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Flexible Chimney Liners Explained
A Flexible Chimney Liner can Breathe
New Life into your Old Masonry Chimney
By Mark J. Donovan
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Old chimneys can be a danger to your home and
family. Old chimneys can have cracked tiles or crumbling masonry
that can allow hot gases and dangerous fumes to enter into your
home. Moreover, sparks from burning debris can potentially seep
through the cracks and cause a fire in the home. If you have an
old and dilapidated chimney you basically have three options.
Your first choice is to no longer use the chimney. In some cases
this may be an impossible option if your main heating system
requires it. |
Your second choice is to tear down the chimney and rebuild it.
Tearing down an old chimney, however, is extremely expensive as it
labor intensive due to the fact that it has to be torn down by hand.
In addition, if the chimney is located in the center of the home major
demolition and restoration is often involved to get access to the
chimney.
Your final option, and often the best solution, is to reline the
chimney with a flexible chimney liner. When it comes to flexible
chimney liners there are two basic types, steel chimney liners and
poured concrete chimney liners. Steel flexible chimney liners come in
two basic types. There are heavy duty flexible liners made from
stainless steel, and there are lightweight stainless steel liners. The
lightweight stainless steel liners are most commonly used. There are
also very lightweight aluminum chimney liners, however they are
typically only used for gas appliance applications.
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Poured concrete chimney liners involve inserting an inflated tubular
bladder down the chimney, pouring concrete down the chimney around the
bladder, and then finally deflating and removing the bladder to create a
circular shaped chimney flue. The chief concern with a poured concrete
flexible chimney liner is that they can dramatically reduce the chimney
flue size and impact the chimney’s draft performance. As a result,
furnaces, wood stoves, and fireplaces may not operate as well.
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When installing a steel flexible chimney liner it is important to
install the widest one possible. If too small of one is installed the
same draft problem associated with a concrete poured chimney liner can
occur. To install a metal or steel flexible chimney liner the chimney
should first be checked for and cleared of any obstructions. A
comprehensive chimney cleaning is not required since the steel liner
will form the new chimney flue. Depending upon the particular
situation the new steel chimney liner can be installed from the base
or the top. If installed from the base, a winch is used to pull the
flexible chimney liner up through the chimney as new sections are
attached to it at the bottom. In other cases it may be pulled from the
top down. Due to various chimney contours the liner may need to be
slightly forced and massaged down or up through the chimney. Due to
the fact that the chimney liner is flexible it can take the flexing
and contouring without being damaged.
After the steel flexible chimney liner has been positioned into place
and permanently installed it should be insulated. Insulating the
chimney helps by keeping the inside of the chimney flue warmer which
in return helps with creating a sufficient updraft. Either ceramic
wool blanket material or a vermiculite and concrete mixture can be
used to insulate the flexible chimney liner. The ceramic wool blanket
insulation typically requires more space and as a result reduces the
size of the chimney liner. If a ceramic wool blanket material is used
to insulate the flexible chimney it needs to be wrapped around each
section of chimney liner as it is installed into the old chimney. In
addition, a wire mesh has to be installed over the insulation blanket
to enable the insulated chimney liner to be installed into the
chimney. If insulating the chimney liner with the vermiculite and
concrete mixture, it is simply poured down the original chimney flue
and around the new flexible chimney liner to insulate it. As a result,
the best way to insulate a new steel chimney liner is with the
vermiculite and concrete mixture.
In general most flexible chimney liners are fabricated similarly.
Some, however, have titanium added to the stainless steel to increase
their resistance to high heat, and to add a little more strength.
Depending upon the manufacturer they’re may be some slight variations
in supporting clamps, clips, brackets, and screws that come with the
chimney liner kit. Though a skilled do it yourself homeowner could
potentially install a flexible chimney liner, in most cases it should
be left to the pros. Not only is it hard work, it’s also important
that it is installed right for the safety of your home and for proper
operation.
For information on maximizing your
wood stove’s home heating efficiency see
the “Installation
of Hood over Wood Stove Ebook”.
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