Rules Of Designing Chimney Flue Liners

To carry the fumes and air pollutants from the stove or hearth effectively and safely

The chimney flue liners must be designed so that:

- they have the same inner diameter along the whole chimney;
- condensates,_the_advanced_chimney_solutions.php">chimney liners should be as vertical as possible, the deviation from the vertical run shall not be more than 15 degrees but can never exceed 30 degrees in one segment;
- the non-vertical (slant) segment of the chimney flue liner must not meet (run through) any of the roof framing components;
- the flue liner should be either round-shaped or square. If it must be a rectangular chimney flue liner, the long/short side ratio should not exceed 1,5/1.

The minimum chimney flue liner diameter

The minimum chimney flue liner diameters (based on European EN norms) are as follows:
- 100 mm (3,94 inches) for the gas stoves;
- 110 mm (4,33 inches) for the liquid fuel burning stoves;
- 120 mm (4,72 inches) for the solid fuel burning stoves (but here the minimum intesection area must be at least 0,015 square meters or 0,16 sqare ft, which with the round shaped flue liner represents minimum 140 mm or 5,51 inch diameter);

The effective height (length) of the chimney flue liner

The effective chimney liner height (or length) depends on the draft demand of the stove and chimney flue liner diameter. Anyway, the minimum chimney liner height is:
- 5 m (16,4 ft) flue liner for the solid or fluid fuel burning stoves;
- 4 m (13,12 ft) chimney flue liner for the gas burning stoves;

The maximum chimney flue liner height

The maximum flue liner height (length) is also limited by the EN regulation. The chimney liner length shall not exceed the liner diameter multiplied by 185. Means that the length of the flue liner with 100 mm (3,94 in) diameter should not exceed 18,5 m (or 60,7 feet).