The joy of having a fireplace or cozy wood stove can be all but lost if your house begins to smell of smoke. Of course, the smoke is supposed to go up the chimney, not in your home, which requires adequate draft or movement of the smoke. Diagnosing the problem may require a professional chimney sweep, but the following is some information that could help you figure out the cause of the drafty problem.
It’s possible that your house is sealed too tightly to allow adequate airflow up the chimney. Try opening a window just a crack; if the smoke then begins going up the chimney, you’ll know that what’s probably needed is an outdoor air supply. Most of the time, however, inadequate airflow is caused by other appliance fans exhausting air from the home or by a stack effect. The stack effect, in simplest terms, involves the flow of air in and out of a structure.
It’s not a very common problem, but sometimes a chimney is the wrong size for a wood-burning appliance. The general guideline to go by is that the chimney should be about the same size in diameter as the appliance’s flue outlet.
A chimney that’s too small will hinder the needed draft, since the smoke doesn’t have adequate space to be carried outside as it should.
The chimney can be too large, and the flue outlet on an appliance is also the guide to determining whether it is. A stove that has a collar that is 6 inches in diameter shouldn’t have a chimney greater than 8 inches in diameter. The chimney, in other words, shouldn’t be more than twice the cross-sectional area of the appliance’s flue outlet. An oversized chimney causes the gases in the flue to cool, which creates a draft in the home.
The height of the chimney could be creating backdrafts. There are guidelines for chimney height provided by The National Fire Protection Association’s (NFPA), but the suggested heights are considered by experts to be absolute minimums. There are different factors which affect how much air is potentially pushed down the chimney, such as nearby obstacles. A chimney could be so high that drafts are significantly increased.
A professional chimney sweep can help you determine whether your chimney is too wide, narrow, tall, or short.
If the flow of air is hampered, backdrafts could be the result. The most common causes of blockage are creosote in the flue lining or chimney, creosote in the chimney cap screen, birds’ nests, dampers which don’t seal properly, and broken pieces of masonry chimneys. Have a professional chimney sweep clean your chimney at least annually, to be sure all hazards and obstructions are removed.
Joints in stovepipe connectors aren’t usually a cause of a loss of draft, but it happens. If there is any significant leakage in the chimney’s lower half, overall draft will be reduced. Check to be sure that cleanout doors are shut, and look for significant deterioration.
If the air in the flue is too cold, the chimney draft can be adversely affected. This problem is most common with exterior masonry chimneys which lose a significant amount of heat and therefore cool the gases.
Wind usually increases chimney draft. But in some situations, such as on an ascending roof-line, rising winds can create back puffing. Sometimes a chimney cap will deflect rising winds into a chimney.
The solution to a drafty fireplace or wood stove varies, depending on what is causing the problem. But no matter what the cause, it’s important to resolve it. Excess smoke fumes are hazardous to your health. Call one of our professionals for help solving one of the most common and frustrating chimney woes – a drafty fireplace.
Northeastern Chimney, Inc.
formerly Nayaug Chimney Services, LLC
37 Cody Street, West Hartford, CT 06110