Typical draft problems occur from basic problems that can be corrected. The picture to the left shows the basic air flow in a chimney. A damper left open can allow heat to escape and cold air to enter your home. When you start a fire in the fireplace the warm air heats the interior of the chimney liner and changes the pressure between the house and the outside. This starts the venturi effect which makes the chimney draft the smoke out the chimney.These issues have easy solutions, but sometimes the problem is not your chimney but your home itself. Here are some of the issues that can cause these problems.
Sudden bursts of smoke into the room- This is typically what they call a downdraft. Wind blowing across the top of the chimney shifts and the wind essentially blows down the flue instead. Then it self regulates back to its original draft. This sudden burst of air blowing down the chimney causes a puff or even cloud of smoke at the bottom.
Solution- A special chimney cover can be installed to increase the venturi effect upon the chimney.
Smoke that does not vent properly- This problem can be several things. The damper may have closed on accident or was never open to begin with. The chimney may also have blockage. Either excessive creosote build up or even worse the collapse of interior components such as flue tile and brick.
Solution- Check to see if the damper is open. After the fire is out and it is cool. Look up the chimney to see if you can see a visible blockage. If you see a blockage or do not feel comfortable attempting this, call us for an inspection of your system.
Lazy smoke that lingers in the fireplace- This is typically a problem with the home and not the fireplace. Smoke that seems slow to vent or puffs out periodically usually is a problem with negative pressure. Today's homes are well insulated and the windows are so good sometimes your home can be air tight. The fire burning needs oxygen to burn. Typically it gets this oxygen from the room the fireplace is in. If the room is to air tight. The fireplace will draw its oxygen for combustion from the flue itself. This negative or sometimes even pressure makes the fire lazy.
Solution- Try cracking a window in the room the fireplace is in. If this helps an outside air induction unit can be installed to create a alternative air supply so the fire can burn efficiently.
Smoke that constantly rolls from the top of the fireplace- This problem is typically construction. A fireplace has a mathematical formula that it has to have in order to vent properly. The fireplace opening has to be relevant to the square area of the venting flue. If the fireplace was built with the wrong fireplace opening dimensions it can lead to a under size opening resulting in a improper draft.
Solution- A smoke guard can be installed on the top of the fireplace opening. This simple solution reduced the fireplace opening size and increases the natural draft of the fireplace.
The pressure of the outside air is relevant to the draft of the chimney. Air rushing across the top of a chimney is what starts the venturi processes that allows for proper draft. Sometime environmental issues can effect this process. A tree that stood next to your home for years that was cut down will effect the air flow.