Say you're inspecting the subfloor area of a building in climate zone 3, and you're looking at a wall that is 8 metres long. The building uses old-fashioned terracotta vents with an opening size of 3,840 mm2.
How many vents should there be in the wall?
Step 1. Find out what the total ventilation area should be in the wall
In climate zone 3, the minimum requirement is 6,000 mm2 per metre of wall.
This wall is 8 metres long. Therefore, the minimum requirement is:
8 (metres) x 6,000 (mm2) = 48,000 mm2
Step 2. Divide the total area by the area of one vent
48,000 mm2 ÷ 3,840 mm2 = 13 vents (rounded up to the nearest whole number).