Kvantifiering av växthusgasutsläpp från en byggnad under byggskedet

Sammanfattning: According to the national climate policy framework adopted by Riksdagen (the Swedish parliament) 2017, Sweden should reach zero net emissions of greenhouse gases in 2045. For this to be successful, the construction and real estate industry, which annually accounts for one fifth of Sweden’s territorial greenhouse gas emissions, needs to minimize its emissions. One step towards reducing the emissions is to track and quantify them and that is why in 2022 a new law will come in to force that requires the developer to make climate declarations on all new buildings. This study has investigated how and when climate calculations of planned buildings should be carried out in order to be as beneficial as possible. Furthermore, the study examined material choices and emission allocation in order to reduce greenhouse gas emissions caused by the construction process. A building information model (BIM model) of an educational building which is planned to be built, served as a case study for this project. The BIM model was imported to a spreadsheet program in order to create three different versions of the building in three common framing materials; wood, concrete and steel. A list of all used building components, construction resources and associated quantities was produced and exported for each model. The list was imported to a climate calculation tool, based on Life Cycle Assessment (LCA), to manually link the construction resources with their corresponding LCA data. General waste fractions and general transport scenarios were entered for each construction resource. Theresults showed that the wooden frame model emitted 28 %less carbon dioxide equivalents (CO2e) than the concrete frame model and 22 % less than the steel frame model. The wood frame itself generated a 54 % less greenhouse gas emissions than the concrete frame and 45 % less than the steel frame. Concrete and insulation were the two resource groups that caused the greatest climate impact in five out of six cases. The production of the building components caused 88–90 % of the total climate footprint for all three models. Transport of the building components to the construction site and resource waste at the construction site both caused between 4–6 % of the climate impact in all models. The study also found that the climate calculations should be carried out as soon as the general architectural model of the building is created, in order for the calculations to serve as a decision basis in the project planning where design choices are made. The price for the climate calculations at an early stage in the construction process is low because the BIM model is relatively simple and therefore the calculations are not time-consuming. If the climate calculations occur at a later stage of the construction process, the emission figures become more accurate, but the price for the calculations increases. In addition, it is more difficult and much more expensive to make changes at a later stage. Thus, the probability is that the climate calculations will not be used in any decision. Nyckelord