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Why should you even bother to install a liner? They aren’t cheap, but their benefits definitely outweigh their cost. The liner will protect your flue system, damaged or not, from the transfer of heat in your system to nearby combustibles.
Liners also keep your masonry safe from byproducts of combustion that can be extremely corrosive and damaging to your flue system. The gases produced by combustion will actually eat away at or deteriorate the mortar located in between the flue tiles in your chimney.
Flexible Stainless Steel Chimney Liners
If your existing flue system has been deemed unsafe to burn due to cracked flue tiles, missing mortar joints, etc., then looking into a flexible stainless steel chimney liner may be beneficial. Although rigid stainless steel liners exist, chances are that you may not be able to use this type of liner for your chimney. If your chimney has even the slightest bend to it, then a rigid liner just will not go down into the chimney. Also, you must be sure to use a flexible liner if you are installing for a new woodstove insert because more often than not you are required to bend the liner a little bit to fit it to the stove correctly. Consult a professional when deciding what type of liner will work best for you.
After you purchase your liner in the correct size and material for your particular flue system, carefully remove the liner and lay it out flat on a flat surface. Be cautious, the edges of the liner can be very sharp and potentially cut you. Start by attaching the bottom termination connector. Then tighten the hose clamp, being very careful not to over-tighten it on the liner. After measuring the exact length of the chimney (from the bottom to the very top of the crown,) add twelve to eighteen inches and cut the liner using tin snips. You need to properly install the bottom termination connector.
Chimney liner insulation is necessary along the entire length of the liner. To determine the correct width of the insulation, its time for a little grade school geometry: multiply the diameter of the liner by 3.14 (pi) to get the circumference of the circle, and then add on inch to this number because a one inch overlap is necessary to properly insulate the liner. So long as the insulation will fit in the chimney it is not necessary to have this exact number, it just cannot be any less.
Lay the insulation on the ground with the foil side facing the ground and place the stainless steel liner in the middle. After the liner is wrapped, use foil tape over the seam to keep it snug. After it is secured use one long piece of tape the length of the liner as a whole to cover the seam. This continuous piece of tape will secure the insulation the best.
Wire mesh is also necessary when it comes to insulating the liner. If this was not in place then the insulation itself can be damaged when being lowered into the chimney. Make sure your mesh covers the entire length of the liner. Do not forget to encapsulate the bottom connector piece as well. Hose clamps are the best for attaching the mesh, and they are usually included in the liner kit. Use the clamps to attach the mesh to one end of the liner. Pull the mesh on the other end of the liner until it fits tightly and use the hose clamp to secure it. For safety reasons, use the same tin snips as before to cut away any extra.
Click here for a complete chimney liner insulation kit that has everything you need to install a chimney liner.
Working on a roof, no matter what you are doing, takes many safety precautions. Be sure that you take all of these precautions and you have enough people to safely install the liner. You will be, basically, dropping the liner down through the top of the chimney and feeding it the whole way through to the bottom. It may become necessary for a rope to be tied to the bottom of the liner and someone standing inside the home pulling from the bottom. Be sure to keep the liner as centered as possible while dropping it down into the flue system. This will prevent any damage to the insulation or the liner itself.
After your liner is in the correct position, it is time to cut the top of the liner to fit correctly. Be sure to leave four extra inches showing on the outside of the flue system so that the liner is equal to the height of the crown. Hold the bottom connector in place firmly and apply silicone caulk to the top of the first terracotta flue tile or the chimney crown itself. Then, place the top plate over the liner and press it into the caulking. Tighten the connecting clamp or band around the liner to secure the liner to the top plate. Then, install your stainless steel cap by placing it over the collar of the top plate.
If you are connecting your liner to the appliance vertically, simply connect the appliance connector to the liner and bottom termination point. If you are using a vertical connection then you are finished! If you are connecting horizontally, decide upon the point where the pipe will come through the wall to connect to the tee body. Cut a hole through the insulation and mesh to indicate where the tee snout and tee will connect. Secure the snout and body of the tee using a metal band that should be attached and wraps around the tee body’s backside. Insulate the snout of the tee and fill the hole around the snout with brick and mortar.
Be careful to follow any given directions for your particular flue liner, keep the edges of the stainless steel smooth and be cautious of working with anything on the rooftop of any structure. You can buy a chimney liner kit online here.
Cincinnati Chimney Sweep, Clay Lamb owner of American Chimney Sweep. Executive Producer of Ask the Chimney Sweep Podcasts and YouTube channel.