Chimney height

A tall chimney applies more air-pressure to its base than a short one. All things being equal the chimney in the tall building at right will generate a stronger, more stable draught than the short chimney in the lower building.

A short chimney of the type often installed into chalets, mobile homes and top floor sitting rooms may struggle to generate adequate draught particularly when flue gas temperatures are low, as is the case when a stove is run at reduced output.

Note that whenever height is added to a chimney the likely impact on temperature must always be taken into account. In the building at right, adding height has caused the chimney to stick up like a flagpole in a way that will cause its upper section to run cold. In such cases the benefits of extra height may well be cancelled out by excessive heat-loss from the exposed section. In addition, any chimney that runs cold at its upper extremity is likely to foul up rapidly owing to the large volumes of condensate produced.