Audit of the cooling energy performance of an office building retrofitted with Thermally Activated Building Systems (TABS)

Thermal mass activation of existing structures is aimed at exploiting the energy storage capability of buildings for their climatization, in combination with low-grade energy production systems. The integration of thermoactive elements in existing buildings is not always feasible and effective due to several limitations. In the case of building energy retrofitting, there is a need for a case-by-case design due to the many variables involved in defining the performance of thermoactive elements for building climatization (weather, passive design strategies, use patterns, etc.). This paper provides an emblematic Case Study in which the efficiency of Thermally Activated Building Systems (TABS) is investigated and compared with the energy performance of rapid-response systems. TABS are analyzed within their practical application in a refurbished office building in Madrid, Spain. A Building Management System (BMS) allows the monitoring of operative parameters and the management of setpoint values via its control interface. This paper focuses on the analysis of the energy response of TABS during the cooling period. The results show that significant energy and economic savings are achieved by applying appropriate control strategies for TABS. The effect is the minimization of the energy consumption for air conditioning during the summer while reducing the operation of rapid-response systems to provide the necessary cooling for peak energy loads. The complexity of the building-plant system, along with the experimental character of the intervention, requires the development of an effective auditing system. This paper shows the abilities and limitations of the application of the energy signature method for complex buildings in cooling. Furthermore, it suggests how energy signatures can be used diagnostically and qualitatively to analyze energy savings while neutralizing the weather influences on the energy consumption for climatization.