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Metsä Wood director, Jussi Björman, explains how hybrid construction delivers sustainable buildings without changing current construction methods.

Metsä Wood and its partners have designed a hybrid sandwich wall element which will renew offsite construction.

The innovation combines concrete with Kerto LVL (laminated veneer lumber). The first construction project to use the elements is Metsä Fibre’s Rauma sawmill.

The need for more sustainable solutions is acute, as construction causes 30 per cent of all CO2 emissions. Combining concrete and Kerto LVL, the hybrid sandwich wall elements offer an easy way to replace concrete which is used in most residential multi-storey buildings.

More importantly, this is an innovation that guarantees efficient construction.

The hybrid construction helps to increase the share of wood to build more sustainable buildings efficiently. This joint development is our effort to support the construction industry.

Thr connections between the wall elements are similar and so are the lifting loops compared to the ones used in concrete elements.

Metsä Wood collaborated with JM-Rakenne, Peikko and Arkta-Reponen to design the optimal hybrid sandwich wall element, which can be used in residential, office or industrial multi-storey buildings.

We have combined Lipa-Betoni's concrete know-how with Metsä Wood's wood experience. The goal was to design a practical element, which is easy to produce and use in construction. The first hybrid sandwich wall elements were produced at Lipa-Betoni's factory in Pieksämäki, Finland, for Metsä Fibre's Rauma sawmill construction project.

On a global scale, the potential is huge. We are currently working with both European and Australian companies to produce similar ideas that fit local construction methods. Half a dozen designs are being prepared for publication this year.

These designs and the hybrid sandwich wall element design are already available at the Open Source Wood platform, which aims to facilitate knowledge sharing, co-creation and growth in modular wood construction.

The starting point for the new element design was a common residential seven-storey building with a concrete structure including hollow-core slabs and party walls made from concrete as well.

In the hybrid sandwich wall panel, the internal load-bearing core panel is replaced with a Kerto LVL Q-panel. Otherwise, the structure of the element remains the same; the façade is made from concrete and the element has an insulation layer.

As a material, Kerto LVL is very comparable with concrete. The compressive strength of the Kerto LVL panel is as high as that of C25 concrete, 26 MPa. Also, the tensile strength of the panel is at the same level, whereas in concrete it is 10 per cent of the compressive strength without steel reinforcement. In a hybrid sandwich element, the reinforcement is only needed in the façade

Kerto LVL is a light material, the hybrid sandwich wall elements are faster to produce at the factory and to transport to the site.

Hybrid construction not only reduces construction related CO2 emissions it creates long term carbon storage. For example, 30,000 tonnes CO2 eq. emission reduction and 95,000 tonnes of carbon storage, in CO2 eq., can be achieved when one million square metres of hybrid sandwich elements are used.

About the Author

Jussi Björman is director, business development, construction, Metsä Wood

Jussi Björman has a Master of Science (Technology), graduating from the Aalto University School of Engineering in 2010. After graduating, he worked as a structural engineer in renovation and export projects. Björman joined Metsä Wood in 2011. 

He is currently the development director responsible for global business development in the construction industry and for technical customer service. He specialises in project management and Kerto LVL (laminated veneer lumber) products.

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