Why does the hood blow in the opposite direction in an apartment: the main reasons and ways to eliminate reverse draft

If the hood in an apartment blows into the apartment, this immediately affects the comfort, and often the safety of living. And something needs to be done about this. Do you agree? After all, no one wants to breathe stale air, suffer from respiratory diseases, or constantly be under the threat of a gas explosion.

Moreover, in some cases it is not difficult to solve the problem, even on your own. And we will talk about how to do this correctly in our article - we will analyze the main reasons why backdraft occurs in an apartment, and we will also provide recommendations for eliminating the problem.

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:

1. Visual inspection of the ventilation system;
2. Checking the correct installation of ventilation system design elements;
3. 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:

• channel status air ducts and other structural elements;
• integrity of the air duct structure 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, you should install deflectors. 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, etc. will reduce the efficiency of the system. gratings, valve.

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.

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 requests for violations security measuresif 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 when gas explosion - anti-explosive. 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 next article.

Conclusions and useful video on the topic

The first video talks about the problem with ventilation due to sealed windows:

The following video helps you understand how you can solve the backdraft problem yourself:

Backdraft in the ventilation system is an unpleasant and very common phenomenon. And the residents of thousands of Russian high-rise buildings suffer from it. Nevertheless, it is possible to normalize air exchange, although in most cases this will require the interest of all or at least the majority of residents of the entrance.

Are you familiar with the backdraft problem firsthand and would you like to tell us how you managed to get rid of it? Or would you like to supplement the above material with useful information? Write your comments, share your experience, participate in the discussion - the feedback block is located below this publication.