Next to air temperature, humidity, and air quality, it is sound emission that exerts a significant impact on the driver's and passenger's comfort. Major progress in vehicle acoustics has motivated vehicle manufacturers and systems suppliers to evaluate HVAC systems no longer by their air conditioning performance alone. Sound emissions and sound quality have become additional important criteria for the development of new HVAC systems.In the initial conception phase, where systems and packaging considerations are made, acoustic optimization must begin with preliminary system studies and feasibility studies. In this phase acoustics should be based on fairly general systems specifications which describe the desired degree of acoustic comfort. In the subsequent design phase follows the specification of the acoustic goals and the optimization of the HVAC unit. Detailed analysis and optimization of air flow and blower are the common targets for improvement at this time. Finally, component optimization starts with including the detailed design process and the mounting of possible noisy components.The paper further outlines four pillars, on which good acoustics of an HVAC system is based, focusing on the subsystem ‘air flow’. These are reduction of pressure drop, flow optimization, sound proofing and sound deadening, and at least the insulation of structure borne sound.