May 2009 – Ask the Chimney Sweep

Regardless of whether you use your chimney or not, every chimney needs a cap. A chimney cap does several things. It keeps animals like racoons, bats, and squirrels from entering the chimney. It also prevents rain and other moisture from dripping down into the chimney flue or seeping into the insulation between a metal flue liner and the masonry surface. A chimney cap can prevent heat loss in the winter and loss of your air conditioning in the summer months and will protect your chimney's crown from the elements, including ice, extending its life and decreasing the risk and likelihood of cracks. A couple of things you should be aware of when installing a chimney cap: Improper design or installation may restrict the draft of your chimney. This will increase the likelihood of smoking problems down the road. Make sure that the chimney cap you are installing is compatible with your chimney type and that it is installed according to the manufacturer's directions. Often times, the screen on your cap can become clogged with chimney byproducts, further decreasing the draft of the chimney. After installing a chimney cap, check it at least once a year to make sure the screen is not clogged. In high winds, caps can potentially blow off, so make sure that the cap is fastened securely to the chimney. Prevent Water Leaks With a Chimney Cap If water is leaking inside your flue, it can actually increase your allergies. A damp, warm environment are the perfect conditions for mold and mildew growth. Also, rain will rust away your metal flue or the grate that your gas logs rest on. If you've ever had a leaking chimney, you may have noticed an odor coming out of your chimney. During the warm summer months, creosote inside the chimney can evaporate with the water leaking into the chimney, creating a foul odor. By capping your chimney, you can prevent water from entering your chimney, thereby reducing or eliminating any odor. Stainless Steel Caps There are many different types of Stainless Steel chimney caps available. Standard caps usually come with screens to keep animals out. Stainless steel is the most common cap material, as it doesn't rust and discolor the brick or stucco on your home. It also hold up to the elements better. Stay away from painted metal chimney caps, as runoff can stain the chimney. Galvanized Chimney Caps Galvanized chimney caps are frequently used because they're inexpensive, but the downside to these is that they have to be constantly repainted. If you do choose this type of cap though, it's best not to use it with gas logs. The exhaust from the logs, which is very caustic, will eat right through the cap in a few years. Copper Chimney Caps If you use gas logs, you may consider using a copper chimney cap. This type of cap can withstand the corrosive exhaust from the gas logs. Copper chimney caps are the most expensive type and while they look very nice when first installed, after a few storms they begin to look like an old penny. Draft Increasing Caps Another type of chimney cap is designed for draft increase. If you have draft problems in your chimney, you may want to consider this type of cap. They are designed to increase the draw in your chimney, preventing smoke from entering your home. Stay away from mechanical caps which rely on windvanes or turbines. The creosote and smoke coming out of your fireplace will clog up the mechanics and quickly gum up the workings of these caps. Caps With Internal Damper Systems Some caps come equipped with internal damper systems. While more pricey, these types of caps can be great at preventing energy loss in your home. Lock-top and Seal-tight are two great manufacturers of this type of cap. These caps are retrofitted to the chimney and controlled by an inside mechanism. When closed, you can rest assured that none of your energy is floating up and out of your chimney. Precautions If you are installing a cap on your own, be sure to take these precautions under consideration. Wearing gloves is essential, seeing that sheet metal may have sharp edges. Be sure not to use silicone sealants on metal flues. The metal will get hot enough to ruin the sealant. If the cap you purchase comes with screws or adhesives, use them! This will protect you from possible fires and will better ensure that your cap will stay attached despite the elements.