Why Does My Fireplace Smoke?

Smokey FireplaceThere are many variables involved with causing a smokey fireplace.  When customers come to us and explain that their fireplace smokes when they use it, there are no simple “snap” answers as to why this happens.

Main cause of a smokey fireplace

Basically, the chimney has to do its job to pull the smoke up and out of the building.  If this does not occur, smoke can roll out the top of the fireplace opening and “spill” into the room.  There are many different variables that may affect the way a chimney functions. Discussing when the smoking occurs and understanding the construction of the firebox, height of the chimney and flue, layout of your home, what you are burning and how you are burning it, all come into play when we are determining why your fireplace has smoking problems.

Burning wood

Wood should always be burned on a wood grate/basket that is placed as far back in the fireplace cavity as possible. If the fire is near the front of the fireplace, smoke has a much better chance of rolling out the top of your fireplace opening. Raising the wood off the floor by using the grate or basket helps the combustion process and brings the smoke higher up into the smoke chamber.

The type of wood that you burn can potentially create a smokey fireplace. Burning unseasoned or green wood can produce a very smoky fire. Half of the weight of a piece of freshly cut wood is water. To properly season wood can take 9 months or longer.

Chimney construction

The construction of the fireplace and chimney, as well as the location of the system within your house, could create many different drafting scenarios. If the opening of the fireplace and the size of the flue are not to proper ratios smoke will not be pulled up fast enough. You can check to see if the height of the fireplace opening is causing the smoking by experimenting with a piece of aluminum foil across the top of the opening to reduce the height. If lowering your opening 4” across the top of the fireplace does the job of re-directing the smoke up the chimney, you can install a “Smoke Guard”. A “Smoke Guard” is a tension-mounted black plate that attaches into your fireplace to reduce/lower the opening by 4inches.  If the fireplace is shallow, or if the damper is not installed in the proper location, smoke could roll out of the front of the fireplace.

The height of the chimney in relationship to the house and other structures around the house can have a major impact on draft. According to building codes, a chimney needs to extend at least two feet higher than anything within a 10 foot radius. Some chimneys built to these specifications still may have drafting problems. We have seen this occur when a single story addition is built off a two story house. Wind currents that travel up over the roof of the main building may actually shoot down the shorter chimney of the addition’s fireplace. Increasing the height of the chimney can solve that problem. Trees and hills surrounding the chimney — even where the house is located — can also affect the draft.

By code, fireplaces that are newly installed require a source of outside air to assist in the combustion process. Newer homes and renovations can result in a “tight” house. A fire needs air for the combustion process. If the fire cannot get sufficient air, or if there are other appliances (furnaces, kitchen/bathroom ventilation fans, clothes dryers, etc.) that are also taking air from the house, smoke may spill out into the room. Turning off fans/ventilation systems or appliances and/or cracking open a window or door slightly may correct the draft.

One unusual, but not uncommon, situation may occur in fireplaces that have an ash dump and ash pit. In many homes, the cleanout door for the ash pit is located inside the basement of a home. It is common to have the furnace and laundry room located in the basement as well. If you are having a fire and smoke starts spilling into the room, it could be that the furnace has just kicked on and is pulling air down the chimney and through the ash dump area. Supplying a source of outside air to the furnace or laundry area may resolve this problem.

Infrequent smoking can happen when wind blows hard or comes from a certain direction. The location of the house in relation to trees, hillsides, or a body of water can make matters worse. In some situations, a chimney cap can help mitigate a smokey fireplace. In many situations, however, Mother Nature is in control and the smokey fireplace is only temporary.

Double-sided fireplaces

A double-sided, or see-through, fireplace can be very problematic. A single-sided fireplace uses the back wall to deflect the smoke and send it up into the flue. With a see-through fireplace, air comes in from both sides and turbulence is created above the fire. If the fireplace is not carefully planned and properly built, the system will not be able to pull that smoke upward and cause a smokey fireplace.

Customers often ask us if putting glass doors on one or both sides of the fireplace will solve the problem. Glass door enclosures are made with tempered glass and are meant to be open when the fire is going. If the doors are closed, the temper will wear over time to the point that the glass will shatter during use. Putting doors on one side of a see-through fireplace and keeping the doors closed will actually turn the tempered glass into the “back wall” of the fireplace. The constant pounding of heat as the fire deflects off of the glass will wear the temper out at a faster rate.

If you are burning wood in your see-through fireplace, a suggestion our Swept Away professional will make is to have a fan installed at the top of your chimney. This electric fan is mounted on the top of your chimney and pulls the smoke up and out of your chimney.