The target in this study was to decrease the energy use for transportation of air (fanenergy) with a factor of three. Two real systems composed of existing componentswere constructed in a laboratory; a mechanical exhaust system and a balanced system.The flow rates through the systems were set at values according to the Dutch BuildingRegulations. This situation is called the reference situation. A number ofimprovements have been tested and studied. Some improvements studied: aerodynamic shape of the fan housing better aerodynamic shape of fittings more effective duct lay out developing a low pressure air terminal deviceThese measurements include: flow rates pressures differences in the ducting and before air terminal devices fan powerThe results achieved show systems that have half to one third of the reference fanenergy.To show people in the field effects of duct lay out, duct sizing, fan choice, etc, adynamic calculation model have been developed.