The following study is a degree project of 15 credits at the School of Engineering in Jönköping and has been done in collaboration with bsv arkitekter och ingenjörer ab.The construction industry accounts for a large part of the world's energy consumption and one way to change the direction of this can be to promote the renovation of existing buildings instead of producing new buildings, and in connection with this be able to use environmental certification systems. The aim of the study is to investigate theperformance of an existing apartment building in relation to Miljöbyggnad iDrift 2.0, and to learn from the experiences of experts in the industry regarding environmental certification of existing buildings.

A case study with a triangulation of different techniques has been used as amethodology to achieve the objective of the study and to obtain information on thesubject. Document study and observation were used to investigate an existing building’s relationship to Miljöbyggnad iDrift 2.0. Interviews were also conducted with several respondents to identify the experiences, opinions, and insights of industry experts.

The existing building was analysed by collecting a large amount of documentation,which was then related to Miljöbyggnad iDrift 2.0. The case study showed that the existing building did not fulfil the requirements for certification and could therefore not be certified. Furthermore, a positive attitude towards environmental certification could be identified among both property owners and principals. A consistent reason why property owners carry out environmental certifications on properties was to contribute to sustainability work and fulfil sustainability goals. However, most respondents felt that the economic benefits could not be specified.

The results of the study generated good knowledge about the building, which was shown to be consistent with results from previous research. Research further suggests that environmental certification systems lack flexibility, as there is strict judgement inscoring during the certification stage. The results of the study were consistent with the following theory, as the analysed existing building could not satisfy the points due to lack of evidence.

According to previous research, the economic sustainability aspect was found to have a small impact on the structure of environmental certification systems, compared to the social and ecological sustainability aspects. The study reported that respondents emphasised some problems with the following distribution, as the economic aspect was considered relevant to be taken into account to a greater extent. Theoretical evidence suggests that Miljöbyggnad constantly strives for low costs, which the study's respondents did not confirm. The economic issue should be addressed both practically and theoretically to continue to encourage more environmental certifications andc ontribute positively to the sustainability development of society.