How to choose and install the air duct for the hood

Choose and adequately install the air duct for the chimney – an essential point in the kitchen arrangement. This will depend on the air in the room, the noise level, the aesthetic appearance of the kitchen. And ultimately the health of the whole family.


Differences between the kitchen exhaust system and ventilation

The ventilation system is designed for constant updating of the air in the room. It is equipped in the kitchen and toilets. Most often, the scheme of natural urge is used. The capacity for the kitchen is 60 cubic meters per hour, for the bathroom – 25. With poor ventilation, condensation accumulates in the house, over time, a fungus may appear. This is dangerous for the development of diseases of the respiratory system.

In the ventilation device, air exits through special channels inside the walls to the roof or the attic. The movement of flows is carried out due to the temperature difference inside the house and outside and the pressure difference. Inside the room comes new air through the cracks of windows, doors.

The exhaust system is installed in the kitchen to remove odours, excessive humidity and oil waste generated during cooking. The chimney thanks to the work of the fan, forcibly draws air from the kitchen, then it is diverted through the duct into the ventilation duct. Installation of air ducts for the kitchen chimney should not disrupt the room’s ventilation.


Is it always possible to install the chimney?

It is forbidden to connect the air duct to natural ventilation tightly. On the way to the exit, the air must overcome obstacles from the oiled mesh, motor and turbine. In addition, air intake is carried out not under the ceiling, as expected, but from the chimney level. All this makes ventilation inefficient, especially in the summer, when the thrust is weak. In addition, a complete blockage of general ventilation can lead to the accumulation of natural gas in the event of a malfunction of gas equipment and cause an explosion.

Therefore, the air ducts for the chimney are mounted in unique ventilation grilles with a check valve. There is a hole for the air duct in such a grid on top and slots for ventilation at the bottom. When the chimney is turned off, air freely passes through the holes and air duct. During the operation of the device, the valve does not allow the exhaust air taken by the umbrella to return to the kitchen.

The check valve can be in the form of:

  • film
  • plastic disc on the axis,
  • one-piece partition.

You need to install it vertically at an angle of 2 degrees. In this case, the valve opens under the influence of its gravity, although it does not protect 100% from the back ingress of dust.

It rarely happens that there is no ventilation shaft in the house; there is no entrance hole in the fitting room. Or, in old houses, natural ventilation is severely disturbed, and the air drawn out of the kitchen gets to the neighbours. For such cases, recirculation chimneys are suitable. The principle of their work is that they take attitude from the kitchen, pass it through filters (carbon, fat), and return it. The disadvantage of such a system is the need to change the filters constantly. It’s expensive and uncomfortable. In addition, such chimneys do not solve the problem of high humidity in the room.


Types of air ducts for extraction. Advantages and disadvantages

air duct

The air duct to the chimney can be attached flexible or rigid. The most popular models are made of plastic and aluminium. The choice of the buyer also depends on the financial capabilities and the overall style of the kitchen.

Plastic air ducts for extraction

They have a neat appearance, fit into almost any interior of the kitchen. Flat surfaces are less polluted and easier to clean; they do not rust. Less noise is created when air passes through the pipe. Since this is a rigid product, a more accurate size calculation is required. Adapters and connecting elements are mandatory when installing an air duct made of plastic for a kitchen chimney. Turns are sharper than flexible products. It costs more.

Plastic is not as resistant to high temperatures as metal. If necessary, it can be covered with moisture-resistant and heat-resistant paint in the tone of kitchen furniture.

In the form, there are:

  • round – in this case, you do not need an adapter to connect to the chimney;
  • oval;
  • square;
  • Rectangular air ducts. They are convenient to hold along the wall above the kitchen furniture. You can assemble the design of any trajectory. One of the options for rectangular is flat air ducts, which take up very little space and are almost invisible.

Transitions from round products to rectangular ones and vice versa are possible.


Corrugated duct

Corrugation is made of different materials: aluminium, steel, plastic. The most common is a ridge made of aluminium. This metal is lightweight, withstands high temperatures. The groove should be installed in the most stretched state. Then there will be less resistance to the passing air, lower noise level. However, tried, it can no longer be squeezed back. It is easily deformed, so you need accuracy when installing it.

The aluminium duct is a flexible design, easy to install, cheaper. Installation is carried out with the help of clamps: the chimney is attached to the flange of the umbrella, to the ventilation pipe behind the grid with a check valve. The joints are treated with a sealant (silicone) or strengthened with aluminium tape. You can’t use superglue.

The appearance is not very attractive, so the groove is often masked. Special ready-made boxes made of polyvinyl chloride, aluminum, stainless steel or wood are installed on top. The choice depends on the interior of the kitchen. Some air ducts are immediately sold, complete with casings.

Make the design and plasterboard. It is putty, primed and painted in the desired colour. At the same time, local lighting is installed. Built-in air ducts are carried out inside the kitchen cabinet. If the installation of the exhaust system is carried out at the stage of repair in the kitchen, you can hide it behind a stretch ceiling.

Disadvantages of such an air duct: higher noise level, soot, dirt, oil are delayed in corrugation folds. Aluminium is characterized by good thermal conductivity, so sometimes condensate can accumulate in the kitchen.

Steel ducts are smooth, durable, non-deformable and resistant to high temperatures. They are inexpensive. There are galvanized versions and air ducts made of stainless steel. Of the shortcomings, the enormous weight of the structure should be noted, which requires reliable fixation to the walls; unique means are needed for sealing. When the exhaust system is running, a lot of noise is created.


Duct diameter calculation

The diameter of the duct must coincide with the diameter of the entrance to the ventilation shaft. If the cross-sectional area of the chimney is smaller than the ventilation duct, the chimney’s efficiency decreases.

Ventilation passages in buildings have a diameter of 14 cm; there are square, size 13 * 13 cm or rectangular 10 * 15 cm. Their capacity is about 300 – 400 cubic meters per hour. It makes no sense to put a more powerful chimney; the effect of tipping the thrust may occur.

When choosing flexible products, it is recommended to take no more than three turns along the way. Otherwise, the resistance will significantly increase during the passage of air, and the entire system’s efficiency will decrease. Also, you can not put several turns in a row without sections for dispersing the air. The total length of the duct for the chimney for the kitchen should not exceed three m.significantlyentire system’s efficiency.

The instructions for the chimney, as a rule, indicate the technical requirements for the duct, including the recommended diameter. Most chimneys have an outlet diameter of 125 mm, less often – 100 mm. You can not make the diameter of the duct much smaller than the diameter of the outlet pipe on the chimney. This will result in significant vibration and noise. The most standard diameters are 125, 150, 160, 200 mm.

For rectangular air ducts, the following parameters are suitable:

  • dimensions 110 * 55 mm required for chimneys with a capacity of up to 300 cubic meters per hour,
  • 120 * 60 mm at a power of more than 350 cubic meters per hour,
  • 204 * 60 mm for devices up to 1000 cubic meters per hour.


Is it possible to do without an air duct?

Alternatively, it is possible to install chimneys that work on the principle of recycling. Usually, their power and efficiency are lower. Installation of the duct for such a chimney is not required.

Sometimes they organize the removal of air to the street. A hole is made in the wall after coordination with the BTI and housing and communal services. According to SNiPam, the distance to the nearest window should be at least 8 m. As a rule, this is possible only on the upper floors.

Or install an external box, through which the air rises to the level of the roof. This is necessary so that the exhaust air from the kitchen does not enter the neighbours of the upper floors through the windows. This option is often used by the owners of cafes and restaurants located on the 1st floor of a multi-storey building.

So, you need to correctly connect the chimney to the ventilation not to disrupt the air exchange in the room. This is important primarily for health. In many modern projects of houses, several channels are provided at once: one for ventilation with natural current, the other for connecting the chimney. Their upper stages are separated. If the house is already built, it is essential to consider all the nuances:

    • The volume of the room
  • The frequency of cooking
  • The size and capacity of the ventilation passages

Only after that to purchase the chimney and air ducts, having thought in advance how to arrange them aesthetically.

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