Cree pioneers innovative timber and concrete hybrid technology that enables architects to design stunning tall wood buildings up to 30 stories.

To take new paths, you have to rethink. As part of the internationally renowned Rhomberg Group, Cree is the logical outcome of four generations of experience in construction. Not just a construction company, Cree is an innovative company, pioneering tall timber building architecture, and new building strategies involving the sustainable handling of natural resources. With a vision to bring wood as a primary building material into cities, the company is creating a new basis for modern, urban architecture by enabling reduced life cycle costs, higher conservation of building value, best possible comfort and state-of-theart safety requirements through its LifeCycle Tower (LCT) system.

Borrowing the philosophy and lifestyle of the North American natives of the same name, which in its modern interpretation means Creative Resource & Energy Efficiency, Cree is also a source of ideas and initiator of new strategies of sustainable treatment of and coexistence with nature and its resources.

Certified ISO 9001 (quality) und ISO 14001 (environment), the company's LCT system offers a wealth of benefits including energy and resource efficiency, an extremely reduced carbon footprint, completion time almost halved, low lifecycle costs and the latest safety standards, to name but a few.

Why the future is about doing more with less

Cree's building philosophy is based on the premise that building better naturally means using more renewable raw materials. On the one hand, countless prestigious and architecturally sophisticated buildings are constructed all around the world on a daily basis and this urban development is based primarily on conventionally produced prototypes. However, the complex construction work that this involves goes hand-in-hand with high building costs, long construction times and high planning risks.

A closer look at the facts reveals that the construction industry's conventional construction methods today accounts for some 40 percent of energy and resource consumption as well as 40 percent of waste generation and CO2 emissions. The construction industry is also responsible for 60 percent of the world's transportation emissions. Given that over 50 percent of the world's current population lives in urban areas and with this trend increasing, resources are becoming ever scarcer and CO2 emissions from the global construction industry even higher. As such, it is hardly surprising that the global debate focuses on sustainability when considering the future.

Having a deeper understanding of today's climate and global living conditions, Cree's vision stems from the realization that new strategies are imperative. Given that cities today account for over three quarters of world energy consumption, Cree aims to construct large hybrid buildings that are based on a sustainable, natural main component. The company's vision can be summarized as: We build in wood - and we do it in a system.

Nature as a role model

According to the experts at Cree, if you want to build economically and sustainably, you should work with a system. The fewer the detail solutions to be implemented, the shorter the construction period and the less dust, noise and waste will be generated on the site. Further, implementation of complex details, which are hard to control on site under normal building conditions, is completely eliminated by series prefabrication. However, meticulously planned standard solutions do not necessarily mean the end of all individuality. The modular construction of the LCT system components - slab, columns, facade and building services - is fast, efficient and standardized. This saves resources, time and money but leaves plenty of scope for visionary design ideas.

The rationale behind the LCT system is that an innovative system can grow better than individual projects. In essence, the LCT system is 'individual industrialization'. Based on a sustainable wood-hybrid system for mid and tall buildings that has been thought-out down to the last detail, the LCT can be designed individually and constructed off-site in short order, to guarantee the minimal use of resources and energy over its whole lifecycle. A LifeCycle Tower can also be converted to another use at any time in its lifecycle, and its modular design makes renovation much easier. When a building has reached its full useful life, urban mining of the LCT system can be employed, extracting materials to reuse, recycle or convert into bioenergy, thus protecting landfills from unnecessary waste.

LCT: The wood-hybrid high-rise

The LCT system can simply be defined as a hybrid timber construction system for large buildings that guarantees minimized use of resources and energy over its full lifecycle. The result of this concept of individual industrialization is the world's first LifeCycle Tower in Austria - LCT ONE. Whilst essential elements of the building services are already contained in a LifeCycle Tower, the various system components (core, slab, façade columns) are prefabricated on an industrial scale and are therefore suitable for modular installation. The LCT system therefore is suitable for a variety of commercial uses including offices, hotels, restaurants, and public buildings (museum, library, town hall, etc).

The LCT building system uses prefabricated components manufactured to an architect's exact specifications. The wall facades are made from glue-laminate posts, while the floor slabs are constructed from a hybrid of glue-laminate posts and concrete. While these components are manufactured off-site, the foundation of a building is laid and the structural elevator shaft core is erected. This core, made out of either steel and concrete or wood, stiffens the building and provides a frame from which the walls and floors can hang. The slabs and posts are then assembled by interconnecting the preset pins and holes of the components. With this skeleton structure, architects can design a wide variety of layouts and exterior skins, to create dramatic and sustainable buildings.

With no structural dividing walls, the system is highly flexible and allows individual division of space. The building can be converted throughout its lifecycle - and the materials installed hold their value significantly from a deconstruction standpoint, even viewed over many decades. Moreover, the LCT system components can be produced by many different enterprises and provide excellent opportunities for regional craftsmen and the timber industry. Significantly, in contrast to other timber construction projects, Cree takes a top-down approach, whereby all components are planned in such a way that they can be easily adapted to the requirements and regulations of different countries.

LCR: Indoor environment quality that only nature can provide

Building on the success of the LCT system, Cree is working on creating LifeCycle Residential (LCR): a system specifically adapted to the requirements of residential and hotel buildings, which incorporates many of the well-known advantages found in every LifeCycle Tower. The main difference contributing to an even better indoor environment quality and comfort is found in the LCR system on the ceiling. The building services can be integrated in other places, which allows for ceilings with a solid visible timber underside. Through LCR, the company is positive that living in harmony with nature and using global resources responsibly can be achieved in the city center in future.

The LCR system is compatible with the LCT system, so that multiple-use buildings such as apartment and office towers are possible without any problems. And the system allows for much shorter construction periods - particularly compared with conventional reinforced concrete and masonry apartment buildings. As in the case with the LCT system, individuality does not have to be sacrificed when using the LCR system. Flexible division of space, optional comfort solutions in the package and variable façade design, and a much wider variety of configurations can be achieved than would be expected with a pre-specified system.

Building a future with wood

Cree's innovative timber and concrete hybrid technology enables architects to design stunning tall wood buildings up to 30 stories, that can be erected as quickly as a storey a day. An environmentally feasible option, the innovative LCT system is a slab and post wood design method that requires up to 50 percent shorter construction time compared to reinforced concrete and steel construction. The LCT system also requires 39 percent fewer resources, over the life of a building and takes advantage of engineered timber products. By combining wood and concrete together, the LCT system substantially reduces the amount of concrete used in the building, resulting in a lighter structure, with a smaller foundation and up to 90 percent lower CO2 emissions.

Some might argue that building with wood is not sustainable. The truth is that constructing buildings with conventional designs requires resources in abundance - wood on the other hand grows back.

Nature supplies us with the building material of the future that offers all the characteristics demanded by innovative urban architecture. It is naturally resistant, of high structural quality and has indeed the very best fire prevention properties, which makes it perfectly suited for system building and prefabrication of complete building sections. As a natural raw material, wood can also be found in many parts of the world and has a positive impact on the world's carbon footprint. According to Cree, the wood used as building material in the LCT system can grow in the world's forests, normally within a few hours, depending on the size of the project.

One major concern is the fact that wood burns. However, it is important to note that wood burns safely, because through science we can predict how long wood will withstand the flames. This is in striking contrast to conventional buildings made of reinforced concrete where the steel, can collapse very quickly at certain temperatures. A number of large-scale fire tests have been carried out in Europe for the floor slab elements of the LCT system. These tests show the technology is able to withstand up to a two-hour fire test. Based on the results of these tests, the Cree components have been optimized leading to a reduction in the amount of concrete used, and the granting of the required REI 120 certificate.

Another misconception is that wood is not durable. Wood is extremely durable if used properly. Wood is not only durable outside, but inside as well, where it requires no chemical protection. Thanks to its natural resilience, the world is surrounded by wooden structures that have stood the test of time. In fact, one of the oldest wooden buildings in the world is the five-storey pagoda at the Horyu-ji Buddhist temple in Ikaruga, Japan. It is important to note that even if a timber building is demolished after several decades of use, it still produces usable materials in reclaimed wood and bioenergy.

© Timber Design & Technology 2013