When a fireplace spills smoke into a room, it's at best annoying and at worst hazardous to your health. Considering the great enjoyment (not to mention the resale value) a working fireplace adds to your home, it's good news that you have a choice of effective solutions, ranging in cost from nothing to $2,000 or $3,000.
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If a fireplace spills smoke into the house only on windy days, the problem is downdraft, resulting from a too-short chimney or environmental situations beyond your control. Consider extending the chimney or installing a wind-deflecting chimney cap or fan.
Flow reversals typically occur when the operation of exhaust fans, including those for clothes dryers, causes negative pressure in a tightly closed house. Either open a window or install an air-intake kit to supply the needed combustion air. A leaky attic in a multi-story house can create a chimney effect and cause chronic depressurization. The solution is to seal all openings between the living space and the attic.
Inadequate flow can occur when the size of the fireplace opening is too large for the size or length of the flue. Compare your flue's dimensions with the standards published in architectural manuals, available in the reference section of most public libraries. Solutions range from reducing the size of the opening with a metal smoke guard to major projects such as installing a fireplace insert, rebuilding the firebox, adding to chimney height or installing a chimney fan.
Determine the cause
Install a wind cap. Consult a chimney professional who can install a wind-diverting chimney cap. Although the installation itself is relatively simple, working safely at a chimney top isn't, and some suppliers will only sell products to professionals.
Install a chimney fan. The demanding conditions these fans must endure, such as extreme heat and corrosive flue gases, make them very expensive (about $2,000 installed), but they are guaranteed to solve the problem.
Increase the height of the chimney. A chimney must be 2 feet (60 cm) higher than a roof or any other structure within 10 feet (3 m). If your chimney is not high enough, consult a mason to extend a masonry chimney or an appropriate professional to extend a metal chimney.
Reline to enlarge a flue. If the flue in an old chimney is too small, there may be enough room between the flue and the brick to knock out the existing flue and install a new one. A metal liner for a single-flue chimney costs roughly $2,000, and a solid flue, which is poured around a form lowered into the chimney, costs $500 to $1,000 more. Both are professional installations.
Install an intake air vent in the firebox. Remove firebrick and exterior brick or stone facing, then drill a hole for a stainless steel vent that extends from outdoors right into the fireplace. Alternatively, you can install some models into the ash pit below the firebox and admit air through a special floor vent.
A much easier alternative for do-it-yourselfers is to install an airintake vent through the wall of the room. Although the vent itself is available only through fireplace shops, the installation is identical to that of a dryer vent, a common DIY project.
Lower the lintel with a metal shield, such as SmokeGuard. This shield, available in several widths, heights and finishes from fireplace shops, snaps into place. Some glass doors for fireplaces may also effectively lower the lintel.
If the convenience, energy efficiency and appearance of a gas fireplace appeals to you, installing a sealed-combustion gasfireplace insert will resolve any draft problem.
Implement the cure
Tips and warnings
- Test for depressurization by opening a window in the fireplace room, waiting about an hour, and starting a fire. If smoke still spills into the room, depressurization isn't the issue.
- Deal with licensed, experienced professionals only and obtain references.
- Make sure you have the necessary permits and inspections.
- Depressurization can increase radon infiltration and cause carbon monoxide poisoning from combustion appliances such as water heaters, furnaces and boilers.
- Due to the sometimes high costs and considerable risks involved with modifying a fireplace or chimney, never act without consulting a professional and your local building department.