A comparison between embodied and operational carbon in a building envelope from a life cycle perspective

Abstract: Sweden’s building sector contributes over one third of the country’s total energy consumption and over a fifth of its greenhouse gas emissions. To achieve the energy and climate goals that have been adopted by the Parliament in Sweden, work must be done within this sector to reduce its climate impact. The climate impact of a building is generated both during its service life, known as operational carbon, and during the production and processing of materials before and after construction, referred to as embodied carbon. Historically, operational carbon has made a larger contribution to a building’s total climate impact, resulting in operational carbon being the focus for reducing a building’s total climate impact. However, with improvements in the energy mix and buildings becoming more energy efficient, the operational carbon has been reduced, causing the embodied carbon to contribute more considerably to a building’s total climate impact. A building’s envelope protects the environment within the building from outdoor conditions, thus maintaining a stable indoor climate that is comfortable for the occupants. The amount and type of materials used in the building envelope impact the building’s heat losses and gains. Consequently, the material types and amounts used influence the operational carbon as well as the embodied carbon. By adding wall and/or roof insulation, or improving the windows’ U-value, the operational carbon is reduced, while the embodied carbon increases. With insulation and window changes made to improve the building envelope and reduce heat losses, this study aimed to investigate whether there is a point at which the reduction in operational carbon no longer outweighs the increase in embodied carbon, i.e., a break-even point. This aim was achieved by using a reference building based on which in a number of different cases of insulation and window options the operational carbon was estimated using IDA ICE and embodied carbon was estimated using One Click LCA. The results showed that none of the studied cases reached a break-even point. The cases in which reaching a break-even point was closest were those in which PIR wall insulation and glass wool roof insulation were used. Each of the studied insulation cases followed the expected trend of reduced change in operational carbon nearing the increase in embodied carbon. The continued increase in insulation would be impacted by cost related benefits and limitations.