Single or multi-family properties; administrative, office or retail buildings; in the city, countryside or on the coast. Cross Laminated Timber system is growing in popularity around the world due to its benefits for architecture and reduced environmental impact.
CLT (Cross Laminated Timber) consists of using solid wood panels made of planks which are glued, layered and then stacked in alternating directions. The cross laminated timber panels have a symmetrical crosswise structure made up of at least three layers.
The system first appeared in the 1990s in Austria and Germany, from where it spread across the globe. CLT offers architecture outstanding freedom of design and shorter construction times. Other benefits include its lightness, excellent thermal and acoustic insulation, as well as outstanding sustainability.
Architecture in general and CLT in particular were the topics of our recent conversation with Ari Artigas. An architect at Lacol Cooperativa, she boasts long-standing experience in architecture in wood, with many major projects to his name, including the six storey CLT La Borda building in Barcelona.
What are CLT’s main contributions to architecture?
I would say that sustainability is one of the greatest contributions CLT has made to architecture.
The benefits start with the production process, with plantations of trees grown solely for the building industry, which, in comparison with other materials such as concrete, have a low environmental impact. What’s more, if it is produced in the same region as the building project, then we could be talking about a proximity or net-zero emissions product.
CLT wooden frame house in Mirasol-San Cugat (Barcelona). Lacol Arquitectura/House Habitat
Wood is also reusable, so if a building is demolished, for example, it can be reused as fuel or as a component for other materials, leaving hardly any traces behind, thereby guaranteeing a low ecological footprint.
In terms of the building process and structural calculations, its reduced weight enables us to cut back on the foundations – which are normally reinforced concrete – as well as the earthwork. What’s more, it allows for lightweight foundations, using small pilotis, and avoiding the need for concrete.
How would you explain its rising popularity around the world?
Timber structures in the building industry have been common in many countries for some time now. In the specific case of CLT, I’d like to think that it is partly due to the growing environmental awareness of the agents involved in the building process: users, developers, technicians, builders and public administrations.
The fact that it allows for faster, more precise and mechanised assembly is another reason for choosing this building system.
House Habitat and Lacol have worked together on housing projects using CLT in San Cugat and Sant Esteve de Palautordera. What factors would you highlight about them?
In the case of both homes, both the users and experts were eager to use sustainable materials that would reduce CO2 emission levels.
Another key factor is the time involved which, thanks to the wooden structure, is considerably shorter in comparison with more conventional building techniques.
CLT wooden frame house in Sant Esteve de Palautordera (Barcelona). Lacol Arquitectura/House Habitat
In terms of thermal comfort, wood offers us a certain degree of insulation and does not cause thermal bridges, thereby improving the level of interior airtightness. Stone cladding materials were used to improve the thermal inertia, which is one of the deficiencies of wood.
In the case of Sant Cugat, a municipality with high levels of humidity, the natural hygrothermal qualities of wood enabled us to control the interior humidity. Moreover, the combination of wood and radiant flooring (which provides heating in winter and cooling in summer) guarantees excellent thermal comfort.
In Sant Esteve de Palautordera, the decision to use a CLT structure and leave it visible and cladding-free, cut costs as well as building times. It also has a sense of structural sincerity that enables us to delight in the changes time works on a living material such as wood, characterised by its warm feel and appearance.
