If your fireplace drafts poorly, it is not only annoying in terms of making your house smell like smoke, but it is also wasteful and dirty. A poorly drafting fireplace burns wood inefficiently, belches smoke with little heat into the house, and sends smoky incompletely combusted gases up the flue, where layers of thick soot and creosote are deposited every time you build a fire. You may be able to solve these problems by installing a flexible stainless steel chimney liner inside your flue. A flexible liner is installed by inserting an insulated length of corrugated stainless steel into the flue, where it is fitted into a mount above the firebox and suspended at the top of the chimney with a fitting that seals off the space between the outside of the round liner and the inside of the square flue. This space can be filled with additional insulating material, or left as dead air which also offers some insulating properties.

A flexible stainless steel chimney liner improves the performance of your fireplace and chimney in several ways. It makes the flue easier to keep clean for two reasons. First, less creosote and soot is deposited in it to begin with, and second, a round flue is easier to clean than a square flue. Since the liner insulates the flue from the outside chimney structure, the combustion gases rising up the chimney do not cool off as much as they did inside an uninsulated flue. This results in less condensation of water, creosote, and corrosive combustion compounds since the flue gases are still hot when they reach the outside air. A round flue is easier to clean than a square flue since there are no corners to worry about, plus the expansion and contraction of the corrugated liner with heating and cooling from the fire helps to keep creosote from adhering so tightly to the inner walls of the flue.

Unless its inside diameter is too small for the fireplace it serves, a flexible chimney liner will improve the drafting ability of the fireplace. It accomplishes this because the round cross-section allows smoother passage of the swirling combustion gases than a square cross-section, which tends to trap gases in eddies and dead air spaces. The insulated liner also keeps the gases hotter, which improves draft because hot air rises faster than cooler air.