Radiant heating and cooling systems, and Thermally Active Building Systems (TABS) in particular, have several advantages such as benefiting from the low temperature heating and high temperature cooling principle, coupling with renewable energy sources, peak shifting and peak load reductions.

When using TABS, most building simulation models assume an uncovered ceiling; however, this might not be the case in practice, due to the use of free-hanging horizontal (or vertical) sound absorbers for the control of room acoustic conditions. The use of sound absorbers will decrease the performance of radiant ceiling cooling systems. Therefore, the quantification of the effects during the design phase is important for predicting the resulting thermal indoor environment and for system dimensioning. In this study, a two-person office room equipped with TABS was simulated using a commercially available simulation software with a recently developed plug-in that allows simulating the effects of horizontal sound absorbers on the performance of TABS and on the thermal indoor environment. The change in thermal indoor environment and in performance of TABS were quantified, and the simulation results were compared to measurement results.

The measurement results show that with horizontal sound absorbers, the cooling performance of TABS decreases by 11%, 23% and 36% for ceiling coverage ratios of 43%, 60% and 80%, respectively. The developed simulation model was able to predict closely the cooling performance reduction of TABS, the ceiling surface temperature, and the thermal indoor environment in most cases. While the model can be improved in certain aspects (prediction of mean radiant temperature and cooling capacity coefficient), the accurate prediction of the surface temperature of the TABS makes the model useful for further studies, which may use differently constructed radiant surface heating and cooling systems.