Any apartment building has a ventilation system. It is responsible for the flow of fresh air into the room and the removal of stagnant air. But situations may occur when dirty air flows back into the house. This phenomenon is called backdraft. It interferes with the comfortable functioning of people and also carries potential danger. You can correct the situation yourself when there is no malfunction of the system itself. In other cases, you need to contact a special service.
Definition of backdraft
With reverse draft, the flame is directed towards the room.
Draft in the ventilation system refers to the directional flow of air masses that occurs when there is a difference in pressure in the house and outside. Air flows naturally move into low pressure areas. General building ventilation operates on this principle. First, the air heats up, its density and mass decreases. It is directed upward and discharged into the ventilation hole. Fresh cold air comes through the cracks and fills the entire space.
The thrust force directly depends on the height between the air inlet and outlet. For this reason, residents of the top floors are more acutely aware of the lack of fresh air.
The phenomenon of reverse draft in the ventilation of an apartment in an apartment building is the impossibility of removing dirty air. It returns back into the rooms and brings with it bacteria and an unpleasant odor. You can understand that the system is not working correctly by the following signs:
- Fogging of windows, condensation, mold and mildew. Excess moisture is also removed through ventilation. If the system is not working properly, the water will not drain and will begin to settle.
- Stuffy, stale air, often accompanied by an unpleasant odor.
- Draft from the vent. If you put your hand near it, you can feel what is blowing from the ventilation into the apartment.
The simplest test can be carried out using a regular sheet of paper. You need to attach it to the ventilation hole and look at the direction of vibration.
Checking that ventilation is working correctly
You can diagnose a malfunction in ventilation yourself.
To ensure that the air exchange rate in the apartment is sufficient, you need to check the efficiency of the ventilation holes. The simplest and most effective way is to attach a sheet of paper or a piece of newspaper to the grille covering the channel with the door, window, transom or window previously open. If the leaf sticks to it and holds without outside help, aeration is effective. Otherwise, the reverse air flow into the apartment will blow the sheet onto the floor.
The “test by fire” consists of examining the behavior of the wick of a burning candle held close to a ventilation duct. Ineffective draft or improper operation of ventilation is indicated by the immobility of the flame or its deviation towards the room and not the grille.
Natural air circulation in the house
Reverse draft can occur when installing metal-plastic windows and doors.
The ventilation system in a house is a complex of different technical devices, blowers and shafts, which have a single riser from the basement to the roof. Thanks to it, draft is created due to the temperature difference in the house and outside. As this difference increases, the hood will work harder.
Perpendicular pressure also has an effect on the principle of cross sections. This is a situation in which the wind blows horizontally relative to the riser. As a result, it draws air out of the ventilation.
To ensure that there is an air flow in the house and a vacuum does not form, vents are made in the foundation during the construction phase. You can also make several holes in the floor on the first floor.
This is how natural air circulation works in an apartment building. The system may not work if there is no supply ventilation or if the temperature in the house is lower than outside. The second reason occurs infrequently, so it is due to the lack of decent air flows that draft appears. Ventilation shafts in the apartment are made in the bathroom, toilet and kitchen. Air enters through the windows. The use of double-glazed windows and sealed doors significantly reduces the influx of air masses and causes reverse draft. To solve this problem, use special valves on windows or walls.
Also, air flow disruption can be caused by a system malfunction, installation of fans and hoods, or improper design. If the hood blows in the opposite direction in the apartment, you need to look for the problem and fix it.
Installation of supply channels
Supply channels are holes that are made from the street side to create additional air flow directed into the room. The flow direction is controlled by two valves. But it is better if the valves are installed in advance in plastic windows to improve tightness and the possibility of normal air circulation.
Ventilation valve in window frame
Principle of operation
Each valve has a grille inside to protect against excess debris entering the room. And for sound insulation, a special box is installed on the outside of the hole.
You should choose only high-quality valves. Cheap models cannot function normally at large temperature ranges or air will pass through even when closed.
An important condition is the creation of a good indoor microclimate. For this purpose, cleaning filters, ionizers, and control systems are installed. The devices will allow air to be humidified and ionized for disinfection purposes.
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.
To identify and eliminate backdraft, you should contact a specialist. It is better to choose independent experts who will conduct a comprehensive analysis of the entire air duct system in the building and give recommendations on how to improve the situation.
System check
To check the ventilation, an air sample is taken.
An inspection is carried out to identify problems and troubleshoot problems. It consists of the following steps:
- Study of design documentation. Checking its compliance with GOST norms and standards.
- Assessing the effectiveness of installed equipment, the correctness of its installation and operation.
- Checking the quality of installation work of air ducts, channels and other elements of home ventilation.
- Taking an air sample.
- Search for unauthorized channel blocking.
Based on the inspection, specialists decide how to eliminate backdraft.
Elimination methods
Supply valve on a metal-plastic window
To remove reverse draft, you need to bring the ventilation system into working condition. The main ways to restore work that you can do yourself include:
- Installation of a check valve. The device will not allow old air to return to the room again.
- Installation of supply valves on windows. Thanks to this mechanism, fresh air will flow into the house, even if the window is closed. The intensity can be adjusted. You can also install fans, debris screens and other attachments in the valves for cleaning, heating and cooling air masses.
- When installing a powerful hood, it is necessary to balance it in terms of performance. The volume of incoming air must be equal to the volume of air being displaced.
If weather conditions are the cause of the draft, you need to wait until the temperature and humidity, as well as the wind direction, return to normal. Such factors are temporary and do not depend on the person. With frequent influences of weather conditions, you need to think about redesigning the system.
Once every 5 years it is necessary to clean the ventilation
If damage has occurred due to which the hood is blowing in the opposite direction in a private home, you need to call a repair service. Specialists carry out the following activities:
- They protect the mouth of the mine if draft is formed due to strong gusts of wind.
- Restore damaged structures, repair or replace them.
- The channels are cleaned. It must be carried out at certain intervals. It is prohibited to clean the ventilation yourself.
It is not always possible to correct the factors that affect cravings. For example, the layout of the room may be such that stale air will be returned to the room. In large rooms without walls and partitions, drafts will appear, which affect the overall ventilation system in the house. Stagnant air masses can also return from the stairs to the second floor.
If the cause is incorrect design of the ventilation duct, you should redo it.
Looking for a solution to the problem
Is the ventilation in your apartment not working? And the reason for this may be the lack of air flow through natural channels, which means it’s time to take care of installing a supply valve. They put it on the window. With it, there will be a constant flow of fresh air even if the windows and doors are tightly closed. Moreover, it is adjustable, which means control of ventilation is completely in your hands.
The optimal solution to the problem is a supply valve in the wall
Its installation is quick and uncomplicated. You can call a specialist, or you can do it yourself, especially if you choose a model that is mounted on the wall. In fact, this is a round pipe that passes through the wall and is closed on both sides with grilles. It contains filters that clean the air from dust and contaminants. And the internal grille can close and open the supply valve. It is installed mainly near a window so that the air warms up.
A supply valve is not a cheap pleasure, but the benefits from it more than cover all the costs of its installation.
But what to do if restoring the air flow using the supply valve turned out to be useless and the problem has not gone away? Chances are, your vent, or even part of your home's overall ventilation system, is clogged. And such repairs to ventilation in an apartment will be more difficult and may be expensive.
It’s good if the blockage is shallow in the channel and can be cleaned right from the apartment. Most often it is cleaned with a long stick wrapped in tow or other long object. You may just need to break off the ice that covers the shaft and the problem will disappear.
Cleaning ventilation is one of the effective ways
What if this didn’t help? Then, perhaps, a mistake was made when designing the ventilation and its design was incorrect. Most often, its cause is the grille, which is located on the passage channel. Typically, one channel unites several rooms that are located vertically. To fix this, you need to put a plug at the very beginning of the channel so that the air entering it does not enter the lower channels. That's right when it rises. If this is not the case, then this leads to the formation of reverse draft.
Typically, residents of the first floors do not experience these troubles, unlike those who live above. Air rises through the common shaft channel, but without entering your ventilation sleeve. This forms a reverse draft, which means that the polluted air from the apartment has nowhere to go. Installing a plug will help eliminate this problem. Its purpose is not to allow air flows from the lower floors to pass through, which will smoothly collect in the collection channel.
You can increase air exchange using a special deflector. This is a kind of pump that takes air from the general ventilation duct, directing it to your home.
Preventive measures
Installing a deflector helps prevent wind from blowing into the channel.
Eliminating the backdraft problem can take a lot of effort, time and money. To avoid this, you need to take preventive measures. Basic tips:
- The system must be in good condition.
- Fans and hoods should not be installed in ventilation ducts. You can use only recirculating hoods or vent their exhaust to the street through a wall or window.
- Deflectors and rotary turbines are installed at the end of the riser.
- Organizing the flow of fresh air from the street in any available way, including in winter.
- Installation of interior doors to block the possibility of drafts affecting reverse draft.
- Cleaning the system from ice and snow in winter.
- Periodic ventilation check.
These measures will help to avoid most of the problems that cause back draft and cold air to blow from the ventilation into the apartment.
Reasons for ineffective hood operation
Problems with the operation of the exhaust system are familiar firsthand to owners of apartments built in the Soviet era. Residents of new buildings are, for the most part, deprived of the pleasure of being present at their neighbors' meals, since new houses are equipped with modern forced ventilation systems.
Such systems do not allow foreign odors to enter the apartment.
Cobwebs, dirt and dust accumulated in the exhaust duct are one of the main reasons for insufficient air circulation in the room
Reason #1. The decrease in ventilation efficiency in old houses is, in principle, a fairly predictable process. The main reason is a simple blockage of the ventilation duct, which over time accumulates debris, dirt, dust and other waste coming from the premises.
As a result, the outlet narrows and becomes unable to fully process the dirty air taken in.
In apartment buildings united by a common ventilation shaft, pollution from individual ducts enters the general building system. Gradually, the mine becomes clogged with debris and can become completely clogged. A process that lasts for years can lead to the functioning of the ventilation system being paralyzed.
This problem can be solved by restoring the air ducts and eliminating the root causes of their partial or complete blockage.
Reason #2. Another prerequisite that contributes to the deterioration of air exchange is the presence of a powerful kitchen hood in the neighbor’s apartment. However, this is quite understandable. Intra-house natural ventilation is designed for air flow up to 90 m3/hour.
One hood creates an air flow of more than 1000 m3/hour; naturally, neighboring ventilation ducts that go into the common shaft suffer from this. What if there is not just one hood, but every other neighbor has one? The answer is obvious.
A hood significantly improves the microclimate in a neighbor’s kitchen, but it can also have a negative impact on the operation of natural ventilation in other apartments connected by a common building ventilation shaft
Reason #3. Replacing wooden windows with metal-plastic ones is also a factor that negatively affects the performance of the ventilation system. It turns out that the tightness inherent in modern double-glazed windows does not always play into the hands of residents of old houses.
In Soviet times, only the lazy did not scold builders who made mistakes in installing windows and doors. As it turned out today, the “culprits” worked strictly according to instructions for the benefit of the residents, because For the full functioning of natural ventilation, cracks are needed, which were abundant in old wooden windows.
The holes provide a constant flow of fresh air from the street, and sealed metal-plastic structures, on the contrary, block it. As a result, humidity in the room increases, windows fog up, and mold and mildew form on the walls.
Modern double-glazed windows cannot provide adequate air exchange in an apartment in a multi-storey building that uses a natural ventilation system. Foggy windows indicate excessive humidity in the room and the need to use forced ventilation devices
Reason #4. To a large extent, the operation of the ventilation system depends on the season. Most often, problems with the hood appear during hot periods, while in winter the exhaust hatch functions properly.
The fact is that the efficiency of a natural ventilation system is directly dependent on the difference in temperature inside and outside the building.
In summer, the temperature outside and in the apartment is almost the same, which is why problems arise. According to the old SNiPs, it was assumed that in hot weather air exchange would be carried out by ventilating the room with open windows.
Where to contact
The ventilation of an apartment building is general. If there are problems, reverse draft will appear in all apartments, so you need to act together. First of all, you need to discuss the problem with all the residents of the entrance. Perhaps one apartment has a very powerful hood, which harms the operation of the entire system.
Next, you should contact the management company with a request to find and solve the problem. If cold, musty air appears, you can contact Gorgaz. This decision is due to the fact that ventilation is a safety system. It is the presence of reverse draft that makes it impossible to ventilate the room from energy carriers and combustion products.
If backdraft appears in the house with a certain frequency, and it is impossible to eliminate it, you should replace some of the windows with anti-explosion ones.
Summarize
Many people do not know what to do if the ventilation is blowing into the apartment. But the comfort of living indoors depends on this. High humidity, heavy stale air, mold formation - all this is the result of incorrect ventilation.
However, in an apartment building it is difficult to fix the problem on your own. To restore normal air flow, it is necessary for the management company to contact a specialized organization.
Specialists will assess the problem, find the cause of the violation and eliminate it.
