An aggregate space or assembly compartment arranged between an engine compartment or a trunk and a splash panel of a motor vehicle. The aggregate space is closed off by means of a hood which can be swung upwardly and has an air inlet slot between an end edge of the aggregate space on a window side thereof and an adjoining zone of a body portion of the motor vehicle. The aggregate space accommodates an aggregate part of a heating/ventilating and/or air conditioning unit which in the interior of the aggregate space, takes over air deflecting and air distributing functions. The aggregate part includes a jacket for enhancing a water deposition or separation and a water drainage. Fresh air entering the aggregate space is conducted and deflected along the jacket and then passed to an air inlet opening set into an underside of the aggregate part. The air leaves the aggregate space through the inlet opening in an essentially upwardly oriented direction.