The environmental impact of concrete compares favourably with other building materials when analysed over the entire life cycle of a building. Over its life, the operational CO2 emissions of a house have far greater environmental impact than the embodied CO2 of the materials used to build it.
When looking at the whole life cycle of a building (including material production and construction), the use phase (heating, cooling, lighting etc.) often accounts for up to 80% of the CO2 emitted. This is where concrete can make a very positive contribution, as its durability, thermal mass and air tightness qualities help to reduce energy consumption and CO2 emissions. A building’s environmental impact does not stop once it has been built.
Concrete is a mixture of cement, water and aggregates. Aggregates make up approximately 60-75% of the mixture by volume and cement and water make up the rest. When the CO2 emitted during the extraction, transport and manufacturing of all these ingredients is taken into account, a typical concrete mix has an embodied CO2 of 50-150kg per tonne. Research has shown that the additional embodied CO2 is fully “paid off” early in the lifetime of a concrete building thanks to concrete’s thermal mass which reduces the need for air conditioning and 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.