Understanding the development of a problem would help a lot in fixing it. The way chimneys work may include some confusing technical explanations. A simple draft problem can become the cause of a very uncomfortable living environment. That is why, before starting to fix your chimney or even understand the draft problems, we should know what draft is in the first place.
Fireplace drafting is how well your fireplace gets rid of the products of a fire, up the chimney and out into the atmosphere. If you face a drafting problem, the result would be that the combustion products would back up and enter your house. Then, you will be left with some unpleasant and unsafe conditions. A draft working correctly means that the harmful gases and the smoke from the fire are exiting through the chimney flue as they should be.
Draft problems can be caused by many things. However, the solutions for this type of problem are usually quite simple. Nevertheless, the first step is to find the problem.
The way that a chimney works
The way that chimneys work depend a lot on the concept that hot air rises. This is the basis for how chimneys work. This concept, which is also known as the stack effect, can be explained as the following: when hot air and combustion gases caused by the fire rise to the top of the chimney, the empty area must be then filled with cooler air that will help the hot air to continue ascending through the chimney flue and out to the atmosphere. When this process is working properly, the combustion products leave the chimney and no gas escapes into the room of the house. Problems start when the hot air is prevented from leaving through the chimney flue because of a negative air pressure. This would cause a back draft, and that means that instead of the air leaving through the top of the chimney, it enters the house. Back drafting put harmful chemicals and soot into the rooms of the house, and this creates a huge problem.
Problems with your fireplace draft can be caused by various elements. These include a blocked chimney flue, an incorrect firebox size, or installation mishaps. A plugged or closed damper, or even a blocked off chimney flue are some simple problems that can be easily fixed. Some less obvious causes include a dirty chimney cap, a cap that does not fit properly or that was installed incorrectly, some structural damage, uncompleted repairs, or even unwanted animals and insects that have picked an inconvenient spot for a home. Also, a creosote (or soot) buildup along the chimney walls or spark arrester can partially close off the chimney flue, and that would cause a serious problem because it might lead to chimney fires taking place.
When the chimney has a clogged passageway or stopped up chimney cap, the harmful gases cannot get through outside the house, so they get backed up inside instead. The materials that nesting animals bring up into the chimney can create serious blockages and this will affect the drafting function of the chimney. Raccoons, birds, squirrels, or even different insects might make your chimney their summer home. Performing an annual chimney inspection will make sure that your chimney exits are not blocked.
The firebox is the cause of two main problems that will result in some draft issues. In order for the system to work properly, the firebox and the chimney flue must be the correct ratio to each other. Every 10 square inches of firebox, a one square inch of chimney flue is needed to handle the smoke and combustion gases resulting from a firebox that size. An incorrect ratio will result in a harmful backup into the house. Another thing that should be considered is that the firebox should be no more than one inch from the back wall of the chimney. The cause behind this is that the smoke and gases resulting from the fire are sometimes too close to the front of the firebox to be brought up with the draft and this way they will enter the house. To make sure that the gases will not escape into your house, push the grate all the way back against the back wall of the fireplace before starting a fire. Also, always build your fire on top of the fire grate so that the fire gets enough oxygen.
The Chimney Design
Sometimes the chimney design can cause draft problems. Making sure that the fireplace is designed following the fireplace codes will completely remove any concerns regarding something going wrong during the building process. Sometimes the fireplace is manufactured incorrectly. Another problem is an improper firebox to flue ratio. In addition, a shallow firebox (less than 20 inches) will cause the smoke to enter the room instead of appropriately leaving through the flue. Another cause for the problem is flue angles; the heat may not produce enough force to leave a the chimney walls if the passageway was not vertical. Also, creosote build-up can partially block the screens on the chimney caps, and that would reduce the drafting capability of the flue system.
Some External Factors
Sometimes, the problem is not in the chimney itself, but it is in the house or in the room where the fireplace is. As mentioned before, the chimney needs the stack effect to function. If there is another appliance in the room pulling the air outside, it may cause some draft problems. For example, air vents can cause this problem. Air vents like central vacuum, clothes dryer, or forced air furnace that exist in the same room as your fireplace, and they are both working at the same time, then this will cause a problem because they are both sucking the air out of the room. Thus, the fireplace may back up and then release unwanted smoke in the room instead to pushing the gases to the outside.
In addition, tightly sealed walls may have problems in replacing the air leaving through the top of the chimney. The air that leaves along with the gases and smoke should be replaced by something else. If the house is too tight and new air is not let in, a back draft will happen. Resolving this problem can be as simple as keeping a window open. Another cause for this problem is strong wind; smoke may be pushed back down the chimney and right into the room instead of exiting from the top.
Don’t Burn Green
To avoid draft problems, you should burn the correct fuel for your fire. Burning green or wet wood would cause the fire to not burn hot enough for the air to rise up and be replaced by cooler air. Draft problems will thus be caused and the smoke and gases will stay in the room.
If you keep having the same problem, here are some things that you can do:
- Calling for help is a great place to start with. Call your local certified chimney sweep who will do the necessary inspections and recommend the needed corrective actions to be taken. Paying a small fee will certainly be worth the peace of mind.
- Before starting a fire, place the metal fire grate as far back as you can.
- Use a metal screen to shield your hearth from any flying sparks and embers.
- Make sure that the damper is open when you are using the fireplace.
- Turn off all other air vents in the same room as the fireplace when you are using it.
- If your house is less than 25 years old, it may be sealed too tightly, so open a window when a fire is lit.
- You may want to consider increasing the height of the chimney to get more draft. However, remember that this is not always an appropriate fix because there is a limit to the amount of height you can add because of frictional forces.
Although you may want to figure out the way to solve all your excess smoke problems, it would be advisable to consult your chimney professional to make sure that your house is safe because there are many health effects associated with a back draft. And now, with your new expertise on chimneys and the way to prevent harmful combustion gases from going into your house, you will not have to worry about starting a fire.