The primary culprit in chimney breakdown is the acidic moisture that comes from condensed flue gases. This acidic moisture attacks the chimney from the inside.
That is why a chimney may look good on the outside, but the inside can be a totally different story! Years of normal use with hot and cold cycles and seasonal weather conditions all take their toll on a chimney.
Did you know, that for every cubic foot of gas burned, two
cubic feet of water vapor is created? That is a lot of water!
How can this water vapor affect your chimney?
Water vapor always travels up your chimney - it is only
when flue gases drop to 120oF, that condensation begins.
When water vapor condenses, ‘rain clouds’ form, and it literally rains in your chimney! Countless drops of acidic moisture soak the flue.
This is more of a problem now than it was in the past due to modern,high-efficiency furnaces. High-efficiency furnaces, as their name indicates, extract more heat from a given amount of fuel than conventional furnaces, and less heat is lost up the chimney.
However, since less heat is sent up the chimney, the temperature in the flue is often below 120o. The acidic ‘rain’ happens frequently, and the flue seldom has a chance
to dry out. Herein lies the side effect of high-efficiency furnaces: excessive acidic moisture in the flue. In turn, this acidic moisture wreaks havoc on terracotta flues and masonry.
It happens thousands of times each year. Damaged chimneys equal disaster. Carbon monoxide quietly leaks unobserved through cracks in the flue lining and into the home. Even small amounts can make you and your family sick. The risk of a chimney fire turning into a house fire is another serious risk. There are two ways that a chimney fire can ignite your home:
1) A chimney fire is like a huge torch, and the flames can escape through cracks in the flue tile and then through cracked mortar in the surrounding brick, and directly set your house on fire.
2) Chimney fires can rage at temperatures upwards of 2000 degrees. This extreme heat can bring structural materials surrounding the chimney to a flash point, and just by heat alone, can ignite materials in your house.
A cracked flue tile is serious business!