Quantifying the greenhouse benefits of the use of wood products in two popular house designs in Sydney, Australia

As the average wood products usage per unit of floor area in Australia has decreased significantly over time, there is potential for increased greenhouse gas (GHG) mitigation benefits through an increased use of wood products in buildings. This study determined the GHG outcomes of the extraction, manufacture, transport, use in construction, maintenance and disposal of wood products and other building materials for two popular house designs in Sydney, Australia.

The life cycle assessment (LCA) was undertaken using the computer model SimaPro 7.1, with the functional unit being the supply of base building elements for domestic houses in Sydney and its subsequent use over a 50-year period. The key data libraries used were the Australian Life Cycle Inventory library, the ecoinvent library (with data adapted to Australian circumstances where appropriate) and data for timber production from an Australian study for a range of Australian forestry production systems and wood products. Two construction variations were assessed: the original intended construction, and a “timber-maximised” alternative. The indicator assessed was global warming, as the focus was on GHG emissions, and the effect of timber production, use and disposal on the fate of carbon.

The timber maximised design resulted in approximately half the GHG emissions associated with the base designs. The sub-floor had the largest greenhouse impact due to the concrete components, followed by the walls due to the usage of bricks. The use of a “timber maximised” design offset between 23 and 25 % of the total operational energy of the houses. Inclusion of carbon storage in landfill made a very significant difference to GHG outcomes, equivalent to 40–60 % of total house GHG emissions. The most beneficial options for disposal from a GHG perspective were landfill and incineration with energy recovery.

The study showed that significant GHG emission savings were achieved by optimising the use of wood products for two common house designs in Sydney. The switch of the sub-floor and floor covering components to a “wood” option accounted for most of the GHG savings. Inclusion of end of life parameters significantly impacted on the outcomes of the study.