First, prepare the fuel load in the firebox. Then roll up a piece of newspaper and light one end while holding it inside the stove in or near the connector. Once the proper draft has been established, light the fuel load without allowing smoke into the house. If the inside temperature is close to the outside temperature, there may be problems with the initial draft. If there is always a problem with initial draft, the chimney would be known as a “non-self-starting chimney.”
A progressively decreasing stove draft can indicate a blockage developing at some point in the venting system. You should schedule an immediate examination of the venting system in question. A progressively decreasing stove draft is a potentially dangerous situation: the house can fill with toxic smoke if the flue becomes completely plugged.
Drafting problems with fireplace inserts indicate the need to check the chimney for proper height requirements. Negative air pressure affects draft, so even if a chimney satisfies minimum code requirements for proper height, it may not be high enough to draft properly if the home sits lower than surrounding buildings. To establish a proper draft in this case, the chimney may have to exceed the minimum code requirements for height. Many smoking problems can be solved by fully opening the draft controls of the appliance. That will increase the velocity of the exhaust, making it less likely that a flow reversal will occur.
Chimney caps keep rain out of a chimney and can prevent subsequent rust and deterioration due to dampness. Premature deterioration of the firebox and liner mortar joints as a result of water entry may be prevented by the installation of a chimney cap. Screening keeps out animals and birds.
Many customers complain about fireplaces which smoke excessively. Several factors may cause this problem. Many times it is due to having a damper plate partially closed during burning. Excessive smoking can also be the result of:
When turned on, exhaust fans in kitchens and bathrooms or clothes dryers vented to the outside can cause smoking problems in airtight homes. Opening an outside door or window slightly often solves this problem. A better solution is to install an outside air source directly connected to the fireplace.
Sometimes, fireplaces continue to smoke even after proper draft has been established because the flue is too small for the size of the fireplace opening. The size of the fireplace opening can be reduced by covering the opening with glass doors or by installing a metal strip across the top of the opening. Determine the size of this metal strip by slowly sliding a piece of 12-inch wide plywood or sheet metal down from the top of the fireplace opening to the position where smoking ceases. Mark this point and measure from this position up to the lintel. The width of the permanent metal strip should equal this measured distance.
A natural updraft should remove all chimney odors. A downdraft, however can carry these odors into the home. Often, opening a window slightly introduces fresh air which helps to remove the unpleasant smell.
Since persistent odors can be caused by a build-up of residue in the flue, they often indicate that the venting system needs a thorough cleaning. Odors are most noticeable when the interior of the chimney is damp or wet. Therefore, it is important to keep the inside of the chimney dry at all times. Tightly sealing the top of a chimney to eliminate or reduce odors may trap air inside the flue causing condensation and conditions that encourage the development of chimney odors. Top-sealing damper devices capture warm air in the chimney that slowly escapes through the top and will normally provide a better seal than the conventional damper. Other items that may help are a chimney cap or the purchase of a commercially sold chimney deodorant. Odors may also be caused by water entry other than through the flue, such as through cracks in the crown wash, wicking through mortar joints and seepage through brickwork.
Why fireplaces work, and how best to build them, has been a topic of hot debate literally for centuries. From the first stone rings stacked around the campfire, to the modern factory-built fireplaces with carefully engineered dimensions, there has been a steady evolution of design parameters to make sure they draw well and cast as much heat as possible. Most of this evolution has been by trial and error, and some designs work much better than others.
Simply put, fireplaces work mainly because hot air rises. When you start a fire, the air inside the chimney becomes warmer and less dense than the air outside the chimney, and consequently it starts to rise. As the warm air rises, cooler air from the room flows into the firebox, fanning the fire, creating more heat in an ongoing cycle. There are also some pressure differentials produced as wind moves across the top of your chimney. There must be at least 100 reasons why your fireplace may not function properly. We will try to cover some of the basics here starting with the easy, obvious solutions and working towards the more arcane.
Please bear in mind this is a very simplified list of the more common reasons that fireplaces don’t work and a true understanding of fireplaces requires extensive knowledge of air flow patterns, pressure differentials, and actual fireplace construction techniques. If the information provided here does not help you solve the problem with your fireplace, consider hiring Brickliners as an experienced, certified chimney sweep in your area. Often the problem is obvious to someone with enough experience once they can actually look over the entire situation.
Everybody eventually forgets to open the damper. Many dampers also cease to fully open because of water damage or soot buildup behind them on the smoke shelf. A good professional cleaning can usually solve this problem.
Remember the main reason your fireplace works at all is the heat inside the chimney. If your wood is not dry and well- seasoned it makes more smoke than heat and there simply may not be enough heat for the chimney to work properly.
The gradual accumulation of soot can seriously affect the way your chimney performs. Thick layers of soot of course can physically restrict the flue so there is no longer enough free area to vent the fireplace properly, (see problem 5) but as little as a 1/4″ to 1/2″ inch buildup can make more difference than you might think. Consider that a 1/2″ buildup will restrict the air flow by 17% for a typical masonry fireplace chimney, and by a whopping 30% for the average prefab. Birds and small animals also think your chimney looks like a hollow tree in which to set up housekeeping. Sweeps often find chimneys literally packed full of leaves, twigs and baby animals. The solution of course is a good cleaning and a chimney cap.
To function properly, the chimney should be at least 10 or 12 feet in overall height. Where it projects above the roof, the chimney should be at least 3 feet tall, and at least 2 feet higher than anything within 10 feet of it-including other buildings, trees, etc. If your fireplace smokes because your chimney is too short, the problem is usually worse when the wind blows.
There are many variables that can affect this including: overall chimney height, how warm the flue stays, throat configuration, etc., but the basic rule of thumb here is that the area of the fireplace opening can be no more than 10 times the area of the flue (12 times for round flues). An undersized flue simply can’t handle the volume of smoke produced, and some of it will spill back into the room. Since there is no practical way to make the flue size larger, the solution may be to make the room opening smaller with metal smoke guards or some creative masonry work. In fact there are now some pre-manfactured refractory firebox retrofits that work well with a 15 to 1 ratio and deliver twice the heat of conventional fireboxes.
Remember that warm rising air is the basic engine involved here. If you have a large masonry chimney on the outside of the house, and it’s cold outside, the air inside of the chimney will also be very cold, and it will want to fall down the chimney instead of rising. This can even happen a day or two after it’s warmed up outside. These chimneys may be hard to start and they may smoke as the fire burns low. To help get the fire started many people light some rolled up newspaper and hold it up near the damper to get that cold plug moving upwards. Keeping a moderate sized but bright, actively flaming fire can also help this situation. Remember that as the fire dies down, it will revert to the original direction of flow.
Fireplaces require large volumes of air to burn. Visualize a 12″ x 12″ column of air rising up your chimney and exiting the top the entire time your fireplace is working (but don’t visualize your heat bill!). This air comes from inside the living area and must somehow be replaced. With modern energy-efficiency concerns most houses have been carefully insulated and weather-stripped to keep out the cold drafts, but an undesirable side effect is that there is often nowhere for all that air leaving the chimney to get back in. This can lead to fireplaces that burn sluggishly and smoke. A temporary solution is to open a window to let in a little make-up air, preferably on the windward side of the house. It can also lead to very dangerous carbon monoxide buildup if your fireplace and furnace must compete for combustion air, and a permanent solution should be found at once.
A house that leaks too much air to the outside, especially a multistory house that leaks air in the upper levels, can actually set up its own draft or chimney effect strong enough to overpower your fireplace chimney, particularly if the fireplace is located in the basement on a cold exterior wall. Be sure the attic access door is in place and that all upstairs windows are tightly closed.
As the fireplace consumes air and cold air moves into the house to replace it, the furnace is likely to come on. When the furnace comes on, air is drawn into the return competing directly with the needs of the fireplace.
Aside from the chimney being too short or too small, the chimney can also be too large, too tall, too crooked, etc., ad infinitum! Most of these details are fairly technical in nature, and again, inviting one of Brickliners certified chimney technicians into your home may be your best bet.
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