Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 26·5.16
Subfloor ventilation opening area requirements
Subfloor ventilation openings must provide a minimum opening area calculated as either 1500 mm² per meter run of external wall or 500 mm² per square meter of floor area, whichever is greater.
The openings should be not less than either 1500 mm2/m run of external wall or 500 mm2/m2 of floor area, whichever gives the greater opening area.
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