When the cold winter winds of Washington DC start to blow, many people turn to the comfort of a cheery fire burning brightly in their home. Gathering around the fire to watch Sunday night football or playing family games in front of the roaring blaze are traditions that many families look forward to during the winter. Failure to perform preventive maintenance such as getting an annual chimney sweep can result in backdrafts. Periodic chilly breezes or lingering smell of smoke can be an unwanted side effect that is often caused by a drafty chimney.
Diagnosing A Drafty ChimneyWhether you light a fire every night or have the occasional blaze when guests are over, no one wants to experience the unwanted side effects of a drafty chimney. Avoiding a smoke-filled house or an unwanted chill running through your living room is made easier when you properly diagnose the reason behind your drafty chimney. To get you started on the right path, here are five reasons why you might have a drafty chimney.
Reason #1: Chimney BlockageIf the flow of air into the chimney is blocked, it can prevent smoke from going up your chimney and instead cause it to billow into your home. There are many common causes for a blocked stack, including:
- A build-up of soot in the chimney cap screen.
- Bird nests inside of the chimney, on the cap screen, or over the top of the chimney.
- Creosote build-up inside of the flue lining.
- A blocked damper that isn’t opening fully.
- Broken pieces of masonry that are sticking out at odd angles inside of the chimney.
Reason #2: Restricted AirflowDid you know that a chimney needs a bit of airflow in order to pull the smoke up and out of the house? If your home is tightly sealed, then your chimney might not be receiving enough airflow, which could cause the smoke to remain stagnant or filter back into the home. More often than not inadequate airflow is caused by other in-home appliances, such as exhaust fans. You can experiment with opening a window near the fireplace to resolve this drafty chimney dilemma.
Reason #3: Flue TemperatureHot air rises, while cold air sinks. This might seem like a “no-brainer” statement, but it is important to remember if you are experiencing a drafty chimney. When the flue is too cold it can cool the combustion gases and cause them to sink back into the chimney. This particular drafty chimney issue is most common with exterior masonry chimneys, which typically lose a significant amount of heat due to their positioning.
Reason #4: Chimney SizeThe size of your chimney might be the reason that it is creating a draft. The NFPA has a list of suggested heights and guidelines for chimneys, however, as is all too often the case that these specifications aren’t followed. If you have a drafty chimney, be sure to examine the following factors to determine if size is the root cause.
- Has the chimney been built to the correct height specifications, or is it too short for the associated architectural structure, including roofline?
- Is the chimney too high and thus in an area with increased drafts?
- Does the chimney have the same diameter as the wood-burning appliance’s flue outlet?
- Is the chimney more than twice the cross-sectional area of the wood-burning appliance’s flue outlet?
Reason #5: Wind PatternsDid you know that certain wind patterns can actually increase chimney draft? There are several characteristics that can lead to a drafty chimney, including:
- Wind that blows directly across the tops of chimneys can cause drafts.
- Rain caps might not prevent wind drafts, but a draft reducing cap can help to reduce the impact of the wind-induced downdraft.
- Tall trees or nearby tall buildings can also affect wind patterns to create a downdraft.