Traditionally most of the human built environment was made of stone or wood, but nowadays reinforced concrete is one of the world’s most commonly used construction materials. This trend needs to be reversed if we are to reduce climate change, and I would like to see much more wood used as structural, insulative and decorative elements in future Macau buildings.
The manufacture of cement (a key ingredient in concrete) involves high temperature kilns and produces about 6% of global carbon emissions as a waste product. Similarly, steel is made by smelting iron in a furnace which generates about 8% of global carbon emissions. Building construction is then also very energy intensive so that it also generates a lot of carbon emissions. Finally, in operation, buildings account for around 40% of global electricity consumption – to heat and cool them and to run the equipment within them – and so they produce even more carbon emissions. Thus a large part of the world’s climate change problem can be attributed to problems with how we make and use the human built environment.
In contrast to concrete and steel, wood is a sustainable and renewable natural resource that is effectively carbon neutral. Plants absorb carbon from the environment to grow and this carbon is trapped within wood that is used in buildings. After use, wood decomposes and naturally releases its carbon and other nutritious constituents back to the environment for reuse.
Modern timber construction does not use traditional wooden posts, beams and planks. Instead, wooden sticks, fibres or sheets are glued together into cross- laminated beams and panels. Most people are familiar with plywood and oriented-strand panels, but we now also have glue-laminated beams and panels that are becoming increasingly popular, especially in Europe. Glue-laminated wooden construction materials can be made using just a small fraction of the energy needed for the equivalent steel reinforced concrete materials. They are also much lighter for the same strength and easier to join together. These characteristics explain why bamboo scaffolding is so popular in Asia, for example.
The substantially lighter weight of wooden building elements mean that they are much easier to prefabricate in a factory and then transport and assemble on-site. Building pre-fabrication has many advantages, especially in reducing the amount of labor and the time needed for onsite construction.
Wood is also relatively fire resistant and burns much, much more slowly and predictably than the aluminum clad plastic facades that are often used now – remember the recent Grenfell Tower disaster in London. If you have ever seen the aftermath of a forest fire you will know that while the light branches and leaves of trees have burnt away the main tree trunks are often still standing. You can readily make wooden fire doors that are lighter and as fire resistant as steel ones.
Building heating and cooling is needed to maintain comfortable indoor conditions in the face of adverse outdoor weather so that a major issue with buildings is how well the materials used resist heat transmission. Aluminum is a very good heat conductor, which is why it feels hot or cold depending on the temperature of its contents. Compared to aluminum, steel has about 20% the thermal conductivity, wooden panels and concrete have about 0.1% the conductivity, and wood fiber insulation has about 0.005% the conductivity. Thus properly made wooden buildings need much less heating and cooling than similar steel or concrete buildings.
Modern wood materials are now being successfully used to make quite large high-rise buildings, eg the 85m tall Mjostarnet Tower being built in Norway, or the 18 story Brock Commons Student Residence in British Columbia that was completed in 2016.
Governments in Finland, Canada, the Netherlands, New Zealand and Tasmania have proclaimed Wood Encouragement Policies and I would really like to see something similar in Macau. It is yet another way we could promote our environmental credentials, lead the technological development of the region and nurture a regionally competitive local engineering consulting industry.