Hood for bathroom and toilet: the subtleties of creating a project and the nuances of arranging the system

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Oleg Zubarev
Last update: May 2019

An effective hood for the bathroom and toilet is not just an aesthetic component, but also equipment that helps maintain a comfortable and healthy indoor climate.

Ventilation performance should ensure that conditions are close to natural. If this is not so, then soon you will have to deal with fungi on the walls and other problems. Agree, the prospect is unpleasant.

We suggest figuring out how to correctly design a ventilation project in the bathroom and calculate the power of the system. In addition, in the article we identified important points that should be taken into account when arranging the exhaust openings, installing ducts and a fan.

Ventilation system design

Creating any hood starts with writing a technical task. It is it that will allow us to correctly assess the situation and understand how to proceed further.

When drawing up the terms of reference it is taken into account:

  • location toilet, bathroom, other rooms, engineering facilities that may affect the creation procedure, the efficiency of the hood;
  • volume of roomswhere ventilation is needed;
  • sealing level all housing, bathroom, toilet.

The last point is also important and cannot be ignored, since modern doors, windows lead to a violation of natural air exchange. And a correct assessment of the situation will help to identify this and choose equipment that can solve the problem.

Step # 1 - determining the right amount of air

The room will have a healthy microclimate, if you do not just use any separate element in the form of a ventilation hole or fan, but arrange a complete system based on the laws of physics.

At the stage of creating the terms of reference, a number of important nuances are taken into account. For example, how many people can be in the bathroom at the same time.

This is relevant for situations when the specified room is non-standard large and saturated with various equipment. Which, for example, can be a multi-seat or hot tub. The reason is that the more people are in the room, the more actively the air is polluted.

Ventilation scheme
In order for the air to become clean, it is necessary to create an influx of fresh air masses (1), to ensure their supply to the desired room (2) and the removal of polluted air outside the bathroom, toilet (3). All of these procedures can be carried out naturally, if necessary, you can use equipment that will increase productivity, efficiency. In order for the above processes to help organize the correct arrangement, you need to start with planning, that is, with the project

In addition, when writing a technical task, they find out the requirements that must be observed when creating ventilation. So these include the amount of air needed for the normal functioning of the premises.

Air exchange rates:

  • bath - not less than 25 cubic meters m of clean air hourly;
  • restroom - from 50 cubic meters m for every 60 minutes;
  • combined room - per hour from 50 cubic meters m;
  • the room where the bidet or sink is, - not less than 25 cubic meters. m

If the bathroom is equipped with a jacuzzi or shower, the standard is at least 75 cubic meters. m, and hourly. In non-standard equipped bathrooms, the volume of passing air must exceed 150 cubic meters per hour. m

All of these standards are minimally acceptable and do not always ensure the maintenance of an optimal microclimate. Therefore, they are often adjusted upward.

What is desirable to do at the preparation stage, but in many cases the error can be corrected after the start of the use of ventilation. Although in the latter case, financial losses are inevitable.

Step # 2 - calculation of the main parameters

An important indicator is the frequency of updating the volume of indoor air. Since it will help to purchase the appropriate equipment or properly configure it. The average value of this parameter is the change in 4-8 volumes of air per hour.

Ventilation project
The figure shows the ventilation project of a private house. Where air exhaust in the bathroom and toilet is only one of the subsystems. As you can see, design is a complex process. But in standard apartments, everything is simpler and the whole procedure will be to draft terms of reference and create a simple scheme

When choosing a ventilation method and the necessary equipment, the speed of movement of air masses should be taken into account - it should not exceed 0.3 m / s. If it is larger, then the probability of drafts is high, which negatively affects the comfort of living and the health of users.

An important point is the temperature of the supplied air.

It should be in winter:

  • bathtub and WC - about + 25 ° C;
  • individual toilet room - about + 18 ° C.

Humidity should always be in the range of 50-65%, since deviations in any direction will lead to the fact that the microclimate will be considered unhealthy.

Step # 3 - calculation of system power

The result of the preparation of the terms of reference is the calculation of an acceptable hood power.

What is the formula used for:

L = n * V,


  • L - the necessary power indicator of the fan;
  • n - this is the rate of air exchange;
  • V - the volume of the bathroom, toilet.

Although this calculation is the simplest, it allows one to identify the main parameters of the system.

At the design stage, you need to decide type of ventilation system.

Two options are possible:

  1. Natural. The most affordable and low-cost method, but today it is becoming less and less relevant, since air exchange is disturbed due to the tightness of the housing, especially in winter. For this reason, the hood becomes ineffective.
  2. Forced. It requires large investments, since it is planned to use additional equipment, for example, at least 1 special exhaust fan.

The effectiveness of the second option is several times higher than the natural replacement of air.

Placement of elements of the ventilation system
When designing, you must take into account that the ventilation hole with the air duct should be located as far as possible from the supply air source and as close to the ceiling as possible

Forced ventilation is also divided into three types:

  • exhaust - in this case, the output of contaminated air masses is carried out in a special mine or out, an example of arrangement - wall valve mounting;
  • supply - provides for the creation of air currents that displace the old;
  • mixed - combines the main features of the two above options; this solution is often used in cottages and private homes, using forced-air and exhaust installations.

And also during the preparation of the terms of reference, it is necessary to determine whether the hood will be channelless or channel.

An example of the first is the ventilation system in most Soviet apartments, when there was a mine between the bathroom and the toilet, that is, there is no need to use any additional devices to remove polluted air there.

Channels will have to be laid in non-standard housing, where there are no ventilation shafts nearby, and accordingly there is no way to remove the exhaust air outside the housing. This method should be used as a last resort, as it is expensive and time consuming.

Ventilation design elements
The entrance door to the toilet, bathroom should have openings for the passage of supply air, and from the bottom. They can be decorated in the form of a decorative lattice, as in the photo, or the gap between the door itself and the frame, floor

It should also be taken into account the fan noise figure, if any. This indicator should not exceed moderate 35 dB.

The terms of reference are considered completed when all the necessary information is collected about the future system. The presence of any "white spots" is not allowed, as this may affect the effectiveness of ventilation.

Step # 4 - Complete Ventilation Design

An important feature of the technical specifications described above is that the information collected during its compilation often allows you to get all the necessary information.

And this makes it possible to do without drafting a project, but this feature applies mainly to simple cases when there is no need for channels.

That is, owning all the information, it will be enough to create a simple scheme of where individual elements of the system design will be located and which ones.

Design Features
It should be understood that channeling should be a last resort. And, if there is no choice, it is better to use plastic boxes, as indicated in the photo, as this will be the most practical and durable solution

If the case is complicated and you have to lay channels, then a project will be needed, but it will be better when such work is done by specialists.

Because, this type of ventilation is quite expensive, and even minor flaws can lead to inefficiency of the entire system and the accumulation of polluted air in the premises.

The full scope of the design consists of the following steps:

  1. Calculation of the required volume of air exchange. This procedure is carried out in the process of drafting the terms of reference.
  2. Development concept with calculation of the cross section of the ducts (pipes leading air out), sound pressure in the system (noise). In most cases, this is not difficult, since all that is required is to purchase a fan whose sound during operation does not exceed moderate 35 dB.
  3. Preparation of drawings.
  4. Preparation of documentation for related work. For example, on electricity. That is, it is necessary to determine where the fan connects to the network, the control method.

Ventilation design in the toilet or in the bathroom must be done during a similar procedure for the whole house, so that it becomes an organic and effective part.

Recommendations for arrangement

Work on the arrangement of the hood can be done on its own, but if you doubt your own abilities, it is better to invite a specialist. Next, we consider the main points that should be given special attention.

Vent location

To begin with, it is necessary to determine the place where the ventilation hole will be located. What is quite simple to do: in most apartments for this you need to find out the location of a special mine, and in a private house you can organize the removal of polluted air outside it almost anywhere.

Ventshacht hole
Ventilation openings should be located as close to the ceiling and opposite the entrance doors, which should have special openings, openings for free air circulation

Do-it-yourself hole for the duct should only be when the wall is brick. If it is concrete, then it is better to use the services of a specialist who will perform the so-called diamond drilling. From the resulting hole, you must remove debris, dust.

Subtleties of selecting ducts

The installed duct must be placed with a slope of 5-10 ° towards the street. This is necessary to drain the condensate. The outer part of the duct should be insulated, which eliminates problems in cold weather.

For transportation of polluted air, it is better to choose plastic pipes. The reason is that this material is durable, especially in difficult conditions, and also its smooth surface does not create friction when moving air masses, which makes this procedure less costly, noisy.

Arrangement of a ventilation system
Corrugated pipe will be the best solution if the exhaust hole is in a hard to reach place. And also a photo will help to understand how to design ventilation if the exhaust shaft is located only in the toilet or bathroom, and not in both rooms

Corrugated boxes will be the best option when you need to connect in hard to reach places.

Fan Requirements

If you plan to use a fan, then it is better to power it from the box, designed to illuminate the bathroom, toilet. To do this, you just need to buy a switch with one additional button.

The fan itself should be at least splash-proof, and better if waterproof. But even such range hood models should be installed away from water sources, which will reduce the likelihood of it getting on the appliance.

Sewerage system checks
The arrangement of any system is considered complete after successful verification of its operability and effectiveness. Including the absence of excessive sound pressure, as indicated in the photo

The arrangement of the hood is best done during repairs in the apartment, house.

Drilling procedures for subsequent installation will lead to damage, cracked tiles, and other design elements. Disguise which will not work.

Conclusions and useful video on the topic

The first video will help you understand how the ventilation system works.

The following video will allow you to deepen your knowledge on the topic, which will allow you to better cope with design.

Ventilation systems designed for the toilet, bathroom, for moderate investment, increase the comfort of living, contribute to the establishment of a healthy microclimate.

To get the expected result from installing the hood, you need to understand the essence of the issue and do everything right. When there is no desire or opportunity to delve into every little thing, it is better to use the services of specialists.

Do you have personal experience in designing and arranging hoods in the bathroom and toilet? Want to share your knowledge or ask questions about the topic? Please leave comments and participate in discussions - the feedback form is located below.

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Visitors Comments
  1. A fan was installed in the country, since we have a toilet combined with a shower. The room itself is small, and without windows, so ventilation is really necessary so that the fungus does not develop and is fresh in the room. The fan also removes unpleasant odors in the toilet. This is important, as many people live in the house. It turns on from the button, quite noisy, but doesn’t really bother.

  2. Sergei

    Our kitchen is separated from the toilet by a wall. Guests, having come to us for the first time, do not immediately realize that there is a bathroom in front of them. Drilling a wall to install the pipe under the hood was not difficult, since I have an old hammer drill. Only here there are subtleties. Drill with a crown only when a hole is drilled with a drill. So the device is easier to hold and it does not go away from the intended place. And he took a hood more powerful. To reduce noise and odor, he trimmed the partition with a penofol.