The article presents the thermal modelling and simulation work that will constitute the basis for the design of an outdoor test cell. The facility aims at characterizing the thermo-physical properties of transparent and opaque envelope components under real weather conditions, and to study the impact of different air-conditioning configurations on the indoor thermal comfort and indoor air quality. The response delay of the calorimetric measure is particularly critical when trying to achieve a good quality of measurement in rapidly-varying weather conditions. For this reason, the thermal behaviour of the test cell has been described, by means of a lumped parameter model, to simulate a range of operating conditions. The results are used to evaluate the thermal inertia of different solutions, refine the design choices and the most promising control strategies. The article presents the thermal models used to compare the test cell to a traditional installation in terms of calorimetric accuracy under transient external conditions
