RELINING MASONRY CHIMNEYS

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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 one of MOTHER's staff members was fortunate enough 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,

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