Natural and mechanical ventilation, AirDeck and AirCore active fabric energy storage ( FES ), air conditioning ( including conventional systems and chilled ceilings with mechanical ventilation ) and combinations of these systems were modelled for a typical UK steel-framed office building. Both summer and winter performance were considered. Active FES enhanced thermal comfort and reduced energy usage and emissions. When compared with conventional and natural ventilation systems, the FES systems reduced temperature excess hours and peak temperatures, generated cooler air, and reduced chilled consumption, boiler ratings and emissions. The annual operating costs of the active FES systems were 13% higher than those of naturally ventilated systems, whilst combined systems gave a reduction of 35% compared with mechanically cooled options. 3 refs.