100 Reasons Your Fireplace Doesn’t Work

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. As a result, there 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 premanfactured 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 back to the original direction of flow.

Fireplaces need a large volume of air to burn. Imagine a 12″ x 12″ column of air rising up your chimney and exiting the top while your fireplace is in use. This air comes from inside the living area and must be replaced. With modern energy efficiency concerns, most houses have been carefully insulated and weather-stripped to keep out cold drafts. However, a side effect is that there is often nowhere for all the air leaving the chimney to get back in. This can result in fireplaces burning sluggishly and smoking. A temporary solution is to open a window to let in some makeup air, preferably on the windward side of the house. It can also lead to dangerous carbon monoxide buildup if your fireplace and furnace must compete for combustion air, and a permanent solution should be found immediately.

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.