40 Calling for a shift in focus
Frank Werling of Finnish wood specialists Metsä Wood says the green agenda in construction must shift towards sustainable production of building materials – and timber leads the way as an alternative to steel and concrete
A brief history of timber
Timber is the oldest building material known to man. Since the dawn of construction, when early hunter-gatherers used wood and rudimentary tools to build shelter, through to modern times, timber remains one of the most important and versatile construction materials available. In comparison, steel and concrete have only found their way into construction over the past 250 years, and despite being the construction materials of choice ever since, timber is now enjoying a resurgence. With the dawn of engineered wood products (EWP) such as Laminated Veneer Lumber (LVL) during the second half of the 20th century, the dimensional restrictions related to tree growth have disappeared. Today, with the inherent predictability and accuracy of physical properties, timber products are now finding their way back into construction.
Light and strong
Building with LVL from the ground up, makes the structure significantly lighter when compared to traditional choices like concrete and steel. The lighter weight of the building materials means less pile-driving and earth-moving when preparing the foundations. When the components are pre- fabricated it also means transportation to site and the actual building process costs significantly less because there are fewer building elements. LVL is not only light but also extremely
strong. The weight-strength ratio of a building material can be expressed in the length a rod of material in tension before it ruptures from its own weight. For concrete this is approximately 0.5 km – and for steel approximately 5.0 km. LVL can achieve one of the highest available strengths for any EWP with approximately 12 km. The excellent strength-to-weight ratio of
LVL enables long spans of up to 25 m. Other benefits of building in timber are that it is warm to touch, i.e. it does not transfer
The focus of improving efficiency has to shift to the production of materials – the most energy-intensive phase in a building’s life cycle
the heat away. Furthermore, it can be used as an effective insulation material as the heat is retained. It also means if it catches fire, it insulates the structure from the fire. Much has been made of the fire risk of timber, however, the rate of charring for timber is very predictable whereas the heat of a steel element cannot be established. Therefore a timber element protects itself in a fire whereas steel requires additional safety measures.
Case study: Achieving energy self- sufficiency through bio heating
A significant part of global energy consumption is eaten up by the production of steel, aluminium and concrete. Wood, however, is an extremely sustainable alternative. LVL uses as much of the wood as possible. Part of the sawdust and wood chips that are generated in processing the engineered wood are used in pulp production but also in bio energy. An example of this can be seen in the running of the Metsä Wood Mill in Lohja, Finland, which produces LVL. At Lohja, a bio heating plant has been built next to the mill in order to capture the full potential of the production. The heat energy produced at the plant covers the needs of the mill, resulting in complete energy self-sufficiency. At the same time, the remaining heat from the production process is sold for district heating to the town of Lohja and
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ADF OCTOBER 2016
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