The invention relates to an Air Handling Unit (AHU) that combines a centrifugal plenum fan, a flow straightening structure with a rotary heat exchanger of an optimised surface area that is tilted. This improves the ratio of flow rate to unit height over prior art designs, whilst maintaining the energy usage/ energy recovery and noise levels seen in traditional AHUs providing the same delivery flow and pressure. The invention also optimises the serviceability and access to the unit's filters and fans when the unit is placed in confined spaces.
