390x190 mm vent, with 316 stainless steel spark arresting 1.65mm aperture x .45mm diameter wire. They give 17,400 Sq mm of ventilation per vent.

 The Australian Building code 3.4.1 deals with sub-floor ventilation. There are 3 climate zones, Zone 1 is central Australia and requires 2,000 sqmm of ventilation per linear metre of external wall, using Aleta 390x190 vents in Zone 1 would mean spacings at 8.7metres. Zone 2 is in land Australia and requires 4,000 sqmm of ventilation per linear metre of external wall, using Aleta 390x190 vents in Zone 2 would mean spacings at 4.4 metres. Zone 3 is coastal Australia and requires 6,000 sqmm of ventilation per linear metre of external wall, using Aleta 390 x 190 vents in Zone 3 would mean spacings at 2.9 metres.

It should be noted that extra ventilation may be required if : excessively damp sub-floor or if all walls can't be ventilated.

Vents should be placed no more than 600mm from corners and evenly spaced around the building.