Which is better for the environment – wood or steel house framing?
Wood: the most renewable of all building materials
- Growth and production of one tonne of wood absorbs a net 1.7 tonnes of CO2 from the atmosphere. (Based on the amount of carbon stored in the timber – making an allowance for all the energy used, and CO2 produced, in its growth, harvesting and processing.)
- One tonne of steel has added 1.2 tonnes of CO2 into the atmosphere.
- A typical steel house frame has added 4.5 tonnes of CO2 into the atmosphere – the equivalent to the emissions from driving 22,500 kms in an average car.
- A typical wooden house frame has absorbed 9.5 tonnes of CO2 from the atmosphere – the equivalent of 47,500 kms of driving in an average car.
- Timber frames mean years of CO2 “in the bank”
- Energy usage of a well-built, properly insulated home will be similar whether built with a steel or wooden frame (although steel frames will “leak” more heat than wooden frames if not properly insulated).
- The choice of wood or steel makes the difference between starting with either a healthy CO2 credit or deficit.
- An average house uses around 10,000 kWh of energy per year for heating and lighting, which represents CO2 emissions of 2.3 tonnes (based on electric power).
- Choosing a wooden house frame will provide over four “free” years of CO2 emissions.
- Using a steel frame is the same as adding an extra two year’s worth of average household CO2 emissions into the environment. Steel and timber: the afterlife
- Most construction timber is buried in a landfill at the end of its life. Up to 97 percent of the carbon in the wood is permanently stored under the ground – capturing CO2 released by fossil fuels and returning it back beneath the earth’s surface.
- At the end of the building’s service life, steel frames can be recycled for other uses. This requires significant processing energy, although this is a fraction of what was required to produce virgin steel.