An overview of how the construction sector affects climate change and ways to reduce greenhouse gas emissions
Carbon dioxide (CO2), which is a greenhouse gas (GHG) works to trap heat close to Earth. It helps Earth hold the energy it receives from the Sun, so it doesn’t all escape back into space. Up to a point, CO2 and other GHG are good but even a small increase in CO2 in the atmosphere can cause Earth to get even warmer. In April 2020 the average concentration of CO2 in the atmosphere was the highest since measurements began in Hawaii in 1958. Furthermore, ice core records indicate that such levels have not been seen in the last 800,000 years . Almost ¾ of GHG emissions is CO2 arising mainly resulting from the combustion of fossil fuels  to produce electricity and heat, used to heat buildings or to produce materials such as steel, plastic, cement and other. CO2 can also be released during the production processes to make materials, such as the decarbonisation of limestone to make cement, one of the key components of concrete.
The last decade brought the highest ever registered temperatures. 2019 UK heat record (38.7°C in Cambridge) was beaten in 2022 by 1.6°C at Coningsby in Lincolnshire reaching 40.3°C. In Spain in 2021 in Montoro the temperature record was 47.4°C and in Italy in Sicily 48.8°C. In the last decade the highest temperature of 38.3°C in Poland were reported in 2019 in Radzyn and in 2022 in Slubice. This gives tangible evidence that we are dealing with climate change. Apart from the high temperature, extreme weather such as hurricanes, floods, droughts and wildfires are being affected by climate change .
Impact of construction industry on the climate
Buildings and construction industry accounts for almost a half of global energy-related CO2 emissions , 60% are related to the use of buildings such as heating, cooling, lighting, and the use of appliances. The remaining 40% are related to materials used in construction, mainly concrete, steel, aluminium or glass. Concrete and steel alone in construction are responsible for more than one-tenth of global CO2 emissions. Moving towards non-emitting energy sources, the carbon emissions from material production used in construction (named embodied carbon or carbon footprint) will approach 100% of total emissions in construction . With global population increase and a significant increase in the urban population, it is expected to double the global floor area by 2060 compared to 2015 (86% by 2050) . This means that, according to these forecasts, the area corresponding to Paris has to be added to the existing building stock every week. In developed countries such as the United Kingdom, 80% of buildings will have already been built in 2050, so most of the buildings and infrastructure will be needed in developed countries, a half of which will be in China, India and Africa .
In 2018, the Intergovernmental Panel on Climate Change warned that global warming must not exceed 1.5°C to avoid the catastrophic impacts of climate change. To achieve this, emissions must halve by 2030 – and drop to net-zero by 2050 . For the global construction industry this means that, with almost doubling the floor space of buildings with adding related infrastructure, all construction must become a net-zero emitter by 2050.
New solutions in the construction industry
Energy and emission reduction in the construction industry is a key to achieving climate goals and should include two aspects: reduction of emissions from the operation of the building (heating, cooling, cooking, lighting, and the use of devices in buildings) and reduction of emissions from material production and related processes. The former applies to both existing and new buildings. Approximately 64% of energy in the EU domestic buildings sector is heating and therefore improvement of building thermal insulation as well as switching all boilers using fossil fuels to electric can bring more than 80% energy related CO2 savings. The same with cooking that accounts for a quarter of the energy of households. However, emission reduction will bring benefits only when electricity is generated from low-carbon or non-emitting sources. A transformational change is needed in countries that use coal to produce electricity (e.g. in Poland that leads in Europe in coal electricity generation reaching 70% of all electricity compared to 29% in Germany) to switch to non-emitting energy sources.
From the material perspective, the greatest carbon savings can be achieved by extending the life of buildings (circular economy principle), reusing materials (circular economy principle as well), increasing structural efficiency and using low-carbon materials. Recent studies have indicated that the real life of buildings tends to be shorter than the design life, especially for non-residential buildings such as office, commercial and industrial buildings. Reuse of materials is not common practice, especially in developed countries, where it accounts for 5% of construction waste. An interesting fact is that 30-40% of structural materials in buildings are not necessary to perform the required service and therefore are a waste. Using low carbon materials, such as low carbon steel (produced from steel scrap or / and using hydrogen – if electricity production is decarbonised) and low carbon concrete (with high addition of low carbon additives) leads to minimising carbon footprint of main structural materials. Nevertheless, both of these options have limitations. There is not enough steel scrap worldwide to cover the entire steel demand, and low carbon concrete additives are also limited. Using natural materials such as sustainable wood, stone or compacted earth can make the biggest savings in carbon emissions. However, they cannot be used for certain applications such as medium and high rise buildings or large infrastructure. The availability of these materials, especially wood, is also limited. The greatest savings in construction can be done if only all industries follow the embodied carbon reduction strategy from the World Business Council for Sustainable Development . This can bring significant both embodied and operational carbon savings.
Figure 1 Embodied carbon reduction strategy, WBCSD 
Emission reduction in construction
What determines the level of emission in the construction industry the most:
- need for construction, so: Do we have to build? What do we really need? Can we use what we have? (private and public client, practitioners responsibility),
- decarbonisation of the grid but: When does this happen? (government responsibility),
- switching to electricity, but: When does this happen? (government, private and public owners responsibility),
- better use of materials (both new and old), but: How should we change legislation, current practice, and education? (government, practitioners, academia responsibility),
- low carbon materials / technologies, but: How fast can we have those? What volume can we have? (material producers, technology providers, academia responsibility),
- structural efficiency, but: How to convince industry to use less materials? What are alternative structural systems to deliver the same service? (practitioners, academia responsibility).
There is no ‘silver bullet’ solution or ‘one size fits all’ to decarbonise the construction industry, especially that the construction sector is much more fragmented than other industries. Only combined efforts and the contributions of all actors from the construction supply chain and close collaboration is essential to reduce GHG emissions in the construction industry and therefore meet the climate target.
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Michał Drewniok, Joanna Rancew