Climate change and fossil fuel depletion foster interest in improving energy efficiency in buildings. There are different methods to achieve improved efficiency; one of them is the use of additives, such as phase change materials (PCMs). To prove this method’s effectiveness, a building’s behaviour should be monitored and analysed. This paper describes an acquisition system developed for monitoring buildings based on Supervisory Control and Data Acquisition (SCADA) and with a 1-wire bus network as the communication system. The system is empirically tested to prove that it works properly. With this purpose, two experimental cubicles are made of self-compacting concrete panels, one of which has a PCM as an additive to improve its energy storage properties. Both cubicles have the same dimensions and orientation, and they are separated by six feet to avoid shadows. The behaviour of the PCM was observed with the acquisition system, achieving results that illustrate the differences between the cubicles directly related to the PCM’s characteristics. Data collection devices included in the system were temperature sensors, some of which were embedded in the walls, as well as humidity sensors, heat flux density sensors, a weather station and energy counters. The analysis of the results shows agreement with previous studies of PCM addition; therefore, the acquisition system is suitable for this application.