Ductless ventilation - Refurbishing an old listed building into modern energy-efficient offices

This paper presents an application ductless balanced ventilation with heat recovery, non-invasively retrofitted into a naturally-ventilated old building at Akershus Fortress, Oslo. The system exploits the building's architechture to best effect, using original brickwork air stacks, high ceilings and thermal mass. Staircases and corridors transport supply air to each room, and air is exhausted via the stacks. A quality-based cleaning regime minimizes the supply air pollutant load. The paper describes the design studies (CFD, mulitzone airflow and dynamic building thermal modelling), and experiences from 5 years of operation. The air distribution is stable, and contaminant spread is not a problem. Window airing is discouraged to limit infiltration. Simulations indicated that summer overheating is less of a problem than for a ductwork system. Occupants are satisfied with the indoor environment. Hovwever, there remains a teething problem with temperature differences between rooms, due to temperature rise along the supply air flow path.