Air spaces

Prevents non-occupiable volumes from being counted as floor area while providing a spatial reference for building services.

Description

• Air spaces such as atriums, stair voids, multi-storey rooms, or other non-occupiable volumes within the storey volume.
• Deducted from storey volume to obtain countable floor area or usable volume.
• Provide a reference space for building services engineers.

Modelling guidelines

• Fill every larger cavity in the building with an air space - e.g. atrium, stair void, multi-storey rooms, air space above the uppermost stair flight.
• Model as a volume with the space tool, storey by storey.
• Bottom = top of the space volume below; top = underside of the raw slab or boundary of the storey volume.
• Assign to the matching storey; no overlaps with usable spaces or duplicates.

Discussion point

• Air spaces are still rarely modelled as separate volumes. Instead, teams often create a storey volume for urban-design evaluations and building volume together with a storey-area model. A separate air space can be evaluated directly, reused for subsequent area and volume calculations, and made available to building services as a spatial reference. It also represents a real spatial condition that is intuitively understandable, whereas interpreting a storey-area model requires knowledge of the underlying standard.