Wood is composed of about 50% carbon. Buildings made with this material can contribute to reduce di CO2 emissions in the air, because they act as ‘reservoirs’: each cubic meter stores about one ton of carbon dioxide that would end up in the atmosphere after the end of a tree’s life cycle. If used correctly, wood can store more carbon than is released for its operations of harvesting, transformation, transport and assembly. And its “gray energy,” of the total energy required for the operations connected with its life cycle, is far lower than that of other construction materials. If the use of wood is accompanied by construction systems with higher performance or prefabrication, creating parts prior to assembly at the worksite, the ecological advantages are even more pronounced.
The sustainability of wood according to AHEC
David Venables, director of AHEC (American Hardwood Export Council) in Europe, can help us to clarify matters. “Wood’s sustainability should be evaluated across the entire chain of supply and production, not just the sourcing of raw material but also the life cycle assessment (LCA), in relation to the correct use of the material and the selected species. Life cycle is a matter of design. Besides low carbon footprint, in its industrial application wood consumes only small quantities of fossil fuels and relies on fewer resources – like water – as opposed to other construction materials. So its sustainability is tangible and measurable”.
A rich catalog
“Today we can see a vast catalogue of construction systems – from panels of solid or cross-laminated (CLT) wood for walls, floor slabs and roofs, to laminated wooden beams for complex engineering – which are lighter, thus requiring fewer foundations, making for a quicker construction process, because the semi-finished products arrive ready for use. The savings for transport reach a level of up to 70%. Wood systems offer greater thermal insulation, with less expenditure of energy for functioning, along with extraordinary design flexibility”.
Training and knowledge
“In spite of these advantages, the main obstacle to the spread of this type of building has to do with levels of education and knowledge in architecture schools and the construction industry. One of the missions of AHEC, in fact, is to spread knowledge of hardwood and to promote experimentation to demonstrate its functional and aesthetic potential. We also encourage research on species with lower impact, like American tulipwood, often called yellow poplar, which has excellent characteristics of strength in relation to weight, making it suitable for load-bearing structures in laminated wood (CLT). We also focus on American red oak, a widespread species in the United States, which has lower costs than other types of oak while providing the same levels of strength and stability. It is perfect for floors, for example.”
Rubner Haus: the advantages of prefabricated systems
Wooden architecture implies the design of construction technologies. The Rubner Group is based in Alto Adige and operates in the fields of wood, construction engineering and large turnkey projects. We spoke with Daniel Gasser, in charge of product development and innovation, about the advantages of prefabricated construction systems and the management of the chain of production in this area. “Inside Rubner,” Gasser says, “we have developed three construction systems: Residenz (frame construction), Blockhaus and Casablanca. The first provides a structure composed of horizontal and vertical parts, into which we insert – directly during production – the electrical system, plumbing, windows and sunscreens, sills, mosquito screens and entrance doors. We arrive at the worksite with a wall that needs only the last layer of coating. Blockhaus is a construction system in solid wood without metal connections: red spruce boards are overlapped and fastened with finger joints, ensuring great stability and tight sealing of the house. Finally, Casablanca is the stucco-finished Blockhaus system. The dry assembly at the worksite makes the process faster and more efficient. Everything is designed a priori.”
Nothing is thrown away from the wood
Wooden architecture clearly addresses important issues of sustainability: “We oversee the entire production chain,” Gasser goes on. “The trees grow in certified forests in the Alps; at our sawmills in Alto Adige and Austria we cut timber according to high quality standards, and in the group’s other companies we make everything from sawn timber to windows, doors to large architectural complexes. We use everything from the wood: timber, cork, fiber. Cork is an excellent natural insulator, waterproof, flame resistant. It breathes and prevents mildew. Wood fiber is free of chemical additives; it absorbs sound, conserves heat, and it is extraordinarily durable. A wooden house can be dismantled and reassembled, updated by parts reutilizing walls, slabs and the roof itself. If the foundation and semi-basement are properly made, namely to prevent entry of water and humidity, a wooden house has no limits on its life span.”
"Made in the factory" by More
Speaking of custom projects and design flexibility, More is a company that creates and implements residences through prefabrication systems. It was founded in 2010 as part of the Moretti group, a reference point in Italy for industrialized construction in reinforced concrete, laminated timber and mixed approaches. Valentina Moretti, founder and creative director of More, explains prefabricated houses. “First of all,” she says, “we should clarify the fact that everything around us is prefabricated: literally ‘made in the factory.’ This situation guarantees high levels of quality, because it is controlled, produced in a stable climate by a team of specialized workers, avoiding the variables of the construction site. Furthermore, we have to get beyond the concept that prefabricated construction is a sort of game of building blocks, made with standardized pieces, like a sum of items selected from a catalogue. A market like that of Italy demands uniqueness".
Overcome the design constraints
“The real difference with prefabrication is that everything is designed a priori. And the cost of the house is determined by that design: the structure accounts for about 20% of the final cost, while the other 80% is for cladding, mechanical systems, glazing and finishes. After a number of years of production of unique buildings, our clients can recognize the archetypes, and ask us to base things on those models: for example, the single-story house, the house with overhangs, or particular types of roofs. Everything is totally made to measure, however. The design constraints are dictated for the most part by the dimensions of the construction systems and their connections, which also depend on the specific conditions of the site and the geographical aspects of transport. This year we have opened an entire division for research and development, to study materials and new technical solutions, which for example can eliminate internal counter-walls, leaving the concrete or the wood on view; or wall systems that reduce the number of pipes needed for physical plant; or overhanging structures in compliance with anti-seismic regulations. All to take the possibilities of custom construction to new heights.”