Why Chimney Designs work and whats the best way to build them; This has been a very long time argument, because so many houses have been damaged due to chimney fires. Most masonry chimney construction has been by trial and error, very few standards have been set except the last few years. Mostly known was what did not work. Some chimneys just simply worked much better than others.
Plainly put, Fireplace Chimney Designs work basically because hot air rises. When you start a fire, the air inside the chimney gets warmer and less dense than the air outside the chimney; (cold air is much more dense than hot dry air), and consequently it starts to rise. As the warm air rises, cooler air from the room flows toward the firebox, feeding the fire, creating more heat in a continuous cycle. There are also some pressure differences produced as wind moves across the top of the chimney.
There are several reasons why your fireplace Chimney Designs do not function properly. We will try to cover the basics starting with the easy and most obvious solutions and working towards the more difficult. A complete understanding of fireplaces and chimneys require extensive knowledge of air flow patterns, pressure differences, and actual fireplace and chimney construction.
If the information given here does not help you solve the problem concerning your fireplace or Chimney Designs, consider hiring 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 chimney and make a more definite evaluation.
1. Make sure your damper is fully open. It's easy to forget and leave the damper closed and many dampers will stop working if they get wet due to rain or snow and soot buildup. A professional cleaning job can usually solve this problem.
2. If your firewood is too wet or green, it will not generate enough heat to get the warm air to rise up the chimney and the cycle going, remember, you have to have heat, not just smoke for the chimney to draw properly. Sometimes the heat from the house will generate this draft but it's usually too cool if you are making a fire. This is usually blamed on poor Chimney Designs.
3. If your chimney is too dirty, it will not draw properly. Soot will eventually clog your chimney due to burning pine, or not very hot fires. Even a half inch can reduce the inside diameter by one inch, seriously reducing the flow. Sometimes birds, squirrels and small animals will build their nests in chimneys or leaves from close by trees. Clean these out by using a shop vacuum with hose extensions or call a chimney sweep professional.
4. If your chimney is not at least ten feet tall it may not draw properly. If smokes up your house because your chimney is too short, the problem will usually be worse when the wind is blowing.
5. Is your flue big enough for the fireplace opening? The basic rule of thumb 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 because they are smaller inside). A flue that is too small simply cannot handle the volume of smoke produced, and it has nowhere to go but back into the room. Since there is no practical way to make the flue size bigger, the solution may be to make the room opening smaller with smoke guards or some creative masonry work or in other words reduce the size of the place where the fire will be. There are now some premanufactured firebox retrofits that work well with a 15 to 1 ratio and deliver twice the heat of conventional fireboxes based upon a certain flue size.
6. If your chimney is on the outside of the house, and it's cold outside, the air inside of the chimney will also be cold, and it will want to fall down the chimney instead of rising it may take longer to get the warm air draft cycle going. This can happen a day or two after it's warmed up outside because masonry holds its temperature quite well. Chimney Designs that are this way may be hard to start and they can smoke as the fire burns low. To help get the fire started, light some rolled up newspaper and hold it up by the damper to get that cold air moving upwards. Keeping a moderate sized but quick burning fire can also help this situation remembering that dry crisp wood will work much better for priming the chimney. As the fire dies down, it will go back to the natural direction of flow which is down for cold air pushing smoke back into the house.
7. Fireplaces require large volumes of air to burn properly, if your home is well sealed, you may want to feed the fire by cracking a window. Air is going up your chimney and it has to have somewhere to draw from, it comes from inside the living area and must somehow be replaced. With modern energy efficiency most houses have been carefully insulated to keep out the cold drafts, but an undesirable side effect is that there is no way for the air to come in to feed the fire. This can lead to fireplaces that burn slow and smoke up the house. This is another thing blamed on a poor Chimney Designs. A temporary solution is to open a window to let in a little air but a better and more permanent way is to run an adjustable vent from outside to feed the fire the air it demands.
8. A house that is too drafty, especially a multistory house that leaks air in the upper levels, can actually set up its own draft or chimney effect going up the stairs strong enough to overpower your fireplace Chimney Design, especially if the fireplace is in the basement on a cold outside wall. Make sure the attic access hole door is in place and that all upstairs windows are closed tightly, also check for any broken windows or an uninsulated attic can be a problem too.
9. If there is a return air grill in the same room as the fireplace, it can compete with the fireplace for the air in the house. If this is the case, move the return air to a different location.
10. A chimney can also be too tall, too crooked, and may have cracks in the flue (leaking smoke into the wall between the flue and the structure, this is generally what causes cracks, and will eventually fall in all together). Many things can cause a fireplace to not draw properly, but these are a few that I hope are helpful aside from total replacement which can be very expensive. If need be contact a professional chimney contractor.