Technical Booklet K Ventilation·Page 22·2.9
Design Air Permeability Guidance
Guidance is provided for each system to cover all design air permeabilities, so the as-built permeability does not need to closely match the design permeability for ventilation purposes.
For each system, guidance is given for dwellings to cover all design air permeabilities. Therefore, for ventilation purposes, it is not necessary for the as-built permeability to be close to the design permeability.
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