rown. One cubic metre of timber stores one tone of CO2. No doubt, steel and concrete are great building materials, until you consider their ecological footprint: 5 per cent of all GhG emissions worldwide come from concrete, while each ton of solid wood panels has sequestered around 1.6 tonnes of CO2. New engineered timber outperforms both concrete and steel: During manufacture a ton of steel emits 1.5 tonnes of carbon; and the production of a ton of cement emits over 1.1 tonnes of carbon. Fast growing softwoods will be the future, planted for laminating into large structural panels.
The aim is to evolve systems and designs in timber to tackle the significant negative environmental impact of buildings. Innovative uses of wood technology offer new ways of constructing efficient and affordable structures that demand fewer resources from the environment while maintaining functionality and aesthetic appeal.
Mid-rise urban infill projects—insertions within the existing urban fabric (not high-density and high-rise, but mid-rise, 4 to 10 storeys)—are gaining in popularity. The inner-city residential buildings of tomorrow will focus on construction speed, carbon emissions and weight reduction by using low-carbon lightweight construction systems and cladding; these prefabricated systems will increasingly use high-performance timber panels such as CLT panels, as these can be easily handled on-site. Building more mid-rise infill with timber is highly desirable, as carbon sequestered in trees is thus stored in wooden building components for the duration of the building’s life. This will enable us to turn buildings into ‘carbon sinks’, while avoiding GhG emissions, and increasing resource efficiency and buildings’ adaptability.
Recently conducted research on sustainable forest management, the lifecycle of wood products and the use of timber in infill construction has attracted the construction industry’s interest. For example, new findings report that instead of keeping wood growing in forests for hundreds of years, it is beneficial if the wood is regularly harvested and used in construction (to increasingly replace concrete or steel); in this way, carbon dioxide can be removed from the atmosphere . Only a small portion of Australia’s forests are ‘carbon dense’; most are lower density open forest or woodland. A considerable proportion is regrowth from previous harvesting and over 90 per cent of timber production is concentrated in those areas.
Lippke and his team have identified a number of possibilities for the use of engineered timber panels to replace fossil fuel-utilizing construction systems of reinforced concrete and structural steel. According to their findings, sustainably managed forest plantations in practice offer a two-way flow of carbon dioxide: they absorb carbon dioxide during their growth and when the tree dies and decays, falls back or burns, the carbon returns to the atmosphere; thus the plantation remains carbon neutral . For instance, Lippke’s team calculated that the use of engineered wood joists (weighing around one metric ton) in place of steel floor joists reduces CO2 emissions by approximately 10 tonnes. In another example, the use of wood flooring in place of concrete slab flooring reduced the CO2 emission level to 3.5 tonnes for every ton of wood utilized. Therefore, they recommend: plantation of rapid growth tree species, cropping the wood before the trees become less active, utilizing them in place of steel or concrete in construction, or using the wood as biomass to produce energy or bio-fuels to replace fossil fuels. This suggests that a detailed evaluation of each forest will have to be done, as older forests are slower in their absorption of carbon dioxide, but continue to offer numerous other ecological benefits (e.g. high biodiversity). Life cycle analysis will help to compare the different options’ carbon footprints.
Timber is one of few materials that have the capacity to store carbon (other materials, such as straw and bamboo can also store carbon), which means that CLT construction systems are an