A chimney pot set on top of your chimney, or more than one if you have multiple flues, can enhance the look of your chimney while improving the draft. The pots are generally earthenware and are set in a bed of mortar on the masonry of the chimney cap. A properly sized chimney pot will not overhang the flue liner by more than 3/4 of an inch at the corners. The flue liner may extend up into the chimney pot to ensure there is no overhang and to enhance stability.
To find the right size chimney pot, measure the flue opening and note the widest dimension. Purchase a chimney pot that is at least that wide. For maximum draft enhancement, if the chimney pot tapers inward toward the top, you want to make sure that the top dimensions are still as wide as or wider than the flue's widest dimension.
A superior chimney pot should come with a rain guard, usually of the same material as the pot itself, to keep moisture from accumulating inside. Extra care should be given to this when installing on a wood case chimney. Leaks around the base can cause the wood to rot.
You may also want to consider additional anchoring to protect the chimney pot from hurricanes, tornadoes, or earthquakes, depending on where you live.
A spark arrestor can be added as well, provided it's up to code. The net free area of the arrestor should not exceed four times the net free area of the chimney flue's outlet. The screen must be heat and corrosion resistant, equivalent to 19-gage galvanized or 24-gage stainless steel. The openings must block spheres larger than 1/2 inch while passing spheres less than 3/8 inch. The screen must be removable for cleaning and access to the flue. A second benefit to a spark arrestor is that it keeps birds from building a nest in your chimney.
By extending the length of your chimney, a chimney pot can help increase the draw, bringing smoke up from below. For this effect to work, each flue needs its own chimney pot. It may be tempting to cover two adjacent flues with a single, large pot. But this "solution" proves to be more of a problem. It sets up turbulence and disrupts the draft far more than it helps.
Once the physical necessities have been addressed, you can start thinking about design. Chimney pots come in all sorts. A cylinder with a lip around the top can provide all the beauty you desire with its clean lines and simple design. Or choose one with four sides, either square or rectangular, with rounded edges. You can even get a hexagonal or octagonal footprint, with edges round or crisp. Try a rounded column with a square base for a Greco-Roman feel. Or maybe a lighthouse or castle tower design will provide the look you want.
Some chimney pots come with caps on top and ample openings around the sides for venting. These won't generally provide as much draft enhancement, but you might feel they add just enough class to make it all worthwhile.
Chimney pots are fired at high temperatures, making them durable in all weather conditions. They do not need a lot of maintenance or cleaning, but they should be inspected once a year for signs of damage.
Locating chimney pots can be difficult since they are often made of clay and are difficult to transport. They also take up a lot of showroom space. However, chimney pots are avilalbe at most fireplace retailers or distributors. Here are two online retailers that have quite an extensive selection.
Chimney Pot Shoppe: Carries one of the most extensive lines of chimney pots available with many sizes, shapes, and colors.
Clay Chimney Pots: Offers many different clay style chimney pots along with sizing and use instructions.