Digitalization provides significant opportunities for innovation, new business models, and services for the building sector. This paper describes the implementation of a concept for providing "Indoor Climate as a Service", based on a case study of digital transformation in a modern office building. This concept can accelerate the energy savings and reduce power demand in the existing building stock by implementing digitalization (sensors and actuation, together with data integration and analytics platform), and providing full incitements for energy investments at the same time as the contracted indoor climate is secured and verified using real-time data. The digital transformation included obtaining data from different sub-systems (climate control, IoT-devices and Space booking system etc.), applying the RealEstateCore ontology to organize the data, and the development of an IoT-Edge computing solution. A key objective of this study is to explore the types and quality of data (for example, from sensor signals) needed to implement the concept in a modern office building. Key indoor air quality and energy performance control parameters were analyzed with relevance to developing a robust business model. The results of the study demonstrate the significant potential of utilizing digital infrastructures for implementing Indoor Climate as a Service.