Ventilation Deflector: Best Way to Improve Air Circulation

Ventilation Deflector: Best Way to Improve Air Circulation

In order for a person to be comfortable in the room, it is necessary to ensure normal air circulation. Continuous air exchange creates a properly organized ventilation system, but its efficiency depends on the internal draft. If you do not install a ventilation deflector, there is a risk that the duct will become clogged with debris and stop functioning.

What is an air deflector?

The effective operation of the ventilation system is primarily influenced by the strength of the wind, its direction, as well as the air temperature. For example, in summer it is very hot outside, and due to the fact that the air heats up, the draft decreases and, accordingly, the air circulation decreases. To reduce the impact of such negative influences, devices such as deflectors are installed. The use of structures is considered mandatory when organizing a chimney because a deflector is primarily a device that normalizes the operation of a ventilation system.

Ventilation deflector
A dome, ball, or other structure that is installed on the roof and acts as a deflector

Fact! To understand what a deflector is, refer to the images of the outlets of the ventilation pipes. It is the dome, ball or any other structure located on the roof that is the deflector. The main task of the device is to ensure normal ventilation of various kinds of premises by using wind loads.

By and large, the deflector is a fairly simple device that was previously used only when equipping chimneys, and now it is the crown of the ventilation system. At the same time, one should not think that the only role of the device is protective.

In fact, deflectors are aerodynamic devices that reduce the negative impact of weather factors on ventilation. It functions according to the principle of the Bernoulli effect. The main task of ventilation deflectors is to provide better traction within the system by regulating the airflow.

That is why the devices are installed at the highest point of the pipe. Gadgets can be seen in most garages, which are topped with pipes emanating from basements or basements. In addition, deflectors are located almost everywhere on the roofs of houses.

The main task of the deflectors is to provide better traction within the ventilation system.

What does a vent deflector do?

As already noted, after installing the duct deflector, the thrust increases significantly. This is because the structure deflects the air currents and forms a zone of reduced pressure at the outlet of the ventilation. It is for this reason that the air masses inside rise through the pipe and compensate for the lack of pressure.

On trading floors, you can find a large number of design varieties, but, despite this, they all work on a similar principle. Some manufacturers produce deflectors with narrower channels to increase the speed of air passage over the pipe head. In this case, the “airbrush principle” is triggered, and the thrust effect becomes several times greater.

Ventilation deflector
Chimney deflectors increase draft and provide a protective function

Choosing the right air deflector can significantly increase ventilation efficiency. Sometimes productivity increases by 20%. Devices installed on ventilation ducts, characterized by a large number of horizontal and winding sections, work best.

The main task performed by the deflectors installed on the roof is considered to be the shelter of ventilation ducts from the penetration of contaminants, as well as birds and other living creatures from the outside. Even in a short time, small debris, fallen leaves, dust, and other particles accumulate on the walls of the pipe, thereby leading to a narrowing of its diameter. For these reasons, the entire system can fail. Other instrument functions:

  • protection against atmospheric precipitation;
  • increased traction;
  • increasing ventilation efficiency up to 20%;
  • extinguishing sparks and ensuring fire safety;
  • preventing the appearance of the reverse draft, the so-called overturning effect of ventilation.

Elements of ventilation deflector

In order to better understand how the deflectors of ventilation systems work, you need to know what the structure consists of and what the circuit of the device looks like. So, the main components of the ventilation attachment are:

  1. Diffuser. It is a cone-shaped base with a truncated bottom. The lower part of the cylindrical flask is attached to the upper part of the ventilation duct that opens onto the roof, which results in a slowdown in the airflow and an increase in pressure.
  2. Umbrella. Detail preventing the penetration of debris into the ventilation duct. It looks like a protective cover attached to the top of the diffuser.
  3. Housing. Visible detail of the deflector. It is represented by a shell or rings, which are connected to the diffuser using two or three brackets. It is due to the fact that the elements of the body cut the air flow that reduced pressure is formed inside the cylindrical flask.

To prevent precipitation from entering the system, the diameter of the diffuser must be larger than the size of the inlet. The housing is installed in such a way that the air creates the so-called suction through the recesses of the adjacent rings. In this case, it will be possible to accelerate the removal of air masses from the ventilation system.

Ventilation deflector
To prevent precipitation from entering the system, a protective umbrella is installed

It is interesting! The ventilation deflector is designed in such a way that the air currents that rise from the bottom up are reflected from the roof, and then begin to descend again. Most often, this happens when the wind is blowing from below. If such a problem is present, it is better to install a two-cone structure, where the elements are connected by one base.

You must also understand that if there is a side wind outside, then the air flow will come out through the lower and upper parts. With a vertical wind direction, only air outflow from below will be present. In short, the principle of operation of the deflector installed on the hood looks like this:

  • wind streams are captured by the device;
  • the air flow enters the diffuser, forks and leads to the fact that the pressure in the upper part of the duct decreases;
  • the exhaust air from the room rushes upward – to where the discharged void has formed and is discharged into the street.

If you choose the right size of the deflector and correctly install the structure on the upper part of the exhaust duct, the pressure difference will be optimal, as a result of which the rate of air exchange is normalized.

 diffuser slows
The diffuser slows down the air flow and increases the pressure

Types and characteristics of deflectors

If you look at the photo of the deflectors, you will notice that they all look different, but nevertheless they perform the same functions. Therefore, before giving preference to one of the models, you should pay attention to the following criteria:

  • material of manufacture;
  • principle of operation;
  • design features.

Basically, all models are made from the following materials:

  • aluminum;
  • of stainless steel;
  • galvanized;
  • copper;
  • plastic;
  • ceramics.

Checked! Ventilation experts believe that deflectors made of steel or aluminum are optimal in terms of price / quality ratio. Copper devices are also good, but due to the high cost, they are rarely used.

Devices are divided into the following types:

deflector can be made of aluminum
The deflector can be made of aluminum, stainless steel, galvanized, copper and plastic
  • diffuser;
  • Volper cylindrical ventilation fungus;
  • a weather vane cap;
  • H-shaped pipe deflector;
  • turbo-reflector, which is a spherical rotary nozzle;
  • open-type static-dynamic device Astato.

Some also include the regular umbrellas at the top of the canal. It should be understood that such devices only help to cover the ventilation from rain, but do not in any way affect traction.

Open structures also differ in shape, the following devices are considered the main ones:

  • flat;
  • semicircular;
  • with opening lid;
  • gable.

In addition to the fact that the devices are divided according to the type of weather vane, they are also classified according to the principle of operation:

  • rotary;
  • deflector;
  • turbine.

The device, according to the principle of operation, can be rotary, deflector and turbine

Chimney deflectors are primarily installed in order to improve draft, which removes smoke and carbon monoxide outside. In addition, after the installation of the device, heat transfer increases, and the fuel burns out better. Various photos of deflectors on the chimney also make it clear that with the help of the device, the pipe is protected from precipitation and other debris brought from outside.

Deflectors for the air conditioner, which in appearance differ from conventional devices, can be distinguished into a separate group. This design is a reflector screen that redistributes the air flow. As a result, the bundle of cool air is not directed directly but parallel to the ceiling. Despite the fact that the air is dissipated, the pressure does not change from this.

Deflector and other designs

The basement deflector is primarily intended for the ventilation of basements and lower floors. After installation, not only the circulation of fresh air is established, but excess moisture from the surfaces also evaporates. It is considered convenient that devices can be mounted in the case of both forced and natural ventilation.

In addition, the advantage of the deflector is that it protects basements and basements from the penetration of rodents and other small pests, as well as from precipitation. When installing, it is better to take a pipe with a margin in length, because it can always be reduced to the desired height, but it will not work to grow.

Ventilation deflector
deflector consists of a glass, a cylindrical body, an umbrella-shaped cover and mounting posts

The design was developed back in the days of the Soviet Union and is still used with success. If you refer to the drawing of the deflector, you can see that it consists of the following elements:

  • a glass located at the bottom of the structure with an extension at the end;
  • a cylindrical body, represented by a shell made of steel;
  • umbrella-shaped cover;
  • fastening racks made of metal strips.

The principle of operation is as follows: due to the blowing of the housing, a rarefied zone is created, located above the open diffuser. The exhaust air, mixed with carbon monoxide and other components, rises through the duct to the area of ​​the formed low-pressure zone and goes out. Here it is picked up by the wind and completely removed.

Important! The performance of the roof ventilation deflector depends on the resistance of the duct system crossing the roof. The actual volume of the device is determined by the height of the pipe extension. The indicator is also influenced by the temperature difference between indoor and outdoor air.

Despite the fact that the device was developed a very long time ago, it is still considered the best ventilation deflector for increased traction. The high rating of the device is due to a large number of advantages:

  • providing maximum protection against the penetration of precipitation;
  • preventing the thrust from overturning, that is, drawing exhaust air back into the system;
  • lack of dynamic details;
  • reliability;
  • the minimum coefficient of resistance, which does not exceed 0.6.

Among the advantages, the fact that it is quite easy to make a deflector with your own hands also stands out. And most importantly, the productivity of the installation is completely unaffected by wind currents, although it should be noted that the device does not work effectively at low wind speeds. So, if the external air flow moves at a speed of less than 2 m / s, the efficiency of the deflector tends to zero. For the sake of fairness, it should be noted that in calm weather, most of these devices do not work well.

Over time, the design of the device nevertheless improved, because, in the manufacture of the latest serial models, the lower glass was insulated (in those cases when the cap was mounted to a sandwich pipe on the roof).

Ventilation deflector
The correctly sized deflector will provide the optimum pressure difference

Other variants of ventilation deflectors series 5.904 51

Volper’s static umbrella is more of a wind deflector than a traction enhancer. Despite this, the nozzle successfully compensates for the pressure loss at the outlet of the stream. According to the drawings, the structures consist of the following elements:

  • a lower glass or branch pipe;
  • the upper glass of cylindrical shape, characterized by concave walls;
  • umbrella in the form of a cone;
  • connecting strips.

The nozzle is mounted on an air duct with a circular cross-section, and in the presence of a rectangular shaft, a special adapter is used. The principle of operation of the Volper umbrella:

  1. Direct wind streams are reflected up and down due to the concave surface of the upper shell.
  2. Air masses, which pass between the umbrella and the plane of the glass cut, form a low-pressure region inside the nozzle.
  3. The air from the hood changes the direction of movement, that is, it comes out through the gap located under the “fungus”.

In terms of efficiency, the Volper umbrella is significantly inferior to the work of deflector, but at the same time, it more reliably protects the air duct from sudden gusts of wind. Because it is technically difficult to make an exhaust umbrella with a curved glass with your own hands, many simplify the design and give it the shape of a cone. To increase productivity, a similar glass is installed in a mirror image, which is placed under the umbrella.

The H-shaped deflector is presented as a tube assembly and has the shape of the letter “H”. In this case, the hood is connected to the middle part of the crossbar. After installing such a structure, it becomes unimportant from which side the wind blows into the open pipe, because the flow will in any case eject, it is easier to say, carry away the flow of polluted air from the ventilation riser.

Among the advantages of a deflector for an H-shaped ventilation pipe are:

  • almost 100% protection against wind ingress;
  • prevention of reverse thrust effect;
  • no possibility of moisture penetration or freezing of the system.

In addition to the advantages, there are also disadvantages of installing the nozzle:

  1. Violation of aerodynamics. To go outside, the exhaust air flow needs to overcome 2 turns located at an angle of 90 degrees. Despite the fact that the wind flow compensates for this deficiency, the traction force still increases minimally, due to which the extraction performance decreases.
  2. Large construction size. Due to the fact that the device is quite cumbersome, difficulties may arise during the installation process.
  3. Not too attractive appearance. The volumetric structure brought out to the roof is characterized by the presence of 2-3 channels, which are crowned with such caps, which may look strange from afar.
H-shaped deflector
The main advantage of the H-shaped deflector is 100% wind protection

Helpful advice! To assemble a ventilation deflector with your own hands, you will need to take several ready-made tees and connect them together. Such a device is suitable for ventilation of both a bath and a warm barn.

What are turbo deflectors and weather vane

The designs can be safely combined into one group because they are not only similar to each other but also have a similar principle of operation. If we consider the drawings of turbo deflectors, you can pay attention to the fact that a distinctive feature of the devices is the spherical shape of rotary devices with blades in the form of semicircles, which rotate under the influence of wind force. In this case, rarefied air, which increases the efficiency of the hood, is formed inside the sphere above the pipe head.

The productivity of the weather vane is ensured by the fact that the blades of the device always turn with their “backs” to the wind, thereby preventing the ingress of air flows into the channel. A low-pressure zone is formed behind the structure body, the so-called aerodynamic shadow, which facilitates the rapid removal of polluted air from the vertical channel.

Among the advantages of a ventilation turbo deflector are:

  • protection of the ventilation duct from overheating in summer, which allows you to reduce the cost of cooling the room on hot days;
  • prevention of condensation formation under the roof by regulating the temperature in the heat;
  • no need to connect the device to the electrical network;
  • ensuring efficient operation, because the productivity of the turbo-reflector in some cases is 200% higher than that of static models.
 turbo deflector
The main advantage of a turbo deflector is that there is no need to connect the device to the mains.

In addition, we can separately note the fact that the nozzle has an attractive appearance. Unlike other models, the device looks like an elegant ball-shaped hood. After installing the deflector, excess heat, moisture, fine dirt, and carbon monoxide vapors are independently drawn from the mine and the under-roof space. This increases the useful life of important building elements.

Before purchasing a ventilation turbo deflector, you should also familiarize yourself with the main negative aspects of the device:

  • if there is no wind outside, the blades of the structure will not rotate and, accordingly, the thrust will not improve;
  • deflector rotation units require constant maintenance, at least regular lubrication;
  • if not noticed in time, complete or partial freezing of the nozzle is possible;
  • design features do not allow the device to reliably protect ventilation from the penetration of precipitation, especially on windy days;
  • in strong winds, there is a possibility that the jammed weather vane will lose its integrity.

The relative disadvantages include the fact that the price of dynamic type deflectors is higher than the cost of static models. For example, the cost of umbrellas and deflectors of ventilation systems 5.904 51 does not exceed $ 20-30, while turbo deflectors can be purchased for at least $ 35-40, while the equipment requires constant maintenance.

Ventilation deflector
The productivity of the weather vane is provided by the blades, which always turn the device “back” to the wind

What is Astato roof ventilation deflector?

An important advantage of the deflector is productive work in any weather, even when there is no wind at all. If you study the drawings of the deflector, then you can pay attention to the fact that the structure is a nozzle made of two truncated cones, which are turned tops towards each other. On the upper part of the device, there is an umbrella and an axial electric fan. The side opening with an aluminum mesh is closed from birds and other animals. Among the features of the device, the following points stand out:

  1. In strong winds, the nozzle acts as a static amplifier. Even if the fan is off, the exhaust air flow passing between the mirrored cones is picked up by the street air and removed.
  2. In calm weather or in low wind conditions, a pressure sensor, the so-called pressure switch, is automatically triggered, which transmits a signal to the EOL control unit. After that, the controller activates the fan, the forced removal of contaminated air from the mine begins.

It is interesting! The controller response threshold is determined and configured by the user independently. A universal static-dynamic deflector can be triggered without expensive automation, because the function of switching on manually or from a temperature relay is available.

Ventilation deflector
The Astato roof ventilation deflector is one of the most expensive devices of this type.

A significant disadvantage is the high price of a ventilation deflector: even a nozzle with a minimum diameter of 16 cm will cost the user 1300-1400$. If you want the device to automatically respond to changes in the ambient air, you need to add to this price the cost of the EOL unit, which is 1520$.

How to choose a ventilation deflector?

If you need to choose a traction amplifier with minimal financial costs and not think about additional maintenance, you should opt for static deflectors: it can be a Volper cap or a nozzle. The main advantage of the second option is that it is quite simple to construct such a deflector with your own hands.

Basic recommendations for choosing a forced draft device:

  1. If there is a lack of trust, it is better to choose dynamic models of the hoods – this can be a rotary deflector or a weather vane.
  2. There is no need to save money when purchasing a rotating blade design. In cheap models, there is often an installed open hinge that will freeze in winter. When choosing a turbo deflector or wind vane, make sure that the bearing is closed.
  3. If the amplifier is planned to be installed in an area with predominantly windy weather, an H-shaped nozzle is recommended. If, on the contrary, the weather is often calm, the option of choice is deflector.
  4. The Astato nozzle, although it works in all weather conditions, requires regular maintenance. And this despite the fact that the cost of construction is very high.
Ventilation deflector
If there is a lack of trust, it is better to give preference to dynamic models of deflectors.

Features of the installation of the device and useful tips for correct installation

To correctly calculate the deflector, you need to measure the diameter of the exhaust shaft. If there is a rectangular exhaust duct, you should choose a device with a circular cross-section, the value of which is equivalent to the size of the duct. That is, you need to calculate the cross-section of a rectangle and take a circle with a similar area. It should also be remembered that in this case, for installation, you will need to additionally use an adapter.

So, first of all, you need to pay attention to the height of the ventilation pipe and the hood, which is determined depending on the location on the roof:

  1. Height 50 cm, if the duct is located closer than 1.5 meters from the edge of the roof.
  2. At the same level with the ridge or slightly higher, when the distance from the parapet to the ventilation shaft varies from 1.5 to 3 meters.
  3. If the pipe is removed by more than 3 meters, the height is selected so that the top of the deflector is not lower than the deflection line drawn from the ridge down to the edge of the roof at an angle of 10 °.

Important! If the building has a flat roof, the device must be installed at a height of at least 50 cm.

Ventilation deflector
It is optimal when the deflector is installed even at the stage of roof installation

Additional points to consider during installation:

  1. Do not mount the deflector in an area covered by the aerodynamic shadow of other buildings.
  2. The device should be installed where there is free airflow. It is best when the hood is the highest point of the roof.

When organizing the ventilation system, one should also not forget about how to properly install the ventilation grill – up or down. Most craftsmen focus on the fact that in the presence of forced ventilation one way or another, air will enter the mine, so when installing it is better to focus on how the wall will look after installation and whether the grill slots will be conspicuous.


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