Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 92·C.3
Assessment approach for air permeability of older dwellings
Failure to implement most of the sealing measures will likely result in air permeability exceeding 5.0 m³/(h.m²) at 50 Pa. Assessment should consider both overall dwelling and individual room air-tightness; when in doubt, assume lower air permeability and fit appropriate permanent ventilation or seek specialist advice.
C.3 Failure to implement even a few of these measures will typically mean that the overall air permeability will probably exceed 5.0 m³/(h.m²) at 50 Pa. However, individual rooms in some older houses with solid walls and solid floors can be inherently air-tight when fitted with modern glazing. The situation may therefore need to be assessed with respect both to the overall dwelling and to the individual room where the appliance is to be fitted. If in doubt then assume that the air permeability is lower than 5.0 m³/(h.m²) at 50 Pa and fit the appropriate permanent ventilation or seek specialist advice.
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