In new buildings or installations, it is recommended to use air water/refrigerant systems instead of all air systems. Please refer to the information on air water/refrigerant systems. However, in existing buildings it may not be possible or cost-effective to replace existing all air systems with air water/refrigerant systems. Therefore, this part presents options to improve the energy efficiency of all air systems. Cost effective energy savings of up to 40-60 % are possible in all air systems.