Real measurement data of indoor climate in buildings provide a valuable foundation for models, their calibration and validation, as well as for control. Hence, the present paper describes a respective experimental measurement setup. We mainly collect temperature and humidity data in three different buildings: A newer office building exemplarily represents buildings with modern infrastructure supporting wired sensors. Lacking this prerequisite, the setups in an older building and a laboratory depend on radio communication only, for which we largely use Internet of Things (IoT) technologies. Since the choices regarding data acquisition, transfer, and processing strongly influence the quality of the data, we focus on communication and back-end infrastructure, as well as visualization and data treatment. We provide methods and tools as open source packages.