How A Chimney Works

Have you ever wondered how a chimney works? Nothing beats a chilly night in front of the fireplace. If you have a functional fireplace, your chimney is vital to its effective operation.

Republic Roofing is here to help you learn about how a chimney works if you have not already!


So, Republic Roofing will analyze your chimney’s anatomy and explain its operation.

Here’s How a Chimney Works

Chimneys operate by removing byproduct gases from the air, such as carbon dioxide. Its job is to remove hot gases from your home‘s heating system, not hot air. Indeed, any heat source that consumes fuel (wood, oil, gas, coal) requires a chimney.

A gas stove, for example, has a chimney. This chimney operates much like your wood-burning fireplace.

What Is the Stack Effect?

A working chimney requires ventilation. The reason is the stack effect. These phenomena cause warm air to ascend and out of your chimney. 

This rising heated air is termed a draft in a chimney. A strong airflow draws gases and smokes out of the residence through the chimney. But, when your chimney doesn’t work properly, there’s an insufficient draft. Thus, your fireplace’s flames can snuff out or your interior spaces can fill with polluted air.

Four Main Elements Affecting Draft

1.     Air Pressure

Air pressure is the weight of atmospheric pressure on the Earth. When your home’s air pressure is in balance, the amount of air going into and out of the house is equal.

Your chimney allows lighter, warmer air to rise and out, and heavier, cooler air to replace it. Therefore, airflow in a house is not always a bad thing.

This is not quite the case, despite what you would believe. Negative air pressure occurs when a house is sealed too tightly or when too much air is blown out.

A fire may not burn, or a gas furnace may not function correctly if the home’s air pressure is negative.

On the other hand, if a house has many air leaks, it will operate like a chimney. As the heated air rises, it will go out of your house through the roof. Hence, your energy expenses will rise.

Do you want to know if your chimney is working properly? It is possible to discover and address the reasons for imbalanced air pressure in your house with the aid of a local chimney sweep or HVAC professional.

2.     The Flue

When too much air exits the chimney, it causes heat loss. But ff the flue is tiny; air cannot depart the chimney quickly enough. So, it would generate smoke in the room.

Also, flue liners improve a chimney’s efficiency. Every 10 square inches of fireplace opening requires an inch-wide flue. So, this 10:1 ratio allows air to flow freely through the flue.

3.     Chimney height affirms that taller chimneys provide a stronger draft. But how tall is “tall”?

·       The chimney should be 15 feet tall from the fireplace base (or insert) to the top.

·       The tip of the chimney should extend 3 feet beyond the roof penetration.

·       If your chimney is within 10 feet horizontally of another building or structure, it should be 2 feet taller than that barrier.

Extending your chimney’s height serves two purposes:

·       Lower wind-induced downdraft

·       Reduces risk of hot sparks or embers dropping on the roof

4.     Obstructions and damage

Finally, a drafty chimney must be clear of obstacles and damage. Still, a chimney’s compact, protected area combined with your home’s warmth makes it ideal for birds and squirrels to nest and store food. Likewise, bats and chimney swifts prefer dark and vertical spaces.

Flotsam or fowl, these impediments limit air passage and provide a fire risk.

Fortunately, the remedy is simple and inexpensive: a chimney cover keeps strange things and beings out of your chimney. Also, they keep water out and scorching sparks from landing on your roof.

Inspect your chimney

Annual chimney inspections can also help prevent damage and keep your chimney safe. The CSIA divides chimney inspections into three tiers. Based on its descriptions, select the appropriate level.

Now you know how a chimney works.

Then, you will need a roofer who understands that no two roofs are alike. Objects on or near a roof -like a chimney- can alter it. 

But we are here to help you improve your chimney and roofing system’s performance. We will work with you to create a roofing plan that includes our 50-year warranty.

Every Republic Roofing roof is a source of confidence. Call 901-437-5278 or contact us online to receive an estimate, book a free in-home consultation, or ask any concerns about house roofing. We service areas near Collierville, Memphis, Lakeland, and Bartlett, TN.