Whether you’ve been doing some research about chimney relining and flue systems, or you’ve had your chimney inspected by a certified technician, there’s a good chance that you’ve heard about flue relining or chimney flue relining. What is chimney flue relining? Well, the best way to answer that question is a quick lesson on chimney anatomy.
All chimneys have flues. The term chimney refers to the entire brick or steel structure, from top to bottom. But the pipe that vents the products of combustion from furnaces and fireplaces is called the flue. And the innermost area of that pipe is the flue liner. Flue liners can be made from terracotta clay, poured in places ceramic systems, or stainless steel (Some natural gas burning units can also be vented through aluminum flue liners.) The primary purpose of the flue liner is to ensure that all of the products of combustion–soot, sparks, heat–are safely vented from the fireplace or furnace out of the top of the chimney, with no chance of leaking anywhere else before they are clear of the top of the chimney structure. This way, there is no chance of soot, sparks, or heat escaping and causing a fire to the home. When the flue vents gas appliances like furnaces, boilers, and water heaters, the flue liner ensures the containment and proper ventilation of carbon monoxide, an odorless, colorless gas that kills hundreds of Americans in their homes every year.
A proper inspection of your flue liners using a camera scan system is one of the most important parts of a chimney inspection, and that’s why it is included in every one of our inspections and chimney cleanings. When flue liners are damaged or have been installed improperly, they must be repaired or replaced to be up to proper safety standards. Cracks or gaps in a fireplace or wood-burning stove flue can greatly increase the risk of chimney fires, and increase their chances of their spreading to the rest of the home.
Ensuring that a flue is properly sized for a furnace or water heater is an essential to making sure that harmful flue gasses from furnaces and water heaters are properly vented from the home. Advances in energy efficiency have created a perfect storm for improperly venting gas furnaces and water heaters–as homes become tighter and tighter to air exchange to the outside in order to keep the warm air in and the cold air out (or vice versa in the summer time), homes develop negative air pressure relative to the outside.
This means that cold air from outside is trying to force its way down your furnace flue, which can push exhaust from the furnace back into the house. Combine this with increasingly efficient gas heating units, which put out less total exhaust (since they burn less fuel) at lower temperatures (since more of the heat from combustion goes into the house), and you have a situation where the furnace may vent poorly or not at all. Poorly venting furnaces can result in a buildup of carbon monoxide inside the home that is deadly to humans and pets. Often, when older homes have been refitted with newer gas heating units, the flues are vastly oversized for the units. This can be fixed by relining with a smaller size flue liner, ensuring the best possible ventilation for your gas units.
At Rooftop Chimney Sweeps, we generally have two ways of relining chimneys. If they are in good enough condition, they may be eligible for a HeatShield flue repair. HeatShield is a proprietary repair that recoats your old flue liner, bringing it back up to standard and saving you money by avoiding the process of removing your old liner.
When liners are damaged beyond repair, they should be replaced with stainless steel flexible liners. These liners are extremely durable, and are in many ways superior to original terracotta flue liners. Their round shape gives them better venting characteristics, and because they can be installed in one or two pieces for the length of the flue, there are no joints that might deteriorate or become disconnected. Their high quality means they can take more heat that a masonry flue liner – though the hottest chimney fires can still damage them. That’s why every stainless steel liner we sell is manufactured right here in the United States of America, and comes with a lifetime warranty!