Your chimney liner is one of several components in your home’s fuel burning systems.
These components include:
- The fuel burning appliance (a fireplace, woodstove, oil or gas burning furnace, or a combination of one or more of these venting to a single chimney)
- The chimney flue
- The chimney liner
- The chimney structure
- Controlling features such as dampers, fans and thermostats
- External features such as chimney caps or top-sealing dampers
If all of the components of the system are properly sized in relation to each other, your home will be safe and your appliances will burn their fuel efficiently. If one or more of the parts of the system are not properly sized, then you could have problems with poor draft and backflow of noxious gases or smoke into your house.
If your chimney liner is made of the correct materials and is sized properly, it will improve the venting of combustion gases from your fireplace, woodstove or furnace. Your stove or furnace manufacturer can tell you the diameter of liner that you should vent the appliance into for the most effective operation.
A chimney liner that is too narrow for the appliance it is venting will not be able to carry all of the smoke and other combustion products up the chimney quickly enough, which may result in inefficient burning of the fuel, accumulation of creosote and moisture in the liner, and leakage of noxious gases into your house. On the other hand, a liner that is too large may inhibit proper venting because it does not heat up enough from bottom to top to encourage a strong updraft out of the chimney.
Insulation has a big impact on how a chimney liner affects venting. Your chimney liner should be insulated from top to bottom if the chimney is built on an outside wall of your house. If your chimney is entirely surrounded by insulated rooms, then you should at least have your chimney liner insulated for the portion of the chimney that extends into an un-insulated attic or above the roof-line.
Effective liner insulation will keep the combustion gases venting up your chimney hot all the way to the top where they leave your house. This will inhibit down-drafts caused by having cooler gases near the top of the chimney and will provide a healthy updraft that pulls smoke and other gases out of your house. An insulated chimney liner will also have less creosote and ash buildup on its walls which can inhibit smooth venting by increasing the friction between the exhaust gases and the liner wall.
If your chimney liner is properly sized, correctly installed, and adequately insulated, it should improve the venting of combustion gases from your home. Good chimney draft is critical for getting smoke and noxious fumes out of your house and for inhibiting buildup of creosote and water inside your chimney.
If you have problems with smoke backing up into your house when you are using your woodstove or fireplace, consult with your chimney sweep or other chimney professional about ways you can improve venting from your house. He may be able to recommend steps you can take to improve how you use your fireplace or woodstove, or he may conclude that you need to install a different chimney liner to improve your system’s venting ability.