This paper is related to the H2020 project EN-TRACK, dedicated to developing a platform for gathering data on the performance of energy efficiency investments in buildings. The project aims to collect and harmonize data from different sources and provide services supporting investors and building owners in decision-making and de-risking building retrofit projects. The paper focuses on the methodology and the semantic technologies used in the development of the platform’s data model, which enables the interoperability of data, and supports the service functionalities for tracking building energy performance and benchmarking savings from energy efficiency investments.