In his thesis on the principles of fireplace design released in1799, Count Rumford emphasized the significance of the size of the flue as compared with the size of the fireplace opening. He recommended that the cross-sectional area of the flue should be about a tenth of the size of the opening. However, fireplaces had the tendency to be smaller sized after the mid 19th century. Modern flue liner manufacturers prefer a ratio of one to seven, and there are sizing charts published that offer details on current standards.
If your fire smokes or wont burn properly, see if opening a window improves matters Visit this site . If it does, you need much better ventilation in the room. One option is to install a window vent, although this could cause a problematic cross draft. A far more efficient form of ventilation is either a single ducted vent set into the floor in front of the fireplace, or twin ducted vents set into the floor or external walls on each side of the chimney breast.
When wood and coal are burned, flammable gases, tarry substances, acids and dust are emitted. However, since domestic stoves are relatively inefficient, not all these substances are consumed. Instead, they rise up the chimney and some of them condense on the inside of the flue. Unburned carbon combines with these tars and acids, creating soot, which builds up over a period of time, thus decreasing the size of the flue. It is important to have regularly used chimney sweeps at least twice a year, preferably before, during, and at the end of the heating season. The regional trade directory sites contain details on fully qualified and appropriately insured sweeps. A soot filled flue is a fire risk, since the unburned elements of the soot can fire up, triggering a chimney fire which can reach high temperature levels and damage the chimney.
If a flue is too big, its size can be reduced to enhance its effectiveness by the fitting of a liner. A variety of methods and materials are used, consisting of flue liners made from flexible stainless steel, ceramic, lightweight concrete sections, or concrete that has been cast. Other methods of decreasing the size of the fireplace opening in order to enhance fire efficiency, is to raise the level of the hearth or to fit a baffle across the top of the opening. If raising the hearth level or including a baffle is not practical or is unattractive, then it may be worth asking a fireplace specialist whether fitting a metal smoke hood or canopy in the opening is the best option.
