If your flue vents directly into the air at the top of your chimney, there are a lot of reasons why you should install a chimney cap. A chimney cap covers the flue, allowing enough space for smoke and gases to escape unimpeded. It keeps snow and rain out of the flue and off the masonry crown and may be screened to keep trash and small animals out. The type of chimney cap you choose will depend upon your chimney configuration, the functions you want the cap to perform, and your individual decorating preference.
Chimney caps are made from several different metals, including copper, aluminum, steel painted black and stainless steel. The top cover is wide enough to keep precipitation off of the chimney top. The open spaces around the sides are usually enclosed with screen or course mesh. This acts as a spark arrestor as well as keeping leaves and squirrels, bats, birds and other small animals out of your chimney and out of your house. Most chimney caps are made of corrosion resistant metals or have corrosion resistant finishes, so you can choose the metal and color that best fits your exterior home decoration.
Chimney caps are manufactured with different bases to fit the type of flue you have. If you have a cylindrical metal chimney liner, you can find caps with round bases to fit the top of the liner. If your chimney has a rectangular tile flue liner, you can buy a chimney cap with a rectangular base that fits over the outside of the top tile. If you have a chimney with multiple flue openings, you can get a chimney cap that is sized to fit over all of them, or you can buy individual caps for each flue.
A basic chimney cap protects the chimney from precipitation and keeps things from falling down the chimney. In some cases the geometry of a basic cap also improves the draft of the chimney, although soot buildup on the screened openings can impede draft. For windy locations, special chimney caps that are designed to create a vacuum inside the flue when it is windy can help to alleviate down drafting problems.
A chimney cap that includes a top sealing damper is an effective way to improve your home’s energy efficiency. Old metal fireplace dampers that don’t seal well even when they are closed tightly let cold air infiltrate the house when a fire is not burning in the fireplace. A top sealing damper chimney cap has a cable that runs inside the flue to a lever that can open and close the damper from inside the house. With the damper closed, you will immediately notice fewer cold drafts in your room.
The variety of ready made chimney caps on the market should let you find what you are looking for by shopping online or at your local chimney supply store. If you have a special situation that lend itself to standard solutions, most chimney cap manufacturers can build a custom cap exactly to your specifications for a reasonable price.