Throughout human history, thermal comfort has been by far the most important factor when evaluating well-being. Although, there are numerous studies regarding thermal engineering in HVAC systems, their scope has primarily been focused on analyzing buildings or automobiles, but have barely fixated on buses. Moreover, in the field of computational fluid dynamics, there is virtually no research aimed towards this kind of vehicles. This thesis tries to fill this void by analyzing the heating system of a public transport bus in Turin, using the ASHRAE-55 standard, which is a guideline for thermal design in enclosed spaces. This work serves as a base reference for all the processes involving CFD simulations and thermal comfort analysis of a bus cabin.