What to do if the ventilation is blowing into the apartment

Why does the ventilation system fail?

There are many reasons for the occurrence of reverse draft, but they are always based on the same physical process, as a result of which higher pressure appears in the ventilation ducts than in the premises. This prevents moisture, odors and harmful substances from leaving the building.

In addition, under the influence of increased pressure, contaminated air and steam are squeezed out of the ventilation system channels into all nearby openings. For example, in cracks and crevices of channels.

And the worst thing is that air from the area of high pressure mostly enters the home, since this is the easiest way.

Backdraft is a process in which the direction of movement of air masses does not correspond to the design direction. As a result, air exchange is not carried out

When the system works in the opposite direction and there is no extraction of odors or moisture from the room, then residents have to think about what to do to fix the problem.

And you can achieve the desired result by performing a number of procedures, which include:

Visual inspection of the ventilation system;
Checking the correct installation of ventilation system design elements;
Checking design documentation.

At each stage, performers look for the causes and places of occurrence of high pressure zones that lead to reverse draft.

The photo shows a fungus that actively develops indoors when reverse draft occurs. In addition, various harmful substances accumulate in the apartment, which threatens various diseases, including asthma. And the worst thing is that housing becomes a dangerous place for residents to stay, as the likelihood of a gas explosion increases, and significantly.

Since the problem of reverse draft directly affects the comfort and quality of the microclimate in housing, it is necessary to learn more about the reasons for its occurrence.

Reason #1 - foreign objects in the ventilation duct

Any change in ventilation design can lead to a decrease in air exchange efficiency. And this happens often. But what simplifies the task of identifying a fault is that it can be done quickly and without any costs. Since all that is needed is to perform a visual inspection, which you can do yourself if you wish.

But you should not abuse this opportunity. Because at the same time, you still need to have some skills, and most importantly, know and follow safety precautions.

When performing a visual inspection, pay attention to:

condition of air ducts and other structural elements;
structural integrity of air ducts and other parts of the system.

In the first case, the presence or absence of foreign objects in the air ducts is detected. Which significantly affect the performance of the ventilation system.

Detecting reverse draft is quite simple, since all you need to do is light a match or lighter and bring them to the ventilation grille. If the system is operating normally, the tip of the flame will tilt towards the ventilation duct. When backdraft is present, then the fire will tilt away from the ventilation grille. What will confirm the presence of inlet air flow

The reason is that when foreign objects get inside the channels, air exchange is disrupted, which in turn leads to reverse draft.

And the worst thing is that almost any third-party object can create problems, including leaves, tree branches, soot, plastic bags, scraps of paper and any other debris.

To get rid of debris and other objects that should not be in the ventilation duct, you need to perform cleaning.

Over time, the design of the ventilation system deteriorates, this leads to the appearance of gaps, cracks and other defects. Which ultimately causes a decrease in equipment efficiency. And there is only one positive point in this - all of the listed shortcomings are relatively easy to identify

To reduce the likelihood of foreign objects and moisture getting into the air ducts, deflectors should be installed. They also protect from wind, which can lead to reverse draft.

Reason #2 - mechanical damage and wear

If inspection of the condition of the internal channels does not produce results, then you should ensure their integrity.

Why is it necessary to inspect system elements for absence:

mechanical damage;
signs of wear;
traces of aging of the material from which the ventilation design elements are made.

Backdraft can occur due to mechanical damage such as the unauthorized appearance of additional holes in the walls of the air ducts. An example is cutting out a seat to accommodate a fan.

A malfunction such as reverse ventilation in an apartment can occur due to the fact that individual elements, due to wear, deteriorate the performance of the ventilation system. For example, if the fan provided in the design jams, then a high-pressure zone may appear on the floor above, which the air removed naturally will not push through.

An example of aging can be corrosion of the material from which the deflector is made, the occurrence of cracks and crevices on the surfaces of ventilation ducts and air ducts

The listed defects are eliminated by sealing cracks, holes, replacing failed structural elements or cleaning them, which is true for fans, deflectors and other equipment.

Reason #3 - difficult climatic conditions

Often difficult climatic conditions lead to partial or complete blocking of air ducts. For example, fog, severe frost or wind, precipitation.

The reason is that at negative temperatures, ice deposits can occur on the internal surfaces of the channels, and significant ones at that. As a result, the natural air exchange procedure can be disrupted for a long time.

In case of strong wind, fog, or precipitation, reverse draft may occur for a short period of time. But, nevertheless, this still leads to a decrease in the level of comfort and safety in housing.

The only effective way to eliminate the problem of ice deposits in ventilation ducts is cleaning.

Reason #4 - installation errors

It often happens that poor-quality or incorrect installation significantly affects the parameters of the ventilation system. For example, an air duct installed at the wrong angle or its leaky joints can provoke the appearance of a zone of high pressure, and, consequently, reverse draft.

Improperly installed deflectors, heads, fans, grilles, and valves will reduce the efficiency of the system.

The photo shows the head of a ventilation pipe, which was torn from its seat under the influence of strong winds. As a result, precipitation began to enter the internal channels of the system. What led to a change in ventilation performance characteristics and the occurrence of reverse draft

Problems are eliminated through high-quality installation of structural elements.

Reason #5 - ignoring project documentation

It almost always happens that some specialists design, while others carry out the installation, while many standards are only advisory in nature. As a result, it often happens as in the famous fable about the swan, crayfish and pike.

Therefore, an installed deflector of the wrong type or a ventilation duct of the wrong size will result in areas of high pressure.

Problems can be created by:

the heads are the wrong length;
air ducts whose cross-section differs from the design one;
fans whose performance exceeds the design, etc.

Moreover, the listed reasons are easy to identify, but there are many options that only specialists can deal with.

If you violate at least one rule indicated in the diagram, then a phenomenon such as wind backup will periodically occur. Which leads to the emergence of a high-pressure zone that the air flow from the premises will not push through. As a result, he will come back

For example, this could happen if:

the volume of the ventilation duct or its internal design does not meet the requirements;
the cross-sectional dimensions of channels, pipes, hoods, and ends do not allow for the removal of the required volume of air;
there are more consumers than planned;
inappropriate temperature in the air ducts, etc.

Reconciliation with design documentation is the most difficult way to identify the causes of backdraft. But in this case, it is necessary to have a significant supply of knowledge and skills, since it is often necessary to carry out control and verification procedures.

The functionality of the system is restored by replacing structural elements that do not correspond to the design.

And when this is not possible, methods such as:

lining, which is the placement of thin-walled pipes inside the ventilation shaft that can change the characteristics of the system as a whole;
increasing the length of the ventilation pipe.

The last method of eliminating backdraft is one of the most effective, and in most situations.

The photo shows a thin-walled pipe that was placed in the duct of the ventilation system. And this is one of the most effective and universal ways to eliminate backdraft

Thus, an extension of just 1 meter can eliminate the possibility of recurrent reverse thrust in a number of situations. Moreover, in many cases it will not be necessary to eliminate the shortcomings that led to the problem.

Ventilation malfunction

If the window panes begin to fog up and mold appears on the window slopes, it means that there is a malfunction in the ventilation. One of the problems during ventilation operation can be reverse draft. This happens when the hood is unable to completely remove the exhaust air. Instead of removing unpleasant odors and dust, ventilation forces them into the apartment. This indicates that the hood is working in the opposite direction.

To correct ventilation, the cause of backdraft is first determined. They can be very different, for example:

complete sealing in plastic windows, because of this there is no air flow;
Incorrect calculations were made when installing the ventilation system;
the mine shaft is clogged;
unapproved renovations in a neighboring apartment are blocking the ventilation duct;
poor heating of premises in the autumn-winter period;
snow and ice have accumulated in the ventilation shafts;
strong wind;
storm stream.

All these factors increase backdraft in ventilation. To organize work, you need to contact the Housing Office with an application. Employees will inspect and check the hood, draw up an appropriate report and make their decision.

Batteries in the apartment do not heat well: faults and their elimination

Reverse draft in the ventilation of an apartment in an apartment building - what to do? 2021

The presence of errors in the design of a residential building can lead to various unpleasant phenomena, one of which is reverse draft in ventilation. The purpose of the ventilation system is to remove polluted air, and the influx must be through windows.

However, if there are violations, the ventilation does not work properly and brings polluted air into the rooms from other consumers. To eliminate this problem, a plug with a check valve is used - it prevents air flows from entering the apartment, and they move in a common shaft.

To find out what causes deviations in ventilation operation, you need to invite independent specialists to check the operation of the system. They compare the obtained indicators with the data given in regulations. Specialists describe in detail deviations in the operation of the ventilation system, and make a conclusion about the operability of the system, and also give recommendations to the customer.

The examination can be divided into three stages:

Checking all available design documentation related to the ventilation system. At this stage, specialists evaluate the rationality of using design solutions and existing equipment, the correctness of its use and the compliance of documentation with building codes and GOSTs.
Checking installation work. This stage consists of assessing the quality of the installed elements of the air duct, duct and other equipment.
Search for breakdowns and defects in work. The condition of the system and its performance as a whole are assessed. Real air outflow indicators are compared with the data included in the project.

To determine the reasons for the improper operation of the ventilation system, specialists check indoor air parameters. To search for places where natural ventilation channels are illegally blocked, a video endoscope is used.

Incorrect operation of the ventilation system in apartments can be caused by various reasons. The simplest and most obvious ones can be determined by inspecting the stove or fireplace. To understand traction problems, you should find out the location of the pipe and the exit to the roof.

If the initial inspection does not produce tangible results, it is necessary to look for the reasons for the malfunction of the system inside the apartment.

In many cases, the causes of back draft in ventilation are incorrect or insufficient air flow into the room. The problem arises from modern sealed windows. Unlike old wooden windows, for which most multi-storey buildings were designed, plastic windows do not allow air into the apartment. To solve this problem, it is recommended to install supply valves or an additional ventilation system that provides air flow.

In order for stoves or fireplaces to function properly, they require a constant flow of air into the room. It must be taken into account that ventilation ducts operate in a more active mode compared to the chimney. When using small cross-section pipes, the air flow inside them has a high speed due to the fact that the air is heated quickly.

If an apartment or cottage has a staircase, then it should be taken into account when designing and creating a ventilation system. A staircase, at its core, is a huge pipe through which air moves. If there are errors in the design, it can lead to a change in the direction of flow in the ventilation ducts.

It should be borne in mind that a curved staircase has less impact on the operation of the ventilation system than a straight one.

Also an important factor in disrupting the proper operation of ventilation is a powerful kitchen hood. The effect of its action is enhanced if it is located near the fireplace. The most productive models of hoods are capable of distilling up to 1.2 thousand cubic meters. m 3 air per hour of work. Neither fireplace networks nor air ducts can cope with such a volume.

Common causes of backdraft ventilation in an apartment:

Features of the location of the pipe on the roof. There is a possibility that the pipe is in the so-called zone. “wind shadow”, when protruding parts of the house block air flows. The wind may also blow in the opposite direction, preventing air from moving into the pipe.
Clogged ventilation ducts. They get various debris, ice and snow, soot and the consequences of the activity of birds living on the roof.
Accumulation of a large volume of steam or cold air in the ducts, which impedes air movement.
Incorrect operation of hoods, compressors and fans. A similar problem arises from drafts that blow in large rooms that do not have partitions. In apartment buildings, a situation often occurs when intensive removal of air from one apartment leads to reverse draft in another.

To understand in detail why there is reverse draft in ventilation, you need to analyze all the important parameters. Many environmental factors can disrupt the operation of the system, such as atmospheric pressure and humidity, convection currents, and inversion isothermal phenomena.

One solution is to place a deflector, which is a mechanical fan that sucks air from the shaft. A gate that regulates reverse draft can act as a flow amplifier. In some cases, it is enough to open the windows to ventilate the room well.

A preventive measure is periodic cleaning of the chimney and installation of a special tee that performs cleaning. In winter, frozen areas of the canal must be cleared of snow and ice. If the efficiency of the system as a whole is low, then it needs to be repaired or modernized, the program of which may include raising the pipe so that its opening is above the wind shadow.

Reasons for the appearance of reverse draft in apartments

There are different reasons. One of them is improper air flow into the rooms. Sometimes the problem is aggravated by plastic windows, which are made from materials that do not allow air to pass through at all.

List of the most common causes of backdraft:

improper ventilation arrangement in multi-storey buildings : violation of the location of the pipes of the ventilation shaft or channel or their insufficient height;
clogging of ventilation ducts with snow, ice, debris, incl.

the appearance of bird nests there;

abnormal operation of the hood or additional equipment.

Another reason is renovations from neighbors with redevelopment and alteration of the ventilation system. For example, during repairs, neighbors may block the ventilation riser, which will disrupt the operation of the entire system, and air flows with unpleasant odors will flow towards adjacent apartments.

The reverse draft effect is one of the problems for owners of apartments on the top floors. Optimal air circulation occurs if the air can travel at least 2 m to the roof. Sometimes apartment buildings do not have this option. Therefore, owners of apartments on the top floors often upgrade their ventilation systems with individual valves.

Backdraft in an apartment: consequences and “first aid”

Sometimes the effect of backdraft becomes noticeable and obvious to apartment residents immediately. Sometimes it's not so easy to recognize. If suspicions and concerns arise, this can be checked in the following ways:

Open the window and place a piece of thin paper on the ventilation grille. If the sheet stays on the grill, then everything is in order, the air flow attracted it. If the sheet does not hold, then there is a problem with the ventilation system.
Bring a lit lighter or candle to the grate: the flame should bend towards the grate. If it is directed towards the apartment, the air does not flow where it is needed.

Consequences that reverse draft in an apartment can lead to:

fogging of windows, appearance of dampness, unpleasant odors;
development of dangerous respiratory diseases in apartment residents, for example, bronchial asthma.

cold in the apartment if the air drawn in through the ventilation comes from the street and not from neighbors.

In general, apartment owners should not repair the ventilation system themselves - this is the job of the management organization. But sometimes, if the duct is not very clogged and the clog is located close to the grille, a simple household method is effective - cleaning the ventilation duct with a vacuum cleaner. Of course, this method only works in the simplest cases.

What to do in other situations? The management company should deal with the issue of normal operation of the system. The management company must accept the complaint and send a specialist to the apartment who will check the system to see if the ventilation duct is clogged, if there are other problems or malfunctions, etc. After determining the cause, the specialist must take measures to eliminate the backdraft effect.

In some cases, installing an air conditioner and specialized supply valves, the power and parameters of which are calculated based on the parameters and size of the apartment, helps correct the situation. If a supply ventilation system is installed in the apartment, then it is necessary to consider a sound insulation system.

Ventilation system of an apartment building

The comfort of living of apartment owners depends on the quality and serviceability of the ventilation system in the house. Regular maintenance and checking of ventilation in an apartment building should be carried out by the management company, and when necessary, take measures (carry out repairs ) to eliminate malfunctions.

If mistakes were made when designing a residential building, in the future an unpleasant phenomenon such as backdraft in ventilation may appear. The effect develops if the shafts and channels were cast in solid panels. Ventilation is disrupted and brings a whole bouquet of unpleasant aromas towards the room. To eliminate this problem, a plug is usually used in an apartment - it cuts off air flows and redirects them into a common shaft.

To identify problems, independent specialists are invited to check the ventilation system and its compliance with regulations. Evaluating effectiveness involves using an integrated approach. Specialists must describe in detail all existing deviations in the performance of the system, make a general conclusion and give recommendations to the customer. The examination includes three stages:

Detailed verification of all existing project documentation regarding ventilation and climate control systems. At the first stage, specialists must assess the rationality of using the equipment, the relevance of its operation, and also check the compliance of design documents with GOSTs.
Expertise of installation work of ventilation systems. At the next stage, it is necessary to carefully check the quality of the installation of air ducts, channels and other equipment.
Search for breakdowns and defects, check the current condition. After a preliminary check, specialists evaluate the performance of the system as a whole.

When determining the causes of ventilation malfunctions, experts must measure air parameters in the apartment, determine the location of unauthorized blockages of natural ventilation channels using a video endoscope, and compare air flow rates with design data.

Ventilation in an apartment may not work correctly for many reasons. Some of them can be determined immediately after inspecting the fireplace or stove. To understand why the draft is broken, you first need to study the location of the pipe. You should also pay attention to its access to the roof. If the initial inspection does not produce results, you need to look for other reasons for poor ventilation in the apartment.

Most often, ventilation works in the opposite direction due to improper air flow into the room. The problem can be made worse by sealed windows. They are made from modern types of plastic and double-glazed windows - materials that are strong and durable, but completely impermeable to air. An alternative option would be to install wooden windows. In European countries, this issue is solved with the help of supply valves and the installation of a ventilation system.

The tightness of plastic windows can cause a lack of fresh air flow

For proper operation of a fireplace or stove, air flow towards the room is necessary, since ventilation ducts work much more actively than the chimney. In pipes that have a small cross-section, the air temperature rises more quickly, and it rushes upward.

Another reason for the formation of reverse draft in an apartment or cottage may be the presence of stairs in the building. In fact, it is a huge pipe that can change the direction of air flow even in ventilation ducts. A curved staircase has less impact on the system than a straight one.

Also a factor in the malfunction of ventilation is the kitchen hood. If the kitchen is located close to the fireplace, backdraft may form. The latest models are capable of processing up to 1200 cubic meters of air per hour, which leads to the failure of the fireplace network and air vents.

The most common causes of backdraft include:

Specific pipe location. If it is located in a wind shadow area formed by protruding parts of the house, air circulation may be impaired.
Wind that blows in a certain direction.
Accumulation of a large amount of cold air and vapors in the ventilation ducts, which impede the movement of draft.
Ventilation ducts becoming clogged with snow and ice.
Accumulation of debris, bird nests and soot deposits.
Drafts that blow inside large rooms that are not divided into compartments.
Incorrect operation of exhaust systems, compressor equipment and fans.

To understand why backdraft occurs, we need to analyze all the components. Environmental factors such as atmospheric pressure, humidity, the activity of convective flows, the presence of isotherm and inversion can disrupt the balance of ventilation.

One way to solve the problem is to install a deflector - a mechanical fan that sucks smoke from the chimney shaft. The damper can act as an amplifier in the chimney - it is used to regulate the reverse draft. They are usually installed in the chimney duct and in the oven door. Sometimes the issue can be resolved very simply - just open the doors and ventilate the room.

This problem often occurs if the stove or fireplace has not been used for a long time. Heavy air can accumulate inside, which impedes movement, and smoke is drawn through the fireplace towards the room. If the phenomenon occurs periodically, a draft stabilizer for the chimney will help to cope with it - it optimizes the movement of air in the ventilation. The safety valve protects against sudden pressure changes.

As a preventative measure, it is necessary to clean the chimney from time to time and install a special tee for cleaning. To troubleshoot problems, use the following troubleshooting methods:

Exiting the pipe above the wind shadow zone.
Repair the ventilation structure as necessary.
Creating an influx of fresh air flows.
Cleaning channels.
Clearing frozen areas of snow and ice.
Changing the layout of the room, creating organized flows and installing doors.

Reverse draft in the apartment leads to fogging of windows, dampness and unpleasant odors. This can also lead to the development of dangerous diseases such as bronchial asthma and many other respiratory diseases.

If there is concern that the ventilation is faulty, there are several ways to check. You should open the window slightly, take a sheet of thin paper and bring it to the ventilation grille. If the air flow attracts it, then there is no problem; if it does not hold, the ventilation is impaired. You can also use a lighter or a lit candle - the flame should bend to the side. In hot weather, the air becomes heavier and the wind does not blow, so it is not worth checking at this time.

Apartment owners do not have the right to clean ventilation shafts themselves. To do this, they must call specialists. Residents can only remove the grate and try to blow away debris using a vacuum cleaner. If this does not help, all that remains is to turn to professionals.

One of the reasons for the appearance of reverse draft in an apartment may be unauthorized redevelopment of neighbors. During repairs, they can block the ventilation riser and create a negative microclimate and unpleasant odors towards adjacent apartments.

To improve ventilation, air conditioning and specialized supply valves are used. Power is calculated based on the size of the apartment. If you install a supply ventilation system, you need to consider sound insulation of the system. The device can be hidden under a suspended ceiling or installed in walls.

In apartment buildings, the problem often appears on the top floor. This is explained by the peculiarities of ventilation. For normal air circulation, it is necessary to travel at least two meters towards the roof. On the top floor this is difficult to achieve, so modern methods of removing excess air are used. For this purpose, individual channels are being built up.

4. Hygienic requirements for heating, ventilation, microclimate and air environment of premises: 4.7. Natural ventilation of residential premises should be carried out by air flow through vents, transoms, or through special openings in window sashes and ventilation ducts.

Those. it is stipulated that air should enter through cracks in wooden windows (everyone probably remembers how they were blown out) or an open window.

But there won’t necessarily be condensation, humidity, or mold in the room. Air also penetrates from the neighbors below, on the side. Everyone’s finishing materials are different, some have higher air permeability... therefore, some get more air. For example, the required 15 cubes to avoid the problems that I wrote just above.

With a greater air flow, the backdraft in the toilet also decreases (see picture).

Many thought: “Everything is clear, we need to install a turbo deflector or a fan on the channel with reverse draft, let it force the air out.” This won't help the situation! Thanks to forced draft, it will become stronger than the kitchen one. It will capture the required volume of air from the kitchen. Now reverse draft will appear in the kitchen!

In order for ventilation to work properly, air must be supplied from the street. The optimal solution, in our opinion, is to install the KIV-125 valve, sometimes called an “alpine window”. It is a plastic round head on which the air flow regulator is located. Such a device is installed next to the window; for this, a through hole with a diameter of 13 cm is drilled in the wall to the street, a grille is installed outside, and insulation is mounted inside the drilled channel. Modern construction equipment allows you to complete this work in just 2 hours, without dust and dirt!

Advantages of the “alpine window”:

There is no draft
No noise from the street
The filter prevents the entry of midges, mosquitoes and other insects.
A small amount of fresh air from the street will constantly flow through the valve.

You can see more about it by following the link: https://brizer-m.ru/catalog/kiv-125/

The cost with turnkey installation is about 5500 rubles.

Supply valve KIV-125 1900 RUR

Such a valve is necessary in every living room. In many cases, installing a KIV relieves you of reverse draft. In a two-room or three-room apartment, 2 or 3 nozzle valves, respectively, provide the necessary air supply. But it happens that in a one-room apartment the following situation occurs:

The capacity of one KIV-125 valve is not enough to completely correct the reverse draft. It is enough to: reduce humidity in the room, get rid of condensation on windows, mold. Of course, all situations are individual; for some, 1 valve is enough.

So, the valve was installed, the backdraft did not disappear. You can do it in a cunning way. Reduce the “appetite” of ventilation exhaust ducts. To do this, you need to reduce the area of the hole, for example, cover it with paper tape, until the reverse draft in all channels (in the kitchen and toilet) disappears.

Some people thought: “Why couldn’t this have been done before the kivas were installed?” Then there will be 100% mold in the apartment, and mold means that the conditions are not acceptable for living. There will definitely be health problems in the future.

There are also more advanced devices that force air in a large volume; when they are turned on, the apartment is not stuffy even when there are 4 adults. Such devices are called breathers. They have good air filtration, heating, and automation.

If you can afford such a device, be sure to take it, you won’t regret it!

Minus of the nozzle valve and natural ventilation in general, in principle. The draft in the ventilation duct is formed due to the temperature difference, but in the summer the temperature in the apartment and outside is the same. Natural ventilation must work when the temperature difference is at least 13 degrees. For example, in an apartment it’s +18, and outside it’s +5.

It happens that in the summer the opposite situation arises: the temperature outside under the sun is high, but in the apartment, in the shade, the temperature is lower. As a result, reverse draft occurs.

With breathers, which force air into the apartment using a fan, reverse draft will not occur even in summer.

Unfortunately, the ventilation system sometimes does not work correctly. This is when the ventilation starts to blow back into the living areas of the house. The air from the ventilation shaft brings with it unpleasant aromas, and this is felt immediately. You should not put off solving this problem for a long time, because it will not be solved by itself. Let's figure out why ventilation works in the opposite direction.

What is this ventilation system? Essentially, this is a complex of air ducts in a private house or a system of shafts in an apartment building, in which there is one main riser stretching from the basement to the roof. It is this that creates the draft due to the temperature difference between indoors and outdoors. And the greater this difference, the stronger the hood works. Let's add wind perpendicular pressure like cross sections. This is when the wind blows in a horizontal direction relative to the riser, and it pulls air from the ventilation with it. That is, air is sucked out of the premises naturally, and not with the help of additional equipment such as a fan.

Of course, in such a system there must be an air flow so that a vacuum does not form inside the house or the draft does not decrease. Therefore, vents are left in the foundation or holes are made in the floor of the first floor.

If the ventilation system is not working correctly, there is a reason for it. There are many of them, but the main two are:

There is no supply ventilation.
The temperature inside is lower than outside. This usually happens in the summer when it is hot.

But the main reason is the lack of supply air flows. Typically, in apartments, outlets to the ventilation shaft are made through the bathroom, toilet and kitchen. And the air flow occurred through the windows (their leaks) and the front door. Today, when plastic windows are installed instead of wooden windows with complete sealing of joints and connections, the problem of inflow has become serious. Most often, backdraft appears because of this. This problem is solved by installing supply valves into window systems.

Other causes of traction failure and reverse flow include:

malfunctions of the system itself;
installing fans instead of grilles;
installation of a flow hood, which is connected to the ventilation duct;
absence of an umbrella on the roof or destruction of the mouth of the canal.

The causes of the malfunction can be attributed to a large number of factors. The main thing you need to understand is that when there is blowing from the ventilation system in an apartment, it is not the same thing if the same effect appears in a private house. That is, faults in two buildings may be different, because the traction failure in them has different causes.

For example, in an apartment this most often happens due to the installation of a fan or hood in the kitchen, which begins to press through its channel, and the air inside, moving to the riser with pressure, does not have time to pass the entire mass upward. That is, part of it ends up in the adjacent channel of the toilet or bathroom. It is in these rooms that the opposite effect occurs. The same thing happens in the opposite direction, if the fan in the kitchen is turned off and the fan in the toilet is on. This also happens with neighboring apartments located one above the other.

This suggests that you cannot thoughtlessly install additional exhaust devices without calculating their power. And the more powerful the fan, the stronger the reverse draft of the ventilation system in the apartment of a multi-story building.

For this reason, this cannot happen in a private house, because at the design stage today they try to distribute ventilation ducts to all rooms separately. That is, the kitchen has its own riser, and the toilet and bathroom have their own. But sometimes another problem arises in the house. Most often, risers are combined into one or two common channels inside the attic, and then one or two pipes are discharged through the roofing. And here horizontal sections appear in the ventilation system. The main task of the designer is to use as little of this type of air duct as possible, and to minimize the angle of inclination of horizontal sections (the reduction should be minimal). That is, the steeper this section, the better the upward air movement.

And three more reasons:

Lack of thermal insulation. Cold air in winter enters the air ducts, where it freezes, turning into ice. This usually occurs at the mouth of the canal. The consequences are a reduction in the cross section.
Lack of an umbrella (visor), which can lead to rain and reduced traction. This disrupts air exchange.
The ventilation in the house is clogged with debris.

So, in order to remove backdraft, you must first understand why it appears.

As mentioned above, reverse draft in ventilation appears for two main reasons:

Complete sealing of the premises.
Installation of additional exhaust devices in ventilation ducts.

All other reasons are secondary, some of which do not create reverse draft, but simply the ventilation stops working. Ventilation in an apartment is more difficult, because the system itself is a complex set of channels, often made of concrete. Branches extend from the riser throughout all apartments, through which air from the premises must be removed to the street. And if a neighbor on the lower floor installs a powerful kitchen hood, then not only he, but also the neighbors on the floors closest to him will feel the reverse flow of air masses.

In a private house, reverse draft occurs for other reasons, because the ventilation in the apartment differs from the ventilation system of a private house. This is where installing fans can solve the problem. But you just need to determine the installation location using different risers.

There are two ways:

The simplest one is to place your palm with the ventilation hole, and if the ventilation is working properly, you should feel the movement of the air flow.
Place a napkin or paper sheet on the grill. If the first holds on to the second, it means the traction is good, there is no reverse effect.

Ventilation problems usually occur after many years of using a home.

Its cross-section becomes smaller due to debris, rodents and birds that have fallen inside.
Destruction of the walls of ventilation ducts due to condensation.
The absence of a head is due to precipitation trapped inside.

All this reduces cravings, which means that the humidity inside the apartments increases, and unpleasant odors will become eternal companions of the rooms. What to do?

Many people probably thought that the conversation was about installing fans in place of ventilation grilles. Nobody forbids doing this, although it has already been described above what this can lead to.

We are talking about a fan that is installed in the system on the roof. This may be a mechanical deflector or a rotary turbine. Both devices are powered by the wind, so they are of no use in calm weather. Although, as practice shows, it is the installation of these devices that sharply increases traction and prevents reverse flow.

To do this, you need to calculate the volume of the kitchen. For example, a room area of 3x4 m with a ceiling height of 3 m, the volume will be 36 m³. Now we multiply the resulting value by a factor of 12-20. At the minimum value, the fan performance is 432, at the maximum 720 m³/hour.

What needs to be done to prevent backdraft from forming.

Keep the ventilation system in good condition.
Do not install fans or hoods into ventilation ducts. Use a recirculating hood or vent it outside the room to the street: through a wall or window glass.
Install baffles or rotary turbines at the end of the riser.
Organize air flow into the premises by any means.
Install interior doors that block air movement between rooms. Strong drafts are also causes of backflow.
Clean the ventilation system from snow and ice in winter.
Check ventilation periodically.

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Causes of reverse thrust

As mentioned above, reverse draft in ventilation appears for two main reasons:

Complete sealing of the premises.
Installation of additional exhaust devices in ventilation ducts.

Causes of reverse thrust

If the ventilation duct is clogged, reverse draft occurs or ventilation does not work.
The main reason for the occurrence of reverse draft is a violation of the principle of natural air exchange. It is caused by the following factors:

Application of plastic windows and sealed doors. They are able to completely block access to fresh air into the room.
Alteration of the ventilation duct or illegal demolition.
Incorrect pipe design or incorrect placement. If it is installed in a wind shadow area, circulation will be disrupted.
Change in wind direction.
The ventilation duct is clogged with small debris and birds get into it.
Design errors.

Why does backdraft still occur?

The previous part of the article listed the traditional causes of problems in the ventilation system. They appear and will continue to appear as long as people use air ducts. As a result, effective technologies have long been developed that make it possible to quickly and inexpensively restore the functionality of any ventilation system.

But over the past few decades, our country has begun to actively use technologies that require an integrated approach and the participation of all residents. And problems arise with this regularly.

It often happens that the reason for the inoperability of the ventilation system is the illiterate or negligent attitude of the residents themselves. And the worst thing is that often domestic legislation cannot even influence this

Therefore, residents of many houses are unable to cope with a number of reasons leading to reverse draft:

mass installation of modern sealed windows;
the emergence of a high pressure area above the upper floors due to significant loads on the system;
inconsistency of actions and illiteracy of residents.

Since the ventilation systems of a significant number of multi-storey buildings are ineffective due to the above reasons, you should familiarize yourself with each of them in more detail.

Replacing old windows with metal-plastic ones

Before you begin restoring the functionality of ventilation, you should understand that in most modern houses it is based on the principles of natural air exchange.

This means that there must be a so-called slot air flow. Moreover, most of it should enter the home through windows, but modern metal-plastic models are sealed. That is, they do not have cracks and there is no influx.

At the same time, no one has canceled the hood, and it removes air at the required capacity. But until the pressure in the room drops below the same parameter in the air duct, which will lead to reverse draft.

And the worst thing is that it will not be possible to restore normal air exchange, and none of the methods listed in the first part of the article will work as long as the windows are closed. But in many cases, to restore normal air exchange, it is enough to keep the windows slightly open. That is, nothing else will need to be done.

The photo shows a wall inlet valve, which can be used to solve one of the most important problems in arranging ventilation in modern conditions. Which is the lack of supply air due to the tightness of the windows

But since ventilation is not always possible, it is better to use:

supply valves to the wall (wall);
window valves for organizing slot micro-ventilation.

It should be taken into account that in many cases the efficiency of the ventilation system can be restored if the supply valves are installed by a large part of the users. And it can be difficult to convince people of this.

If the solutions listed above are unacceptable, then you can drill one hole in the area of the entrance door to the entrance, and the second, with a diameter of 1 cm, above the entrance door to the house. And this method is often enough to get rid of backdraft forever. The fact is that stairwells are usually the most powerful hoods in homes. But the described option is only suitable when there is no smoking in the entrances. But, if this is not the case, then you should look for another solution.

Insufficient height of the ventilation duct on the top floors

Natural ventilation is effective when air particles can move vertically at least 2 meters. And homeowners on the penultimate and lower floors are lucky. Since there is enough distance reserve in their ventilation systems.

Residents of apartment buildings should understand that in most cases, eliminating the causes of reverse draft can only be done through joint efforts

But above each top floor there is a horizontal ventilation duct or a warm technical floor. As a result, in the first case, the air flow is slowed down by the ceiling of the duct and a high-pressure zone is immediately created. Therefore, part of the air returns back and enters the ventilation hoods of the upper floors, since this is the easiest way.

The situation is aggravated by the increasingly active use of hoods and fans. Moreover, a mixture of vapors and odors from all floors enters the housing.

This situation can be dealt with by increasing the height of horizontal ventilation ducts (2-3 times) and installing devices called “cutting” in them.

But the opportunity to use the methods listed above is not always available. Therefore, to solve the problem, sometimes it is necessary to create an individual channel that cuts into the shaft on top of the common boxes.

But this procedure is called redevelopment, and the air duct to which you need to connect is common property. As a result, it is necessary to obtain the consent of all neighbors (which is not always easy) and go through the approval procedure with the housing inspection.

The photo shows an individual ventilation duct that the owners of the apartment on the top floor created for themselves (after completing the approval procedure). This did not come without expenses, but they are not that significant, especially against the backdrop of the positive result obtained.

In the case of warm technical floors, the polluted air from the apartment on the top floor simply slows down. Yet traction provides the system with efficiency. But if there are gaps, cracks or open doors from the technical floor, it overturns and polluted air goes to the apartments on the upper floors.

In this case, they create their own individual channel, which should be lengthened and slightly tilted towards the common shaft. But, again, all of the above can be done only after obtaining permission from neighbors and completing the approval procedure.

Reluctance of residents of the entrance to act together

But it should be remembered that ventilation is a common system for the entire entrance. And if one of the residents has installed an exhaust hood that is too powerful, and you suffer from the fact that the ventilation system cannot cope and the exhaust air not only returns back, but also foreign odors also begin to enter the apartment, then you need to act together. First, if reverse draft occurs, you should discuss this problem with other residents of the entrance. Since in many cases this problem is common to all users.

After which it is worth collectively contacting the management company with a request to solve the problem comprehensively. In this case, the described method of combating backdraft is the most effective.

But, unfortunately, in many cases there is a problem with the organization. Since in critical situations, many residents prefer to solve problems in easier and faster ways (as it seems to them). For example, installing air conditioning and recovery systems. And without even realizing that it is impossible to replace natural ventilation with anything, especially for houses where there is gas.

It is worth entrusting the identification and elimination of backdraft to specialists, as they have the necessary skills, experience and special equipment, which will make it possible to make the optimal decision

And, if unpleasant cold and musty air is blowing from the ventilation, and the neighbors do not want to fight it, then you can call on gorgaz to help you. For example, exhausting their specialists with complaints about violations of safety measures, if the smell of gas is clearly felt in the room. But this happens quite often - reverse draft does not make it possible to ventilate the room, both from the energy carrier itself and from the products of its combustion (for example, carbon monoxide).

By the way, if reverse draft even sometimes appears in the house, then at least some of the windows should be replaced with those that are destroyed during a gas explosion - anti-explosion ones. This will reduce the likelihood of a serious outcome.

But the problem of reverse draft is relevant not only for residents of high-rise buildings, but also for the private sector. We discussed the common causes of its occurrence and their elimination in the following article.

Where to go with problems in the ventilation system

When independent methods of eliminating backdraft do not lead to the desired results, you need to contact specialists. First, an application is made to the house management, indicating the problems. Then, the organization servicing the house will send a specialist who will determine the causes of the malfunction. And, accordingly, depending on the conclusions of the professionals, either they fix the problems themselves or give recommendations to the residents.

To draw a correct conclusion, craftsmen will have to study the correctness of the developed ventilation project and its non-compliance with construction standards. Also, check the impact of equipment installation on its correct operation.

Self-determination of cravings

There are two ways:

The simplest one is to place your palm with the ventilation hole, and if the ventilation is working properly, you should feel the movement of the air flow.
Place a napkin or paper sheet on the grill. If the first holds on to the second, it means the traction is good, there is no reverse effect.

Expert review

To obtain a professional assessment of the ventilation condition, you will need to invite an appropriate specialist who, after the inspection, will draw up regulatory documents where the system parameters are entered. The status report will include ways to address existing deficiencies.

The examination includes three stages:

Study of project documents.
Equipment check.
Finding the reasons for malfunction.

A video endoscope is used to search for blocked wire paths. All identified deficiencies are eliminated within 45 days.

Preventive measures

What needs to be done to prevent backdraft from forming.

Keep the ventilation system in good condition.
Do not install fans or hoods into ventilation ducts. Use a recirculating hood or vent it outside the room to the street: through a wall or window glass.
Install baffles or rotary turbines at the end of the riser.
Organize air flow into the premises by any means.
Install interior doors that block air movement between rooms. Strong drafts are also causes of backflow.
Clean the ventilation system from snow and ice in winter.
Check ventilation periodically.

Traction force

The occurrence of reverse draft occurs due to errors in planning the ventilation system. For example, for small private houses, supply and exhaust ventilation is designed with zero volume of inflowing and outflowing air space at any time of the year.

In apartment buildings, it is mandatory to install ventilation systems that operate on a similar natural supply and exhaust basis. Exhaust ventilation is installed in bathrooms, toilets and kitchens. Residential apartments are equipped with supply ventilation maintaining specified volumes of incoming flows

It is very important to keep the following values constant:

temperature;
humidity;
oxygen balance.

With the help of a ventilation system, excess moisture and various odors are removed from buildings and premises, and clean air enters inside. Warm air currents rise and enter the ventilation ducts. The traction force depends on the pressure difference between indoors and outdoors. The greater the temperature difference, the more powerful this force is, because air flows from an area of high pressure rush to an area of low pressure.

Many residents living on the top floor complain about the efficiency of the ventilation system. The essence of the problem is that in order to effectively ventilate a home, the air needs to travel about two meters vertically. If such difficulties are not observed on other floors, then with the last floor things are somewhat different, since the attic space interferes with the passage of air. To solve this problem, the attic is used as an intermediate ventilation chamber. The air entering there is redirected through the common ventilation duct to the outside.

How to check the presence of draft and ventilation in an apartment

How to detect reverse draft in a chimney?

Nowadays, one of the most modern ways to detect the presence of backdraft in a chimney (in non-obvious situations) is considered to be an anemometer test. This is an easy-to-use device, today it is not only mechanical, but also digital: just bring it to the inlet and outlet of the pipe, and it will show the current pressure. If its indicators are lower than the already mentioned 10-20 Pa, it’s time to sound the alarm. There is only one thing: this equipment will take readings only in the presence of a wind flow of more than 1 m/s.

What to do if such equipment is not at hand? Use traditional methods:

Light a match, or better yet a candle, bring it to the heating unit and see how the fire behaves. If the tongue pulls into the channel, then everything is in order, but if it remains motionless, there is no air circulation, if it goes to the side, there is a problem.
Visually, that is, see if the room is smoked - even the slightest signs of billowing steam indicate reverse draft. Although this is the most inaccurate way.
Bring the combustion mirror closer to the working furnace - if it fogs up, it means the steam is not being fully released.
Pay attention to the color of the flame when burning wood (peat, gas). If it is golden, everything is fine, if it is white, the extract is too strong, if it is reddish or red, there is a return effect.
Bring a tape, paper sheet, or plastic bag to the firebox, holding it by the edge, and see where it moves

If it stays in place, there is no air circulation; if it moves away from you, the system works correctly; if it moves toward you, there is a problem.

What is thrust and reverse thrust

Draft is a directed flow of air that occurs due to the difference in pressure inside and outside the room. Air currents tend to move from an area of high pressure to an area of low pressure. General ventilation in an apartment building operates according to a similar natural supply and exhaust principle:

The air in the room heats up and becomes lighter (density decreases).
Warm air tends upward and is forced out into the ventilation.
Cold air enters the room through cracks and openings.

The indoor air has a higher temperature. According to the laws of physics, it rushes upward. The greater the temperature difference between outside and inside the room and the greater the difference in height between the point of entry and exit of air masses from the apartment, the stronger the draft. Therefore, as a rule, residents of upper floors feel the lack of fresh air more acutely. Backdraft in ventilation occurs when exhaust air does not go outside, but returns to the room.

Causes of reverse draft in ventilation

Reverse draft occurs due to miscalculations in the design of the ventilation system or its insufficiently qualified execution. But since air has well-studied physical properties, it is easy to identify the causes of the problem and find ways to eliminate it.

Law of conservation of volume during ventilation

When modeling air exchange for small volumes according to the law of conservation, which are typical for private houses, it is possible to neglect such air parameters as the degree of compression and uneven density.

In this case, the basic physical law of supply and exhaust ventilation can be formulated as follows: the difference in the volume of incoming and outgoing air for any period of time is zero.

Exhaust ventilation is installed in places with the greatest accumulation of polluting aerosols. These are the bathroom, kitchen and service areas. Some hoods are equipped with fans to forcefully increase the volume of air removed.

This is necessary to accurately maintain microclimate parameters such as temperature, humidity and oxygen conditions.

Thus, most often the volumes of air intake in different places of the house are fixed, and the distribution of outgoing air among the openings is variable.

If at a certain point in time a part of the exhaust system passes a flow greater than that provided by the supply ventilation, the missing volume is compensated through the holes designed to release air.

To prevent such a scenario, it is necessary to perform the following set of actions when developing a ventilation system:

install a check valve on each exhaust hole to prevent air flow through it;
organize one or more reserve supply openings of a natural type to compensate for the missing volume.

The cross-section of the holes in the backup air supply devices must be calculated in such a way that they can collectively compensate for the maximum volume of missing air. Each of them must be equipped with a check valve to prevent the outflow of air. This is fraught with icing and blockage of inflows in winter.

Unaccounted for air exchange between ventilation and the street

Filtration plays a role in the air balance of a house - the uncontrolled passage of air through cracks and leaks, that is, the so-called unaccounted air exchange with the street. If this phenomenon is intense, then it is impossible to accurately calculate the parameters of the ventilation system.

In addition, infiltration (inward-directed filtration) allows air to penetrate into the room without treating it with dust filters and without heating it to the desired temperature in winter. Therefore, this phenomenon must be completely eliminated or its impact on the overall air circulation must be made insignificant.

Open windows, balconies and attic doors create additional air exchange. It is impossible to reliably calculate it in advance, since the speed and even the vector of the flow depends on many factors, primarily external and internal temperature, as well as the direction and intensity of the wind.

In cold weather, the chimney serves as an additional variable-power exhaust device. Hot air with combustion products exits through it, making a significant contribution to the total volume of the exhaust flow.

The volume of air exiting through the chimney depends on the power of the boiler. For factory products, it is easy to calculate, since the instructions contain tables that indicate the minimum cross-section of the chimney and the rate of emission of combustion products for a specific model.

If we consider the chimney as an exhaust duct, then its specific feature is the impossibility of installing a check valve on it. An integrated smoke exhauster can be an alternative, but only if its installation is technically possible. Then heating can be included in the model as an extractor hood with a fan.

Calculating the air balance in the presence of a chimney must be approached responsibly. Even a single flow reversal can completely ruin the interior of the room. In addition, with a large flame, there is a risk of fire, as well as the possibility of poisoning people from combustion products.