Chimneys look so simple – a vertical conduit that funnels smoke and heat from your fireplace to the outdoors – but they require precision to function properly. Chimneys must be carefully designed, skillfully installed and regularly maintained to do what seems like an easy task. Most quietly work well. But oh, woe is the homeowner who has coughed through a chimney gone rogue.
“Problem chimneys pour smoke into the house instead of sending it up the stack,” says Andrew Golkin, President, Paul Davis of Suburban Virginia. “This can be a continuing issue – the room gets a little smoky every time a fire burns– or a single occurrence, when a large burst of smoke clouds the room and endangers occupants. Both situations require professional cleaning to remove smoke odour and residue – and a chimney professional to solve the chimney’s issues.”
Chimneys operate by leveraging a natural principle: hot air rises. As hot gasses from the fire rush up the chimney, a pressure differential is created that pulls air from the room into the fireplace, feeding the fire. As this new air heats, it departs up the stack, too, pulling in more air to further fuel the cycle. The hotter the fire, the greater the pressure differential, the faster the air rises and the better the chimney functions. Sounds simple, right? Unfortunately, this cycle can be interrupted by many factors.
Poor design. Poorly designed chimneys may be improperly insulated, allowing gasses to cool before they exit the stack. A chimney may have too many twists and turns, which blunt the pressure differential that should “pull” the smoke up and out. Perhaps their channels aren’t properly sealed inside, allowing outside air to mingle before the hot gasses exit. A chimney could also be improperly placed in relation to the roof or nearby buildings, blocking free airflow. Too narrow, too short, wrong location – the ways chimney design falls short are legion. Improperly designed chimneys rarely function well.
Downdrafts. Downdrafts happen when air blows down the chimney. They can be caused by chimneys that aren’t high enough – their conduit is not long enough to develop a robust pressure differential. More often, downdrafts occur periodically on very windy days. Professional chimney companies can install special devices that prevent downdrafts.
Improper airflow. Chimneys need a free flow of inside air to replace what is going up the stack. Our increasingly tight, energy-efficient homes sometimes choke off that air flow. The chimney can’t develop the pull – also called a “draught” – and smoke drifts into the room instead. This issue can be resolved by installing room air vents.
Obstructions. Birds and rodents love the cozy confines of a chimney flue during warmer months when fireplaces are idle. If a fireplace suddenly smokes when you light the first fire of the season or after a long period of disuse, suspect a blockage.
Lack of maintenance. Chimneys, like all parts of a home, require regular maintenance. They must be periodically cleaned to avoid the buildup of creosote, a fire byproduct that can block proper airflow or even ignite. Chimneys must exclude rainwater, which lowers the temperature in the stack and again, impedes proper draught. If your fireplace tends to smoke when it rains or snows, you may have a water seepage problem.
“It’s important to quickly address a malfunctioning fireplace because soot and smoke degrade materials and belongings fairly quickly,” Golkin concludes, adding that smoke causes health problems, too. “Smoke rarely affects just a single room – and the odour lingers. We’ve cleaned many a home for customers who got tired of the smell months after a single smoke event from their fireplace.”