Useful Information on Flues and Flue Liners

twin wall flue bend imageFlue is of vital importance for safety and performance of your wood burning stove. It allows the exhaust gases to travel to the outside as well as proving vital air to the combustion chamber of the stove. But how can you tell if your flue system is compatible with your new stove? Will you need to modify your chimney? Why is it a good idea to install flue liners? These are only a few of many questions most people face when choosing the right flue. We will therefore take a look at the key things to remember about flues and flue liners.

Amount of Combustion Air Required

An average wood burning stove needs about 15 to 25 cubic metres of combustion air which shouldn’t be a problem considering that a typical living room in Britain and Ireland has about 50 cubic metres of air volume. But it is also true that supply of air can be problematic in well-insulated rooms. In the latter case, you are highly recommended to strictly follow the Building Regulations’ recommendations on ventilation and air supply in order to make sure that your stove receives enough combustion air for optimal performance and avoid potential risks to your safety.

Taller Chimney Doesn’t Necessary Means Better

In order to understand the role of the chimney in your flue system, it is important to understand how the combustion gases travel through your chimney. Gases that are produced during wood burning are hot and as a result, they are lighter than the cold outside air. This creates a pressure difference and allows the up-draught. In taller chimneys, the draught is typically better but since the gases cool down as they move up the flue, having a tall chimney isn’t necessarily an advantage. Also, chimneys that are designed for open fires may not work well for a stove because the temperature of gases produced by a stove is incomparably higher than of gases from an open fire.

Who Should Install a Flue Liner

Flue liner is of vital importance if you have chimney problems such as rough inner surfaces, loose mortar joints, porous brickwork, chimney exposed to strong wind or any other issues that may affect the pull, and safety and performance of the stove. Flue liner is also a must if you intend to install a boiler stove because it doesn’t produce as hot gases as conventional wood burning and multi fuel stoves.

How To Choose the Right Size Flue Liner

If it isn’t possible to fit the recommended size flue liner, it is recommended to install a smaller one, usually with a diameter of 5’’. But if you live in England or Wales, you can fit a flue liner with a diameter of 5’’ only if you bought a DEFRA exempt wood burning stove. Choosing the right size flue liner can be quite complicated which is why it is best to follow the manufacturer’s or a licensed installer’s recommendations.


Please keep in mind that any modifications of the chimney, including installation of flues and flue liners are subject to the Building Regulations and must be carried out by a qualified professional.