Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 41·Table 3.3, Note 4
Treatment of vertical flues on outside walls
A vertical flue fixed to an outside wall should be treated as equivalent to an inside flue emerging at the nearest edge of the roof.
A vertical flue fixed to an outside wall should be treated as equivalent to an inside flue emerging at the nearest edge of the roof.
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