outlet 26 and through the vent conduit to the exterior environment large debris in the dirt laden air is collected in a removable waste bucket 42 alternatively the clean air fan and the stale air fan could be driven by separate motors further another type of heat exchanger could be used in place of the heat wheel 36 including a shell and tube type heat exchanger and a plate type heat exchanger as a further alternative the stale air fan could be powered by the vacuum motor and also be used to generate a vacuum at the vacuum inlet 24 further in this arrangement in order to provide sufficient suction a diverter valve not shown may be provided which automatically closes the stale air inlet 32 when the unit is in vacuuming mode in a normal or a ventilation mode the ventilation motor 16 is operated at a low speed to draw air from within the interior environment to be replaced with fresh air from the external environment all air passing through the intakes 30 32 34 is filtered by the air filters 28 38 40 to remove debris and either supplied with or stripped of heat energy by air from the opposite environment with the ventilator motor 16 operating in this mode a minimal amount of noise is produced in order to use the unit 10 as a central vacuum cleaner for vacuuming floors and the like the unit is switched to a vacuuming mode in the vacuuming mode the vacuum motor 14 is energized to create negative pressure at the vacuum inlet 34.