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The correct chimney design is important not just to blend the chimney with the overall look of a fireplace or stove, but also for its proper functioning. The purpose of a chimney, after all, is to serve as an exit for smoke, and it should be able to do this effectively. A range of chimney designs are available to fit both local chimney code requirements and aesthetic considerations.
The most common types of chimneys are masonry chimneys. Made from brick, concrete or stone, the chimney masonry is part of the general building construction. This sort of chimney construction is used to give a place a traditional or rustic look.
Masonry chimney designs include visible chimneys that extend up the wall from the fireplace, hidden chimneys that are tucked away within the wall, and chimneys that are located on the outer side of the building. Inside chimneys generally given a better draft than outside chimneys. Draft is the hot air or hot gas that rises up from the fire and escapes through the chimney.
Chimneys operate on the natural principle of air and gases always moving from high pressure to low pressure areas. Hot gases from the fire move up in a draft up the chimney, rising faster if there is a large temperature difference between them and the outside air. In their wake, the hot gases create a low pressure area that is then filled with fresh air, which aids in combustion and keeps the fire going. If the hot gases are unable to exit the chimney rapidly enough, there are issues like down drafting, formation of tarry creosote due to smoke condensing on the chimney surface and a poorly burning fire.
As these problems are exacerbated by bends and obstructions in the chimney design, the ideal chimney design is a straight one; other building considerations, however, do not always allow a perfectly straight chimney. The size of the chimney flue, the opening through which the gases exit the chimney, is also an important factor in good chimney performance; too small or too large flues can obstruct or slow down the departing draft. The chimney also needs to be preferably located at the highest roof point and be at least three feet (91.44 centimeters) above the roof.
Apart from masonry chimneys, factory-made chimneys are also very popular. Made from a metal like stainless steel, these chimneys are much less expensive and much easier to set up than masonry chimneys. Chimney installation in this case is only a matter of reassembling the parts at the location.
Factory-made chimneys are available in different chimney design types, like mass insulated chimneys, air insulated chimneys and air cooled chimneys. All three are made up of two metal layers, with a mass material and air acting as heat insulators in the first two cases and air serving to dissipate heat in the other. It is also possible to get chimneys that are a combination of heat insulating and heat dissipating principles.
Whether of masonry or factory manufactured, chimneys require to be overhauled and cleaned from time to time. A chimney service company can be hired for this purpose, and they may also undertake any chimney repair if essential. A well-designed, well-tended chimney can make all the difference in the effective performance of a fireplace.