A combined system that couples radiant ceiling technology with mixing air systems may be a solution to improve thermal comfort in offices, but the thermal transient response can be slower than all air systems when the room is subjected to a sudden change in thermal loads.

The main objective of this study is to assess the changes of the Predicted Mean Vote (PMV) and the Predicted Percentage of Dissatisfied (PPD) indices under transient conditions in a cooled office environment under two different thermal loads. An experimental study is carried out in a full scale test room to evaluate transient thermal comfort conditions in an office with a combined mixing air and radiant ceiling cooling system.

Experimental tests are carried out in a full-scale test room at the University of Cordoba. Four thermal manikins are used to simulate the people in the room. The test room is provided with hot-sphere anemometers, thermocouples, resistance temperature, globe temperature and humidity probes. It has been obtained the PMV and the PPD as well as the operative temperature generated by the combined mixing air and radiant cooling system in the room.

The results show the evolution of the thermal comfort conditions, the time needed to reach the thermal comfort category A and category C and the time required to reach steady state conditions in different case studies. The results of this study can help to improve the strategies used for the control of hydronic radiant ceiling systems, reducing the time of response to changes in thermal loads.