Such a simple thing as a cap on the chimney pipe raises many questions: what should it be, how to make a visor with your own hands and in general, whether it is necessary to install it? Discussion and debate on this topic occupy more than one page of a popular forum, but you will not find a definite answer there. Let's try to solve these problems on our own, starting with the need to install a protective cap.
Chimney umbrella - pros and cons
The following arguments speak in favor of installing a variety of caps (other names - fungus, umbrella, flygar, chimney) on the tips of the chimneys:
- the umbrella partially covers the mouth from blowing by the wind and thus reduces the likelihood of tipping over;
- the smoke box serves as protection against ingress of debris and moisture in the form of precipitation;
- if you apply a mesh structure, then inside the chimney can not nest birds;
- the product extends the life of the tip of the brick pipe, destroyed by wind, rain and snow;
- fungus with decorative elements complements the architectural style of the building.
Note. In compiling the list, we did not take into account the inaccurate information of advertisers. Statements that umbrellas increase draft in chimneys and increase efficiency of coppers are the purest fiction.
Now consider the counterarguments. The main negative point is that the visor to the chimney in the form of a fungus stands in the way of combustion products. That is, it prevents the free exit of gases, creating a tangible aerodynamic drag. This means that the chimney umbrella does not increase traction, but rather reduces it.
The second minus from the use of nozzles is repeatedly confirmed by sad statistics. The fact is that one of the products of the combustion of hydrocarbons is water vapor, leaving the atmosphere with smoke. Diesel and gas domestic boilers with high efficiency emit gases with a low temperature (up to 120 ° C). Rising through the pipe, they cool, then come in contact with the metal of the hood.
Water vapor immediately condenses and freezes at minus temperatures, which is why icicles form on the umbrella, blocking the cross section of the chimney, as shown in the photo. As a result, the waste goes into the room and poisons the residents of the house. There are other arguments against mounting fungi:
- In modern round chimneys, there is nowhere for birds to settle, so it is not necessary to cover them with a net.
- A well-constructed gas duct has a condensate collector with a drain at the bottom, where water that flows into the pipe in the form of precipitation will safely drain.
- The thin galvanized caps installed on the chimneys of solid fuel boilers and furnaces burn out in 3-5 years due to constant contact with high temperature gases (150-200 ° C). It is necessary to put a stainless steel reflector that increases the price of the product.
Should I put on a cap - recommendations
Regarding the installation of umbrellas on chimneys, regulatory documents from different countries put forward various requirements. For example, in European countries it is allowed to mount nozzles only on ventilation ducts, and chimneys are strictly prohibited. In Ukraine, caps cannot be placed on pipes connected to gas boilers. There is no direct prohibition in the Russian Federation and Belarus, but the wording of SNiP is very vague:
"Deflectors, umbrellas and other nozzles in the chimneys must not impede the free exit of combustion products."
We suggest approaching the issue from the point of view of safety and practicality, and only then think about beauty. Before you make and put the hood on the chimney, consider the following recommendations:
- Round steel pipes that remove smoke from highly efficient boilers with an efficiency of more than 85% cannot be closed with a traditional fungus. Use a cone nozzle in the form of an open nozzle that does not ice up in any frost.
- A brick chimney without inserts connected to a heat generator with high efficiency can be protected with a nozzle in the form of a cover with a through-through pipe, as is done in the photo.
- Umbrellas are allowed on vertical channels from furnaces and TT boilers. In order for the iron peak to perform a protective function on the chimney for a long time, provide a stainless steel plate inside.
- It is very desirable to mount gable or hip caps on chimney blocks made of brick and equipped with side vents. The goal is to close the upper part of the masonry from precipitation and wind, without touching the flue holes on the sides.
To protect the brick block, where the exhaust and chimneys are open at the top, order or make a box with several through pipes to be inserted into these channels. Place ordinary fungi on the top of the ventilation leads, and cone nozzles on the gas ones, as shown in the photo.
How to make a visor on the chimney
First of all, you need to find out the external dimensions of the head, where you plan to mount the umbrella, and then sketch by hand a sketch with the image of the future design. To develop it, use simple rules:
- the dimensions or diameter of the product should be 10 cm larger than the dimensions of the pipe so that the edges protrude 50 mm from all sides;
- slope angle of slopes - from 30 to 45 °;
- the minimum height from the cut of the chimney to the fungus is 100 mm, as shown in the drawing.
In addition to the traditional umbrella, there are other design options - a deflector and a rotating weather vane - “sneak”. The first allows you to really increase traction due to wind pressure, which creates a vacuum inside the cylindrical body, where the smoke channel exits. But in calm weather, this device not only loses its advantages, but also worsens the traction in the pipe, creating increased resistance at the exit of the combustion products.
For reference. The same effect is created by rotary spherical nozzles, whose example is shown in the picture.
A semi-cylindrical weather vane, assembled from several segments and rotating on a special bearing, was called "sneak" due to the ability to turn in the wind. If it were not for the high price and dubious reliability of the bearing, it would be an ideal cap for any round chimney, since it successfully protects the mouth from blowing and precipitation.
Various materials are used for the manufacture of chimney visors - sheet steel with zinc and polymer coatings, stainless steel and even copper. To make a cap on a pipe with your own hands, we recommend the first 2 options - galvanized or painted metal with a thickness of at least 0.5 mm.
Making a simple round fungus
To carry out this work, you will need ordinary tools - metal scissors, a drill, a hammer and a rivet tool. Having determined the required size of the fungus, proceed in this order:
- Screw 2 self-tapping screws into the wooden plank at a distance equal to the radius of the product plus 15 mm. Get an impromptu compass, with whose help outline the center of the circle on the metal and draw its outline.
- Cut the workpiece with scissors, and then draw a sector with an arc length of about 120 mm (the figure resembles the first piece of a round cake).
- Cut this wedge, and then with effort, combine the outer edges of the circle and fix them in a vice.
- Drill 3 holes along the resulting seam and connect the ends of the part with rivets or M4 screws with nuts. The top of the flyboat is ready.
Rectangular gable umbrella
For the manufacture of this kind of caps, it is advisable to use a machine - bending machine or apply for this service to the appropriate workshop.In an extreme case, you will have to bend the elements manually along the line, gently tapping the metal with a rubber mallet on a wooden bar.
As in the previous version, the first step is to remove the outer dimensions of the brick chimney, and then calculate and sketch the pattern, as shown in the drawing. Here are the formulas for determining the lengths of the sides of the elements depending on the initial dimensions of the pipe and the height of the flyboar.
Tip. The lower part, encircling the mouth of the smoke channel, is best done in the form of a Z-shaped profile with angles of 90 °, which subsequently "sits" on top of the head. Then these profiles are joined into a solid frame with rivets.
Making a cap on a pipe with your own hands is relatively simple - you need to cut the metal according to the drawing, bend along the dashed lines and connect the parts with rivets. It is proposed to take ready-made corners of painted metal with a thickness of 0.5-0.7 mm as rigid racks. How is the assembly of a gable windshield and a visor in the form of a lid with a pipe passage, clearly shown in the video:
Conclusion
As you probably managed to notice, for the manufacture of a round and rectangular hood chimney does not need to be a master of tin works. It is enough to have a desire, stock up on patience and time to save money on the purchase of this simple part. For those who are not interested in the traditional designs of fungi, we suggest watching the latest video on self-assembly of a weather vane - "sneak".