As a manufactured product CLT (Cross Laminated Timber) is produced from layers of spruce wood arranged crosswise on top of each other and glued with a pressing power of 6 N/mm2 to form large-sized solid wood elements.
The innovative aspect of CLT is its thickness which allows using it as a stand-alone structural element with outstanding strength and stiffness properties. The large dimensions, its easy handling and versatile applicability opens new markets for timber engineering.
Cross Laminated Timber (CLT) has been popular in Europe for more than 20 years, with extensive research and a documented track record supporting its widespread use. It has propelled wood construction to new heights,worldwide. The most recent and outstanding examples are:
a 18 story high student residential building in Vancouver
in Central London is the world largest building comprises 121 apartments for rent
alongside two ground level courtyards flanked by 1500m2 of retail and restaurant spaces.
14-storey luxury apartment block in central Bergen, Norway
Panels are pre-designed to owner’s requirements and so the assembling time
is greatly reduced. The outcome is an improved efficiency throughout the whole supply chain and also results in a much lower capital cost and in a faster occupancy. Besides, being the structure construction also a manufactured process, the requested time from fundations to roof, becomes a matter of days. Considering a two-storey detached house and the related size of the house, erection time could range from 2 up to 5 days.
Thermal performance is determined by its U-value, or coefficient of heat transfer, which relates to the panel thickness. Furthermore CLT panels are manufactured using CNC equipment to precise tolerances, panel joints also fit tighter, which results in a better energy efficiency for the structure. CLT in our new housing concept plays a key role; nevertheless it has to be seen together with the external cladding and the inner lining provided by gypsum fiber panels.
CLT building systems provide adequate noise control for both airborne and impact sound transmission and so the solid mass of the wall contributes to the acoustic performance. Additional sound-proof benefits, such as the interfaces between the floor and wall plate, come with the use of sealant and other types of membranes as they are consistent with the process.
LIGHT ENVIRONMENT FOOTPRINT
The key issue in environmental footprint is C02 emission. Wood products unlike others continue to store carbon absorbed by the trees while growing; so the use of wood in construction results in zero C02 emission.
A a matter of fact, wood manufacturing process requires much less energy than other building processes and so in less greenhouse gas emissions.
CLT’s thick cross-section provides valuable fire resistance because panels char slowly and once formed, char protects the wood from further degradation.
Because of their dimensional stability and rigidity, CLT panels create an effective lateral load resisting system. Researchers have conducted extensive seismic testing on CLT and have found panels to
perform exceptionally well with no residual deformation, particularly in multi- story applications. In Japan, for example, a seven story CLT building was tested on the world’s largest shake table (magnitude of 7.2 and acceleration of 0.8 to 1.2g). It survived 14 consecutive seismic events with almost no damage. In addition CLT also offers good ductile behavior and energy dissipation.
CLT panels are manufactured for specific applications, and tailored to customer’s specifications from the design step to on-site assembling, which has no job site waste. Plus, CLT manufacturers can reuse fabrication scraps for stairs and other architectural elements, or as biofuel.
It is relatively easy to increase the thickness of a CLT panel to allow for longer spans requiring fewer interior support elements. Manufacturers useCNC equipment to cut panels and openings to exact specifications, often to meet very tight tolerances (within millimeters). Plus, when field modifications are needed, they can be made with simple tools.