So you just replaced your old gas furnace for a new high efficient gas furnace. This is a great idea with the prices of gas these days. But to save more money down the road you need to do preventative maintenance. You new furnace will destroy a masonry chimney. Your chimney needs a stainless steel chimney liner.
First of all
you may think my chimney has been here longer than I have and it hasn’t
had any problems. Exactly, that is the problem, when was the last time
you did any maintenance on your chimney? People maintain everything
and they understand if you don’t maintain something it deteriorates.
But for some reason people don’t think this applies to chimneys. They
think it is so old it can stand up to anything. Wrong.
Chimneys with terra cotta flues are designed to handle the gases from a
wood or coal fire. They are not designed to withstand the harsh gases
from a gas furnace. So how do you prevent this problem from happening?
Well instead of using a chimney liner that is masonry, such as terra
use a stainless steel liner.
New gas furnaces are extremely efficient. One of the by-products of burning gas is water. In older furnaces or ones that are less efficient, a lot of the heat went up the chimney and the furnace kept that moisture as a hot steam and the steam exited the chimney into the atmosphere. However today, the same amount of moisture goes into the chimney but with much cooler temperatures. So especially in the winter with colder temperatures outside, the moisture and exhaust enter the chimney and as it rises and it cools down the moisture which produces condensation that then soaks into the masonry. This creates multiple problems. The problems start from the top and work their way down. This is because the flue gases cool down the farther they travel up the chimney. When they cool down this is when the moisture condensates and the water soaks into the masonry.
Installing a stainless steel chimney liner for a gas furnace is a job an average handy man can do.