The internal structure of a chimney is called a flue. Chimney flue liners serve numerous purposes like keeping a check on the internal heating of the chimney and increasing the life span of chimney flue. The flue is subjected to extreme heat and pressure conditions. Moreover the smoke originating in the chimney also affects the flue. Flue liners are made of materials that can handle the pressure, heat, and smoke and help the chimney to function smoothly for a long time. Depending upon the type of chimney you have different flue liners can be used.
Types of Flue Liners and Their Advantages
As there are different styles, sizes and types of chimneys, there are as many types of flue liners. Broadly, these flue liners can be divided into the following categories:
Stainless steel flue liners are corrosion resistant and are available in different flexible shapes. These can be used as rigid or flexible section insertions, whereas the non-flexible rigid types work only for straight chimneys. These liners are passive to smoke coming from wood, coal, and other solid fuels, and thus have a long life. Stainless flue liners are available in different sizes and they do not require much effort to install. Their long life and ease of workability make them a favorite among the contractors and engineers.
Cast-in place liners means casting concrete lining in the chimney. The concrete is lightweight but heat resistant and capable of handling extremely high temperatures and thermal stress at the same time. They last for more than 50 years and are almost independent of the fuel being used. The concrete liners do not catch rust and acidic properties of soot and smoke do not affect them. Moreover, these liners promote clean burning of fuel and thus are Eco-friendly too as compared to other flue liners.
Terra Cotta Liners are one of the oldest and longest lasting flue liners, basically they are unglazed ceramic flue liners. These can last for maximum of 50 years and can absorb good amount of heat and pressure. Even today, for newly built chimneys, tera cotta flue liners are used. The only problem they have is their installation, for home chimneys not enough space is available and a skilled and experienced worker only can install these liners inside the chimney, which means increase in installation costs. Clay flue lining is arguably the oldest method of lining inside of a chimney. Clay chimney flue liners are made of clay and shale and before pouring it inside the chimney, it is heated at a high temperature. Clay liners are resistant to heat, do not allow soot build up as they are smooth as compared to concrete liners and can handle thermal stress as well. But clay is vulnerable to very high temperatures and water seepage too.
Why install a chimney flue liner?
Now that you know your answers backed by advantages associated with every type of flue liner, let us have a look at installation guidelines.
Guidelines for Installing a Chimney Flue Liner
Installing a chimney flue liner can be an easy or difficult task depending upon the size of your chimney, type of chimney you are working with, and other working conditions. Below mentioned are some of the important aspects of installation process of chimney flue liners.
The first and most important step is evaluation of chimney condition and if the chimney flue liner has to be installed. The first thing to do is to inform the local authorities because flue liner installation falls under the Building Regulations guidelines.
Concrete lining can be done using a cylindrical tube or by using aluminum boxes that are lowered down into the chimney and gradually taken out while pouring the concrete. Concrete lining does not work for old chimneys and while pouring concrete extreme care must be taken because this process is irreversible and if done with errors, it can render the whole chimney useless.
Always keep in mind the fuel you are going to use with the lining alloy material. Other than stainless steel liners, you can use metal liners as well but it becomes important to check compatibility and adverse effects of fuel smoke on the alloy material. In most of the cases, metal lining fail because of corrosive action of the fuel soot and smoke.
Never forget to insulate your metal liners, insulation increases life of the lining material and also prevents corrosive action cause by soot build up.Insulation wraps and jackets can be used to insulate the flue liners.
Clay chimney flue liners should be fitted with the rebates to prevent condensate running out and the chimney needs to be supported by surrounding masonry.
You can use flue liner kits that are easy to install and modular in shape which make installing flue liners less time consuming.
Chimney Fires, Csia.Org(pdf)
Approval Standard for Chimney and Flue Liner Materials, Fmglobal(pdf)
Total Chimney Solutions, Flueandchimney(pdf)