Increasing the Performance of Your Chimney

by Brice Particelli

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Do you find that you have too much draft coming through your flue? Or too little? Are your energy bills too high because of a drafty chimney? Or do you find that you have water damage around the path of your chimney? Chimney caps are an inexpensive guard against many problems that might occur in relation to your chimney.

A chimney cap serves many functions. A decent chimney or stove will have its own protection against some of these things, but they all still leave a gaping hole into your home that allows anything from bats and mice to rain and wind to get through. Rather than having a flue guard too low in your chimney, it of course makes sense to have a cap on top.

Do All Chimneys Need a Cap?
Chimneys come in all shapes and sizes—brick, stone, metal, or from a pipe to a wide opening and more. Some people use a chimney for a gas fireplace or a wood fireplace, some for a wood-burning stove. All of them need the same things though: access to oxygen, protection from excessive elements like rain and wind, and a way to keep unwanted visitors out. All three of these needs can be met by having a cap, but choosing the right cap has everything to do with the type of chimney you have. To figure this out, climb up onto your roof, count the number of flues (often a square of stone or one or two metal pipes) and write down a good description of each (Do pipes stick up out of the base? How far? etc), and measure each with your handy tape measure. Or, if you're not feeling so daredevilish, ask your chimney sweep or other professional chimney service to come by and take a look for you.

Specific Functions of a Chimney Cap
There are almost as many variations of chimney caps as there are chimneys. Some offer a simple grate, others a set of barriers and blocks that optimize airflow while keeping everything else out. Other caps have an integral damper mechanism, necessary for draft houses or older chimneys that might be missing a damper mechanism. Some are meant to disappear in your home's design, others are meant to accentuate it. Each of these potential functions should be considered in balance with another to optimize energy efficiency and the flue's protection.

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Design
Copper is always going to look beautiful and last the longest. Copper chimney caps come in all the same forms and styles of other caps, but they can be treated to either keep their golden shine or left to weather to that traditional look. Basic design choices run the gamut. They come in copper, brass, aluminum, and galvanized and stainless steel. To meet a specific exterior design look, you might go with something like a European copper chimney cap to enhance your architecture, or if you want something simple, you might just go with a single flue cap. Any chimney professional will be able to offer you a wide variety of cap styles to meet your budget and home design needs. Similarly cap manufacturers can create custom caps to fit odd-sized flues, multiple flues, or specific design needs.

Installation
The real trick is figuring out what kind of chimney flue you have and what kind of cap you need. From there, installation is as simple as a few screws or fasteners. A chimney sweep or other chimney professional can always do this for you, preferably timed during your regular cleaning service, but you can also do this yourself. Just be sure to recognize the flaws in your current system before you go shopping. If it's as simple as protecting from unwanted guests, there's no reason to buy a complex air system that might actually alter airflow for the worse. If you know what you want, it will be a simple process.

Chimney Liners and other considerations
Finally, if you're looking into a chimney cap, you are obviously reassessing the performance of your fireplace or stove. Ask your chimney sweep, contractor, or other chimney professional to look at the whole system. Chimney liners get damaged, dampers become loose, and cracks can open between chimney and roof. It's always best to look at the whole thing and fix it in one shot rather than to piecemeal.

Brice Particelli, formerly a carpenter in Colorado and Kentucky, manages continuing education programs for Columbia University and is a freelance writer for both the home improvement and travel industries.