Wood provides significant opportunities to reduce carbon dioxide emissions to the atmosphere, through

• substitution for other building materials
• substitution for other energy sources
• effective management of the forestry resource as a carbon sink

Managed forests are efficient carbon sinks, as mature trees, which absorb less CO₂ than trees that are still actively growing, are felled before they die and decompose, and are replaced with vigorous new trees. The majority of the carbon in the harvested tree is still kept locked away in the wood product for the life of the product, and beyond through re-use and recycling, before the energy is recovered by using the waste wood as a biomass fuel.

Substituting a cubic metre of wood for other construction materials (concrete, blocks or bricks) results in the significant average of 0.75 to 1 tonne of CO₂ savings.

Source: IIED and ECCM, Using Wood Products to Mitigate Climate Change, 2004

Embodied energy is becoming increasingly important in reducing CO₂ emissions

Currently about 20% of the energy expended by a building during its life (its carbon footprint) is accounted for by materials and construction. This explains why the government has focused on increasing in-use energy efficiency up until now.

As the Building Regulations move progressively towards the goal of the ‘zero carbon’ house in 2016, so the balance is changing, to the extent that materials and construction may end up representing 100% of the building’s total energy expenditure.

‘Embodied energy’ – the energy used in the materials and construction phase – is therefore about to become very much more significant.

Wood has the lowest embodied energy and the smallest carbon footprint of any building material

Here wood has a huge advantage. Although wood is an excellent thermal insulator and will help to increase energy efficiency and reduce heating bills, its real competitive advantage lies in its low embodied energy, or carbon footprint.

The carbon footprint of a material can be examined according to its embodied energy – that is, the quantity of energy required to manufacture and supply it to the point of use. The level of embodied energy in timber is lower than in other materials and, if correctly installed and maintained, timber is as long-lasting as alternatives.

Environmental Profiles from BRE’s Green Book Live, show how much CO₂ can be saved by using different materials in construction and give each method an overall EcoPoints score, which takes into account other impacts such as water pollution etc. All products are measured on a basis over a 60 year life.

The Environmental Profiles clearly show the CO₂ savings to be gained from substituting wood for other materials, as well as their superior EcoPoints scores. For example 4.2 tonnes CO₂ can be saved per 50 square metre wall element by substituting timber frame and softwood weather boarding for brick and block (Warmcell study), while the EcoPoints score improves from 1.0 to 0.46. Even more dramatic savings, of 13.85 tonnes CO₂, are shown when softwood weatherboarding is substituted for PVCU weather boarding (JJI study), with the Ecopoints rating improving from 2.0 to 0.49.