What is the Difference Between a Chimney, Flue and Vent?

Although chimneys may appear to be fairly simple structures, their makeup is actually much more complicated than most homeowners may realize. Your chimney may seem like it’s just the “cherry on top” for your roofline, but it serves a much greater purpose.

You’ll find that chimneys come in all different shapes and sizes. The average person may not know how to tell the flue from the vent, but no worries. In this article, we will provide a detailed description of the main chimney components and define the three terms that are most often confused: flue, chimney, and vent. 

Flue

The flue serves as a passageway for smoke, gas, or other products associated with combustion. It plays an important role in protecting other parts of the home from the heat generated from combustion byproducts, which are produced when burning a fire. 

Most modern-day homes have fireplaces with a lined flue. These flues are typically lined with tiles, asbestos-cement transite pipe, cement, or metal. However, because the materials will likely deteriorate over time, they may eventually require relining. If a chimney has a damaged flue liner, they will need to be fixed with a cast in place or stainless steel liners. This is to ensure that there are no gaps or holes that would allow hot air, gas, embers, or sparks to pass through.

Chimney

The chimney stacks vertically and extends out from the top of your home’s roofline.  This ensures that smoke, gas, and other products of combustion can safely exit your home. It is possible for a chimney to pass through other parts of your home before it actually exits your home. This is typically seen in houses that have a chimney not positioned on an exterior wall or is located on the first floor. 

As a rule of thumb, it’s better to make a chimney taller to avoid wind turbulence. You should aim to have the top of the chimney right above the roof peak. If the chimney penetrates the house envelope below its highest level, the chimney will not function as well. This is because the chilled air will pass through much of the chimney space.

It is common for chimneys to be designed from bricks, mortar, or other masonry. They can even be factory built and made using stainless steel material.  Sometimes factory built chimneys feature a more elaborate design that includes a decorative chimney chase covering, siding, or other roofing materials that complement the home.

In reference to your fireplace system, the chimney is the visible, exterior portion that is exposed to the various weather elements. It’s important that the chimney flue is the same size as the appliance flue collar. If your chimney is oversized for the appliance, this creates more draft which could put your home at risk of experiencing a potentially devastating chimney fire. 

Vent

Similar to fireplaces and flues, vents can also pass through different parts of the house. They also need temperature protection to stop heat from damaging the surrounding building materials. However, since vents are not designed to handle the high heat created from wood burning fires, they are most often installed with gas fireplaces. 

Vents may exit vertically through the top of the roof or horizontally through a wall. Some may even run through a chimney, as long as anything else venting through the space is contained in a separate flue. Vents help remove the byproducts from combustion just like chimneys and flues. At the same time, they also draw in air from the outside to help fuel the fire.  Doing this helps fireplaces with vents function more efficiently than what you will see with open hearth systems. 

If you’re unclear about whether your fireplace system functions using a chimney, flue, or vent, contact Chimney and Masonry Outfitters today. Our team of trained professionals can evaluate the health of your fireplace system and answer any questions you may have about how to keep them functioning at optimal levels.