Operational and embodied carbon
The use of concrete in buildings can lead to questions regarding its embodied CO2, which is often thought to be much higher than other construction materials. In reality, there is little or no difference, and is insignificant when compared to a building's operational CO2 emissions over its life.
In buildings where the inherent thermal mass of concrete forms part of the cooling strategy, any additional embodied CO2 burden can in fact be offset many times over. This can be shown quite simply by comparing the embodied and operational CO2 emissions per m2 for a typical air-conditioned office with those of a typical mixed-mode office i.e. one that is cooled using thermal mass in conjunction with natural and mechanical ventilation.
A source of data for the embodied CO2 of office buildings is life cycle assessment research on steel and concrete framed buildings. One of the conclusions of the study was that overall there is no significant difference between steel composite, reinforced concrete and precast concrete options with regard to embodied CO2. For a small to medium rise office, built to a developer's standard specification, the range of embodied CO2 for different options was equivalent to only 16 months CO2 emissions from an energy-efficient, air-conditioned office [1,2].
Over the life of a home, the operational CO2 emissions of a house have far more environmental impact than the embodied CO2 of the materials used to build it. Some 50 per cent of the UK's carbon emissions are due to the energy used to heat, cool and light buildings. It is essential, therefore, that energy consumption during a building's lifecycle is taken into account when evaluating construction materials. A building's environmental impact does not stop once it has been built.
Independent research, carried out by Arup Research & Development, takes account of experts' predictions for climate change and demonstrates that the thermal mass in masonry homes reduces the need for air conditioning.
It also highlights the additional savings that can be achieved through using thermal mass to capture solar gains, thereby reducing the consumption of winter heating fuel. These savings can offset the slightly higher level of embodied CO2 in a masonry house in as little as 11 years and ultimately lead to the lowest whole life CO2 emissions.
Read the full report: Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change