Any appliance that isn't properly fitted for its chimney can cause a problem, including the energy efficient gas and oil furnaces that have become so popular in recent years. 

Now the National Fire Protection Agency (NFPA) recommends that, when you install a new appliance, the flue be reduced in accordance with their guidelines for that appliance.  When the flue doesn't vent quickly and efficiently, any home becomes a danger zone.

An unlined flue allows gasses and heat to transfer to the structure of your home.

A cracked clay liner could allow heat to the combustibles located in your home.

In historic homes, the burning of high-temperature heating appliances such as wood and coal can cause difficulties in the following areas:

1) High Temperature Appliances & Unlined Chimneys

Chimneys deteriorate from the inside out because of condensation. In historical homes, the mortar has a high lime content; therefore, when it gets wet, it resoftens due to moisture. Eventually, the moisture will deteriorate the mortar, allowing heat and gases to enter the structure.

2) Improper Clearance

Ninety percent of historic homes have wood in direct contact with the chimney.  When wood is new, it has a flash point of 414 degrees F. Subjecting it to heat dries the moisture out of the wood, lowering the flash point to as little as 200 degrees F. This process is known as pyrolysis.

3) Chimney Fire

After a chimney fire, people often look down a clay tile liner and see only hairline cracks, so they then assume that it's safe to continue using the chimney. What they don't take into consideration is that, once the flue gas temperatures rise, those hairline cracks can expand as much as one quarter inch, allowing creosote to leak out behind the liner.

If a chimney fire occurs after this, the situation would be the same as having a chimney fire in an unlined chimney, resulting in a structure fire and endangering the safety of everyone in your household. In a research project conducted by the Housing and Home Finance Agency, it was noted that tile flue liners will crack when temperatures reach 1400-1700 degrees F. Chimney fire temperatures can reach as high as 1900-2000 degrees F.

Another hazard involving tile flue liners is that they have a tendency to shift, thus leaving an opening between the liners, which allows creosote to leak out. Very often we have found a large build-up of creosote behind the flue liner. If you should have a chimney fire, then the fire will spread from the flue liner into the casing.

There is a great need for consumer education on the topic of chimney problems and proper solutions.  Have your chimney cleaned once a year, and do not let any possible damage go unattended.

Call or e-mail us if you have a question. With over 45 years of combined experience, our corporate office personnel will be able to accurately advise you as to your best course of action. Don't take chances with your family's safety!