber can bring significant value to a development.
- The light weight of timber makes it possible to increase the height of a proposed development because it exerts less load onto the underground infrastructure. It also enables developments, where previously not thought possible, as the lighter building can be built on shallower foundations, Gavin White explains.
With London’s High Speed 1 and Crossrail passing under the building site of the Dalston development, the choice for CLT was unequivocal with its lighter construction weight that enabled smaller foundations and a further two stories of accommodation on to the building.
A sprouting global popularity
Little by little, wood has regained foothold as a popular construction material all over the world – from Asia to Europe and USA.
In Ramboll, timber experts have worked with both cross laminated timber and massive wood constructions for over a decade in countries such as England, Sweden, Norway and Finland, constantly pushing the boundaries of this dynamic material.
The renaissance of timber engineering has been bred out of changing attitudes towards high rise timber construction, advances in design possibilities, and by pioneers willing to explore in detail the possibilities of tall timber construction.
In Denmark, Finn Larsen, Senior Engineer in Ramboll, is part of a research group with pioneers and scientist from three universities and a number of companies who is investigating the use of timber in tall buildings:
- Tall timber buildings are here to stay. Both CLT and massive wood has a number of advantages that fit very well into a modern society with sustainability needs as well as the need for denser cities, Finn Larsen explains while referring to the light weight of timber and the low carbon emissions.
In Denmark, the first tall timber building is yet to come. But Finn Larsen is hoping to be able to utilize the experience that Ramboll has gained in other countries to inspire the wider use of timber in Denmark.