Modern construction projects are expected to promote carbon reduction. But how serious is that commitment? One way to tell is to look at material selection and the relative amounts of steel and structural timber.
The choice of materials has implications for both operational and embodied carbon. Both are important considerations for education building programmes.
Cold Steel
‘Cold steel’ is a term we’re all familiar with. It arose out of experience. Steel feels cold to the touch because it does an excellent job of transferring heat from your hand and into the metal.
The thermal conductivity of steel is approximately 45 W/mK. The exact figure depends on the composition and how the steel was treated during production. The science behind this is that the free electrons that allow steel to conduct electrical current easily are also extremely effective at conducting heat. In other words, there’s not much you can do about it other than try to insulate or isolate the steel structure.
Warm Timber
Timber has a thermal conductivity of around 0.14 W/mK and woodfibre board is approximately 0.11 W/mK. In other words, steel is over 300 times more effective at conducting heat.
If you want to be confident about achieving low levels of operational carbon emissions, any use of steel has to be carefully modelled to ensure it doesn’t conduct heat away from warm areas of the building, through the structure and to the exterior.
A simpler solution is to specify structural timber wherever possible.
Embodied Carbon
Construction projects bear a huge embodied carbon burden. Extracting and processing raw materials, fabrication, transport and onsite assembly all involve carbon-generating activities.
Using structural timber is an effective way to balance out the carbon emissions generated by traditional construction materials. Trees are highly effective carbon sinks. The carbon they absorb remains locked into the structure of the wood until it decomposes or is burned. Timber, therefore, has a net negative value for embodied carbon.
One tonne of structural steel, on the other hand, will be responsible for approximately 1.74 tonnes of atmospheric CO2. This figure will reduce over time as energy supplies and the production process are decarbonised. Increasing the percentage of recycled steel will also have a positive impact. But it will never be zero and certainly never negative.
Delivering Carbon Reduction
As new buildings become more energy efficient and source their power from renewables, embodied carbon will become even more significant. Building systems such as i-FAST with a high structural timber content offer a practical and proven way to ensure that buildings are genuinely low carbon, both in construction and operation.
If you’d like to know more about how Innovaré panelised building systems reduce operational and embodied carbon contact enquiries@innovaresystems.co.uk or take a look at our resource centre.
