Often neglected, ignored, or misunderstood, a wood stove chimney is the backbone that supports your wood burning stove.
Think of it as the "behind the scenes" workhorse that drives the entire wood burning system.
Although it's exciting to focus on the most efficient stove or the latest technology, it's easy to forget your stove will only function as well as the chimney it's connected too.
In fact, a majority of problems such as back puffing, poor draft or the smell of soot in the house can be traced back to a poorly constructed chimney.
To learn more, lets look at how a chimney operates and why its design is so important.
In order for a wood burning stove to function properly, the chimney must expel hot gasses up and out of the home. As the gasses rise up the chimney it creates a pressure difference that allows the stove to draw in fresh air used for combustion....kind of like a vacuum.
This movement of gasses up the chimney is known as draft. The temperature of the gasses inside the chimney and the overall chimney height both play an important factor in determining draft.
For example, the hotter the gasses are inside the chimney compared to the temperature of the outside air, the stronger the draft will be. Also, the taller the chimney the more draft it will create.
Outside air currents that form around trees, buildings or roof peaks can create problems that reduce and interfere with draft. To prevent this from occurring, a chimney should extend at least 3 feet past a flat roof and be at least 2 feet above any roof peak within a 10 foot radius.
In general, the overall height of the chimney from the base of the wood stove to the top of the chimney should not be less than 15 feet.
Contrary to popular belief, chimneys that exit the home at ground level and run outside along the exterior walls of the home are extremely inefficient.
Since hot air rises, the outside temperatures cool the gasses inside the chimney reducing draft. These cooling gasses can also create condensation and a buildup of creosote. Creosote forms when warm gasses come into contact with a cold surface, which is exactly what happens when you run a chimney outside.
By locating the stove in the center of your home, the wood stove chimney will extend straight up through the living quarters of your home where the temperature is warm.
These warm temperatures that surround the chimney keep the flue gasses warm which in turn helps create a strong draft. Plus, the chimney exits near the roof peak eliminating the possibility of unwanted problems caused by outside structures.
Besides installing an interior chimney, you should also make sure the chimney flue size matches the requirements of your stove. For example, a flue that is too small can create too much draft and a flue that is too large will have decreased pressure resulting in a reduction in draft.
The stove manufacturer will have a recommendation for which size chimney flue you should install for optimal performance. Typically the flue collar on the stove will determine your chimney flue size.
Limit the number of bends in the chimney by reducing excessive T's or elbows and try to avoid long horizontal runs in the chimney. Think of a chimney like a dryer vent. The more the dryer vent bends and zig-zags, the more lint it collects inside the pipe.
A chimney is basically the same way, only the lint is actually creosote. A straight, vertical path without restrictions will create a strong draft.
So what's the best way to install a wood stove chimney inside your home? Remember these basic principles:
- Install the stove in the center of your home with the chimney running straight up through the warm part of your house.
- Limit the number of bends in the chimney and make sure to use insulated high temperature pipe.
- Match the flue size to the flue collar on the stove.
- A tall chimney is a happy chimney.
Remember, the chimney is the backbone of your wood burning stove. Inspect it regularly for damage caused by high temperatures, moisture or corrosion.
Also, have the chimney inspected and cleaned by a certified professional at least once a year to maintain your investment and more importantly, increase your safety.