The dynamic model ThermiPig was developed to simulate thermal balance at the fattening room scale, as the result of the heat produced by the group of pigs or provided by incoming air and equipment and that lost due to air renewal or thermal conductivity of the walls and ceiling. A growth model (assuming thermoneutral conditions, InraPorc) and a bioclimatic model (ThermiSim) were combined to create ThermiPig. It considers a common time step (1 hour), definition of the pig thermoneutral zone (based on body weight and type of floor), evaluation of impacts of cold and hot exposure on the amount of available energy for growth, and the circadian distribution of heat produced daily by each pig (based on meal partition over the day and post-prandial thermic effect of feed). Data collected in vivo from a group of 96 pigs of the IFIP experimental station were used to evaluate the accuracy of the prediction of ambient temperature (T). Characteristics of the fattening room, regulation rules of the climate box control of the ventilation system, nutritional characteristics of the 2-phase feeding sequence, and outdoor conditions (hourly T and relative hygrometry) observed during the in vivo trial were used as inputs of the model, and simulation were performed on 30 virtual groups of pigs from the same genders and crossbreed. With average in silico growth performance of the 30 groups similar to observed ones, the error of prediction (RMSEP) on ambient T averaged 0.6°C. Thereafter, ThermiPig was used to simulate the impacts of alternative regulations for ventilation or the use of new equipment (heater, pad cooling) on growth performance of pigs, N excretion, and indirect energy (from feed intake) and direct energy (from electricity consumed by equipment) consumption. Comparison of multi-criteria performance in silico helps identify the most interesting option. Economic performance depends on carcass value minus costs of feed intake and electricity (depending on the energy source). Therefore, more accurate prediction of carcass value is expected in the next version of the model by considering effects of ambient temperature on the distribution of body fat and protein metabolism.