Calculation of the hood for the kitchen: how to calculate the power of the exhaust device

Additional functions

Modern household appliances are equipped with many auxiliary functions.

When choosing a hood, you should pay attention to the convenience of their use.

Touch control panels increase the cost, but are preferable to slider ones, as they are less prone to contamination and look more aesthetically pleasing.

All models have a lighting function.It is better if the hood is equipped with halogen lamps. They have a nicer light and less color distortion than incandescent or fluorescent lights.

By carefully calculating the required power of the kitchen hood, carefully choosing its model, you can guarantee not only comfortable conditions in the cooking area, but also a long service life of the purchased equipment.

Design and principle of operation

The principle of operation of the hood - recirculation and flow

When considering the design of exhaust structures, it is important to pay attention to the fact that they are fundamentally different from ventilation systems. The latter are niches arranged in the walls, allowing the exhaust air to be discharged outside in a natural way. The influx of fresh air masses in this case is possible only through the gaps in the door and window openings.

This method of air exchange is characterized by low efficiency and is not able to completely remove odors present in the kitchen, as well as remove soot and other household fumes. For these purposes, special devices will be required that provide forced ventilation and are called hoods. With their help, the vapors coming from the hob or stove are collected in one place, and then through a special duct they are removed through the ventilation ducts.

The influx of fresh air masses in this case is possible only through the gaps in the door and window openings. This method of air exchange is characterized by low efficiency and is not able to completely remove odors present in the kitchen, as well as remove soot and other household fumes. For these purposes, special devices will be required that provide forced ventilation and are called hoods.With their help, the vapors coming from the hob or stove are collected in one place, and then through a special duct they are discharged through the ventilation ducts.

Principle of operation

Charcoal filter for recirculation hood

In accordance with this factor, all devices on the market are divided into three types:

• recirculation (without venting to the existing ventilation);
• flowing;
• combined.

Hoods without a vent to the ventilation duct contain special filters and a forced intake system through a built-in fan. During operation, they pass polluted air through a system of filter elements, and after cleaning it, they return it back to the kitchen room.

Flow models are connected directly to the duct in the kitchen. Fresh air enters through it, after which the contaminated layers are removed by force. Combined type devices are capable of operating alternately in one of the two modes discussed above.

Extractor hoods of various modifications

Grease filter for extractor hood

Modern exhaust products are made in several versions that determine their purpose. Depending on this, they are divided into hoods that only allow you to remove dirty air, as well as models that filter it and return it back to the system in an already purified form. Flow devices contain a set of soft plastic or hard metal pipes of a certain shape. They are used to connect to the ventilation system.

At the bottom of such products there are special filters (grease traps) that delay outgoing from stoves soot and grease. From above, they are masked with special decorative panels, and in the inner area there are fans and a drive motor. Behind these structural elements is an air duct connected directly to the ventilation.

What to look for when choosing depth and height

These parameters must also be taken into account when arranging the cooking zone. Consider how to choose the right depth and width of cleaning equipment.

Depth Selection

This parameter is taken into account for the dome and built-in air outlet. Modern models of dome hoods are square, that is, the depth of these devices is equal to their width. Accordingly, the depth dimensions also start at 45 cm and end at 90 cm. The choice of a square shape is not accidental: hobs are also produced with equal width and depth parameters. And, as we already know, the hood cannot have an area less than the stove above which it is installed.

With embedded models, the situation is different, because the depth can be adjusted during the planning process. However, its body must fit the size of the wall cabinets.

Height selection

If your choice fell on a dome-type hood, then the maximum height of such a design can be 125 cm. This must be taken into account when buying: if you subtract the height of the stove from the height of the kitchen ceilings, then the remaining number should not be less than the standard values ​​determined by safety regulations. The minimum distance between the stove and the lower surface of the hood is:

• for a gas hob - at least 65 cm;
• for electric stoves - at least 60 cm.

For inclined hoods, the installation height should be somewhat less:

• for gas stoves - 550-650 mm,
• for electric and induction surfaces - 350-450 mm.

It is not necessary to reduce the height: a dangerous situation will arise and the hood can be damaged. It is also not recommended to set it higher because it will reduce the efficiency of the work.

It should be noted that there is no such selection problem for recirculating hoods. After all, these are flat devices that can be installed at any desired height.

This table will help you choose the correct size of the cleaning device:

Room features	Hood height	Instrument depth	Width	Hob width
A large room	The height of the appliance is selected depending on the height of the room and the type of cooking unit	Depth parameters correspond to width dimensions	The ideal option would be dimensions that are larger than the hob	The width can be any: a wide cooking area looks organic in a spacious room. It is the main focus in the interior.
small room	The height of the device compensates for the small dimensions of the plate, which saves space	Depth parameters correspond to width dimensions	Do not choose a wide hood, look at compact models	For a small room, choose a stove with a narrow countertop

When choosing a hood for the kitchen, you need to take into account many nuances, but the most important criteria are size and performance. First you need to decide what functions the cleaning equipment should perform: air purification, removal of odors, or simply as a design item. After that, you should measure the hob, the area of ​​\u200b\u200bthe kitchen. After you have decided on the main parameters, you need to choose a brand and model based on preferences and taste.

Power calculation procedure

To make a correct calculation of the performance of the hood, you need to know what tasks will be performed by the device. In accordance with the instructions, he must perform cleaning or removal of polluted kitchen air. Sanitary standards say about 12 air replacement cycles in one hour. So, in the kitchen for an hour, he should change 12 times. That's what the coefficient "12" has in performance calculations.

According to the basic formula, the power is calculated as follows: Q=S∙H∙12, where:

Q is the power of the device, measured in m3 / h;

S is the area of ​​the kitchen area;

H - ceiling height;

12 - coefficient of the number of air change cycles.

Let's look at an example:

kitchen area - 12 m2;

ceiling height - 2.7 m;

Let's substitute the data into the formula: Q=12∙2.7∙12 = 388.8 m3/h. The calculation showed that the device will clear this volume only at maximum power. In this mode, he will not be able to work for a long time, most likely, he will quickly break down.

Important! To reduce the load, it is desirable to increase the obtained value of the indicator by about 15%. So we will create an optimal power reserve for the exhaust device, which will facilitate its work.

We give ourselves the opportunity to select the limit mode only at the maximum smoke level in the room, for example, during the festive cooking of a large number of dishes.

So we will create an optimal power reserve for the exhaust device, which will facilitate its work. We give ourselves the opportunity to choose the limit mode only at the maximum smoke level in the room, for example, during the festive cooking of a large number of dishes.

It should be taken into account that these calculations were made on the basis of averaged data, since the following circumstances were not taken into account:

• type of hob;
• type of exhaust device;
• apartment layout.

Type of hob

The type of plate directly affects the amount of pollution that enters the atmosphere during cooking. The required frequency of air renewal depends on it. The coefficient of air exchange cycles should be changed. The calculation of the hood for a kitchen in which an electric stove is installed is different from the base one, since any combustion products cannot enter the air. Only the vapors of cooking food are present in the atmosphere. In such cases, the coefficient is recommended to be increased to 15, respectively, the formula will change: Q= S∙H∙15.

If you plan to use a gas stove, then it is necessary to increase the coefficient to 20. This is caused by air pollution by harmful products of gas combustion in large quantities. In this situation, the formula will be: Q=S∙H∙20.

Hood type

Depending on the mode of operation, the direction of the exhaust air, exhaust devices are divided into two types:

• ventilation hood;
• recirculation hood.

Ventilation or flow type devices are connected to the ventilation duct in the apartment, through which exhaust gases are discharged to the street. However, to calculate the power of the hood for the kitchen, it is necessary to take into account the throughput of the channel. In an old house with a clogged ventilation shaft, even if you purchase a powerful exhaust device (according to calculations), it will not be able to ensure the complete removal of exhaust gases. At the same time, polluted air will enter neighboring apartments through the ventilation duct.Under such circumstances, it is recommended to build a separate ventilation outlet into the hole made in the wall.

Recirculation type devices are equipped with a filter system and do not imply connection with a ventilation duct. Usually a two-stage cleaning is performed. The first filter is designed to absorb large particles of steam, burning and grease. The air is then cleaned with a carbon filter that removes odors and is released back into the apartment.

Important! Filters, pumping air, create a small resistance, which must also be taken into account in calculating the power of the hood. It is recommended to increase the value of this indicator for such models by about 30-40%

Apartment layout

When calculating the performance of a kitchen hood, do not forget to take into account the design features of the room. If the entrance to the kitchen is made in the form of an arch without a door, or there is a door that you never close, then the volume of the adjacent room must also be taken into account.

If the dining room or living room is combined with the kitchen, then the requirements for the value of the power parameter of the unit increase significantly due to the instant dissipation of odors, which must be urgently eliminated.

What is the difference between exhaust and ventilation?

In modern apartments, an exhaust hood, better known as a range hood, is placed above the stove. Many homeowners are convinced that this airbox is responsible for ventilating the kitchen.

Therefore, with a clear conscience, they lead the ventilation duct pipe from the hood into the ventilation hole designed and built by the designers of the high-rise building.

What happens if the regular ventilation in the kitchen is blocked by an air duct from the exhaust hood? The intensity of air exchange in the apartment will drop sharply.

Hood installers and kitchen umbrella vendors usually claim otherwise. They will say: this technique will significantly improve the quality of the air supply at home, because it has a powerful ventilation unit.

However, the power of the cooker hood has nothing to do with ventilation. The reason is that the air exchange in the apartments of most residential high-rise buildings, especially those built before 2000, was designed with the expectation of supply and exhaust ventilation.

Outdoor air entered through the cracks of the window frames and the front door. And the ventilation ducts in the kitchen, bathroom and bathroom were used to remove "stale" air. It would seem - what is it?

Extractor hood in the kitchen - to extract air. So why can’t you “stick” an air duct from an exhaust hood into it? It's all about air performance.

Air ducts in residential apartment buildings are designed for a certain load. In general, the bandwidth of any communication is carefully calculated at the design stage.

And under ideal conditions (clean walls of the ventilation duct, no interference at the inlet-outlet, etc.), the performance of natural ventilation in a high-rise apartment will be 160-180 m3 / h.

You may also be interested in the information on the normative air velocity in ducts, discussed in this article.

Types of hoods for the kitchen

It will be easier to choose a hood for the kitchen if you know what types of exhaust equipment are, their advantages, disadvantages, and features. First of all, let's define the mode of operation. They are divided into two types:

• Hoods for the kitchen with a vent to the ventilation. They are also called flow or retractor. They remove polluted air to the ventilation system or through a hole in the wall to the street (depending on the type of connection chosen).Their disadvantage is that for normal operation a large-section ventilation duct and inflow holes are required, which provide fresh air instead of the exhaust.

• Kitchen hoods without venting. The second name is recirculation or filtering (cleaning). The air is sucked in from below, cleaned in the internal filters of the unit, and enters the room. The disadvantage of this system is the need to clean and/or replace the filters.

There are models of kitchen hoods that combine both types (combined), the operating modes are switched by a button. These devices are more expensive, more versatile, but have the disadvantages of both types: you need a powerful ventilation system with sufficient performance and filter replacement.

Classification by type of location

To choose a hood for the kitchen, you must also decide on the type of its location. Everything is simple with this - we choose depending on where the stove is:

• Corner ones are placed in kitchens where the stove is in the corner.
• Island (ceiling) put where the stove is in the middle of the room.

• Wall-mounted - the plate is installed against the wall.

You also need to choose the type of kitchen hoods by installation method. The difference is the way you interact with the furniture. On this basis, they are:

Having dealt with the types, you know how to choose a hood for the kitchen according to this principle, but there are still technical parameters and additional functions, and they must be dealt with separately.

Important Mounting Features

Errors in the assembly and installation of the supply exhaust pipeline can negate previous efforts to correctly select the hood, calculate the required cross-section of the pipes used, and select the necessary transition and connecting elements

In order for the exhaust system to work correctly, you should pay attention to the following points of its installation:

• The assembled pipeline structure must not have deflections. If a corrugated pipe is installed, its stretching should be maximum.
• The entire exhaust system must be grounded to dissipate static electricity.
• In order not to damage the air outlet when it passes through the walls, special adapters and sleeves are used.
• The places of all connections (between pipes, pipes and hoods, pipes and an adapter of a ventilation shaft) must be treated with a sealant.
• Bends of the corrugated pipe to radii that are smaller than the diameter of the corrugation used will reduce the pressure and, consequently, the efficiency of the air exhaust system.
• The optimal pipeline of the exhaust system has a minimum of bends and turns, its length is up to 3 m, the bends are obtuse.
• With a large length of the corrugated air duct, after 1-1.5 m it must be fixed with clamps to prevent possible swinging when the hood is running.
• To connect the pipeline with the cavity of the ventilation shaft, use a special frame with a grate for supply ventilation, a flange for fixing the pipe and a check valve. When the hood is in operation, the valve is closed and does not allow polluted air to enter the room back. When the hood is not working, the valve is open - free air circulation occurs.

Turning the pipe at a sharp angle or 90° will invariably reduce the performance of the entire system by 10%. A few such kinks will make it work ineffective, although the exhaust equipment will work with overload. If it is impossible to change the line of the pipe, it is advisable to increase its cross section and the power of the hood.

Suction power calculation

Extraction power is a representation of the number of cubic meters of air sucked in during an hour by the hood in extraction mode. During cooking, depending on the intensity of evaporation, the air in the room is updated about 10 - 15 times per hour.

This parameter can be calculated using the formula:

Kitchen area: 15 sq.m, ceiling height 2.7m

15 X 2.7 X 12 = 486

Each meter from the shaft to the equipment 10% + each pipe bend 10% + take into account the reserve power of 10-20% (in case the food burns)

If your kitchen or bathroom is 15m2 with a ceiling height of 2.7m, the ventilation shaft has a normal air draft, the distance to it does not exceed 0.5m, there are no bends in the pipe, and the hood will work in the air outlet mode, then we recommend buying an hood with a capacity of: 580 m.cub./hour.

Also, to calculate the power of a kitchen hood, you can use our online calculator:

Important! The hood loses its performance factor if the air outlet has sharp bends in the channel. Two 45 degree bends are better than one 90 degree bend.

Performance is lost with each meter and bend of the duct pipe by 5-10%. Corrugated channels create noise during operation and reduce the performance of the hood. Don't forget that during recirculation, the power of the device drops by 25%.

Complicating factors

There may be many. And taking into account absolutely everything is not easy, and it is not always necessary. But the main ones, those that can drastically affect the result, should not be neglected.

Plate type

It directly depends on how much excess substances get into the air during the cooking process. Accordingly, this air will need to be updated at different frequencies.That is, the air exchange coefficient will also change.

You should also consider the parameters of your stove

The electric stove itself does not emit any combustion products. This means that you will only have to get rid of various fumes of water and fat. The coefficient for it is slightly higher than the average and is equal to 15. The formula looks like this: Q=S*h*15.

When using a gas stove, the atmosphere is filled with substances that are formed during the combustion of gas. But fats and evaporation remain the same. This means pollution is increasing. As a result, the figure rises to 20. In mathematical form, this can be written as: Q=S*h*20.

Hood operating mode

Depending on where the exhaust air goes, there are two such modes:

• ventilation;
• recycling.

In the first case, the exhaust duct must be connected to the ventilation duct of the house or brought directly to the street. Here you should consider the condition of the ventilation shaft. And if it is dirty - make the power reserve more than the standard one. Some experts generally recommend multiplying the result by 2. But you can’t overdo it either. Excessive pressure in the ventilation will not bring you any benefit, and it can create problems for neighbors in the riser.

The second mode of operation does not involve connecting the air duct to external systems. What does it mean? The air is not escaping from the room. It's just that with such a system an additional filter element is used, through which the "dirty" flow passes. After that, already cleaned of unwanted impurities, he again returns to the room. In this case, an additional filter creates additional circulation resistance. And, therefore, again it is necessary to increase the power by about 30-40%.

With power, it seems to be finished.You can stop there, but it is better to recall one more characteristic of the operation of ventilation devices. They have a side effect, which should also not be forgotten when calculating the performance of the hood for the kitchen.

Air consumption by multiplicity

But you can’t just “pump” air into the room. It needs to be systematically updated, distributing the flow over the area several times during each hour. To eliminate errors, it is required to carry out the calculation by multiplicity. To do this, multiply the normalized number of air exchanges per hour by the total area and height. The coefficient for residential spaces is 1-2, and for administrative facilities - 2-3. When calculating local and general ventilation, both the multiplicity approach and by number of people, after which the largest value is selected.

The essence of multiplicity calculations is that they determine the necessary quantitative parameters of air movement. The need for them arises from considerations of removing harmful substances. The methodology for calculating the harmfulness has an important variety - the calculation of aggregated indicators. Two formulas are used for this purpose: L=K * V and L=Z * n. The calculated indicators are expressed in cubic meters.

As for variables, they are as follows:

• K is the number of air changes in 60 minutes;
• V is the total volume of a room or other room;
• Z - air exchange (in specific terms per measured indicator);
• n is the number of units of measure.

How to calculate the optimal extraction performance

For the simplest calculation of the power of the device, it is enough to know the volume of the kitchen and the standard air exchange rate.

1. Determining the volume of the room.

To calculate the cubic capacity of the kitchen, you should measure its length, width and height, and then multiply the resulting values. If, for example, as a result of measurements, you get the following results:

- kitchen length - 4 m;
- width - 3 m;
– room height – 3 m,

then the volume of the room will be: 4x3x3 = 36 m3.

2. Choice of air exchange rate.

According to current state standards, the air exchange rate in the kitchen should be at least 10 - 12. The multiplicity means how much air per hour must pass through the hood so that fumes and vapors do not accumulate in the room. If the hostess cooks often and a lot, then it is better to take the maximum multiplicity value (12) in the calculation. With a moderate intensity of cooking, a 10-fold air exchange is sufficient.

3. The formula for calculating the power of the hood for the kitchen.

capacity table for kitchen hoods

Calculated according to the formula:

P = V x N, where

P is the desired power of the device;

V is the volume of the kitchen;

N is the air exchange rate.

In our example, the optimal exhaust power will be:

36 x 10 = 360 m3/h.

With a calculation in hand, you can safely go to the store: you may not see an extractor hood of just such a power there, in which case choose a device that has the closest power characteristic, but not lower than the calculated one. An extractor hood with a capacity of 400 m3 / h is quite suitable for you.

2 Varieties of systems and method of placement

Before calculating the power of the hood by area, it is necessary to understand the structural features of the case. It can be of the following type:

1. 1. Flat models are small in size and do not require additional installation.Most often they are used in small rooms. The main disadvantage of such devices is a short service life. That is why after a few months they will need to be replaced. There are several varieties of flat structures, there are models that are installed at a slight angle to the stove, but the feature of all is precisely their compactness.
2. 2. Dome exhaust devices are considered the most powerful and functional, they are able to clean even very large rooms. Equipment of this type is always quite dimensional, it can be made in the form of a hemisphere or pyramid.
3. 3. Cylindrical appliances are very convenient, they can be adjusted in height. They can be made in any custom shape but are usually cone, circle or square.

There are also built-in designs, but their peculiarity lies in the fact that the appliances can be disguised in kitchen furniture, in a ceiling or wall niche. It is worth considering options for placing exhaust equipment, it can be of the following type:

• hanging - can be installed in any area of ​​\u200b\u200bthe kitchen, but most often mounted on a wall or ceiling;
• corner - should be mounted in the space between the walls, then the kitchen area will be used more rationally;
• island - intended for installation on the ceiling.

Noise component

Since the hostesses are in the kitchen for a long period of time, the comfort of staying there is a determining indicator. Therefore, it is worth familiarizing yourself with how loud the exhaust device works.

In addition, it is worth paying attention to the characteristics indicated in the technical documentation of the hoods. For a comfortable stay in the kitchen, this sound indicator should not exceed 55 dB

For comparison: the average noise level in a quiet room is 30 dB, and a quiet conversation at a distance of several steps is 60 dB.

Modern kitchen hood with minimal noise

Calculation of normal air exchange for effective ventilation of an apartment or house

So, during normal operation of ventilation, the air in the premises must constantly change within an hour. The current guidelines (SNiP and SanPiN) establish the norms for the influx of fresh air into each of the premises of the residential area of ​​​​the apartment, as well as the minimum volume of its exhaust through the channels located in the kitchen, in the bathroom in the bathroom, and sometimes in some other special rooms.

These regulations, published in several documents, are combined for the convenience of the reader into one table, shown below:

Room type	Minimum air exchange rates (multiplicity per hour or cubic meters per hour)
	INFLOW	HOOD
Requirements under the Code of Rules SP 55.13330.2011 to SNiP 31-02-2001 "Single-apartment residential buildings"
Residential premises with permanent residence of people	At least one volume exchange per hour	—
Kitchen	—	60 m³/hour
Bathroom, toilet	—	25 m³/h
Other premises		Not less than 0.2 volume per hour
Requirements according to the Code of Rules SP 60.13330.2012 to SNiP 41-01-2003 "Heating, ventilation and air conditioning"
Minimum outdoor air consumption per person: living quarters with permanent residence of people, in conditions of natural ventilation:
With a total living area of ​​more than 20 m² per person	30 m³/h, but at the same time not less than 0.35 of the total air exchange volume of the apartment per hour
With a total living area of ​​less than 20 m² per person	3 m³/hour for every 1 m² of room area
Requirements according to the Code of Rules SP 54.13330.2011 to SNiP 31-01-2003 "Residential multi-apartment buildings"
Bedroom, nursery, living room	One volume exchange per hour
Cabinet, library	0.5 volume per hour
Linen, pantry, dressing room		0.2 volume per hour
Home gym, billiard room		80 m³/hour
Kitchen with electric stove		60 m³/hour
Premises with gas equipment	Single exchange + 100 m³/h for a gas stove
A room with a solid fuel boiler or stove	Single exchange + 100 m³/h per boiler or furnace
Home laundry, dryer, ironing		90 m³/h
Shower, bath, toilet or shared bathroom		25 m³/h
home sauna		10 m³/h per person

An inquisitive reader will surely notice that the standards for different documents are somewhat different. Moreover, in one case, the norms are set solely by the size (volume) of the room, and in the other - by the number of people permanently staying in this room. (Under the concept of permanent residence is meant being in the room for 2 hours or more).

Therefore, when carrying out calculations, it is desirable to calculate the minimum volume of air exchange according to all available standards. And then - choose the result with the maximum indicator - then there will definitely be no error.

The first proposed calculator will help you quickly and accurately calculate the air flow for all rooms of an apartment or house.

Calculator for calculating the required volume of air inflow for normal ventilation

As you can see, the calculator allows you to calculate both the volume of the premises and the number of people constantly staying in them. Again, it is desirable to carry out both calculations, and then choose from the two results, if they differ, the maximum.

It will be easier to act if you compile a small table in advance, which lists all the premises of an apartment or house. And then enter the obtained values ​​\u200b\u200bof the air flow into it - for the rooms of the residential area, and the hood - for rooms where exhaust ventilation ducts are provided.

For example, it might look like this:

The room and its area	Inflow rates		Extraction rates
	1 way - by the volume of the room	2 way - by the number of people	1 way	2 way
Living room, 18 m²	50		—	—
Bedroom, 14 m²	39		—	—
Children's room, 15 m²	42		—	—
Office, 10 m²	14		—	—
Kitchen with gas stove, 9 m²	—	—	60
bathroom	—	—		—
Bathroom	—	—		—
Wardrobe-pantry, 4 m²				—
Total value				177
Accepted total air exchange value

Then the maximum values ​​​​are summarized (they are underlined in the table for clarity), separately for the supply and exhaust air. And since the ventilation must be in balance, that is, how much air per unit time entered the premises - the same amount should come out, the maximum value of the two totals obtained is also selected as the final one. In the given example, this is 240 m³ / h.

This value should be an indicator of the total ventilation performance in house or apartment.