There are many variables involved with the drafting of a fireplace. When customers come in to us and explain that their fireplace smokes when they use it, there are no simple, “snap” answers as to why this happens. Basically, the chimney has to do its job and pull the smoke up. If this does not occur, the 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, the construction of the firebox, height of the chimney and flue, the 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.
When does the smoking occur?
If the smoking occurs only at start up, the chimney and flue are probably cold. A chimney that is outside of the “envelope” of the house will contain a cold block of air that has to be “pushed” out of the chimney before the smoke can travel up the chimney. That problem can be resolved by pre-heating the chimney -either by rolling up a piece of newspaper, lighting one end of it and holding up to the damper area- or by shooting hot air from a hairdryer up the chimney to push the block of cold air out. Once the flow of cold air coming down the chimney has been reversed and the flow of hot air is heading up the chimney you can start your fire.
If the smoking issue is constant many things could be affecting the draft. The first thing, and most obvious to check is that the damper is fully open. If the damper is open you should check to make sure there are no obstructions in the flue system (a bird’s nest or creosote build-up, for example) or anything blocking the flow of air out of your chimney. The chimney should be inspected yearly and cleaned on a regular basis. The frequency of having your chimney cleaned by a certified chimney sweep will be determined by how often you are using your fireplace and your burning habits. Nordic Stove & Fireplace believes CHIMNEY INSPECTIONS SHOULD BE DONE AT THE BEGINNING OF EVERY SEASON AND ANY TIME THERE IS A SUDDEN CHANGE IN THE PERFORMANCE OF YOUR CHIMNEY.
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, as well as bringing the smoke higher up into the smoke chamber.
The wood that you are burning can potentially create a smoking 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, it can take 9 months or longer.
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 “SmokeGuard”. A “SmokeGuard” 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 that anything within a 10 foot radius. Some chimneys that are 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 is blowing hard or coming from a certain direction. The location of the house in relation to trees, hillsides or a body of water can make matters worst. In some situations, a chimney cap can help. In many situations, it is Mother Nature and it is only temporary.
A double-sided, or see-through, fireplace can be very problematic. A single-sided fireplace utilizes 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.
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, one of the last suggestions we will make to you is to have an Exhausto Fan installed at the top of your chimney. This is an electric fan that is mounted on the top of your chimney which pulls the smoke up and out of your chimney. Not only are Exhausto Fans expensive, they also can be noisy and they will not work during a power outage.
IF YOUR FIREPLACE DOES NOT WORK WITH WOOD LOGS DO NOT INSTALL GAS LOGS. Many people come into our store to purchase gas logs because their fireplace smokes with wood. If your fireplace does not draft properly you will smell- and possibly see- smoke when you are having a wood fire. If you put gas logs into a poorly-drafting fireplace you may see carbon on the mantle of the fireplace, the wall and ceiling of the room, the floor and even the upholstery. You will not smell the carbon monoxide that may spill out into your room.
If you attempt to put gas logs into a fireplace which has an Exhausto Fan installed on the top of the chimney, you may have problems with the gas logs. The suction that is created by the fan will actually pull the flame off the thermopile/thermocouple (the built-in safety mechanism) which will automatically cause the logs to shut off.
Please contact Nordic Stove and Fireplace Center if you have any questions regarding your fireplace.