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).

© Commonwealth of Australia 2014