Reverse draft in ventilation of an apartment building

Any apartment building has a ventilation system. She is responsible for the flow of fresh air into the room and the removal of stagnant air. But situations can occur when dirty air flows back into the house. This phenomenon is called reverse thrust. It interferes with the comfortable life of people, and also carries a potential danger. You can correct the situation with your own hands when there is no malfunction of the system itself. In other cases, you need to contact a special service.

Reverse thrust definition

With reverse draft, the flame is directed towards the room

Draft in the ventilation system is understood as a directed flow of air masses, which occurs when there is a difference in pressure in the house and on the street. The air flows naturally go to the low pressure area. By this principle, general house ventilation works. First, the air heats up, its density and mass decreases. It goes up and out into the vent. Fresh cold air comes in through the cracks and fills the entire space.

The thrust force is directly related to the height between the air inlet and outlet. For this reason, the residents of the upper floors feel the lack of fresh air more acutely.

The phenomenon of reverse draft in the ventilation of an apartment in an apartment building consists in the impossibility of removing dirty air. He goes back to the rooms and brings bacteria and unpleasant odors with him. You can understand that the system is not working correctly by the following signs:

Fogging windows, condensation, mold and mildew. Excess moisture is also removed through the ventilation. If the system is not working properly, water will not be drained and will begin to settle.
Stuffy stuffy air, often accompanied by an unpleasant odor.
Draft from the air vent. If you bring your hand to it, you can feel what is blowing from the ventilation into the apartment.

The simplest test can be done using a regular sheet of paper. You need to attach it to the ventilation hole and see the direction of the oscillation.

Hood - to be or not to be

Exhaust equipment is installed in almost every apartment or private house. Especially the installation is carried out in the kitchen. It is used during cooking. But how could this be related to the reverse thrust problem? Owners of apartments or private houses can observe the following. When the hood is turned on, air starts to blow through the ventilation hole in the toilet or kitchen. And the presence of a mechanical hood can contribute to this.

The reason may be the use of a heavy duty hood. After all, many want her to draw out every vapor and smell when cooking. However, as practice shows, this is not always justified. A working hood simply pulls all the air out of the room. It is for this reason that reverse thrust is formed in the ventilation duct. Windows, doors and other structures are air-tight. He has nowhere to go, so a reverse draft in the ventilation is formed.

That is, the problem boils down to the fact that there is a clear lack of fresh air supply. The worst thing is that the reverse draft of ventilation in the apartment can provoke the appearance of odors in your house from the next apartment and floor. Is it possible to somehow fix the current situation?

The solution to this problem is very simple. You just need to open the door or window at the time of the hood operation. In this case, the operation of the ventilation system of a private house or apartment will work correctly. After all, it is important that air circulation is carried out.And it is very easy to check the health of the system. You can simply attach a piece of paper to the ventilation duct. If it sticks, then everything is fine in your case.

Natural air circulation in the house

Backward thrust can occur when installing metal-plastic windows and doors

The ventilation system in the house is a complex of various technical devices, blowers and shafts, which have a single riser from the basement to the roof. Thanks to him, traction is created due to the temperature difference in the house and on the street. As this difference increases, the hood will work harder.

The effect is also exerted by the perpendicular pressure according to the principle of cross sections. This is a situation in which the wind blows horizontally in relation to the riser. As a result, it draws air out of the ventilation.

So that there is an air flow in the house and a vacuum does not form, vents are made in the foundation at the construction stage. It is also possible to make some holes in the floor on the first floor.

Thus, the natural circulation of air in an apartment building works. The system may not work if there is no supply ventilation or if the temperature in the house is lower than outside. The second reason does not occur often, therefore, it is precisely because of the lack of decent air flows that thrust appears. Ventilation shafts in the apartment are made in the bathroom, toilet and kitchen. Air enters through the windows. The use of double-glazed windows and sealed doors significantly reduces the inflow of air masses and causes reverse draft. To solve this problem, special valves are used for windows or walls.

Also, a violation of the air flow can be caused by a malfunction of the system, the installation of fans and hoods, and improper design. If the hood blows in the opposite direction in the apartment, you need to look for the problem and fix it.

Reverse thrust reasons

If the ventilation duct is clogged, reverse draft occurs or ventilation does not work

The main reason for the occurrence of reverse thrust is the violation of the principle of natural air exchange. It is caused by the following factors:

The use of plastic windows and sealed doors. They are able to completely block the access of fresh air to the room.
Alteration of the ventilation duct or illegal demolition.
Incorrect pipe design or incorrect location. If it is installed in the wind shade zone, circulation will be disrupted.
Change in wind direction.
Clogging of the ventilation duct with small debris, birds entering it.
Constructive errors.

To identify and eliminate reverse thrust, you should contact a specialist. It is better to choose independent experts who will conduct a comprehensive analysis of the entire air duct system in the building and give recommendations on how to improve the situation.

Typical problems in the organization of air exchange

A decrease in the flow rate relative to the design one, even in one supply or exhaust outlet, leads to an imbalance in the air circulation in the house. This affects the operation of other devices, in which there is a compensatory change in the flow parameters, including a reverse can occur. Therefore, it is necessary to examine all the places of air intake and outflow, and then it will be possible to find out why the general ventilation of the house works, directing the flow in the opposite direction.

This example clearly shows that even when establishing the dependence of the occurrence of reverse thrust (in the bathroom) on any condition (turning on the kitchen hood), the reason may be different. Therefore, it is necessary to check all ventilation

Reducing the volume of incoming air

A decrease in air speed in an air handling unit with a fan can be caused by the following reasons:

Loss of engine power, fan vibration and other signs of equipment wear. It is necessary to carry out repairs and eliminate the identified faults.
Failure to configure system parameters. It is necessary to reconfigure the system or repair the control unit.
Dirty filters. The most common reason for a decrease in the supply ventilation capacity. Liner needs cleaning or replacement.
Dirty fans. As a result of the adhesion of contaminants, the geometry of the blades changes. Then, with the same number of revolutions, the pressure characteristic of the device decreases.
Reducing the free area of the channel. It can occur in any node of the supply system through which air passes: pipe, recuperator, air heater, etc. It is necessary to carry out their regular service cleaning.
Partial or complete closure of the outer grille. The filter grid can be clogged with insects, leaves and other debris. In winter, it can be covered with snow. Therefore, you need to periodically check its bandwidth.

With natural supply ventilation, a frequent cause of insufficient supply and sometimes even back draft is the effect of thin air from the street side. This phenomenon can occur on the leeward side of a building. It can be eliminated by using special guards near the air intake.

To prevent the creation of a vacuum zone near the inlet, you need to put a small fence. However, in winter you will have to remove the snow more often.

Hood malfunctions and their elimination

The reasons for the poor operation of the forced-type hood are the same as for the supply device. But most often the problem arises not due to the pollution of the filters (which are not always installed on the hood), but due to the narrowing of the free cross-section of the ventilation duct.

Unlike fresh air, the removed stream carries moisture, vapors, small drops of fat, which adhere to the walls of the ventilation duct. Over time, build-ups form on the inside, creating aerodynamic drag, which leads to a decrease in the volume of outgoing air. In this case, the exhaust device itself can work properly.

In private houses, the ventilation duct is designed so that it can be visually inspected without much effort. This must be done 2-3 times a year and, if the resulting narrowings are found, clean them yourself or with the help of employees of organizations that provide such services.

There are rules for the location of the exhaust pipes on the roof. If you ignore them, then depending on weather conditions, wind back pressure can occur, which leads to a slowdown in the ventilation speed or even to the overturning of the draft. Variables, not persistent airflow problems, are the indicator for this particular cause.

The position of the chimneys relative to the roof elements is regulated by clause 6.6.12 of SNiP 41-01-2003 "Heating, ventilation and air conditioning". It is spelled out in this document on the basis of wind back pressure calculations, so it can also be used for ventilation pipes.

The rules for placing pipes on the roof are quite simple, so you can bring ventilation through the roof at almost any point. It will only be necessary to maintain the required height

Often a situation arises when, when building a house, all the norms for the placement of ventilation outlets were observed, but later there was a change in the landscape, which led to the formation of wind back zones:

modification of the roof geometry (including the installation of a satellite dish);
construction in the immediate vicinity of a high building;
a tree that has grown near.

In this case, you can move the outlet of the ventilation duct to another place, increase the height of the pipe, or try to remove the cause that creates the zone of wind back pressure.

You also need to check the quality of the deflector.If it has mechanical damage or, as a result of poor fastening, has changed its position relative to the pipe, then this can also be the cause of problems. The thrust can be significantly increased by replacing an ordinary deflector with a rotary one.

System check

An air sample is taken to check ventilation

A check is carried out to identify and eliminate faults. It consists of the following steps:

Study of design documentation. Checking its compliance with the norms and standards of GOST.
Evaluation of the effectiveness of the installed equipment, the correctness of its installation and operation.
Checking the quality of the installation work of the duct, ducts and other elements of house ventilation.
Air sampling.
Search for unauthorized channel overlap.

On the basis of the test carried out, the specialists decide how to eliminate the reverse thrust.

Elimination methods

Supply valve on a metal-plastic window

To remove the backdraft, the ventilation system must be brought into operable condition. The main ways to restore work that you can do yourself include:

Check valve installation. The device will not allow old air to return to the room again.
Installation of supply valves on windows. Thanks to this mechanism, fresh air will flow into the house, even if the window is closed. The intensity can be adjusted. Also, the valves can be equipped with fans, debris grills and other attachments for cleaning, heating and cooling air masses.
When installing a powerful hood, it is necessary to balance it in terms of performance. The volume of the incoming air must be equal to the displaced one.

If the weather conditions are the cause of the draft, you need to wait until the normal temperature and humidity values, as well as the wind direction, are restored. Such factors are temporary and do not depend on the person. With frequent influences of weather conditions, you need to think about redeveloping the system.

The ventilation must be cleaned every 5 years.

If damage has occurred due to which the hood blows in the opposite direction in a private house, you need to call the repair service. Experts carry out the following activities:

Protect the mouth of the mine if draft is generated by strong gusts of wind.
Restore damaged structures, make their repair or replacement.
The channels are cleaned. It must be carried out at regular intervals. Do not clean the ventilation yourself.

It is not always possible to correct the factors affecting traction. For example, the features of the layout of the room may be such that stagnant air will return to the room. In large rooms without walls and partitions, drafts will appear, which affect the overall ventilation system in the house. Stagnant air masses can also return from the stairs to the second floor.

If the reason was the wrong design of the ventilation duct, you should rework it.

Ways to solve ventilation problems

Having dealt with the cause of the violation of traction, you can begin to eliminate it. There are several ways to fix the situation:

Cleaning the ventilation duct. The rules for the operation of apartment buildings prohibit residents from accessing public utilities, therefore, in case of serious problems, work should be carried out by employees of specialized services. However, you can remove small blockages yourself. Remove the protective grill and look inside the ventilation duct. Use a broom or vacuum cleaner to clean the channel. In case of serious difficulties, call the management company.
After installing double-glazed windows, provide frequent ventilation of the room.
In a private home, provide a gap between the front door and the threshold for air intake.
Install supply valves or insulating glass units with integrated valves. They are equipped with special curtains that allow, if necessary, to block the air flow. Valves are available for window, ceiling and wall.
For serious problems, use forced air devices. The staff of our company will tell you more about the equipment.
Installation of forced ventilation. An electric fan is mounted directly into the hood to ensure air movement.

If the measures taken did not help, contact the management company.

Preventive measures

Installing a deflector helps to avoid blowing wind into the channel

Troubleshooting a backdraft problem can take a lot of effort, time and money. To avoid this, you need to take preventive measures. Basic tips:

The system must be in good working order.
Fans and hoods should not be placed in ventilation ducts. It is possible to use only recirculating hoods or to discharge their outlet outside through a wall or window.
Deflectors and rotary turbines are placed at the end of the riser.
Organization of the inflow of fresh air from the street in any available way, including in winter.
Installation of interior doors to block the possibility of a draft that affects back draft.
Cleaning the system from ice and snow in the winter.
Periodic ventilation check.

These measures will help to avoid most of the problems due to which reverse draft is formed and cold air blows into the apartment from the ventilation.

How to check the ventilation

If you notice unpleasant odors in the apartment, constant drafts and cold, mold and mildew on the walls or ceiling, there may be a problem with ventilation. To find out exactly, check the system operation. To do this, open a window in one of the rooms and take a thin piece of paper. Apply the paper to the ventilation grill one at a time in the bathroom, toilet and kitchen. See how she behaves.

If the paper is attracted, the ventilation in the apartment works well. If the leaf is not attracted and falls, it does not function. If the paper is flying off the ventilation grill, there is a reverse draft and the ventilation does not work properly, in the opposite direction.

In the case of reverse draft, polluted air, dirt and dust particles, and an unpleasant odor are carried out of the hole. To fix the problem, you need to determine the cause, which are distinguished by several. Let's take a closer look at why the ventilation is blowing into the apartment.

Where to go

The ventilation of the apartment building is shared. If there are problems, reverse thrust will appear in all apartments, so you need to act together. First of all, you need to discuss the problem with all the residents of the entrance. Perhaps a very powerful hood is installed in one apartment, which harms the operation of the entire system.

Next, you should contact the management company with a request to find and solve the problem. In the event of the appearance of cold musty air, you can contact the gas company. This decision is due to the fact that ventilation is a security system. It is the presence of reverse thrust that does not make it possible to ventilate the room from energy carriers and products of its combustion.

If reverse thrust appears in the house with a certain frequency, and it is impossible to eliminate it, part of the windows should be replaced with anti-explosive ones.

Why do you need a ventilation system in the house?

People spend quite a lot of time indoors. Often this is their own home. There they breathe, do household chores and sleep. All the while, they consume oxygen by breathing out carbon dioxide. Cooking, washing, cleaning and so on takes place in the same premises.

Common duct problems

If there are animals in the house, then they also contribute to air pollution in the apartment. The smallest particles of their fur float in space.Active animals raise dust as they run through the rooms. Modern materials from which furniture is made emit various substances into the airspace of the room, often harmful and dangerous to humans.

People are forced to breathe with such a “cocktail”, endangering their health. In a stuffy room, they feel worse, in such conditions it is impossible to get enough sleep, and their performance drops significantly, since a lot of oxygen is needed for the brain to function. In this situation, the ventilation system comes to the rescue. This is an element of the home that is designed to remove unpleasant odors and excessive moisture from rooms. At the same time, pure oxygen enters the house through the vents. Along the way, it is cleansed and moisturized if needed.

Reverse thrust principle

Thus, ventilation in the house performs several functions, allowing a person to maintain normal health and performance.