Dedicated outdoor air systems (DOAS) decouple the heating, cooling, dehumidification and humidification of outdoor air from the space air-conditioning system. Common HVAC systems such as water (ground) source heat pumps, variable refrigerant flow (VRF), fan coils and chilled beams require a DOAS to meet ventilation requirements. But DOAS is a system, not a piece of equipment.
In some parts of the world, a DOAS may not be any more complicated than a supply fan and an exhaust louver. For many locations, conditioning (heating, cooling, humidifying and dehumidifying) will be necessary. Often, the DOAS unit performing this work is one of the highest energy consumers in the HVAC system.
Read an interesting article on “Design Considerations For Dedicated OA Systems!” by Hugh Crowther, published in the ASHRAE Journal March 2016. Read full article here (link).