FLAME Blog

Chimney Liners

Since most of us no longer use fireplaces to consistently heat our homes, did you ever wonder what the chimney was for other than giving Santa a way in? A home’s chimney has multiple purposes.  Yes, they are still used as a ventilation system for the occasional fire, but typically they have a more important job than that.  Depending on the efficiency of your furnace, the chimney is used as a ventilation system for the released steam from the furnace.

Older, less efficient furnaces release steam that is up to 700 degrees Fahrenheit.  This high heat needs the entire space of a chimney in order to escape out the opening.  More efficient furnaces, such as those at 80%  also use the chimney for ventilation purposes.  However, since the temperature of the steam they produce is drastically reduced to about 400 degrees Fahrenheit, they do not need the large cavity of the chimney.  This is where chimney liners become necessary.  As their name suggests chimney liners line the inside of the chimney.  They are made out of metal and they reduce the size of the chimney space, so that the steam can fill it up.  Now, why is this necessary?  Because when the steam of higher efficiency furnaces does not take up the entire space of the chimney moisture can build up.  This can lead to acid seeping in through the mortar to the detriment of the chimney.

Does your home need a chimney liner?  To find out, first ask yourself a couple of questions.

What type of furnace do I have? If it is older and not very efficient, you most likely do not need a liner.  If it is a high efficiency 90% AFUE and above, these systems have a completely separate ventilation system apart from the chimney, so a chimney liner is not necessary.

What type of chimney do I have? If you have a newer home with a skinny metal chimney flue, these are typically already small enough for higher efficiency furnaces.  If you have an older home with a wide brick chimney, you may need a liner depending on how efficient your furnace is.

Do I already have a chimney liner?  To check, look at the top of your brick chimney flue.  If you have one you will see another metal flue sticking out a little bit higher than the original brick opening.

For more information about the uses or the installation of chimney liners, please contact Flame!

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