How to get ducted air conditioning to the lower level of a multi-level house? The ducts are run vertically from the roof space down through robes/cupboards or in some cases through specially designed bulkheads. These ducts are called “droppers”.
The size of the ducts are typically 250mm in diameter. In a larger house where more air is required 300mm ducts are run and if ducts are being run down to smaller rooms e.g. bedrooms then a 200mm duct is used.
The spacing between the floor joists can, in some cases, limit the diameter of the dropper.
The droppers are then framed around and plastered/sheeted over so they are not visible.
The same method is used for an existing house. There is one restriction in that it is not possible to run the duct horizontally between the floor joists (because the ceiling is already plastered/sheeted). In this case the air outlet can only be directly below the cupboard/robe.