Why is there no draft in the ventilation duct. Elimination of reverse draft in ventilation of a private house
The ventilation system is an important part of every room. It is designed to remove stagnant air from the room, while letting fresh air into it. At the same time, in old apartments it happens that the system does not extract air, but rather blows it into the room ... This phenomenon is unpleasant not only because of the draft and the drop in temperature, but you will also breathe polluted heavy air. The article will tell you about why ventilation blows air into the apartment from the street and how you can get rid of it.
How ventilation works in a house with multiple floors
To understand the reasons why the ventilation is blowing into the apartment, it is necessary to understand how it functions in normal mode. Living indoors, each of us carries out a huge number of actions that lead to the fact that the air in it becomes polluted and the humidity rises. When everything works in normal mode, we do not notice, because it is completely cleared, but when any failure occurs, the negative effect is immediately noticeable.
Most of the apartments are not equipped with a mechanical system, usually it supply and exhaust type ... Such a hood works as simply as possible: air enters the house through various cracks, holes or windows. As a result, a draft is generated, which leads the heavy air into the ventilation. It becomes clear that a constant air flow from the outside is a necessity. That is why the old-style standards stated that air must flow through windows, doors and other openings. And modern technologies, on the contrary, create sealed joints that do not allow the formation of an air flow and this becomes the cause of difficulties in the natural ventilation of the room.
Influence of extraction
Modern exhaust systems have high power, which is a definite plus, because it makes it possible to eliminate the vapors that form during cooking. At the same time, there is also a negative impact, in cases where the power is excessively high. The fact is that when it takes too much air from the apartment, a back draft is formed and it comes from the hood, which is located in another part of the apartment, as a rule, this is a bathroom.
This problem can be solved very simply. To avoid the appearance of back draft in the toilet, it is enough to open a window, window or door during the period when the hood is used in the kitchen. This will allow air to circulate freely.
How to check
You don't need to be an expert to figure out how well the hood performs its functions. In addition, you do not need any special fixtures and expensive equipment; in order to check, you only need paper sheet ... Switch the window to ventilation mode, or open a window in any room. Then take the main inspection tool - a piece of paper, you need to straighten it and lean it against the grate that covers the ventilation hole in the kitchen or restroom. If the paper is attracted to the grate, then everything is working correctly. If on the contrary - ventilation is blowing into the apartment, the leaf flies off the grate, then somewhere there is a problem.
Reasons why ventilation is blowing in the opposite direction
In addition to sealed windows and doors, as well as a too powerful hood, there are many other reasons why the ventilation system works in the opposite direction. One of these may be that the channel through which fresh clean air should flow is clogged. Experts talk about situations when, when checking a ventilation duct with a reverse draft, it turns out that it is in perfect condition, the shaft that goes to the roof also does not show any problems. The junction boxes located in the attic are fully functional. It seems that there is simply no reason for this strange behavior, but it turns out that the reason is hidden in the most conspicuous place, in the toilet it pulls due to the fact that a lattice was installed on the passage channel, and a number of apartments are tied to it, which are located vertically.
To eliminate this problem, it is necessary to install a plug at the beginning of that very channel. The air should not be able to escape to any place other than upward. All lower channels must be covered. If this rule is violated, then we get reverse thrust.
Often problems with the operation of ventilation arise because the tenants worsened the conditions for air exchange ... This happens due to the fact that they do not have enough information about how this system works. As you already know, air must come from outside for normal circulation. At the same time, putting a window on airing or opening a window is nothing more than a means of self-assurance. The point is that the air must be supplied regularly.
The apartment has two ventilation ducts. The first is designed to eliminate odors that are formed during cooking, and the second to clean the air in the bathroom. Malfunctions can be of two types. Or there is only one working air duct, instead of the required two, and then the volume of air that is removed from the rooms is halved. Or the mine is filled with air from another source.
In addition to these reasons, a number of those that are not so common can be distinguished, while they can also cause problems with ventilation:
- The pipe was located in a zone of the so-called "wind shadow", that is, in a place where the air flow is greatly weakened.
- The wind is always directed in the same direction.
- The presence of drafts in rooms with a large area, which is not divided into separate areas.
- Ingress of third-party objects into the ventilation duct (debris, bird nest, snow, ice, soot, etc.)
- Large amounts of cold air and vapors that have filled the duct.
- Malfunction of the exhaust system or fans.
Elimination of malfunctions in the ventilation system
After the performance check has been carried out and the cause of the problem has been found, you can start looking for solutions. Consider the most popular options for what to do if air is blown through the ventilation.
To enhance the natural ventilation of the room can be installed .
One of the most radical and costly options is redevelopment of premises to direct the air flow in the desired direction. This method is one of the most effective, while it requires both financial and time costs.
Solving the problem in private houses.
Installing the deflector ... An aerodynamic device is called a deflector, the main task of which is to increase the air draft in the pipe. This becomes possible due to the fact that the device lowers the pressure above the duct. There are a huge variety of deflectors on the market, and you should choose it depending on the diameter of the pipe and the wind load. True, this can increase the efficiency of the entire system by a maximum of 20%.
Strengthening the air draft can be achieved by using gate (special shut-off device in the form of a damper or flap, which is installed in the ventilation ducts to regulate the air flow.) At the same time, we must not forget about the natural ventilation of the room by opening window openings.
Another variant - rotary turbine installation ... This will increase the air draft thanks to the operation of the turbine, which is powered by wind energy.
Sometimes elementary helps too. cleaning pipes from soot, and in winter snow or ice can accumulate in pipes.
Of course, each named method of eliminating reverse thrust has its own advantages and disadvantages. Whatever you choose, you should first get the advice of a specialist. In serious cases, when the ventilation system has been improperly designed, all that remains is one option is to dismantle and create a new system.
It should be noted that the appearance of backdraft in apartments in multi-storey buildings is a common problem, especially with the appearance of windows and doors that ensure complete tightness. Very often, such a problem arises from our own negligence or ignorance, therefore, when carrying out any repairs, it is worth taking this into account and trying to avoid an undesirable effect. After all, this can cause not only heavy air in the apartment, but also the appearance of unwanted odors from neighboring apartments.
Often in the apartments of Soviet-built multi-storey buildings, of which we have the overwhelming majority, the following phenomenon is observed: the cold blows strongly from the ventilation grilles of the kitchen and bathroom. This is especially true in the cold season, when the weather is windy outside. In our material, we will try to explain why ventilation is blowing into the apartment and what to do to eliminate this effect.
Most often, cold air blows from the ventilation in the bathroom, and since the latter already adjoins the staircase with one or two of its walls and the temperature in it is low, then during this blowing it becomes cold in the toilet. To understand the essence of this phenomenon, you first need to understand how the system was designed to work.
Initially, ventilation in the apartment was designed as a supply and exhaust ventilation with a natural impulse. That is, the movement of air flows is based on the principle of pressure difference, when the heated light air has a lower density and, as a result, is forced upward under the pressure of a denser cold flow. In the premises of the dwelling, where the environment is most polluted, exits to vertical exhaust pipes are arranged.
Ventilation work in a multi-storey building
Since the internal air is at a higher temperature than the outside air, it rushes up the exhaust shaft, forming a natural draft. It is the stronger, the greater the temperature difference outside and inside the building and the difference in height between the mouth of the chimney and the entrance opening in the apartment. At the same time, an inflow of fresh air masses is organized into the dwelling through holes made in wooden window blocks.
Reasons why the hood does not work properly
The exhaust ventilation of the apartment, arranged in this way, may stop functioning normally, for which there are certain reasons:
- Sealing of premises due to replacement of windows.
- Incorrect selection and installation of fans instead of ventilation grilles.
- Strong gusts of wind with a destroyed mine head or protective umbrella.
Most often, two, and sometimes three, factors act simultaneously, and then a cold stream or air with unpleasant odors blows from the ventilation into the apartment.
Modern metal-plastic windows, in contrast to old wooden windows, practically do not allow air to pass through, therefore, after their installation, the influx from the outside disappears in the premises. Accordingly, the hood stops working in normal mode, the so-called overturning of the draft occurs in one shaft due to the other channel. That is, an exhaust shaft with a large section and high performance (kitchen), not finding another source of supply air, overturns the draft in the second shaft (toilet), as a result of which ventilation works in the opposite direction in summer and winter.
The effect is enhanced if, in addition to installing windows, axial fans or kitchen hoods are built into the channel openings. Since there is simply nowhere for the inflow to appear, the fan pulls air masses from one shaft to another.
Wind support on the roof, as a rule, only enhances the natural draft power in the channels. But if the gusts of wind are excessive, and the covering umbrella or the mouth of the channel is destroyed, then the flow of cold can periodically penetrate into the house through the ventilation grilles.
It should be noted that a similar effect can occur in the ventilation ducts of a private house. In addition to the reasons described above, in private construction, there is one more: the top of the exhaust shaft is in the rarefaction zone formed by the ridge of the roof. This is a consequence of a violation of building codes by a private developer and a discrepancy between the height of the canal and the standard.
In most cases, the organization of the supply air intake leads to normal operation of the exhaust ventilation of the apartment. Then the connection between the environment and the living quarters will be restored along the route: the supply device - the space of the apartment - the exhaust pipe, and due to the pressure of cold and denser air from the street, a stable air exchange will occur.
When installing fans, you should select their performance correctly, not using the principle "the more the better". And again, one cannot do without an inflow, its amount must correspond to the fan performance to ensure air balance in the apartment. In this case, it is best to use units complete with a check valve.
When ventilation blows into the apartment due to strong gusts of wind, it is necessary to take measures to protect the mouth of the mine, and if this is not possible, then install ventilation grilles with petal check valves in the openings.
Conclusion
The occurrence of reverse draft in apartments of residential buildings is a fairly common problem, and often arises through our own fault. Therefore, before performing any major repair work, it is better to foresee all the consequences and take measures to eliminate them.
Everything about ventilation in an apartment building
How to make ventilation in a private house
How to make supply ventilation with your own hands
How is the calculation of the ventilation system in the room
Any home needs a ventilation system. It is a vital element that removes unpleasant odors from rooms by bringing fresh oxygen into them. However, sometimes situations arise when the air flows are not distributed correctly, there is a reverse draft in the ventilation and instead of pure oxygen, a smell from neighbors or smoke and dust from the street gets into an apartment or house.
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 exhaling carbon dioxide. Cooking, washing, cleaning and so on takes place in the same premises.
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.
Thus, ventilation in the house performs several functions, allowing a person to maintain normal health and performance.
Ventilation system functions
Ventilation at home is essential to maintain a healthy and pleasant indoor environment. The system performs several functions:
- The outflow of unpleasant odors from the house.
- Fresh oxygen supply.
- Purification and humidification of incoming air.
- Protection of wall structures from excessive moisture.
Thus, passing through the ventilation system, the air enters the room already clean and humidified, and the exhaust polluted air is discharged in parallel. This structural element must be foreseen during the construction phase. Without a ventilation system, no room can function normally, especially in apartment buildings and office buildings, when there are many people in a small area. The functionality of ventilation is extensive, so only high quality materials must be used for its construction.
Reasons for the appearance of reverse thrust
The correct ventilation system draws in dirty air and ensures the supply of clean air. Under certain conditions, the opposite effect occurs. This is called reverse draft ventilation. In such a situation, it not only does not fulfill its functions of purifying the air in the room, but also brings unpleasant odors from neighboring apartments or dust from the street.
Backdraft can occur in the following cases:
- The chimney facing the street is not positioned correctly in relation to the currents of the wind. Their circulation is disrupted.
- The ventilation ducts are "clogged" with a huge amount of cold air and steam. This interferes with the movement of the stream.
- Mechanical obstacles to passing streams in the form of snow, ice, debris, bird nests and soot.
- Rooms with a large area, not blocked by anything, have their own streams, that is, drafts. Their movement can create a violation of the outflow of polluted air.
- Various artificial sources of air flow in the room interfere with the natural operation of ventilation. These include hoods, compressors and fans.
Even an ordinary cooker hood can cause malfunctions in the ventilation system. Modern devices have a fairly high power, for which a standard ventilation system is not designed. If we are talking about a house with many apartments, then improper redevelopment of neighboring apartments can also disrupt the operation of ventilation ducts.
Traction violation diagnostics
In order to identify the causes of reverse thrust, qualified specialists carry out a number of diagnostic measures.
- Checking the regulatory documents that relate to the installation of the ventilation system. At this stage, experts decide how rationally the structure was built, whether it is used correctly and how much it complies with generally accepted standards.
- Checking the correctness of the installation. Specialists inspect and check to what extent the norms and requirements have been complied with directly during the construction of ventilation.
- Inspection of the current state of the system. This stage involves checking the operability, the patency of the ventilation ducts and the presence of any breakdowns.
After the performed procedures, a team of specialists examines the design of the system for the presence of blocked natural ventilation ducts. They can also calculate the air parameters, compare them with the design ones.
Backdraft elimination methods
To restore normal air regulation in a room, it is sometimes enough to ventilate it by opening all the windows. Reverse thrust often causes changes in atmospheric pressure or wind direction.
If the reasons for disturbances in the operation of the ventilation system are identified for any other parameters, then it is possible to install a deflector that will restore the normal direction of air flows.
The ventilation ducts need to be cleaned periodically. If the cause of the violation is in the accumulated debris, then specialists must come on call and clean the mines and canals.
If the reverse draft in the ventilation is caused by drafts in the room itself, then it is recommended to make redevelopment, as well as install doors to eliminate drafts.
The staircase in the house also plays an important role in the formation of air currents. Its installation should be planned taking into account possible changes in the ventilation of the building.
Natural ventilation is a system capable of various surprises, including very unpleasant ones. Situations often arise when, instead of the expected effect, the opposite result is obtained, or a constant change in the direction of movement of air flows. This may be the fault of mistakes made during construction, or other reasons. It so happens that outwardly all elements of the system look quite normal, but quality work is not observed. The problem occurs quite often, therefore, you should understand it and clarify the reasons for this condition.
The movement of air flows is due to the pressure difference in the areas from where and where the massif moves. In the atmosphere, pressure drops arise due to uneven heating of the earth's surface, the movement of clouds, displacing air flows, and other reasons. acting on the basis of natural flow movement, use the difference in pressure inside and outside the premises (the so-called natural depression). It remains only to organize the movement in the desired direction, that is, to use traction. It occurs if two conditions are met:
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there is a stable pressure difference
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in a room with high pressure there is sufficient air flow to maintain balance
It must be borne in mind that there can be no strong draft in such systems - even in high apartment buildings, the ventilation outlet can be blocked with an ordinary sheet of paper. The stability of the hood is due to a sufficient supply of fresh air, otherwise the differential pressure will quickly equalize and the draft will disappear.
Often a situation arises when the direction of the air flow is reversed, and the air, instead of leaving the inside of the room, begins to flow inside. This phenomenon called reverse thrust, it indicates that the pressure inside the premises has become lower than outside. The possibility of reverse draft is a consequence of many reasons and the main evidence of the instability and unreliability of ventilation systems based on the use of natural depression.
Traction check
The easiest way to check traction is to attach a piece of paper to. If there is a draft and its direction is normal, then the sheet will press against the grate under the pressure of the air flow. If there is no traction, then no impact on the sheet will follow, which will be felt by the inspector. The presence of back thrust will indicate the deviation of the sheet from the grate. For a more visual effect, a sheet of paper is cut into thin strips. They are more sensitive and able to demonstrate the strength of the air flow.
Expert opinion
Heat supply and ventilation engineer RSV
Fedorov Maxim Olegovich
Important! Sometimes there are attempts to test the cravings using a flame from a candle or lighter. This method clearly demonstrates the direction of flow, but it is not recommended to use it... The walls of the ventilation duct can be covered with layers of dust and fat deposits, and careless movement can provoke a fire and fire, which will be difficult to extinguish. In addition, gas can accumulate in the ventilation ducts, which threatens considerable damage if it ignites.
To study the direction of air flow, it is recommended to use smoke from smoldering wood chips or (better) steam from a steam generator. It is advisable to do without open fire.
Checking the presence and direction of traction should be carried out under different conditions - with closed doors and windows, then sequentially opening them and observing the result. With the normal functioning of ventilation, there is always a reaction - when opening windows or doors, the thrust usually increases. If no changes occur, then the ventilation duct should be checked for blockages.
Advice on attracting some "specialists" to the solution of the issue often appears on the Internet, who will come, check everything and give recommendations. You should not waste time looking for them, you need to contact the management company, which has all the capabilities and is obliged to clean the air ducts.
The main causes of reverse thrust - what to do if it blows into the apartment?
The reason for the appearance of reverse thrust is one - the pressure inside the room is lower than outside. This situation most often occurs due to clogged ventilation ducts. The inner surface of the canal is uneven, especially in old brick houses. Over the years, it becomes overgrown with dust, fat deposits accumulate, sometimes birds make nests in them. A considerable amount of debris and dust falls from above, is carried in by gusts of wind. Careless builders, making repairs or redevelopment, often dump garbage into ventilation shafts, instead of taking it to the trash heap. All these reasons are capable of terminating the functioning of the channel. The solution to the issue is cleaning, but if everything is in order with it, then the reason must be sought inside the room.
The ventilation project for an apartment building takes into account the use of old-style door and window blocks made of wood. Their canvases have a small gap around the entire perimeter, thanks to which the room fresh inflow is constantly injected... It replenishes the air volume in the apartment and prevents the natural ventilation process from stopping.
Windows and doors that are installed now close tightly and have no gaps... This contributes to the preservation of heat in the room, enhances noise insulation, but completely stops the supply of supply air. Without access to the supply flow, the hood is impossible - there is simply nothing to draw out, the pressure inside the room quickly equals with the outside and the ventilation process stops. It can be restored only by forming a hole through which supply air will enter the room. There is a physical process at work here and no other solutions will help.
The staircase from the first floor to the second, which is available in private houses, has a great influence on the mode of natural air exchange. When certain conditions arise, it begins to work as an independent ventilation shaft, redistributing the air flows inside the premises in such a way that the air channels in the walls are no longer involved in the general process or, at least, play a second role in it. In this case, there are several ways to solve the problem, but all of them are aimed at cutting off the flows from the rooms to the staircase.
Backdraft elimination methods
If there is a lack of ventilation, no flow or backdraft, action must be taken. First of all, one must understand that the whole process is governed by physical laws. This means that conditions can be created under which the thrust disappears on a completely natural basis. For example, if the outside temperature exceeds the indoor temperature, which often happens on hot summer days, the indoor air will stop rising and the draft will disappear. This situation is possible, but does not occur often.
If outdoor conditions are favorable, but thrust is directed in the opposite direction, it is necessary to determine the reason for the lack of flow. You can try to open the sash of the window and watch the result. Plastic windows have micro ventilation mode, which the it is recommended to use constantly, if the climate permits or there is no severe frost. Usually the rooms are ventilated by opening the windows wide. This is an effective method, but short-lived.
It is more correct to provide a constant flow of air, then ventilation will be continuous.
The search for a reason may not be crowned with success immediately. You will have to repeatedly check the changes in the air exchange mode, sequentially opening and closing doors and windows, trying different combinations. Nevertheless, sooner or later the problem will be solved, and the cause of the reverse thrust formation will be discovered.
How to solve the problem yourself?
There are several options for an independent solution to the problem:
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experimentally localize and eliminate the cause of reverse thrust
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close the air duct and install a separate supply and exhaust system with intake and discharge of flows through window openings
The likelihood of a favorable outcome more from owners of private houses, having all the possibilities for creating additional ventilation holes and channels, installing additional and other system elements along the entire length. This option is not available to apartment residents; they can only try to increase the inflow through window or doorways, which does not always help. If there are no favorable changes, it is easier to install forced supply and exhaust ventilation.
According to building codes, apartments should be equipped with ventilation, the task of which is to remove contaminated air from rooms such as kitchens, toilets and bathrooms.
The ventilation process consists in air exchange, constant circulation, air movement.
How a good ventilation system should work
A person makes a lot of movements in a dwelling per day, and many of his actions contribute to the saturation of the atmosphere of the apartment with moisture and air pollution. With proper ventilation, air pollution goes unnoticed, since it completely leaves the premises. But if the ventilation is disrupted, it will be extremely unpleasant for the people living in the apartment.
To understand how well the ventilation ducts in the apartment do their job, it is not necessary to be a specialist. You don't need any complicated instruments to check - just one sheet of newsprint is enough. Open a window in any of the rooms in the apartment and attach a newspaper sheet in a straightened form to the decorative grill that covers the ventilation outlet of the kitchen or bathroom. If the sheet is attracted to the grate, ventilation is fine. If he deviated from the grate in the opposite direction, the thrust is obtained, respectively, the opposite, that is, the air exchange is performed incorrectly, and the people living here breathe unwanted odors.
In the presence of double-glazed windows, ventilation should be checked only with open windows.
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Ventilation in multi-storey buildings
In ordinary apartments, there is no mechanical ventilation - only supply and exhaust. Air exchange rates, even at the stage of drafting the project, according to which the house will be built, are calculated as for natural ventilation. In order for the air to go out of the rooms into the ventilation ducts, it first needs to appear from somewhere. According to accepted standards, it is supposed to enter through cracks in frames or door structures.
Both metal-plastic windows with a sealed structure and modern strong metal doors equipped with seals have become widely used relatively recently. Everyone knows about their excellent performance. The problem that arises when using them is that with the advent of new construction technologies, the old norms have been preserved. According to these standards, air enters the house through small holes, cracks, tiny holes, and they are simply excluded in new window and door structures. With the complete tightness of the premises, the conditions for good operation of the ventilation system will be somewhat difficult.
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Ventilation problems when using hoods
People living in apartments often face the same troubles regarding ventilation. In typical apartments where PVC windows and a blind door are installed, there are usually two channels through which exhaust air must be removed. One of them is used for ventilation in the bathroom, the other is designed to clean the atmosphere of the kitchen, and in some places even a cooker hood is put into it.
Residents of such apartments sometimes encounter an unpleasant phenomenon when it blows in the opposite direction from the ventilation hole in the toilet. Sometimes the reason for this is the regular use of the extractor hood.
Modern hoods operate with sufficient power to let in the main part of the air available in the apartment when turned on. As a result, it is thinned out, and all channels through which the additional one could enter (doors and vents) remain closed. With such a violation, the flow of air into the apartment from the bathroom is inevitable.
Even if everything is in order in the ventilation duct of the toilet, it is completely serviceable and functions perfectly, with an insufficient amount of air in the rooms, reverse draft occurs. The ventilation of apartments located above each other is integrated into one system, and odors from the lower floors can begin to enter the rooms.
This problem can be dealt with very simply - for the time when the hood is on, the windows should be opened. If sealed window and door structures are installed in the premises, air will enter through the open window. You should not rely on the operation of the air inlets - they can compensate for the air removed through the ventilation ducts, but provide them with the hood operating at full capacity - the task for them is almost impossible.
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Other possible causes of malfunctions
This may not be the only problem. There are other subtleties in the ventilation device, and if you do not know about them, you can look for the cause of back draft from unwanted places for a long time. The first thing that comes to mind when air starts to blow from the vents in the opposite direction, the channel is clogged. Sometimes it does. But often, when a ventilation duct with incorrect behavior is carefully checked, it turns out that it is completely clean, the shaft overlooking the roof is in excellent condition. There may still be connecting boxes in the attic, and if they are also in good working order, there is simply nothing to complain about. And the simplest explanation of what is blowing is the installation of its lattice on the through channel. In this case, several apartments located vertically are connected to one channel.
In order for the ventilation to function properly, there must be a plug at the beginning of the ventilation duct of the apartment. For air entering the duct through the grate, only the upward direction should be open to exit. There should not be any moves to the lower part - the channel must be closed at the bottom. If this condition is violated, the channel issues a reverse thrust.
It turns out something like the following picture. Instead of a properly functioning ventilation system with a common shaft and satellite channels, the house has several transit branches. This situation is not particularly noticeable on the lower floors, but on the upper floors it can turn into a real problem.
The air flow rising through the channel flies past the ventilation grill, while it either gives a reverse thrust, or becomes an obstacle in the way of the exhaust air leaving the apartment. The installed plug does not allow the lower air flows, directing them through a special opening into the collection channel. This helps to start the ventilation process from scratch, absolutely unhindered, without fighting other air currents - ideally, this should be the case.
As already mentioned, there is more than one reason for a ventilation malfunction. For example, the reason for the appearance of the wind blowing from an outlet in the toilet in the opposite direction may be the location of the apartment. Residents of the upper floors of apartment buildings are more likely than others to be familiar with such a nuisance as back draft in the toilet.
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What can be done to improve air exchange
In order for the system to perform well the air exchange, the air must be allowed to pass through the channel at least 2 m in the vertical direction. This happens on all floors, but not on the last - there, in many cases, the attic room will interfere. To remove the ventilation system from the apartment, you can use one of the following methods.
The first option is when the channels are simply brought out to the roof in the form of a pipe head. Almost all buildings built before the twentieth century were created in this way. When they began to build a lot of high-rise buildings, this method was gradually abandoned. Another popular method - the ventilation elements that reached the attic were hidden by horizontally located boxes, hermetically sealed. They were connected to the shaft, and that went outside and went out over the roof. In modern buildings, a different method is more often used: the ventilation channel is brought out to the attic, which can be considered as a ventilation chamber, and then it goes outside through a common shaft.
When using the latter method, the movement of air is carried out as follows: it is collected from all floors, goes up through the channels, reaches the attic and enters the junction box. The air flow hits its cover and deviates towards the shaft, but with a small internal section of the box, an excessively high pressure may arise in it, the air will try to escape into any suitable opening, even in the opposite direction.
With a conventional design, there can be two such exits - a ventilation shaft and a channel on the upper floor, it is designed specifically for these purposes and is located more conveniently. Sometimes it turns out that the cross-section of the box is sufficient, and the roof is arranged too low. Then the following happens: the air flow, due to the low location of the cover, does not have time to change direction and deviate towards the shaft, it strikes with force into the ventilation of the upper floor, which is deformed and allows all the air and odors from the floors below to pass into the apartment.
It is not easy to deal with this inconvenience, but it is possible. To do this, you can use either of two methods - global or local.
With the global method of correction, it will be necessary to change the cross-section of the horizontal junction box in the attic, increasing its height by 2-3 times, and inside the structure, devices called incisions are arranged. Such actions must be performed by professional workers. It should be borne in mind that it is better not to expand the section of the duct if, on the other side, the same structures are connected to the ventilation shaft.
When choosing a local method, the channels of the floor located on top are separated from the general structure and led into the shaft over the connecting box. Separate channels must be insulated, this will help not to disturb the temperature and humidity in the attic. If everything is done without violations, ventilation in the apartment will work as expected.
There is another option for air removal; in modern living quarters, it is used more often. In most multi-storey buildings, ventilation is carried out according to this principle. Inhabitants of the upper floors often have the problem of too weak traction, and not the fact that it is the opposite. Normally, the air flow, before merging with the general one, should vertically pass 2 m.
But when housing is located on one of the last floors of the building, it turns out not quite so. The air trapped in the channel moves vertically by about 30 cm, after which it diverges, not having time to pick up speed. Therefore, one cannot say that there are no air flows, but in the upper apartment with such movement, air exchange is greatly reduced. If you open the doors in the attic, you get a draft, because of which the draft in the area of the upper floors can change. To prevent this from happening, separate channels must be built up for the upper floors. Pipes with a suitable diameter are put on the outlet holes, the joints are well coated with alabaster. The optimum height for the outlet of pipes is about 1 m. Then they must be directed towards the common shaft, slightly tilted. With this arrangement, the inflow of air coming from the bottom passes next to the pipes, captures and pulls air from the upper floors.
