Articles - Keep The Home Fires Burning In The Fireplace

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Home Pro Inspection
Systems Inc.
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Oakwood, Ontario
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Keep The Home Fires Burning In The Fireplace:

For the past bunch of years as many as 100,000 American homes burn after accidents involving heating with wood. The single biggest reason for so many fires is this: People do not understand the nature of creosote or how quickly it builds up within chimneys. Creosote is a combustible deposit that can catch fire and is the fuel that burns when there is a chimney fire.

fire combine to condense out the unburned gases and tars onto cooler chimney sections. The weaker the draft and the cooler the flue, the greater the buildup of creosote. Also the cooler the chimney, the more likely that third degree or "glazed" creosote will form. This is much denser and more difficult to remove than the so-called "flake" creosote.

The traditional wood stove inserted into a fireplace is a breeder of creosote, particularly if the original masonry fireplace is on an outside wall. NOTE: Inside chimneys tend to reflect the temperature of the surrounding living space.

Fireplaces have large flues built to accommodate an open wood fire. The fire temperature is very high and the draft up the flue is very strong. This type of flue is actually too big, and if on an outside wall, will be too cold to properly accommodate a wood stove. There will never be enough temperature to heat the flue and never enough combustion to force a strong draft. Creosote will precipitate rapidly. The same thing happens when an insert is coupled to a triple-lined, prefabricated metal fireplace chimney. These chimneys have space between the linings to keep them cool. Creosote formation will be very rapid whether the chimney is on the outside or the inside of the house. Either modify these chimneys or plan on removing the stove and cleaning the chimney every two months of operation. (The standard is to clean when one-fourth of an inch of creosote is deposited on the walls.) In any case, check after the first two months of operation to give yourself a gauge. Remember, the colder the weather the more rapid the creosote buildup.

Modifying fireplace chimneys: You can modify a masonry or triple-lined flue to better accommodate a fireplace-insert wood stove. The most practical thing to do is to drop a stainless steel "Z-Flex" liner down the existing flue. This should be connected through a blocking shield at the bottom of the chimney throat to the flue of the wood stove. It is then pulled taut and held from the chimney top. Vermiculite insulation is then poured around the new liner and the pipe is sealed at the top with a combination cap screen. This is best done by an experienced chimney sweep. The flexible liner costs about $10 per foot and the vermiculite cost will vary depending on the space between the liner and the original flue. The entire job should cost around $500. It can cost more than this to remove the tar-like "third-degree" creosote, which can easily form in cold flues.

The lined and insulated flue will now be smaller and warmer. This will yield a stronger draft and far less creosote precipitation. It provides an extra measure of containment in the event of a chimney fire and is removable should you wish to return to fireplace use.

Woodstove operation: Woodstoves can be burned hot (a full load of wood with air inlets wide open) for a short period (about five minutes to 30 minutes) at least once a day. This procedure is called pyrolizing dries third-degree creosote, shrinks it, and causes it to drop down the flue or be expelled upward with the stronger draft.

A few caveats: Pyrolize from day one and you should be okay, but if the flue already has a good deal of creosote in it, this may actually ignite a chimney fire. Beware of "back-puffing." Never open the door to an airtight stove that has been smoldering for a long time. The inrushing air may cause the smoldering smoke to flame up and shoot right out the door. Flames can shoot more than five feet. Always open the air ports so the fire can get going again before opening the door. Open the air ports and then get the wood burning more quickly to add to the fire.

Warning signals: If your stove has always worked well and then begins to smoke around the doors or ports, it may mean that the chimney is restricted with creosote. Let the fire die, wait a day or two, remove the stove and check. If you haven't cleaned the chimney in the last year, you can bet you need a clean sweep. Do not ignore a darkening of your chimney top or brown liquid running down metal flue pipes. Both indicate considerable creosote buildups and merit a relatively immediate check.

A LIST OF NEVERS:

Never hook a wood stove to a flue pipe that is used to service a gas appliance. These have aluminum linings and soon will corrode or burn out.
Never flue a wood stove via an old brick chimney without a terra cotta liner.
Never use anything but Underwriters Laboratory approved equipment.
Never use a screen over a wood stove flue. It will block-closed quickly. (Animals tend to avoid wood stove flues, presumably because of the creosote.)
Never rely on chemicals to keep your flue clean. There are many products on the market that claim to be effective at eliminating or reducing the buildup of creosote in the chimneys. Most of them contain a lot of salt. Take their claims with a grain of salt as well. There is no substitute for the chimney sweep.
Catalytic combustors: Most newer were fitted with catalytic combustors. This is a device that fits over the stove flue. It causes escaping gases to burn, and will greatly reduce creosote buildup. It must first be brought up to a relatively high temperature. If it isn't, it acts as a trap for escaping creosote and contributes to the problem. There are a number of retrofit kits available for various existing stoves. Contact the manufacturer of your stove or even a competent chimney sweep.

The stoves may be cheaper energy sources, but care and discipline are required to maintain their most effective and safe use.

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