Book - School of Science and Technology

Chimney construction 3311000Diameter of flue – mm800600400200F=0.51.02.05.020.00 0.2 0.4 0.6 0.8 1.0 1.2Boiler rating – MWFigure 12.9 Chimney areasChimney constructionDomestic chimneysBuilding Regulations require that all new masonry constructed domestic chimneys be linedwith some impervious materials such as tile. Proprietary flexible flue liners are onlypermitted in retrofit applications.Larger installationsThe importance of keeping the products of combustion in the chimney warm has beenemphasised earlier. With this in mind some form of insulation is a necessity and variousforms of construction are illustrated in Figure 12.10. They are:A An outer stack in brickwork or concrete enclosing an independent lining of firebrickor moler brick with an air gap between.B An outer stack in brickwork enclosing a moler brick lining which may be bonded in.C An outer stack in brickwork lined with fire clay tiles.D An outer stack in reinforced concrete sections lined with insulating moler brick orconcrete.E A welded steel flue within aluminium cladding. The construction may be guyed or selfsupporting. The annular space between flue and cladding may be packed withinsulation material.F One of a family of prefabricated sheet metal chimneys manufactured in lengths ofabout 1 m with socket-and-spigot or twist-lock joints. A wide variety of constructionsis available, insulated and un-insulated.