Building certification systems have become important tools for promoting and assessing sustainabilitywithin the construction and real estate sectors. Among the most widely used systems are the NordicSwan Ecolabel, Miljöbyggnad, BREEAM, and LEED. While all aim to support the development of moresustainable buildings, they differ in terms of structure, assessment criteria, and certification processes.The Nordic Swan Ecolabel can be regarded as a more process-oriented certification system and differsin several respects from Miljöbyggnad, BREEAM, and LEED as a group. To further explore thisdistinction, this study compares the Nordic Swan Ecolabel with Miljöbyggnad. As a case study, theSwan-certified project Spexaren in Uppsala is analyzed and compared with a residential project in Gävlebuilt according to Miljöbyggnad principles.The study was conducted using a combination of qualitative and quantitative methods, includinginterviews, site visits, document studies, and cost calculations. Selected material categories werecompared, including paint, flooring, windows, appliances, roofs, and walls, with a focus on certificationrelated cost differences.The results show that the Nordic Swan Ecolabel is perceived as a clear sustainability profile with strongpublic recognition, which may provide business advantages. At the same time, the Swan-certifiedproject showed higher initial costs in several of the studied material and product categories. Thesedifferences may partly be related to stricter material requirements and a more limited selection ofapproved products. However, these additional costs are often considered justified by long-termbenefits such as improved operational efficiency, quality assurance, and increased legitimacy.The results indicate that Nordic Swan Ecolabel certification increases costs by 20% for paint, 45% forwindows, 4% for flooring materials, up to 63% for appliances, 45% for roofs, 33% for interior walls, and44% for exterior walls due to stringent material requirements. These additional costs are motivated byfactors such as brand value, opportunities for green financing, energy savings, and the strategicbenefits associated with certification.The study concludes that the decision to pursue Swan certification is driven by both strategic andenvironmental considerations, and that the cost effects are selective but manageable. The findingshighlight the importance of adopting a holistic perspective in the early stages of construction projectsand the need for increased knowledge regarding the practical and economic consequences ofcertification systems.