Is raising the profile of bamboo as a building material for high-rise useful or irresponsible? asks Tim Coleridge
More from: 25 Verde in Turin by Luciano Pia
Recently launched conceptual designs for 360m-tall bamboo skyscrapers from a team of Paul Runaghan of Farrells and Jim Fleming of Buro Happold offer an exciting new use of a traditional material hailed optimistically as a ‘green steel’. However, a simplistic rush for bamboo risks causing wider threats to ecologies, societies and the climate in Asia and beyond. Architects must cultivate an evidence-led approach to building design ensuring new materials and forms do not distract from the real impacts of the materials used or the scale of building.
Boldly, but questionably, touted as an uber environmentally conscientious building material, bamboo’s popularity as a wood and fibre substitute has been increasing. Its versatility is exemplified in myriad applications including papermaking, fuel, clothing, furniture, tableware, packaging, and medicines. It is estimated that over one billion people live in traditional bamboo houses, and bamboo is utilised in many building components from scaffolding, roofing, flooring, exterior walls and partitions to doors and window frames. However, contemporary rhetoric supporting the environmental credentials of bamboo is unquestioningly focused on its speed of growth.
Initiatives and policy changes since the late 1990s led to increased production of bamboo products. New bamboo-based industries emerged including engineered panels, particleboard, medium density fibreboard and other construction products. Production of bamboo flooring, in particular, increased significantly after the USGBC’s ‘environmentally preferable materials’ designation of bamboo and other rapidly renewable materials in 2002, giving eligibility for credits under the Leadership in Energy and Environmental Design (LEED) programme. Architects Shigeru Ban, Vo Trong Nghia, Simón Vélez, design collective Penda and others have pioneered experimentation with new structural forms in bamboo to critical acclaim.
Its inherent strength has led bamboo to be touted as an ecological super-material with Farrells and Buro Happold’s proposal joining other conceptual bio-skyscraper designs. In The Case for Tall Wood Buildings, Canadian architect Michael Green advocates wood and specifically mass timber to challenge steel and concrete as the essential structural materials of large buildings. Many tall wooden structures already exist, including the 505-foot Tianning Pagoda in Changzhou, China and Poland’s 387-foot Gliwice Radio Tower; but the Farrells and Buro Happold concepts represent a significant step change from current medium-rise structural timber buildings such as London’s 98-foot Murray Grove Tower.
However, recent research discredits bamboo’s sustainability credentials, demonstrating that its acknowledged benefits have come at a high environmental cost. It debunks the idea that rapidly renewable materials were inherently more environmentally superior to slower growing ones and highlights the degradation of natural forests and over-exploitation from wild harvesting; biodiversity loss; resilience loss in bamboo resources; increased social and environmental risks; and impacts of large-scale monoculture agriculture, including widespread use of fertilisers and pesticides. From approximately 1,250 bamboo types, a single species, Moso, makes up more than 80 per cent of China’s bamboo growing area, 5 million hectares in 2007.
Certification schemes, such as Forest Stewardship Council, provide internationally recognised accreditation of the provenance of timber and non-timber forest products including bamboo; however, specifiers must recognise such labels do not absolve moral responsibility for material specification. Certification of intensively managed, large-scale, monoculture plantations has in itself been drawn into question, with the costs of certification creating a market barrier for smallholders, who comprise the majority of bamboo growers. When Dominique Perrault, architect of France’s Bibliothèque Nationale, used rare exotic hardwoods for lining its reading rooms and external decking, was this arguably as much of an anti-ecological architecture as stacking its library books to bake in fully glazed tower blocks?
A more holistic ecological approach provides good reason to focus on the appropriate use of bamboo, timber and other bio-based building materials.
If sourced and used appropriately, bamboo is a great resource, providing many benefits; research has shown how it can aid prevention of soil erosion, reducing overexploitation of tropical forests and economically assisting impoverished people. The severity of environmental and climatic change dictates the urgency with which adaptation is required for future sustainability, including measures to reduce the concentration of carbon dioxide in the atmosphere and bamboo, timber and other bio-based building materials can all sequester carbon, locking it up for the life of the building component. Bio-based superstructure is a beneficial approach, concentrating sequestration within the largest and longest lasting building components.
Mass timber systems such as cross-laminated timber (CLT) and ‘Brettstapel’, pioneered in Germany and Scandinavian countries where plentiful timber supplies translate to active adoption in the industry, are helping to re-evaluate the ‘automatic’ use of steel and concrete in large buildings. CLT is the rare occurrence of a new structural material, creating new structural possibilities and architectural forms previously confined to origami paper folding. Other UK initiatives, such as Coed Cymru’s ‘Ty Unnos’ system and research into dowelled plank structures, imbue lower grade locally available timbers with added value as structural building materials. London-based practice Architype recently completed the first Welsh Brettstapel building at Coed-y-Brenin Visitor Centre. Other bio-based materials can be employed in building envelopes, providing breathable construction and exceptional insulative and hygrothermal performance, such as a hemp-lime composite used in the the Centre for Alternative Technology’s campus in Machynlleth.
The logical extrapolation of enhanced sequestration is that structures should be scaled up to maximise their mass and storage capacity, leading to a new aesthetic in which less is not more. When students from the Welsh school of Architecture built an experimental arch from homogeneous hemp-lime to investigate its structural performance, the massiveness of this simple form hinted at a radically different design ethos required to maximise the sequestration capacity of bio-composite building materials. This indicated a fresh architectural expression that directly challenges the high-tech minimal ‘eco-technical’ logic exemplified by practices such as Hopkins and Grimshaw, a new tectonic, that works with the inherent qualities of the material rather than squeezing it to fit a predetermined form.
But, while increased scale improves sequestration, it poses greater challenges for overall energy use, especially for high-rise buildings. Studies in the tropics have shown high-rise buildings typically demand higher energy intensity than medium-rise, findings that correlate with recent analysis by Hilson Moran in the UK to determine the effect of building form on energy consumption and CO2 emissions. Even the energy intensity of Ken Yeang’s bio-climatically designed ‘Menara Mesiniaga’ tower has been calculated as approximately twice that of a Passivhaus building. While energy embodied in materials and construction activities is important, operational energy demand still dominates over a building’s lifetime energy use. Studies show that, in a typical building, total in-use energy could surpass embodied energy after as little five years. Even in a low-energy design, it will potentially dominate after 20 years. The evidence again points toward a more humane scale of building also achieving a more sustainable solution overall.
All of this ultimately emphasises the importance of research and evidence informing practice, especially for buildings making grand claims about environmental performance. However, as highlighted by Edge Debate 46 and 54 ‘A New Professionalism?’ the built environment industry currently lacks the culture and practice of genuinely evidence-based design and fails to develop a crucial shared knowledge base, arising from the gaps between professions, between practice and academe, and between design assumptions and how buildings perform in use. In this context, the influence of high-profile practices is enhanced, perhaps artificially so, which comes with added responsibility. ‘Farrells Focus’ brings this conversation to the fore, leading us to ask, is ‘raising’ the profile of bamboo as a building material for high-rise useful or irresponsible?
Architects easily become enamoured with a new material or structural system, especially when a top-flight ‘form giver’ architect pioneers it. This fascination with new forms must not distract us from the need to also recognise that in good design form follows function, and, given that low environmental impact and energy consumption is now one of the most important functions, the forms must be derived from firm evidence.
About the Centre for Alternative Technology
Tim Coleridge writes from the Centre for Alternative Technology in Wales.
The Centre for Alternative Technology’s new MSc Sustainability and Adaptation course will look at the impacts of climate change upon people, ecosystems and the built environment. The course builds on CAT’s considerable experience as a leading voice on renewable energy and sustainable architecture to address the pressing question of how society needs to adapt to climate change, including becoming sustainable. It is the latest in a suite of courses from CAT’s Graduate School of the Environment, which also includes a Professional Diploma in Architecture and MSc in Renewable Energy and the Built Environment.
Pandering to bamboo: on skyscrapers made out of wood