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Chimney Liners
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| Why you may need to have your chimney lined when you upgrade your furnace! |
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Today's high efficiency gas furnaces can be 25% more efficient than the furnaces of just 20 years ago. Much of that added efficiency is achieved by keeping the heat in the furnace and not allowing it to escape up the chimney. This reduces the flue gas temperature, requiring a smaller flue to create proper draft.
Existing masonry chimneys are most often too large to create the proper draft required for today's high efficient gas furnaces and water heaters.
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This is a picture of a clay tile lined chimney flue used to vent a natural gas furnace. Notice the severe deterioration of the clay tile lining.
 This is caused because the flue gas temperatures leaving the furnace are not hot enough to keep the large masonry flue temperature above it's due point. The hot exhaust gases venting into the chimney are cooled by the cold masonry chimney and then the gas is turned into a liquid when it passes by the surface of the chimney walls.
This is exactly what happens when you take a hot shower and the steam escapes the shower and ends up fogging up the mirrors.
The difference is when flue gases condensate into a liquid they do so as sulferic acid which eats away at the lining of the chimney and will eventually do enough damage to cause the chimney to have to be replaced.
The solution is to line the chimney with a properly sized aluminum chimney liner which will protect the walls of the masonry chimney and provide proper draft. |
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| Which type of chimney's need to be lined? |
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This is a picture of an outside chimney. The chimney has two separate flues running through it, one for the fireplace and one for the gas furnace and gas water heater. This chimney should have an aluminum liner in the flue that is used for the furnace and water heater. The liner will also provide a cap for the top of the chimney.
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This home has an inside chimney. The majority of this chimney is located within the climate controlled portion of the home. This helps warm the chimney, which increases the dew point of the exhaust gasses enough to permit them to vent all the way through the chimney without condensing into a liquid state.
Note: The outside portion of this chimney does not begin at the roof line, it begins at the floor of the attic where the chimney is first susceptible to the outside temperatures.
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Is this an inside or an outside chimney?
Because the roof on this home is so steep and the chimney is so far towards the front of the house the chimney is required to extend a considerable distance beyond the climate controlled portion of the home. This chimney should have an aluminum liner installed for best long term safety and economy. |
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This home has a metal chimney, which is used for the fireplace. The gas furnace and gas water heater are direct vented through the side of the home. This can be done only when installing an ultra high efficient gas furnace and a special direct vent gas water heater.
NOTE: There are very specific limitations on where a direct vent appliance may be vented. Ground level as well as window and door placements must be taken into account. |
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Important Note:
When upgrading an older gas furnace to a new ultra-high efficiency model that uses direct venting (No chimney needed.) it is important to remember to install an aluminum chimney liner in the existing masonry chimney if a water heater is going to be left venting into the chimney. |
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