# With regard to Building Regulations for ventilation, how is the term ‘air permeability’ defined?

**URL:** <https://reachback.builtintelligence.com/t/with-regard-to-building-regulations-for-ventilation-how-is-the-term-air-permeability-defined/2798>\
**Category:** Part F Ventilation\
**Created:** [15 February 2013 13:16 UTC](https://reachback.builtintelligence.com/t/with-regard-to-building-regulations-for-ventilation-how-is-the-term-air-permeability-defined/2798 "2013-02-15T13:16:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Build\_Regs\_Advisors](https://avatars.discourse-cdn.com/v4/letter/b/ee7513/32.png) [@Build\_Regs\_Advisors](https://reachback.builtintelligence.com/u/Build_Regs_Advisors)\
**Post date:** [15 February 2013 13:16 UTC](https://reachback.builtintelligence.com/t/with-regard-to-building-regulations-for-ventilation-how-is-the-term-air-permeability-defined/2798/1 "2013-02-15T13:16:09Z")

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**Author:** ![Build\_Regs\_Advisors](https://avatars.discourse-cdn.com/v4/letter/b/ee7513/32.png) [@Build\_Regs\_Advisors](https://reachback.builtintelligence.com/u/Build_Regs_Advisors)\
**Post date:** [15 February 2013 13:16 UTC](https://reachback.builtintelligence.com/t/with-regard-to-building-regulations-for-ventilation-how-is-the-term-air-permeability-defined/2798/2 "2013-02-15T13:16:18Z")

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The existing Building Regulations define air permeability as the average volume of air in cubic metres per hour that passes through unit area of the building envelope in square metres when subject to an internal to external pressure difference of 50Pa.