Independent performance of calculations of the height of the chimney with formulas and examples

Although it may seem difficult, you can calculate a chimney’s height on your own if you have a basic understanding of a few important formulas and examples. For homes and commercial buildings to have adequate ventilation and safely release gases into the atmosphere, chimneys are essential. Achieving the proper height is crucial for both effective operation and adherence to safety requirements.

Taking the draft, or pressure differential that propels the gas flow, into account is one of the basic formulas used to determine chimney height. In order to ensure that smoke and gases are efficiently evacuated from the building without creating backflow or stagnation, the height must be sufficient to generate this draft.

Chimney height calculations for residential applications, such as homes with wood stoves or fireplaces, usually take into account the fuel type and flue diameter. These factors affect the rate at which gas is emitted, which affects the height at which appropriate airflow must be maintained.

On the other hand, because of their higher emission volumes and more stringent environmental regulations, industrial chimneys frequently call for more intricate calculations. Important factors to take into account when determining chimney height include the temperature of the exhaust gases, the direction of the wind, and the dispersion of pollutants in the atmosphere.

The location of the chimney and the direction of the wind: how to prevent swirls

Every building code and regulation stipulates that the chimney must rise a specific distance above the roof. This is required to prevent reverse traction from air on the roof’s protruding sections caused by twisting.

The smoke that enters the room directly from the fireplace is an example of reverse traction. However, the additional height of the chimney is also unnecessary because, in that case, the firewood will burn like a match, giving off no time to provide heat, and the craving will become too great.

Because of this, it’s crucial to determine the chimney’s height as precisely as possible, especially considering the direction of the winds in the area:

The pipe needs to be extended with steel or asbestos-cement pipe if it is situated too close to tall walls or dense trees.

This video contains helpful advice on installing a chimney and resolving height-related issues.

Traction power: how to achieve perfect combustion of fuel

Many significant factors influence the very power of traction simultaneously:

  • chimney manufacturing material;
  • foundation height above sea level;
  • the temperature of the smoke gases at the output of the furnace;
  • the shape of the transverse section of the chimney;
  • smoothness or roughness of the inner surface;
  • violation of the internal tightness of the chimney;
  • the temperature and humidity of the outer air;
  • ventilation of the room with a boiler or stove;
  • the fullness of fuel combustion;
  • the degree of contamination of the boiler (or furnace) and chimney;
  • type of burner used (modulating it or discrete).

Initially, you must ascertain the chimney’s static traction value, which is expressed in size ∆p [PA]. This is the calculation formula:

Tt is the outside temperature, and Tr is the average temperature inside the pipe. By default, it is measured in degrees on the Kelvin scale; however, by adding +273, you can specify Celsius.

It is not hard to calculate the average temperature. It is typically reported to the boiler in technical data, but cooling should also be considered. This is one degree for every meter of brick pipe, two degrees for every meter of isolated steel pipe, and five degrees for an uncovered pipe.

In this instance, it is preferable to use the outside temperature to determine when traction is most problematic during the summer:

Perform an aerodynamic computation to determine the precise height and diameter of the chimney that is required. The difference in the densities of the smoke and air gases multiplied by the house’s height is the traction’s inherent value. The chimney is five meters away, creating a vacuum and a desire for smoke.

What should be done, though, if raising the pipe height is not an option and the thrust is still insufficient for some reason? This is frequently the result of smoke gases cooling too quickly, particularly during the winter. The necessary pipe section is then just insulated to regain traction.

Additionally keep in mind that because of the resistance of the gases inside the pipe walls, real traction is always less static. Because the traction is affected by the loss of pressure along the entire length of the pipe, the more bends, horizontal areas, and the like in the chimney’s passing section, the worse the craving.

The chilly air coming from the fireplace is another issue related to the chimney’s height. Thus, cold air from the street is released from it when it malfunctions. This occurs when the attic is too big and poorly insulated, or when the chimney head is below the ventilation hood’s end.

The design of the chimney depending on the heating configuration

Proceed now. Which chimneys are installed most frequently these days? Brick, ceramic, and both insulated and non-insulated steel are among them.

First and foremost, the minimum indicators of the bandwidth are used to calculate it when designing a chimney. Smoke gases will build up inside the pipe and cause a lot of issues if you make mistakes here.

The chimney’s general layout looks like this:

In cases where the temperature of the released gases is low, such as in contemporary low-temperature boilers, the upper section of the chimney is equipped with what are known as electric smoke exhausters.

They resemble a tiny, bladed fan. By forcing the removal of combustion products from the pipe, this device strengthens the thrust. The height of the chimney is then unaffected by the strength of traction since it is obtained in a different manner and does not depend on "catching the wind."

You will still need to catch the wind if there is no extra device. And in this situation, you must increase the boiler, stove, or fireplace’s current power, which can be discovered in technical documentation. The quantity of fuel burned in an hour of labor is used to express it.

The following formula can be used to determine the volume of the gases if the amount of fuel is known:

B ∙ v ∞ (1+t/273)/3600 = Vg

The outcome will be expressed in m 3 /s. The gases in the pipe are moving at this speed. The following formula has already been used to determine the pipe’s cross section:

And in m 2 is found the resultant value. This is the chimney section’s area, and the following formula determines the diameter:

DT = -4∙ b∙ v∙ (1+t/273)/π∙ ω ∙ 3600

The majority of heating devices share nearly all of the remaining features. Thus, the gas output in a chimney typically occurs at a rate of two meters per second or faster, and the temperature of the gases at the pipe entrance ranges from 150 to 200 degrees.

Additionally, a standard gas pressure of at least 0.4 mm N2Oh, or 4 PA, per meter:

Consequently, SNiP states that the chimney’s height from the grater should be at least five meters.

Roof ignorance: when the spark leads to trouble

In particular, the fueling of the roofing material itself is important. In order to prevent sparks from reaching the roof, the pipe height should be raised by one to one and a half meters after applying a fireproof coating.

Will you be doing the chimney height calculation yourself? Our "All about the Roof" article offers clear, detailed instructions. Learn how to calculate the ideal chimney height using simple calculations and real-world examples. Knowing these calculations will help you ensure effective smoke dispersion and improved air quality in your home, whether you’re using a stove or a fireplace. Examine actual situations to develop the confidence you need to handle this crucial part of house maintenance with ease."

The dependence of the height of the chimney on other roof elements

The distance from the roof’s skate, parapet, or other components to the chimney itself is crucial.

Thus, there are the following guidelines regarding the chimney’s rise over the roof:

  1. Not less than 1.2 meters above a flat roof.
  2. Not less than 50 cm above the skate of the roof, if the pipe is located up to 1.5 meters from the ridge.
  3. Not lower than the skate level if the pipe is located from 1.5 to 3 m from the ridge.
  4. Not lower than the line that can be drawn from the skate to the horizon at an angle of 10 degrees if the pipe is located from the skate of more than 3 meters.

In this instance, the smoke channel ought to be at least a certain distance away from other structural components:

  • 150 mm for pipes with insulation;
  • 500 mm for pipes without insulation.

A pipe’s minimum height is 50 cm. However, these pipes are too low and should only be installed on flat roofs that have no outgrowths. If the roof has a more intricate design, you will need to make adjustments and consider every component that protrudes.

Thus, the pipe is just higher than all of these components if they are all placed 1.5 meters apart from the pipe. The chimney should be at least 59 cm taller than them if they are closer than 1.5 meters:

The location of the chimney exit from the house

They also have their own regulations regarding the installation of chimneys through walls and roofs. Here’s an illustration of a pipe installed straight through the roof:

If a one- or two-story house were constructed, it would not be difficult to withstand the chimney’s height of five meters from the grater to the upper cut of the pipe. However, issues occur if the fireplace is placed on the upper attic floor because there is not enough attic space and ceiling height.

In a slightly different way, the chimney is built into the house or bathroom wall:

Keep in mind that chimney pipes no longer than 0.4 meters should be used to connect stoves to chimneys.

Independently calculating a chimney’s height is an essential ability for anyone working on or building a roof. Comprehending the fundamentals and equations underlying chimney height computations allows both pros and homeowners to guarantee the best efficiency and security of their chimney systems.

First and foremost, it’s critical to understand the variables that affect chimney height. A number of important variables come into play, including the kind of fuel used, the flue’s diameter, and the chimney’s placement in relation to nearby structures. In order to ensure that smoke and gases are properly vented outside, a taller chimney increases draft efficiency.

Second, practical considerations serve as the foundation for the chimney height calculation formulas. For instance, the height is frequently established by weighing the natural draft against outside influences such as wind patterns. It is easier to design chimneys that function well in a variety of situations when one is aware of these calculations.

Finally, examples show how these computations are used in practical situations. For example, a taller chimney may be required to maintain effective venting in colder climates where draft can be more difficult due to temperature differentials. On the other hand, a shorter chimney could be adequate in places where weather patterns are stable.

All things considered, knowing how to compute chimney height gives professionals and homeowners the power to make knowledgeable choices regarding their chimney systems. These guidelines and equations can be used to guarantee that chimneys operate effectively, fostering environmental responsibility and safety at the same time.

Video on the topic

The case is a pipe. Full pipe.

Installation of the chimney of the boiler room

Is it possible to make such a high chimney #shorts

Posom pipes design | Basket design | Boiler room design

Dismantling the chimney by industrial mountaineering

Aerodynamic calculation of the stove chimney Part 1

Sazha caught fire in a smoke pipe.

What do you think, which element is the most important for a reliable and durable roof?
Share to friends
Alexandra Fedorova

Journalist, author of articles on construction and repair. I will help you understand the complex issues related to the choice and installation of the roof.

Rate author
Add a comment