Did you know that concrete accounts for about 8% of global CO2 emissions, four times more than the CO2 emissions of all global air travel ?
The house building industry uses a lot of concrete and now that new housing has to meet NZEB (Nearly ZeroEnergy Building) regulations attention is shifting to the carbon footprint of the construction process. As we build more energy efficient homes the embodied carbon of the construction stage becomes a higher proportion of the building’s total life cycle carbon emissions.
The carbon emissions of the construction stage are between 30% and 70% of the total CO2 emissions of the whole lifetime of a building. The regulations do not yet have a standard for the embodied carbon of the construction stage but DRES understand the environmental impact of what we build so we are working to reduce what is called the “embodied carbon” of our house-building.
DRES has specified and uses low carbon concrete in our foundations and ground floor slabs to minimise our carbon footprint. In a typical house this reduces the carbon emissions of the construction stage by about 8.7 tons of CO2. In 2019 DRES completed about 350 houses and in total saved over 3,000 tons of CO2 emissions by using this low carbon concrete.* This is a very significant amount of CO2 and is equivalent to taking about 1,350 petrol and diesel cars off the road for a year.
The cement and concrete industry has been developing lower carbon cements and concrete to meet these new challenges in the industry. By using recycled materials, developing design mixes for specific uses, and burning alternative fuels instead of fossil fuels in some cement plants, the industry has reduced the embodied carbon of concrete. Concrete mixes can now be specified which range from about 105 kg to 435 kg of CO2 per cubic metre, depending on the source of the raw materials, cement manufacturing methods and the design mix.
Our concrete design mix uses50% GGBS (Ground Granulated Blast-furnace Slag) as a low carbon substitute forOPC (Ordinary Portland Cement). Ecocem Ltd. is a Dublin based company whichimports the crude slag and grinds it into GGBS at their facility in Dublin, sothere is a ready local supply of this low carbon material.
GGBS is a by-product of the iron-making process and has been used as asubstitute for OPC for decades. Concrete with a high percentage of GGBS hasbeen proven to be more durable and have increased resistance to chemicalpollution. There are some local concrete block manufacturers switching their concreteblock production to 50% GGBS without increasing costs, while improving strengthand quality. This will lower the carbon footprint of the homes we build withblock walls.