In order to test the system performance in the current configuration on a seasonal time scale and to investigate the influence of the main system parameters, a dynamic simulation model was developed within the TRNSYS 14.2 environment. TRNSYS is a widely used system simulation programme [10] provided with libraries of subroutines called types which simulate specific components or processes. Beside standard ones, user written subroutines are available.

The model of the test building and of the system was obtained assembling the following types:

— the non standard Duct Ground Storage Model (DST) [11]

— the non standard Type 160 Floor heating and hypocaust [12]

— the standard Type 56 Multizone Building Component

and the types for the auxiliary system equipments (counter current flow heat exchanger, pumps). Data collected in the above described measurement campaign were used to calibrate the model. The main three types were calibrated individually and then linked together. Simulated and measured data agree within experimental errors, as it is shown in Figure 3 for two quantities, namely the air temperature in test room 1 and the thermal power extracted from the test room 1.