Four good reasons to have a chimney liner installed:
* Fire safety
* Improved performance
* Easier, more effective cleaning
* Long-term preservation
Most people think of chimney liners only in terms of fire safety: Especially if you burn wood, you probably know that an unlined chimney, or a chimney with a damaged liner, is a fire hazard. Chimney fires burn hot enough that combustible framing around the chimney can catch fire right through a layer of brick. The liner is there as an essential layer of fire protection.
But suppose it’s not super-obvious that you need a new liner. Maybe there’s a liner in there now, and while it might be old, it still looks okay. Or maybe you don’t use the stove or fireplace very often, or you heat with gas or oil ... all of which adds up to this: You don’t think you’re going to have a chimney fire.
Why would you want to consider re-lining a chimney in that case?
This is where the other three reasons come into play:
Improved performance. A properly-sized flue creates the ideal draft for your appliance, whether it’s a furnace, a water heater, a fireplace or a stove. Over-sized flues (often the case when the flue is unlined) tend to provide too weak a draft for modern appliances. A chimney liner of the appropriate size for your appliance will help improve the draft, which in turn improves the operation of the appliance.
In the case of wood stoves, the difference is sometimes remarkable: With the flue unlined, the stove is hard to start, doesn’t seem to run well, and spills smoke into the room, especially when starting it or at the end of a burn cycle when it’s cooling down again. And, when you’re not using the stove, it stinks: cold, damp, foul-smelling air rushes down the chimney into the house. With a properly sized, properly insulated chimney liner, the stove will be easier to start because the flue will warm up more quickly, and the draft will be improved, so the stove will burn more efficiently. As a bonus, there will be less odor, because the flue will vent combustion products to the outdoors more efficiently, resulting in less buildup, and there will be less cold air in the flue to draw odors into the house.
Why is the draft improved?
In an over-sized flue, there is a larger volume of air that needs to be heated. The result is a cooler column of air, which translates into a weaker draft. A tall column of hot flue gasses, by comparison, translates into a stronger draft.
Easier, more effective cleaning.
Ask any chimney sweep on the planet which is easier to clean: an unlined chimney, or one with a properly sized liner. The lined chimney is always easier to clean, because the improved draft means less condensation of smoke and gasses (less soot and creosote buildup) and the flue is an even, consistent size with an even surface that the brushes can clean effectively.
Aside from chimney fires, earthquakes, falling trees and the like, the number one killer of chimneys is water. Especially in northern climates, freeze-thaw cycles slowly break chimneys apart. You’ve probably seen chimneys with missing bricks, or chimneys leaning to one side due to years of wind-driven rain soaking into the masonry. But water damage can happen on the inside, too. Water vapor is one of the components in flue gasses. In the case of chimneys that are used to vent gas-fired appliances in particular, the inside is sometimes literally soaking wet, just from condensing water vapor.
A chimney liner acts as a barrier against interior damage from condensation, protecting the inside of the chimney from gradual decay cause by water penetration.
What kind of liner is better?
Stainless steel flexible piping is manufactured by forming a continuous strip of ribbed metal into a spiral and connecting it to make a tube. “Seam welded” means that as the tube is formed, the strip is welded, and not folded or crimped together. With some liner products it’s crimped, or folded over on itself into a sliding channel. Crimped liners are also flexible, but only the seam-welded pipe is completely waterproof, and a welded seam is super-rugged and less prone to separation.
Isn’t a heavier liner better?
Some liners, particularly the type that involves a seam that’s rolled over onto itself and crimped into a sliding channel, can be extremely heavy. While you might think heavier-is-better, what’s more important is the type of material and how it’s formed. The corrugated surface of our liner gives it great strength, and the alloys used (matched to the type of fuel you use) are designed for optimal longevity. A very heavy liner of an inferior alloy will actually under-perform significantly compared to our stainless steel liners.
What about insulation?
Insulation around the stainless steel pipe is part of the liner system. Its purpose is to keep the inside of the flue hot, and the outside of the chimney cool, for the sake of fire safety and optimal performance. Depending on the type of installation, we use either a foil-faced ceramic blanket or a lightweight masonry insulation.
As part of a regular chimney inspection we will check the liner and let you know if a new liner is needed.