Very few masonry chimneys, you see, have been (or are now being) built to
suit the gas flow rates common to controlled combustion ("airtight")
heaters,
and the typically too-large masonry flues reduce draft and increase creosote
buildup. Worse yet, many, older chimneys lack any sort of liner to protect
the brickwork from the extreme temperatures that can be generated by a
chimney fire (such blazes can exceed 2000'F). And even flues that are lined
with
tile may have deteriorated under the abuse caused by chimney fires, to the
point where smoke (or flames) can escape into the house through cracks. As
you
can see, then, masonry chimneys often actually produce conditions that can
lead to danger . . . by virtue of their very design.
Nonetheless, no matter what sort of chimney you're using with your
woodstove, you should definitely have the system cleaned and inspected
regularly. Of
course, you may want to leave this vital (and somewhat unpleasant) task to a
qualified sweep, but-with a little bit of study and a steady pair of feet
on the rooftop-there's no reason why You can't learn to do this job.
As you familiarize yourself with your woodburner's ventilating system, one
of the first things you'll have to learn is the size of the chimney brush
needed
to clean it properly. Once you've determined that dimension, you can compare
your flue size directly (if' it's round) against the stovepipe diameter
recommended
by your heater's manufacturer, or calculate the cross-sectional area of a
rectangular stack for comparison with that figure. When checking the
suitability
of your chimney, bear in mind how much even a small increase in size
influences capacity: An eight-inch-diameter chimney, for example, has almost
twice
as much cross-sectional area as does a six-inch one. Thus, what might seem
like a small deviation from recommended procedure could make a big
difference
in performance and safety.
Once you (or your sweep) have cleaned the walls of the flue, the lining
should be checked for cracks or holes, and the mortar joints between the
tile sections
should be inspected for soundness. Most professionals do this by using a
mirror to reflect sunlight down into the chimney, but a trouble light may be
helpful
on cloudy days (and when inspecting chimneys with bends).
Should the examination turn up deficiencies in the size or condition of the
chimney, there are basically only two things you can do: You can tear it
down
and build a safe, properly sized one, or you can have your existing flue
relined. There are a couple of good reasons for taking the second approach:
For
one thing, relining a chimney costs approximately a third of what a mason
would likely charge to disassemble an old one and build a new stack in its
place
... and a relined chimney may actually end up being safer and more durable
than a new tile-lined one!
In the following paragraphs, we're going to describe two methods of lining
an existing masonry chimney. Both systems have their strengths and
weaknesses-which
we'll try to point out-and neither is exactly inexpensive. However, each
approach can produce a chimney that, when used in conjunction with a
controlled-combustion
woodburner, is essentially better than even a new brick chimney. We'll be
featuring a pair of specific systems that we've seen in action, and will
list
other manufacturers of similar products at the end of the article. Of
course, the fact that we've chosen to show you the Insulcrete and Ventinox
reliners
doesn't mean that we necessarily judge them to be superior to all other
products. From personal experience, we do have confidence in their systems,
though
... and we're very grateful to Pete Luter (president of the North Carolina
Guild of Professional Chimney Sweeps and a reliner himself, out of the
Roanoke
Rapids, North Carolina shop called Countryside) for leading us to them.
VENTINOX STAINLESS STEEL
In the past, many people who've found their chimneys to be incapable of
providing acceptable draft for a woodstove have resorted to stringing
stovepipe
up the flue. And, though the practice usually has accomplished its goal,
quite often the owners have been surprised to find that creosote built up
inside
the metal pipe at an alarming rate. Without insulation around the steel
tubing, heat is lost from the smoke so quickly that the products of
incomplete
combustion readily condense on the walls of the flue. Furthermore, if the
material used for such a simple relining is merely galvanized stovepipe, the
system will deteriorate very quickly.
On the other hand, existing chimneys that have been relined with quality
stainless steel pipe have a far better track record for longevity, but still
suffer
from rapid creosote deposition ... unless they're insulated. Unfortunately,
running a factory-built double- or triple-wall chimney up a masonry flue is
cumbersome and expensive (these systems can cost as much as $55 per foot).
This method also does nothing to strengthen a weak brick stack, and can be
downright
impossible if there are any significant bends present in the existing flue.
However, a system commonly used by the Swiss avoids such problems by
employing a high-grade, flexible stainless steel liner (to accommodate
turns) with
a fill of insulation (for good draft and low creosote deposition) or-when
necessary for strength--a mix of insulation and masonry cement. The Ventinox
relining method (as it's called) came to the U.S. less than a decade ago,
when a transplanted Austrian, Martin Wawrla, was faced with the job of
relining
four existing chimneys while restoring his Albany, New York home. After
coating the inside of one flue with refractory cement, a procedure that
involved
opening an access hole every few feet, Martin decided to track down the
owners of the relining system he'd seen so often in Europe. By working
through
the Swiss office of Ventinox, he ended up proposing to the U.S. division of
the company, American Boa, that it bring the European system to this
country.
As a result, Martin is now project manager of American Boa's growing chimney
relining business.
The Ventinox liner is made from a continuous band of 33-gauge 321 stainless
steel that is corrugated, rolled in a spiral, and then bound together by a
computer-controlled
electric welder. The corrugated spiral helps give the comparatively thin
material strength and reduces problems with thermal expansion (which has
been
known to lift the top right off a chimney relined with solidly mounted
standard stovepipe). In addition, 321 stainless is perhaps the steel alloy
that's
most resistant to the corrosive environment in a woodburner's chimney, and
the company guarantees its product for ten years.
Of course, other stainless alloys may last as long as 321 does in most
environments, but the strain imposed by a chimney fire can eventually be the
undoing
of lesser metals. You see, once many corrosion-resistant steels have been
heated to above 2000'F, the chromium in the metal (which prevents corrosion)
may begin to lose its bond with the other elements ... and intergranular
deterioration can then begin. To date, Ventinox is the only stainless
reliner
that's been tested to both Underwriters Laboratories basic (UL 103) and
high-temperature (2100°F) standards.
Installing Ventinox is a straightforward job, and trained crews have been
known to do a basic chimney in just three hours. The procedure consists of
installing
a baseplate, with a hole to fit the diameter of the liner (Ventinox is
available in six-, seven-, eight-, and ten-inch sizes for residential
applications),
on the smoke shelf above the fireplace ... threading the one-piece tube down
the chimney, engaging it into the baseplate, and centering it with spacers
... filling the area around the liner with the appropriate insulative
mixture ... and capping the relined flue.
In order to assure structural integrity (and a leakproof installation),
Ventinox is always installed with at least the first foot (and preferably
the first
five feet) of void around the steel filled with a vermiculite and masonry
cement slurry. From that point on, the area around the liner can be filled
with
insulation alone, as long as the surrounding chimney is sound. Vermiculite
is very resistant to thermal degradation, but--unfortunately--it can absorb
water (Ventinox and other reliners use an asphalt-treated version that is
less susceptible to this problem), so the top of the relined flue must be
carefully
sealed with either a pointed-out masonry cap or a fabricated stainless steel
lid. In addition, the rocks from which vermiculite is quarried also often
contain asbestos, and that carcinogenic material can contaminate the
insulation. Some sources guarantee their vermiculite to be free of asbestos,
but it's
still a good idea to exercise caution (and wear a respirator) when using the
material.
The Ventinox installation we observed was part of American Boa's training
seminars for their certified installers. Like most relining companies,
American
Boa prefers to work through chimney sweeps, since these professionals
already have an intimate knowledge of woodstove flue systems. And even
though it
was their first attempt at the job, the crew of sweeps managed to reline a
25-foot chimney and install a fireplace insert in about six hours. The cost
of the Ventinox reliner itself runs between $15 and $20 per foot (depending
on the diameter required), and labor and other material charges usually
bring
the final figure up to between $30 and $40 per foot.
However, the contract also includes one free inspection for safety and
creosote accumulation ... and-like other relining companies-American Boa
encourages
homeowners to maintain their chimneys properly by making the warranty
contingent on regular inspection and cleaning.
INSULCRETE
John Gusler, a concrete engineer and the developer of the Insulcrete
Relining System, started repairing chimneys about eight years ago in order
to increase
business at his stove dealership. Being a conscientious proprietor, he found
himself in the difficult position of refusing to sell appliances to
individuals
whose chimneys couldn't meet his criteria for safety. The logical decision,
of course, was to start repairing those deteriorated flues.
Insulcrete itself is a proprietary insulating concrete mixture that, through
the years, has seen a number of different pour techniques. The first several
dozen flues were done using metal liners as forms, but-since Insulcrete is
capable of standing up to the woodburning environment on its own-Gusler
began
looking for a way to eliminate the steel. He settled on a rubber bladder
that's inflated by an air compressor.
With the help of a partner (mason Mark Borell), John developed a
kit-consisting of two bladders, fittings, and instructions-to market to
chimney sweeps.
Today, Mark and/ or John hold two-day instruction seminars around the
country nearly every week, and to attend the school in Mark's hometown of
Navarre, Ohio.
As was the case with Ventinox, formed-in-place refractory cement relinings
were first used in Europe ... in England, as a matter of fact. Their
performance
with coal-burning appliances has been well established in that country, and
Insulcrete has been tested to the UL 103 and ULC-S-629M standards by Arnold
Greene Testing Laboratories.
Our session with Insulcrete consisted of dropping a six-inch-diameter rubber
tube down the 28-foot-tall chimney shown in the photos ... installing turned
wooden plugs with clamps ... inflating the former to about 20 pounds per
square inch (PSI) ... centering it with spacers ... and pouring the
Insulcrete
(which is a mix of refractory cement, aluminum silicate, vermiculite,
one-inch-long alkali-resistant fiberglass threads, and water) down from the
top of
the flue by bucket brigade (the partners also have a slurry pump available
for sale to installers, but don't usually find that it's necessary). The
form
is left in place for 24 hours and then can be deflated and removed for
reuse. At that time, the top of the flue is pointed out with regular mortar,
and-if
necessary-the exposed portion of the chimney is parged (coated).
Insulcrete doesn't specify a warranty period to its authorized installers,
but Mark Borell does provide a lifetime warranty (it's even transferable),
as
long as the customer keeps a maintenance contract with his sweeping service.
(Both Mark and John suggest that 15 years would be a conservative warranty
for an installer to offer.) The cost of an Insulcrete relining starts at
about $25 per foot (for the most straightforward job) and will run between
$30
and $40 for anything more complex. Labor makes up a major part of the bill,
partially because the installer must charge enough to pay off the cost of
his
relining kit (which runs between $2,000 and $7,500 ... from the basic model
to the fully equipped trailer).
HOW MUCH BETTER?
As we've already suggested, both Insulcrete and Ventinox can turn your old
chimney into a superior flue for a woodburner. But, you may be wondering, is
it really worth all that money if the chimney is essentially sound? For
evidence of the advantages of a wellinsulated flue, we'll refer you to the
two
photos of existing chimney tops that accompany this article. Both flues were
relined by (or under the direction of) Pete Luter ... and both have
Dura-Vent
stainless steel pipe. One of them, however, was insulated with perlite,
while the other has only an air space. The insulated chimney has yet to be
cleaned
after four years of use, and shiny metal is still visible in places. The
uninsulated reliner, however, has accumulated almost an inch of creosote in
less
than one season of use.
The answer seems clear: The amount of flue-cleaning time that can be saved
(as well as the money that will be saved as a result of less-frequent calls
to
the chimney sweep) with a properly relined chimney is substantial ... and,
of course, no one can put a price on safety!
RELINING SOURCES
You can contact the following companies to find out where a nearby qualified
reliner may be located,
Acu-Set Mazzeo's Chimney Sweep Suppliers Dept. TMEN RFD 1, Box 1245
Rockland, Maine 04841
American Boa Incorporated Ventinox Headquarters Dept. TMEN P.O. Box 1743
Albany, New York 12201
Insulcrete Relining System Dept. TMEN Box 856 Delaware, Ohio 43015
Iso-Kaern Norwegian Wood Stoves Dept. TMEN Box 219 Clarkson Post Office
Mississauga, Ontario Canada L5J 3Y1
National Supaflu Systems Dept. TMEN Box 289 Central Bridge, New York 12035
Permaflu and Z-Flex Energy House Dept. TMEN Box 4035
Manchester, New Hampshire 03108
Readi-Flu D'Arcy Chimney Relining Dept. TMEN Box 387 Windsor, Connecticut
06095
Renew-A-Flue Dura-Vent Dept. TMEN Box 2249 Redwood City, California 94064
Safe-T-Liner Heat-Fab Dept. TMEN 38 Haywood Street Greenfield, Massachusetts
01301
