The smoke that escapes from your fireplace into your house is a result of poor drafting (air moving in an upward or downward direction), or something blocking the way of the draft. We often ask why is fireplace smoke in my house?
A poorly, drafting chimney allows
smoke from the fireplace to enter the room rather than exhausting it to the
outside. A blockage in the chimney prevents
drafting in the same way that a closed nozzle at the end of a hose prevents
water flow. The air being pulled (draft) up your chimney works under the
same scientific principles as water flowing in a hose, and it corresponds to
the amount of pressure in a water hose. The only difference is that the air pressure
is negative, and the water pressure is positive. Similar to the way a kinked or plugged hose
stops water flow, a poorly drafting chimney is the result of an airflow
restriction.
This can be caused by a of multitude of factors such as: excessive creosote build-up, closed or plugged dampers, improper construction, structural damage, chimney height in relation to peak roof height, home renovations, excessive bird nesting materials in the flue, or even a dirty chimney cap. The following are some of the possible reasons and solutions for the undesirable fireplace smoke in your house.
Is the Damper Open?
Heat rises, and if your damper is closed, the fireplace smoke will
come in the house. Many people leave the
damper closed when the fireplace is not in use.
A common mistake is forgetting to open the damper again before lighting
a fire.
The damper is a hinged, metal plate used to seal the fireplace
when not in use, and to regulate a fire in the fireplace by controlling the
flow of air (draft) coming in the chimney.
To open the damper, you usually have to crouch down and peer upward toward the rear of the fireplace. A flashlight will help. A metal lever inside the fireplace controls the damper. Pushing on the lever opens it, and notches along the length of the lever allow you to adjust the opening to get the draft needed for the fire to burn without fireplace smoke backing into the house. The correct procedure for using a damper is to open it fully before lighting the fire, then close it a few notches after the fire is well under way by moving the lever with a fireplace poker. If the fireplace smoke begins to come in the house, reopen the damper a notch at a time until the smoking ceases. After all the embers have burned completely, close the damper.
Open a window
Another common cause of fireplace
smoke in the house is insufficient air in the room containing the
fireplace.
Try opening one or two windows in the
room a few inches while the fire is burning.
This will increase the draft in your chimney by bringing more air
(oxygen) in to the fire, which should allow it to burn hotter.
Energy efficient homes are better
insulated and keep out cold drafts; however, a negative side effect is that
there is often not enough outside air coming in the house for a fire to burn
hot enough to rise through the flue or to cause drafting, which carries that
hot air up the chimney. The chimney flue
becomes the source of make-up air so that as air is drawn down the flue, it
picks up smoke from the fire and delivers it into the living area. Cracking a window eliminates this negative
pressure.
Grate Placement
The fire must always be made in a
grate to provide enough air flow around the logs. Without a fire grate, the fire will smoke and
not get hot enough to ventilate properly, thus bringing fireplace smoke into
your house.
Sometimes smokiness is a result of the
fire being built too far forward in the fireplace. This causes smoke to enter the room instead
of going up the chimney. The remedy is
to build the fire as far back against the rear wall of the firebox as possible.
Use Seasoned Wood
A fire that appears to smolder or make hissing sounds while burning, most likely has a high water content. It simply can’t burn hot enough for the hot air to rise up the chimney flue and get replaced by cooler air. The smoke and gases will not be able to exit the room.
You will have to go without a fire unless you have well-seasoned wood that has been split for a minimum of six months (the longer the better), and stored in a covered and elevated location. A piece of seasoned wood will be lighter (in weight) than the same size, but green (unseasoned, newly cut) piece of wood. It will sound hollow when hit against another piece of wood. Green wood will also be lighter in color and generally have a stronger, fresher smell to it, while seasoned wood will usually appear darker and have little odor. Seasoned wood can also be identified by cracks on the end of the logs.
Stacked Wood Placement
Build your fire with larger pieces of wood on
the bottom, leaving gaps for air to circulate between the wood. Continue stacking wood with each layer going
crisscross to the previous layer, and decreasing in size. Wad up some newspaper and stick it under
small pieces of kindling and wood chips on the top of the stacks of wood, then
light the paper. This will produce a
hotter fire more quickly, and it will burn cleaner because smoke won’t have to
pass through cold logs. This method will
keep smoke going up the flue and out of the room.
Competing Appliances
Many factors influence a home’s
airflow including interior mechanical systems, fuel burning appliances, such as
furnaces, fireplaces, wood stoves, and water heaters.
Make sure no exhaust fans (kitchen, bath,
attic fans) are running while you have a fire.
Also make sure all of the air vents in the same room as the fireplace
are open if you have an air-forced furnace running, or else the return air vent
will suck air from the fire, possibly bringing fireplace smoke into the room. Central vacuums can also create
depressurization by removing large volumes of air from the house.
Wind Factors
If you think of your chimney as a straw, in the same way as sucking fluid up through a straw, your fireplace chimney sucks air up through the flue to the outdoors. If you blow through a straw, the air pressure pushes the fluid out of the straw. In the same way, strong winds can push air down your chimney causing smoke to enter your house if you are burning a fire in the fireplace.
This can be a real problem in homes that are located in windy areas, such as a beach house. If that’s the case a cowl on your flue would be better than a cap. A chimney cowl is designed to prevent wind blowing the smoke back down into the room below. They increase the draft of a chimney and prevent back flow.
We always ask a homeowner “Is your chimney cap safe” during out first visit. A chimney cap extends flue life and is important in the proper functioning of a fireplace.
A chimney cap should be installed, if not already in place. It will keep animals, rainwater, leaves and debris out of the chimney. When water, leaves, and debris mix with the soot behind the damper, an acidic slurry can form, which can destroy the firebrick mortar joints. The metal cap acts as a spark arrester, helping lit embers or sparks that travel up the chimney from landing on the roof, possibly catching it on fire.
A chimney cap can also help in preventing downdrafts. If the wind is blowing in a certain direction, it can introduce a downdraft, and if you don’t have a chimney cap and you’re using a wood-burning fireplace at the time, a wind-induced downdraft has the potential of blowing smoke back into your home. The flat-shaped top of a chimney cap is designed to help prevent wind-induced downdrafts.
Be aware this can be a dangerous job. Often the fireplace cap is located high above the highest point on your roof. It very well may be 3 stories off of the ground. If you are not comfortable climbing ladders and are afraid of heights, hire a professional to be safe for your family.
Before you start a fire each year, your chimney, flue, grate and cap should be inspected. Request a chimney cleaning as soon as possible in the season. You need to be sure your chimney cap is safe before you start a fire.
