The floor space or area is the interior area of a building, calculated in square meters or square feet. The gross floor area is the total floor area of all floors of a building calculated with the external dimensions of the building including structures, partitions, corridors, stairs. The net floor area is the sum of all areas between the vertical building components (walls, partitions, etc), i.e. gross floor area reduced by the area for structural components. The usable floor area is the fraction of the net floor area for the intended use of the building, i.e. net floor area reduced by circulation areas (corridors, stairs etc.) and functional areas (WCs, storage rooms etc.). The conditioned floor area is the heated or air-conditioned floor area. The unconditioned floor area is the unheated or air-conditioned floor area.