Wood, above all other materials with the possible exception of gold, is an emotional material. We humans relate to forests and trees and wood on many different levels from the depths of our psyche to our fundamental and practical needs for shelter, comfort and aesthetic appreciation. “Where’er you walk, cool gales shall fan the glade; Trees, where you sit, shall crowd into a shade” from Handel’s opera Semele evokes the universal human response to trees.
So why harvest forests, cut trees and use wood for buildings? The answer is because we must, and here’s why. First and foremost wood is the most environmentally acceptable material that we have in terms of its low carbon impact on the planet. There is no other building material that stores carbon, which is totally renewable and has such low embodied energy in its production. If we compare wood to mined and non-renewable steel and aluminium, the energy required to refine those metals requires huge energy inputs and creates pollution; whereas wood requires little energy. If we consider glass, the energy input is also much greater than for wood. But when we use wood the carbon is locked up for the life of the product and then can be recycled for such products as MDF, particle board, furniture or even used to create energy at the last. The carbon stored in the Oak hammerbeam roof at Westminster Hall in London has been locked up since 1393 which, with many ancient temples in Japan, also demonstrates the longevity of wood. Only when we build unsustainably must the carbon in wood possibly be returned – all part of the case for sustainable buildings. When it comes to wood as a building material, or for the joinery and furniture that finish and fill a building, there is no other more environmentally friendly choice than wood. Even other recycled materials may originally have been mined or drilled for, or consumed high energy in their original production or recycling conversion. Few, if any, building materials can be renewed naturally, other than perhaps bamboo which may not always be as green as it is made out.
Performance is always a vital factor for architects and engineers and wood has many attributes to those that know it as a material. Wood burns. In fact wood sections form a charcoal layer as they burn, so insulating the core and prolonging their structural integrity; and wood speaks and creaks before it eventually fails, as any fireman will tell. There is no such luxury with steel when it suddenly melts at a given temperature, as the World Trade Centre demonstrated so graphically. Wood also insulates well, perhaps not vital in Southeast Asia but a real benefit to any project north of Guangzhou in cold China, Korea and Japan. Wood stains, colours, paints, takes all kinds of finishes and can be created in a myriad of fashions. It glues, nails, screws, joints and works with other materials mainly without problems as a very flexible material. It moves with moisture and humidity but is predictable and manageable in this respect. Many species can easily be treated to resist the effects of weather and infestation. Many species are naturally durable – as in weather and rot resistance. Some, such as Teak, Iroko, Epe, Ekki and Merbau need no treatment at all; and most grow old gracefully as architect Kerry Hill has demonstrated so well at the Datai Hotel in Langkawi. (See photo: Datai Hotel exterior)
Material performance has other implications too. There is a wood for every use and the Japanese in particular are masters of the art. Wood for strength, wood for bending, wood for a fine finish and so on, are the multiple options that wood offers. Wood is vital as an acoustic material for most musical performance venues as Renzo Piano insisted for his Rome Auditorium. But wood species for these specific uses do not all grow in the same place. Heavily softwood-forested Sweden has to import hardwoods and Malaysia imports temperate hardwoods, are examples. The consequence therefore is that wood needs to be moved around and even shipped inter-continentally. Long distance transportation has been a concern for many users of imported wood, but the latest Life Cycle Assessment (LCA) study undertaken by the American hardwood export industry has provided some answers now based on science. Its LCA project is being continuously carried out by independent and internationally respected consultants PE International located in Austria. Their initial findings, based on worst case scenarios of American hardwood production and extensive transportation over land and sea from central USA to Europe, show that there is very little impact on global warming. In fact the study shows that in all US hardwood species all the energy and emissions used for forestry management, sawmilling, kiln drying, and all stages of transport to deliver 4/4 (1”) lumber to the European market – and by inference to Asia – are more than offset by the carbon stored.
Now let’s return to the human factor. Wood is a great humanising material but not suitable for high rise construction and where maximum light is needed. Here steel and glass structures may be the only choice, but the flooring and interiors panelling and fit-out are frequently fabricated with wood for its aesthetics and interface with people. But that is not the only reason. Wood happens to be the most flexible of materials for which sizing, fixing and finishing is simple, practical, cost effective and can almost always be done on site. And talking of light, consider Portcullis House at Westminster in UK, an iconic building by Hopkins Architects and engineered by Arup. The interior atrium, surrounded by on four high sides, needed to maximise the light through a geodesic roof canopy. Arup were keen to minimise the support sections to maximise the area of glass. They tested steel and laminated American white oak from standard FAS Grade lumber. On a ‘volume to weight’ basis the oak tested stronger and the resulting roof aesthetically more pleasing to the MPs who now work there. (See Photo: Portcullis House)
There are also the issues of plantations and natural forests, both of which have a place in commercial wood production when managed on a responsible and sustainable basis. Dr Ken McDicken of Food & Agriculture Organisation (FAO), at a seminar in Jakarta in March this year, provided a view of the global forest resource over 4 billion ha, representing 31% of global land. While we still have the same area of forest as in 1948 this figure masks regional differences such as a decline of forest resources in the tropics which offsets gains in the Northern Hemisphere. There is no doubt that tropical forests have been overcut and converted since World War II and much of the loss is permanent. Conversely there has been an increase in plantations, particularly in the tropics of Indonesia and Malaysia and in countries like Argentina and Chile and temperate New Zealand. So why not rely just on plantations and preserve natural forests? Firstly, it is not possible to preserve forests which are living and dynamic systems, so conservation would be the only option there. Secondly a natural forest has far more plant and animal biodiversity than any plantation is likely to have. So the best option is to manage and harvest natural forests sustainably, particularly hardwoods. That is because many hardwoods are shade tolerant and can be harvested selectively rather than clear felled, whereas softwoods need to be completely felled and replanted, being shade intolerant. Selective felling of mature hardwood stems removes trees that no longer absorb so much carbon and makes way for younger dynamic trees that grow to reach the now open canopy and maximise carbon absorption. Furthermore in natural forests the most suitable species for the terrain grow up through the competition by natural selection; whereas often plantations species have not been well matched to the site.
Ultimately the real issue is “use it or lose it”. If commercial forests are not given a value and maintained as a place for forest dwellers to work, then the chances are that the forest will be removed and the land converted to other uses such as agriculture, mining and for non forest plantations such as palm oil. It was shown some years ago by the Timber Committee of the United Nations Economic Committee for Europe (UN/ECE) that only 7% of harvested wood is traded across international borders and that the major causes of deforestation are by collection for fuel and shifting agriculture. The argument that commercial logging provides increased access to such activities is countered by the local desire to protect forests that provide valuable wood and jobs. Most important is that sustainable forest management protects biodiversity, inhibits soil erosion and can rotate forever, so long as there is a market for all forest products.
Finally, the last words can be left to former Greenpeace warrior and environmental campaigner Dr Patrick Moore from his book ‘Trees are the answer’. He says “I believe that trees are the answer to a lot of questions about our future. These include: How can we advance to a more sustainable economy based on renewable fuels and materials? How can we improve literacy and sanitation in developing countries while reversing deforestation and protecting wildlife at the same time? How can we pull carbon out of the atmosphere and reduce the amount of greenhouse gases emissions, carbon dioxide in particular? How can we increase the amount of land that will support a greater diversity of species? How can we help prevent soil erosion and provide clean air and water? How can we make this world more beautiful and green? The answer is, by growing more trees and then using more wood, both as a substitute for non-renewable fossil fuels and materials such as steel, concrete and plastic, and as paper products for printing, packaging and sanitation.”