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All About Chimneys

Who doesn't love a nice cozy fire crackling in the fireplace? A fire never ceases to bring people together — whether it's to warm up, roast marshmallows or enjoy a drink and good conversation. None of this can happen however without one very important element, the chimney. While often an afterthought to the rest of a home, the chimney plays a very important role. Just how much do you know about your chimney?

purpose, types and parts of a chimney

Purpose of a Chimney

The purpose of your chimney is to allow smoke and other gases (like carbon dioxide) to rise above the heat source (usually a fire) and out of your home. While it's most common to see a chimney attached to a fireplace, chimneys are also necessary for other fuel-burning heat sources such as gas, oil or coal.

How does it work?

You may be wondering why the smoke and other gasses don't just pour right out of the fireplace itself. Well, the phenomenon that occurs is called a 'draft' and airflow is the key ingredient in this process for a correctly functioning chimney. Ever heard the saying "warm air rises?" The combination of proper airflow and heated air/smoke/gases means that everything will float up and be swept out of the chimney by airflow.

Types of Fireplaces & Chimneys

The type of chimney is usually determined by the type of fireplace.

types of fireplaces and chimneys

Fireplaces types:

  • Masonry fireplace — built from bricks, blocks, stone or mortar they are usually built into the home when it's constructed. They are the most durable and if properly maintained, will last the lifetime of the home. They require little upkeep and can increase the value of a home. Masonry chimneys are usually constructed with this fireplace style.
  • Prefabricated/factory-built fireplace — are made from sheet metal and can be somewhat easily added to an existing home. They are much less expensive than a masonry fireplace but do not have the same life expectancy. The type of prefab fireplace will likely come as a set with a prefab chimney or will outline in detail what type of chimney must be used.
  • Wood-burning stove — typically made of steel or cast iron, these stoves made a comeback in popularity from the 1800s and include a stovepipe that rises from the base (a chimney is still needed). They are great for heating in chilly weather.

Chimney types:

  • Masonry chimney — typically built from bricks, blocks and stone along with mortar. With this type of chimney you can usually stand on the outside of a home and visibly see the chimney run from the ground all the way up.
  • Metal chimney — constructed from metal, they are usually double or triple walled. A prefabricated chimney will usually stick out from the roof with no detectable external part running to the ground.

Regardless of the fireplace or chimney type there should be a cap present made from steel or copper. Cap styles can vary and are often left to personal preference. The cap will help protect the chimney from things like debris, water, and animals.

Anatomy of a Fireplace & Chimney

You may assume that a chimney has a relatively straightforward design. In reality, there are many elements that make up a chimney and allow it to function properly.

  • Mantel — at one time used to catch smoke that escaped from the fireplace, it's now primarily a decorative element
  • Outer hearth — extends outside of the fireplace; built from a fireproof material
  • Inner hearth — floor of the fireplace inside the opening; also where the fire itself is built
  • Ash dump door (optional) — a small door on the floor of the inner hearth where ashes can be pushed into the ash pit for later cleanup
  • Ash pit (optional) — a cavity under the fireplace used to hold ashes
  • Clean out door (optional) — a larger door at the base of the chimney that allows you to access the ash pit for cleaning of ashes
  • Firebox — the interior space of the fireplace where the fire burns
  • Firebrick — the back wall of the firebox
  • Lintel — found just above the fireplace opening, its purpose is to help bear the load of fireplace created by the open space
  • Damper — a plate that closes off the fireplace from the chimney when a fire is not in use; While it can be left open at all times, it lets a lot of heat/AC escape up the chimney; It's best to close while not using a fire but must be open before building a fire
  • Smoke chamber — connects the fireplace and the flue; is designed to compress and push smoke up the chimney without creating a back draft
  • Smoke shelf — a flat "shelf" of sorts found just behind the damper; helps catch anything that makes its way in from the top of the chimney and helps with the transition of smoke up the chimney
  • Flue — the passageway up the chimney
  • Flue liner — in order to minimize the buildup of flammable debris in the flue (and reduce fire hazard), this liner must be used to cover the flue; typically made of stainless steel or a special tile
  • Chimney cap — is used to keep water, debris and animals from entering the tip of the chimney
  • Top-down damper (some fireplaces) — similar to the damper found at the bottom of a chimney, this is a second plate at the top of the chimney to help with drafts
  • Air space — the space designed between the chimney and flue liner to allow the flue liner to expand and contract due to varying temperatures

anatomy of a chimney diagram

Upkeep and Maintenance

To make sure that you enjoy your fireplace (and chimney) for many, many years and to avoid a potential fire hazard, it's important to complete routine maintenance and cleaning.

  • Sweep ashes out of the fireplace regularly. Ashes should not exceed more than 2 inches deep.
  • Clean soot and fire stains. While it can take some extra effort, doing so will keep your fireplace looking and performing great.
  • Have your chimney inspected and cleaned at least once a year. The inspection must be done by a professional and should ideally take place in the summer or early fall before you begin burning fires for the season. They will check for any structural damage and identify anything that needs repair.

    If your fireplace is used infrequently you may be able to go slightly longer between chimney cleanings, whereas if you use it regularly the chimney will need to be cleaned more often. Chimney inspections will identify whether cleaning is recommended and how often you should be prepared to have the chimney cleaned.

Phew! Who knew so much was involved in a chimney and fireplace, right? While a chimney and fireplace can appear rather straight forward, there are a lot of elements that must perform their function just right in order for us to enjoy a nice, cozy fireplace season. So the next time you start a fire, take a moment to appreciate how everything works. Happy marshmallow toasting!

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