Solving a Chimney Drafting Problem

Chimney DraftingIn a properly working fireplace and chimney system, all combustion products & gases will be displaced up the chimney and out into the atmosphere, leaving no traces of smoke in your home. There are times, however, when Atlanta area homeowners may experience chimney drafting problems. This can cause unpleasant and unsafe living conditions when you burn fires. Your chimney & fireplace is a complex system made of many parts and finding the cause of a chimney drafting problem can take some investigating. While there are actually many factors that can affect chimney drafting, here are a few causes and solutions to help fix the issue at hand.

How does a chimney work?

A chimney functions on the principle of something called an “updraft”.  As the air gets hot inside the fireplace when you burn a fire, it will begin to rise along with combustion gases and smoke up and out the chimney. As the hot air rises, the area left vacant is filled with cooler air surrounding the fireplace, then process repeats as that air warms up and ascends in chimney. If your chimney is properly constructed and there are no blockages, all of the combustion products leave up and out of the chimney with none escaping into your home. If there is a problem where the hot air cannot leave through the chimney flue or at the top of a chimney, a backup of smoke and gases will begin to enter into your home which results in harmful byproducts and soot.

Factors that can affect drafting.

There are actually quite a few chimney elements that could be the cause of your fireplace drafting problems. A chimney flue that is either clogged with debris or has critters nesting in it can cause a blockage that doesn’t allow air & combustibles to escape properly out of the chimney. A fireplace box

Chimney Swifts

Critters, like these chimney swifts, can build nests blocking the exit for smoke & gases.

that is not the correct size can also cause a back draft issue. An unintentionally closed damper that was forgotten about can also stop smoke from escaping. There are some less obvious reasons that you should also check should you not immediately spot the issue. A dirty chimney cap, an improperly installed chimney cap, or a chimney cap that is not the correct size can all cause drafting problems. So can structural damage and other necessary chimney repairs that haven’t yet been addressed. A buildup of creosote/soot along the chimney walls or spark arrester may also be blocking air flow out of the chimney. Even if it’s only a partial blockage, a buildup of creosote is a serious issue, not only because of drafting problems but because it can also be the cause of chimney fires.

When a chimney is clogged or has a serious blockage, harmful gases and smoke are not able to escape outside of the home which means they get backed up inside the house, which leads to dangerous and uncomfortable situations for the homeowners. An annual chimney inspection can ensure that your chimney has no blockages and is in proper working order to prevent future drafting problems.

The Firebox

Your hearth’s firebox can actually be the cause of 2 main drafting issues. First, it’s important that the firebox is the correct size. If the chimney flue and firebox are not the correct ratio, the drafting system won’t work correctly. There should be one square inch of chimney flue for every 10 square inches of firebox. Second, it’s imperative that the firebox is no more than one inch from the back wall of the chimney. This will ensure that the smoke and gases are not too close to the front of the firebox to be brought up with the hot air escaping up and out the chimney. The best way to make sure gases and smoke do not escape into your home from the front of the fireplace is to push the fire grate all the way to the back wall. You should also always make sure to build your fire on top of the fire grate so that the fire gets enough oxygen.

Chimney Design

Crooked Chimney

This is NOT a real chimney, but we have seen some that come close to this! Actually this one is located at the Wizarding World of Harry Potter in Orlando. Point is, a poorly designed or deteriorating chimney can cause chimney drafting problems.

If your chimney or fireplace was designed incorrectly, drafting may be a common issue. Ensuring that your fireplace was designed to fireplace codes can eliminate potential drafting concerns. If a fireplace was manufactured incorrectly or if the flue and firebox are not the correct ratio, drafting may occur even on your first use. Also, a firebox that is too shallow for your fireplace & chimney design can allow smoke and gases to enter the room instead of up and out the chimney. Improper flue angles may also be the cause of drafting problems because the hot air may not produce enough force to pass through non-vertical  passageways.

External Factors

There are a few external factors which can cause your chimney not to function properly. If your fireplace is installed in the same room as another appliance that pulls air outside the home, smoke & combustibles may be entering your home due to the other appliance. Air vents like clothes dryers, central vacuums, or forced air furnaces, suck air out of the room and displace it outside of the house. If both the fireplace and the air vent are working at the same time, the air vent may actually be sucking air from inside the fireplace bringing in smoke and gases instead of letting them leave out of the chimney.

Also, new homes often feature tightly sealed walls and windows which can be the cause of chimney drafting issues. In the principle of an “updraft”, the hot air that has escaped out of the chimney must be replaced by cooler air. If the house is too tightly sealed or new air can’t be let in, a drafting issue will arise. In order to solve this problem, leave a window cracked so that air can properly flow through the room and into the fireplace.

Dry Wood

Burning green or wet wood can also be the cause of chimney drafting problems. When wet wood is used, the fire does not burn hot enough for the air to rise up the chimney and causes smoke and gases to back up and enter into the room instead of out the chimney.

If you have checked everything you can think of but are drafting problem still persists, try these fixes:

  • Contact a certified chimney sweep to perform an inspection to identify potential causes. They can offer peace of mind and a quick solution to your drafting issues.
  • Before starting a fire, make sure to push the fire grate all the way to the back wall of the fireplace.
  • Ensure that your damper is open when operating your fireplace.
  • Turn off any other venting appliance that is in the same room as your fireplace when you start a fire.
  • Open a window to increase airflow in the room.

Drafting issues can become serious safety and health issues, so it’s always advisable to contact your local chimney sweep contractor to ensure your fireplace and chimney systems are in proper working order.  An annual chimney cleaning and inspection will help to prevent drafting problems alone with a bunch of other expensive chimney repairs.

Chimney Solutions, Inc.
1155 McFarland 400 Drive, Alpharetta GA 30004
Office 770-771-5501

Chimney Sweep / Chimney Repairs / Chimney Liners / Fireplace & Stove Service
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