A series of experiments and simulations have been conducted to investigate how natural (i.e. buoyancy and wind-driven) ventilation through cavities formed behind steel cladding can influence the thermal and hygric (i.e. moisture-related) performance of walls in Australia. Changes to the National Construction Code (NCC) in 2019 introduced requirements for the thermal resistance of cavities to be calculated using methods outlined in the new standard AS/NZS 4859.2:2018. These calculation methods reduce the nominal thermal resistance of such cavities significantly when they include openings for ventilation between the cavity and the outdoor air (Figure 1).