The construction sector is often considered one of the most harmful for the health of the environment. When people think about pollution, the first images that generally come to mind are tall industrial chimneys and traffic jams in cities. But in reality, smoke stacks and exhaust pipes only account for a small portion of all the pollution produced by mankind, and this has been demonstrated by the studies conducted over recent years. One of the most frequently cited studies regarding pollution caused by the building sector is the report drawn up by the Global Alliance for Building and Construction for the COP25 climate conference in Madrid. This study showed that the building sector is responsible for a third of global consumption of drinking water, 50% of the extraction of raw materials, 35% of global energy consumption, and 39% of global carbon dioxide emissions. All of these data are alarming, but what is most striking at this historic moment is the figure regarding CO2 emissions, which makes decarbonization in the building sector an increasingly key issue. But what does decarbonizing the building sector mean?
The meaning of decarbonization
As we know, the main challenge facing the world is climate change. So the objective to be attained, as was decided at the famous Paris Agreement and emphasized again in Glasgow at the latest Climate Change Conference, is to limit the increase in temperatures to below 1.5 degrees centigrade above average pre-industrial levels. One of the chief causes of the increase in temperatures is the presence of excessive amounts of carbon dioxide in the atmosphere, as a result of pollution deriving from human activities. As we have seen, much of this pollution is generated by the building sector. We know that the concentration of CO2 in the earth’s atmosphere is currently about 390 ppm, that is almost 400 parts per million, whereas in pre-industrial times, the concentration was only 280 ppm.
But as we know, climate change not only involves an increase in temperatures. It is a vicious circle, in fact, which leads to higher sea levels, the melting of glaciers and ever more frequent and more extreme weather phenomena, with droughts gradually becoming more serious and, in contrast, an ever greater risk of flooding. To slow down this process, it is necessary to reduce the concentration of carbon dioxide in the atmosphere, and thus to launch a large-scale and wide-reaching process of decarbonization. At a general level it will be necessary to produce far less pollution, and to proceed to reduce the CO2 present in the atmosphere through appropriate technologies that can “suck carbon dioxide” out of the atmosphere.
Since the construction sector is one of the chief industries responsible for pollution, one of the priorities is also to decarbonize the building industry in a variety of ways.
How to decarbonize the building industry
Sustainable construction is in itself aimed at decarbonizing the whole life cycle of the building sector. There is no doubt that we must go down this road: we simply cannot postpone, or fail to achieve, the objective of carbon neutrality and therefore, in effect, zero emissions. But where should we start? What are the priorities for decarbonization of the building sector? The Green Building Council Italia, a non-profit association that aims at incentivizing the spread of sustainable and circular construction, is one of several organisations that have tried to provide a complete answer to this question.
The first step, according to GBC Italia, should be to incentivize and share information about the use of energy from renewable sources within buildings and entire districts. But it is not enough to be sure of being able to rely on green sources of energy. It is also necessary to construct buildings that are truly energy efficient. And according to the GBC, it is also essential to develop the concept of the circular economy in all aspects, which involves reusing building components deriving from the selective deconstruction of buildings, using recycled materials and so on.
Towards the Nearly Zero Energy Building
The buildings of the future need to be zero-emissions or almost. The label used most frequently to describe these buildings of the future is NZEB: “Nearly Zero Energy Building”, to indicate buildings that have reduced energy consumption and in which the energy used is also produced in a totally sustainable way. To achieve this objective, the sustainability of the building must be worked out on paper beforehand, planning elements such as the insulation in the building envelope, ventilated facades, passive cooling, exploitation of local resources, waste reduction, the potential production of energy on site, and so on.
To provide a full picture we should point out that alongside NZEB, there are also NZCB, Net Zero Carbon Buildings. The concepts might seem very similar, and in fact they are. However, the latter is more closely linked with decarbonization in the building sector, as it focuses directly on the quantity of polluting substances that are emitted, measuring the carbon dioxide in kilograms per square metre of floor area.
Moving towards decarbonization in the building sector
As might be expected, the term decarbonization in the building sector involves a number of different issues ranging from the raw materials used for construction to energy efficiency in buildings and the potential to reuse materials when the time comes to renovate the building.
It might be useful to divide the topic of decarbonization in the building sector into macro-areas, giving separate consideration to construction materials, energy efficiency and sustainable urban development.
Regarding construction materials, decarbonization means reducing carbon emissions in the actual construction process, starting with the carbon dioxide emitted in the processes of transforming the raw materials into brick, concrete, planks and so on.
As regards energy efficiency, we need to start by reducing the energy requirements of buildings in terms of heating, air conditioning, lighting and so on. At the same time, we need to consider the elimination of waste, as well as the use of clean energy, preferably produced on site.
Finally, decarbonizing buildings also means considering urban development as a whole: the aim must be to create districts and cities where it is possible, advantageous and pleasant to move around on foot, by bicycle or using low- or zero-emissions means of transport. So as we can see, the challenge of decarbonization in the building industry does not end with the construction of the individual building.