Urbanization and the evolution of modern cities have led to the development of high-rise building constructions, but what is the real environmental impact of these buildings? Traditionally designed with concrete as the main structural material, their construction implies an increase of CO2 emissions released into the atmosphere, air pollution and a rise in energy and water consumption. These consequences call for the development of new sustainable strategies outside of the industry’s comfort zone, such as the incorporation of wood as a structural element. Cross Laminated Timber (CLT) has emerged as a new structural strategy that Chilean architects have begun to incorporate into the country’s architecture, adapted to local conditions and norms.
The ‘Tamango Project’ by Tallwood architects is an example of the challenges and opportunities of wood construction in the country and the region, as it might potentially be the first 12-storey building with an engineered timber structure. Changing the traditional construction paradigms of the area, Tamango represents a step into sustainable solutions that follow an integrated design process through all the stages of an architectural project.
Why Build High-Rise Architecture in CLT?
Tall buildings in CLT already exist around the world, demonstrating that using wood as the main structural material in high-rise buildings can be the future. Besides being a renewable resource –"which cannot be depleted and is able to supply a continuous source of clean energy"–, wood provides sustainable solutions that, combined with technological advances, cover all stages of its lifecycle, from its fabrication, assembly and application.
During its fabrication, each kilogram of wood captures 1.8 kgs of CO2, and its assembly needs a dry construction that is silent and doesn’t generate waste. When inhabiting the building, wood has excellent thermal and hygroscopic properties (the capacity to hold and release humidity), which contribute to its energy efficiency and user comfort.
The local conditions of Coyhaique, Chile, where the burning of damp wood for heating interiors releases a great deal of CO2 emissions, has made it one of the most contaminated cities in Latin America. In response to this, Tamango's goal was to propose innovative solutions within two main lines: to be sustainable and to develop an efficient construction system, always considering the difficult access to materials and workforce in the area.
Construction System: Tamango’s Material Strategy
Inverting the traditional process, Tamango’s design incorporates a multidisciplinary team –integrated by structural engineers, fire resistance, energy efficiency and acoustics specialists– that analyzed all the possible outcomes from the beginning of the process. Simultaneously, the project developed a study of thermal envelopes with experts in energy efficiency from Chile, Finland and Canada, aiming to create a high-rise building with sustainable strategies that helps with the decontamination of the area.
Using the latest innovations for joining wood layers, Mass Timber products –also known as “compressed layers of wood that create structural load bearing elements”– can have adjustable sizes created for panels, posts and beams, all which enable high-strength systems (much like concrete and steel) but in significantly lighter weights. Tamango’s structure was developed by previously designed wood elements –CLT, LVL and Glulam– together with certified sawn timber with different structural degrees.
According to the Engineered Wood Association, CLT prefabricated panels are composed of several pressed layers –usually three, five, seven or nine– of kiln-dried lumber boards stacked in alternating directions, joined with structural adhesives. Maintaining a right angle when gluing these layers gives the panel structural rigidity in both directions. To achieve accurate prefabricated structure results, the project worked with previous building information modeling (BIM), where the team detailed every panel and their future assembly. Once in the construction site, these panels were rapidly and efficiently joined together, much like a puzzle.
As Juan José Ugarte G. and Gerardo Armanet –Tallwood's architects– specify, wood is a solution that incorporates the design and construction phases through the prior measurement and assembly of elements, or as he puts it, the project is “construct[ed] before construction.”
As a complement to CLT panels, the strategy incorporated Laminated Veneer Lumber (LVL) , a construction material produced by dried and graded wood veneers that are bonded together under heat and pressure in large panels that are usually used for beams, trusses, planks and rafters.
How Does the Final Result Benefit the Environment?
Despite the process’ obstacles –for example the lack of progress in the Chilean code for high-rise timber structures with more than five levels– the 1,870 m3 of wooden structures captures 1,230 tons of CO2, which already surpasses the emissions during its fabrication and transportation. During the design process, it developed an energy efficiency strategy that created heating from electric pumps and a thermal skin that saves 75% of expenses in monthly heating and 60% of energy savings in contrast with equivalent housing projects. In addition, if the building’s life cycle comes to an end, its structural elements are easy to disassemble and become available for reuse in future projects.
As a regional pioneer, Tamango takes the first step and establishes itself as a model for future architecture projects in Latin America, where height is no longer a problem for wood structure systems. Introducing CLT wood in a 12-storey building, it demonstrates the country’s efforts during the last decades and enables new opportunities for the region.
