Why Do I Need To Line My Chimney?

Lining Your Chimney Is Important!

If you have a stove in your home, for it to work correctly then it has to be connected to a good solid chimney and the correct sized flue for it.
Your chimney essentially removes the products of combustion from the appliance in your home and transfers them outside of your home. The chimney will do this without causing danger to the people within your property and without causing a potential house fire.

Your chimney works on the principle that ‘heat rises’ and in order for this to happen your flue has to be well insulated.

Some of you might find this confusing and so it is important to understand the terminology that we are going to use:

Flue: Your flue is the route through which the products of combustion travel away from your stove to the outside air.

Chimney: Your chimney is simply the structure that surrounds your flue.

Flue Liner: These are fire resistant materials that line the flue and are usually made of clay, stainless steel or terracotta pipe.

Stove Pipe: This is simply the pipe that connects your appliance to the flue that is located within your chimney.

There are many factors that can affect the performance of your chimney, such as operating your stove for long periods on very low settings or cool air leaking into your flue. This cool air will cool the gases down and affect the performance. Therefore the gases need to be kept warm and so the insulation value of your lining is important.

Houses that were built before 1965 generally were built without liners. This is mainly due to the fact that Building Regulations had not yet changed. Then flues were rendered, or parged, on the inside with lime mortar. Over a period of time this parging will have been attacked by the corrosive elements that are contained within the flue gases. This can lead to leakage and erosion and you will know if this is happening because a material, very similar to sand, will begin falling down your chimney. This is the old lime mortar and it could also be the mortar that is coming away between the bricks where they have begun deteriorating.

If your house was built after 1966 then you should have a lined flue and it will usually be lined with clay liners. It should be noted though that this type of liner is not altogether suitable for efficient multi-fuel stoves and wood stoves.

If your chimney is built on the outside of your house, and most usually are, then they are very susceptible to the elements. If your chimney does not have a liner then it results in a cold flue.

Stoves are excellent heating appliances because they produce nearly 85% of heat from the fuel burnt within the room whereas open fires can lose up to 95% of their heat. Therefore because efficient stoves lose little heat it is essential to keep a good flue gas temperature so that it can rise.
If your flue is well insulated and lined then it will create an efficient and safe appliance within your home. An unlined flue can often result in building work being needed.

We find that there are a variety of reasons why an old chimney needs to be lined. Here we will give you the reasons in more detail:

• Your flue may be causing smoke and fumes to be entering some or all of your rooms.

• Tar may be seeping through the walls of your chimney, which will cause stains to inside and outside walls.

• Your flue may be too big for the appliance that you are using.

• Your flue may be too cold, especially if it is located on an outside wall and so is not drawing as it should.

• If you chimney was built before 1965 then the flue may be installed the wrong way up, we find that this often happens. If this is the case then tar and condensate leaking could easily take place.

• The surface of your old flue has become eroded and this has led to leakage, poor updraft or chilling.

So now that you know the reasons why we line flues now we need to look at the two different types of flue liners. They are differentiated between Class 1 flues for wood and solid fuel and Class 2 flues for gas.

All multi-stoves and wood stoves have to have a Class 1 flue liner. They are available in various lining materials, such as clay, rigid 316 grade stainless steel, flexible 316 grade stainless steel, pumped refractory concrete or rigid pumice. We find that the flexible 316 stainless steel liners are the most cost effective ones that line an existing chimney. It allows us to complete the work in one day and there is very little mess and they last for years when installed correctly.
Class 2 liners have to be used for gas stoves in order for them to meet safety regulations.

So these are the main reasons why we have to line flues. We hope that you find the article informative.

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