GEOTABS buildings combine an energy efficient heating and cooling system (Thermally Active Building Systems, TABS) with a renewable energy resource (ground, GEO) to heat and cool buildings in an energy efficient and sustainable way. Within the scope of a new EU project (HORIZON 2020-10 project EE-04-2016), hybrid GEOTABS buildings are studied in details in terms of optimal system design and dimensioning methodology, control, and in other terms. Model Predictive Control (MPC) algorithms will be developed by project partners and the developed algorithms will be implemented in demonstration buildings. The three demonstration buildings were an office building in Luxembourg, an elderly care home in Belgium, and an elementary school in Czech Republic. All of these buildings are equipped with hybrid GEOTABS systems; however, they vary in size and function, which requires a unique measurement methodology for studying them. These buildings already have advanced Building Management Systems (BMS); however, a more detailed measurement plan was needed for the purposes of the project to document the current performance of these systems regarding thermal indoor environment and energy performance, and to be able to document the improvements after the implementation of the MPC. This study provides the details of the developed field measurement methodology for each of these buildings to study the indoor environmental quality (IEQ) in details. The developed measurement methodology can be applied to other buildings of these types and to buildings with similar heating and cooling systems.