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How Tall Should a Chimney Be?

Some homeowners find chimney length unsubstantial as long as it can expel smoke from the house and the bricks stay intact. However, proper functioning chimney is vital for your safety and heating performance. All parts of a chimney work together to exhaust fumes and keep the area safe to live in. Although some people say that chimney calculations are not proven science, there are legal codes and recommendations that should be adhered to for optimum performance and efficiency. This article looks at how tall a chimney should be and why chimney length and draft are important.

Chimney Height Rules

The height of a chimney is determined by the horizontal distance between the edge and peak of the high side of the pipe and the pitch of your roof. The 2-foot, 10-foot, 3-foot rule is one of the common formulas used to determine a close approximation of how tall your chimney should be. This means that your chimney should be 3 feet taller than the point where it passes through the roof, or at least 2 feet higher than any part of the roof within 10 feet of the chimney.

Looking it visually from the sides, the chimney should be the tallest point on the house. However, a chimney that is too tall cools off the heated air before it reaches the top of the chimney stack creating a negative pressure that pushes smoke and other gases back into your home. A short chimney leads to poor drafting problems because there is no enough internal pressure to expel the smoke and other gases outside. It can also lead to fire hazards or damage to the roofing tiles surrounding the chimney, which can be expensive to repair in the long run.

Why Chimney Length and Draft are Important

Any equipment that operates on combustion needs to replace the lost exhaust by exchanging it with an adequate source of the intake air. The best way to understand combustion is by looking at the three essential factors required which are, fuel to burn, air to provide oxygen, and heat to start the process. In chimney fire, a match is a flame, the wood is the fuel, and the air that provides the oxygen is in the form of the draft. The chimney height and the heat of gases in the chimney contribute to the draft size. The reason why a tall chimney creates a better draft is that there is a great differential pressure at the recommended height of the chimney.

Chimney Issues and Concerns

Although a proper stack height maximizes the efficiency of expelling dangerous gases and smoke from your home, other issues need to be considered when it comes to proper airflow. Solid fuels like coal and wood produce a high level of creosote, which can infiltrate the walls of the flue liner. This can cause restricted drafting because of the excess build-up of creosote that minimizes the effectiveness of smoke leaving the fireplace. Too much creosote can reignite causing chimney fire that creates a corrosive effect that extends to the outside.

The bricks of masonry fireplaces can retain moisture and freeze over the winter. This process can lead to the flaking and loosening of the bricks used on the chimney stack. This not only reduces its efficiency but also potentially dangerous for your safety and stability of the structure. It is important to follow a regular maintenance schedule to keep your chimney in good shape.

Chimney Sweep and Inspection

Proper sweep and inspection of the chimney are very important because drafting problems occur more often in a poorly maintained chimney. Since this process might be difficult and risky, it is important to hire certified professionals to inspect and clean the creosote buildup that may block the flue and cause smoking problems. Some people may think that the chimney height is not right when the fire takes longer to start or your house is repeatedly filling with smoke. Instead of jumping into conclusions about purchasing a new chimney, hire a trained masonry expert to look into the issue. It is still possible that unseasoned wood, a blocked flue, or a depressurized home could cause such problems.

It is important to install your chimney according to the legal building codes and recommendations as it determines the effectiveness of how smoke and toxic gases from the fireplace leaves the building. A chimney that is too short or too tall can create drafting problems, chimney fires, or negative pressure that pushes back smoke into your home. Even if you have the right chimney height, it is still important to conduct regular inspection and maintenance to ensure your chimney is operating effectively and efficiently.

Posted in Chimney Installation, Chimney Service

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