Why does my fireplace smoke and what can I do about it?

For most folks, an evening in front of the fireplace can be a soothing and relaxing experience. There is however, nothing particularly soothing about unwanted fireplace smoke puffs that spill into the home while the fire is burning. Smoke that escapes through the fireplace opening is the result of poor fireplace drafting which can be caused by a number of factors. Here are some of the most common causes and solutions.

House is well insulated:
Unlike a moderately drafty home, a house that is relatively air tight may not be able to supply enough outside air to the fire resulting in a negative pressure in the home. Well insulated homes can benefit from an outside air supply vent installed in the fireplace to satisfy the fire's needs. Many times, a good mason can retrofit an air supply vent in an existing fireplace. Try opening a window in the fireplace room while burning. If the fireplace starts to draw better, this is likely the problem.

Exhaust fans in the home:
A running kitchen or bathroom exhaust fan could be the cause of your fireplace smoke. Another culprit may be the blower fan of a forced hot air heating system especially if the furnace return vent is in the same room as the fireplace. These types of fans can very easily create a powerful negative pressure hindering the fireplace from drafting correctly. If you make sure that all of these types of fans are off while the fireplace is burning, the smoke problem may go away.

Too warm outside:
Even fireplaces that draft great when its cold outside can be known to puff out fireplace smoke when it's slightly warmer out. The greater the temperature differential from the inside room temperature and the outdoor temp, the better the fire will draft. Take notice of the outside temperature when burning the fireplace. Having a fire when it's colder out may help.

Damper/chimney cap problems:
Make sure that the damper is open all the way. Sometimes there is a rain cap or even another damper on top of the chimney which may be obstructed and need attention. Have a professional take a look to see if that's the case.

Chimney needs to be cleaned:
Creosote build up in the chimney can reduce the the flow of exhaust gasses which can cause fireplace smoke and may also lead to a chimney fire. A shattered chimney flue can also cause drafting problems. Hire a chimney sweep to inspect your fireplace for damage and have the flue cleaned. This is something that should be done at least once a year even if your fireplace operates perfectly.

Wet firewood:
It is not uncommon for the problem to be soaking wet firewood. A fire that appears to smolder or make hissing sounds wile burning may have a high water content. Such a fire simply can't generate sufficient heat to allow the chimney to draw well. If you hit two smaller pieces of dry firewood together, you should hear a crisp, sharp sound. If you hear a dull "thud" the wood is most likely wet. Try building a fire with wood that you are positive is dry like scrap lumber that has been under cover. 

Incorrectly built fireplace:
If you have been able to rule out the possible causes listed above, faulty fireplace design is likely the reason for your fireplace smoke problem. There are critical parts of a fireplace that must be built to specific sizes in relation to other components. Flue volume and fireplace opening size ratios are extremely important. Other factors include smoke shelf construction, size and shape of the damper, chimney height in relation to peak of roof height and so on.

Rebuilding or modifying an existing fireplace is simply not a realistic option for most homeowners. Reconstructing the smoke shelf, firebox, or adding height to the chimney can cost $10,000 or more! Many times such ambitious attempts to modify a smoky fireplace are unsuccessful and the problem persists. Expensive chimney mounted exhaust fans are available that will pull the smoke up the chimney. We do not recommend these units however, since their powerful vacuuming ability actually pulls too much warmth from the home and out the chimney.