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Monday, July 26, 2021

Is building with timber really sustainable?

Hailed as one of the most environmentally friendly building materials, timber is versatile, strong, renewable, and beautiful.

Mass timber construction continues to be on the rise with advocates claiming it as part of a climate change solution. However, wood is often associated with deforestation, and the frequency of forest fires have increased in recent years. Many also question whether the logging and manufacturing required to produce building materials outweigh any benefits. And so, we ask our experts: is building with timber really sustainable?

THE EXPERTS

CÉCILIA GROSS, ARCHITECT PARTNER/DIRECTOR, VENHOEVENCS ARCHITECTURE+URBANISM

Cécilia joined the VenhoevenCS team in 2003, and in 2017 she became a partner architect and director. Her expertise is in realizing highly complex projects that encompass both architectural and urban concerns. Cécilia is project architect of the winning design for the new Aquatics Centre for the Paris 2024 Olympic Games and currently leading the design team to finish the technical design.

“The Covid-19 pandemic has thrown into sharp relief the need for integrated green recovery plans that deal with all the major challenges we face as a society. Think of interconnected issues such as global warming, loss of biodiversity, depletion of raw materials and pollution. These challenges are strongly related to problems with current land use, infrastructure, power generation, water management and economic activities such as agriculture, industry and transportation. These problems are also reflected in the construction industry’s use of timber as a material.

We know that bio-based materials, such as wood, mitigate the impact of climate change. Unlike concrete and steel they reduce a buildings CO2 footprint by storing carbon and being renewable. Yet its sustainability as a material is also reliant on a number of factors including clever forestry, careful sourcing, skillful engineering and experienced design. Considering that the construction sector is responsible for 40% of CO2 emissions, how can we make the best use of timber to maximise its sustainable potential?

In our design for the Olympic Aquatics Centre for Paris 2024 – the only permanent building to be constructed for the games – the lifespan of the building was a key element in choosing wood as a material. It’s made entirely of laminated timber, this not only helps to reduce CO2 emissions during construction but as a part of a legacy building, it also locks up COfor decades to come. This includes future reuse as it was designed so that most of the wood can be reused and recycled for hundreds of years without being limited by form or dimensions.

Alongside sourcing wood from sustainable forests in Europe, we also came up with design solutions to minimise the amount of material required for construction. For the roof we used an efficient system of suspended timber girders set one metre apart and spanning 89 metres, which enabled us to reduce material use. The roof also has a shape that follows as closely as possible the required free space above basins and tribunes. Compared to regular solutions, this dramatically reduces the volume of the hall and the amount of energy required to heat the Aquatic Centre, adding to the building’s overall sustainability.

The use of timber for sustainable construction will be an important part of the green recovery, but we have to take elements such as sourcing, manufacture and transport into account. It’s also not a panacea. Timber isn’t the best solution for every situation such as building cores or foundations. The starting point has to be: the right material in the right place. For those areas where we still need concrete and steel the industry should be creating innovative solutions that continue drive down CO2 emissions.” – www. venhoevencs.nl

ONDŘEJ CHYBÍK AND MICHAL KRIŠTOF, FOUNDING PARTNERS OF CHYBIK + KRISTOF

Ondřej and Michal founded Czech architecture and urban design practice CHYBIK + KRISTOF in 2010. Based in Prague, Brno and Bratislava, with over 50 international team members, the practice aims to bridge the gaps between private and public space while transcending both generational and societal spheres. Taking into account local histories and environmental specificities, the studio works in the fields of architecture, urbanism, research, education and on a wide array of projects, ranging from urban development to public and private buildings.

“We see timber as the most sustainable material, because of its renewability. This is also a question of locality. Speaking from our corner of the world, which obviously presents different conditions than, for example, sub-Saharan Africa, timber is both renewable and replenishable in a continuous cycle, and especially so since CTL (cut-to-length logging) has come into play. Although it is a more expensive harvesting method, it is more environmentally friendly, causing less soil disturbance among other concerns. Finally, timber is all-in-all more expensive to produce, but the time spent preparing it at the building site is drastically reduced due to its “prefabricated” nature.” – www.chybik-kristof.com

YAARA PLAVES, ASSOCIATE AT HAMES SHARLEY

Yaara is head of the National Sustainability Forum (NSF) at Hames Sharley, sharing her knowledge and passion with the team and clients alike. With a deep understanding of sustainability and regenerative design, Yaara is involved in several committees and professional organisations in the sustainability field. With extensive experience in the construction industry, Yaara routinely manages retail, education, residential, commercial and government projects, varying in size.

“As part of our sustainable practice journey – both design and operational – Hames Sharley has established the National Design Forum (NSF), tasked with promoting and educating ourselves and our clients about sustainability. A large part of this conversation centres on materials and what makes a material sustainable.

Hames Sharley has decided to use the ILFI as the framework, using the Declare label and the Red List as the first filters through which we ascertain material sustainability. After that, we have prepared a questionnaire for suppliers that have no accreditation under the above. From this, we have distilled a list of materials that are the basis for our sustainable selections, linked to our BIM processes.

When considering sustainable building materials, timber is an obvious option. As a renewable resource we can replace the timber we cut down and grow more. Other building materials are finite, with raw materials being depleted rapidly.

However, this is only one consideration of the sustainability of materials. Other factors, using the Declare label criteria, are: what is it made of, what is the life expectancy, where is it made, what is the embodied energy and where does it go at the end of its life.

Briefly addressing the first two points, timber is a natural material, which can be very durable if properly maintained. Glue and varnish/paint used for fixing and finishing can have high VOCs so their use should be carefully considered. 

The timber industry in Australia is well regulated and relies on plantation timbers and harvesting of natural forests. Land clearing is a major contributor to carbon emissions and increases biodiversity loss, but according to the ABC, the primary reason for land clearing in Australia is agriculture, not the timber industry.

The use of Plantation timber from USA, Canada and Europe is acceptable, provided it is certified. There are certification programs for timber sourced elsewhere overseas, but the validity and transparency of logging and manufacturing are harder to verify.

Although timber is carbon neutral and renewable, it has to be correctly sourced. There are great opportunities for saving carbon emissions by using timber as a structural material rather than concrete or steel. Using locally sourced plantation timber reduces transportation related emissions. The most sustainable option is recycled timber (a conversation for another time).

Timber lends itself beautifully to prefabrication, being easy to dismantle and reuse and perfect for frameworks such as Buildings As Material Banks (BAMB), where circular economy principles drive the design process. It means that buildings are designed to be dismantled, and the components can be reused in other buildings, rather than using new materials and creating waste. Fixing methods are critical, as mechanical fixings make deconstruction and reconstruction easier.

Overall, considering timber through the above criteria, it is a sustainable option, provided it is correctly sourced and certified. By understanding how to work with timber as a structural element while maintaining fire and acoustic performance, we can unlock the potential for economic and environmental sustainability benefits. There are benefits for using prefabricated timber structures for reduced construction time and waste. There are also possibilities for modular construction that can be deconstructed for reuse. The agility and flexibility of timber make it ideal for adaptive construction systems while reducing the carbon footprint of construction.” – www.hamessharley.com.au

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