A quality chimney cap is the finishing touch to a well-designed chimney system. A variety of chimney cap materials are available to suit different chimney configurations, performance requirements, and exterior styles. After selecting an efficient fuel-burning appliance, such as a fireplace, woodstove, or insert, along with a properly sized and insulated stainless steel flexible chimney liner to safely vent smoke and combustion gases, you should also choose a chimney cap designed to fit the top of your flue. Chimney caps are available in a wide range of sizes and materials to accommodate virtually any chimney configuration.
A chimney cap serves several important purposes. Installed a few inches above the flue opening, it helps prevent rain and snow from entering the chimney. It also directs precipitation away from much of the masonry crown, helping prevent moisture from entering small cracks and contributing to chimney deterioration caused by acidic exposure and repeated freeze/thaw cycles. Many chimney caps feature screened side openings that act as spark arrestors while helping keep leaves, debris, birds, and small animals out of the flue.
In some situations, installing a standard design chimney cap can improve your chimney's drafting ability during windy conditions. The design of the cap can create a low-pressure area above the flue as wind passes over it, helping draw smoke and combustion gases upward rather than allowing them to blow back into the home. If your chimney still has inadequate draft with a standard cap, specially designed draft-enhancing caps are also available. Another option is a top-sealing damper operated by a lever near the fireplace. Top-sealing dampers can improve your home's energy efficiency when the fireplace is not in use while also helping protect the chimney from rain, snow, debris, and animals.
The most common chimney cap materials are: aluminum, painted or galvanized steel, stainless steel, and copper.
Aluminum and galvanized steel chimney caps are generally more affordable, but they can be more susceptible to corrosion from harsh weather conditions and acidic combustion byproducts exiting the chimney.
Stainless steel chimney caps typically cost more than aluminum or standard steel caps, but they offer excellent corrosion resistance and can last significantly longer in demanding conditions. Stainless steel caps are available with a natural stainless finish or a black painted finish, allowing you to choose an appearance that complements your home's exterior. Copper chimney caps are generally the most expensive of these common options, but their distinctive appearance can add an elegant architectural accent to a home's exterior.
Many standard chimney cap designs and configurations are available without the expense of custom metal fabrication. Most can be ordered in the chimney cap materials mentioned above. Chimney caps are available for round rigid or flexible chimney liner openings and come in standard diameters that correspond to common liner sizes. Caps can also be designed to attach directly to a protruding clay tile liner at the top of the flue. These models typically use adjustable screws to securely fasten the cap around the exterior of the flue tile. If your chimney contains two or more flues, you can also choose a multi-flue chimney cap designed to cover several flue openings with a single unit.
A chimney cap is a relatively small investment that can improve the protection, performance, and safety of your chimney system. Whether you choose aluminum, steel, stainless steel, or copper, a properly fitted chimney cap helps keep debris and animals out of the flue, reduces the risk of sparks escaping from the chimney, and protects the chimney structure from moisture and precipitation.