At what pressure must the air leakage rate be reported according to GCSB 149.10 - 2019?

The air leakage rate must be reported at a pressure of 50 Pa according to GCSB 149.10 - 2019. This pressure level is standard in building airtightness testing as it provides a consistent basis for measuring and comparing the air leakage rates across different buildings. The 50 Pa pressure equivalently reflects conditions that are representative of typical indoor pressure differentials created by wind and mechanical systems. Reporting at this standardized pressure helps ensure that the results are reliable and comparable, enabling builders, architects, and building owners to assess and improve building performance in terms of energy efficiency and occupant comfort.