Resumen de Caracterització del sector de l'edificació des del punt de vista de les emissions de gasos d'efecte hivernacle
The accumulation of greenhouse gases (GHGs) in the atmosphere, the outcome of unsustainable management of our resources, is triggering one of the most critical environmental issues worldwide: climate change. To avoid irreparable damage to the climate system, the scientific community has set the goal of lowering emissions to between 50% and 85% of 1990 levels by 2050. Lowering emissions by these amounts entails a major effort from all sectors of society, including the building sector, which is responsible for around one-third of carbon emissions worldwide. The emissions from this sector must also be urgently lowered because many of the buildings that are built and exist today will still be in use in 2050. The goal of this thesis, namely to describe the building sector from the standpoint of GHG emissions, was posited in this context. This description aims to provide a new vantage point or way of understanding the sector which, unlike many of the perspectives applied to the sector to lower emissions today, will enable us to handle the emissions reduction demands in a truly effective way. The process of describing the sector is grounded upon the understanding that the root of the problem of climate change is the unsustainable management of the resources used in our society. Therefore, we begin by defining what sustainable construction is, in order to later identify, describe, classify and relate the main parameters that come into play in the sustainability of the building sector. In order to make the sector sustainable, all the material flows involved in habitability ¿ which is the usefulness that should come from building ¿ should close the material cycles. For this reason, the parameters that come into play in the sustainability of the sector are divided into two groups: material flows and habitability. The former is what should be used to assess the closure of the material cycles, while the latter can be used to assess whether the habitability needs are being met. Of all the possible material cycles, we only consider the ones related to GHG emissions. These emissions, which accumulate in the atmosphere, are a direct indicator of open material cycles. What is more, because of the seriousness of their impact and because they mainly stem from the burning of fossil fuels, which are in widespread use in all of society¿s activities, they can also be considered a reliable indicator of unsustainability. In addition to identifying the main groups of elements that come into play in the sustainability of construction, the consideration of a period of time in the analysis of the sector requires us to subdivide the material flows into two groups. The first group consists of the flows themselves, that is, what enters or leaves the sector during the period of analysis, while the second group consists of what are called fund of service, that is, the stock of buildings that remain unchanged and are composed of materials that were and will be material flows in another period of analysis. Thus, the main parameters of the description are the material flows (resources), the fund of service (stock of buildings) and habitability (occupation). The theoretical description is complemented by a numerical description of the Spanish building sector. In this case, we use the methodology of quantifying the elements that come into play in the sustainability of the sector, while we also identify the information that is unavailable but that would be necessary to make an accurate quantification. Finally, we critically compare this description with other visions and strategies that act to lower the building sector¿s emissions, stressing the factors that do not dovetail with the description proposed in this thesis which might be one of the motives impeding an effective and efficient drop in emissions.
