Reverse draft ventilation in a private house: common causes and their elimination

How ventilation works

To understand the possible cause and how to fix it, you need to figure out how the ventilation system of a private house works. In most cases, a mechanical ventilation system is used in a private house. Its principle of operation is relatively simple. Openings are made for the inflow and outflow of air. So, fresh air enters through one hole, and polluted air is squeezed out through the other into the street.

That is, without a good inflow, polluted air will not be removed from the room.

Therefore, it is extremely important that this system, the fresh air supply system in a private house, works properly.Very often, fresh air enters through cracks in windows, doors, floors, etc.

However, modern technologies are aimed at completely eliminating the influx of fresh air. For example, metal-plastic windows are installed that do not allow air to pass through them. This also applies to doors and other surfaces. As a result, natural ventilation ceases to work absolutely.

How to check the ventilation in the apartment

Before checking the ventilation in the apartment, think carefully if you have done any work with your housing lately? This is very important, because you should be aware that the operation of the ventilation system may deteriorate:

1. Due to the installation of new plastic windows and doors;
2. Due to the installation of fans, kitchen hoods, etc.;
3. Due to the modernization of the ventilation system itself.

In addition, ventilation may also deteriorate due to the actions of unauthorized persons, for example, a neighbor, performing repairs from above, clogged the ventilation duct or did something wrong. In general, before checking ventilation, you should carefully analyze all of the above points.

Checking the ventilation in the apartment yourself is quite simple. To do this, you need to bring an open flame from a match or lighter to the ventilation duct and see what will happen to it. If the flame does not react in any way and does not deviate towards the hole, then you can be sure that the ventilation duct is tightly clogged.

You can also take a small sheet of paper and perform the same manipulations with it as with a lit candle. If the reaction is zero, then most likely the problem is the lack of traction and the ventilation will have to be thoroughly cleaned to get rid of problems with glass fogging and high humidity.

What to do about poor ventilation in the apartment?

However, it also happens that the ventilation is not clogged, but there is still no draft in it. Then both the simplest solutions, in the form of an ajar window on the balcony or interior doors, and more complex ones can come to the rescue. More complex solutions to this issue include the installation of a wall valve or fan.

A recuperator for the home, which simultaneously performs several important functions, will also help solve the problem. In any case, when choosing a particular device, it is better to consult with experts in this field about the maximum efficiency of a particular device.

As for the installation of the fan in the ventilation duct, it is important to understand what needs to be obtained, supply or exhaust. In other words, what should the fan do - "draw in or pull out" air from the apartment

This is a fairly simple and at the same time effective solution, for the implementation of which it is necessary to have ventilation that is not clogged with debris.

Causes of the malfunction

Due to the pressure difference, the smoke from the stove goes out through the pipe and does not harm the people in the room. It was by people's ovens for centuries heated their homes. Back draft is dangerous because the room will fill with smoke, and this is fraught with carbon monoxide poisoning. In addition, flammable objects near the stove may be ignited by sparks flying out with smoke.

Now stove heating of houses is a thing of the past. In private dwellings where there is no central heating, gas heating systems are installed. But the problems are reversed draft in the chimney of a gas boiler may also arise.

In order to create a pressure drop to remove smoke from the combustion of firewood, pipes and chimneys are created, but they do not always cope with their functions. The reasons for this can be simple or complex.

Good to know: do-it-yourself chimney.
Bad weather is one of the causes of reverse thrust

Simple causes of reverse draft in a chimney are:

• the presence of cold air in the chimney (when the stove has not been heated for a long time, it is cold outside);
• clogging of the pipe;
• rarefied indoor air;
• bad weather.

Dealing with these issues is relatively easy. If the stove has not been heated for a long time, then when the fire is ignited, the room may fill with smoke. But as soon as the heating device warms up, normal smoke removal resumes. A clogged pipe is also fairly easy to clear.

It is worse when the causes of reverse draft in the furnace are complex:

• the cross-sectional area of ​​​​the chimney is disproportionate to the size of the furnace;
• incorrect location of the chimney (pipe);
• pipes shorter than 5 m or below the roof ridge;
• bottlenecks in the chimney (pipe);
• the presence of tall trees or buildings near the house.

In this video you will learn about draft in the chimney:

Effective ways to increase chimney draft

The design of a chimney is complex and responsible, the efficiency and safety of using a heater depends on the correct implementation of it. Not a single heat generator is able to function normally without a pipe that removes smoke from the room. Smoke is a mixture of gases containing residual products of combustion of fuel. The appearance of smoke inside the heated room is a sure sign of an incorrect calculation of the chimney system, which entails the risk of fire and carbon monoxide poisoning.This article will tell you what reverse draft in a chimney is and how to prevent it from occurring.

Measurement methods

If you doubt that the draft of the chimney channel of the stove, fireplace or heating boiler is sufficient, you need to check it. The easiest way to dispel doubts is to check with your own hands using an anemometer. If the device shows a thrust of 10-20 Pa, then it is considered normal. The problem of this method is the low measurement accuracy of inexpensive anemometers, if the thrust is less than 1 Pa, then they will show that it does not exist. More accurate professional instruments are expensive, stove-makers use them.

If you do not have an anemometer, use one of the popular methods for determining the chimney draft force:

1. By smoke. The most obvious sign that there is no draft is the presence of even a small amount of smoke inside the room, a large amount of smoke indicates a high risk of fire and carbon monoxide poisoning.

Note! The draft inside the chimney duct is created due to the difference in pressure outside and inside the building. In a heated room, the temperature is higher than outside, so there is more pressure

Heated air, propped up from below by colder air, is squeezed out into a zone with lower pressure, that is, into the atmosphere. If you take measurements in summer, when the temperature difference between inside and outside is minimal, you will get a lower result than in winter.

Causes of malfunctions

After making sure that there is not a sufficient level of draft inside the chimney system, it is necessary to determine and eliminate the possible cause of this defect.Experienced craftsmen say that the most common causes of failures in the operation of smoke ducts are:

• Design error. The choice of the chimney pipe should be based on the volume of the furnace. If the diameter is less than the calculated parameter, a weak one will not allow smoke to leave their premises.
• Insufficient pipe length. A pipe length of less than 5 m does not provide a significant difference between the pressure inside and outside, which creates a weak draft.
• Incorrect location of the chimney tube. Furnace masters advise laying the chimney vertically, as narrow turns trap smoke inside the chimney, reducing draft.
• Long horizontal sections. If, when laying a chimney, it is not possible to avoid horizontal sections, then make sure that their length is no more than 100 cm. Otherwise, she will need an amplifier.

The first step in detecting problems in the chimney system is to eliminate the most obvious causes of insufficient draft. When inspecting, make sure that the connections of all pipe segments are tight, that there are no soot blockages. Check that no moisture has entered the flue ducts and that the atmospheric pressure is correct.

Ways to increase traction

If the traction force is in the chimney channel of the heater, it is not always easy to eliminate this defect. Experienced stove-makers use the following methods, ways to increase it:

1. The first thing to do if you suspect insufficient draft in the chimney is to clean the pipe. To do this, call a chimney sweep or remove soot deposits from the inner surface of the chimney with your own hands using a metal stove brush.
2. A significant increase in the power of the chimney can be achieved by increasing the height of the chimney above the roof surface by extending it with several additional segments. In the same way, the chimney is removed from the area of ​​\u200b\u200bwind backwater from the ridge or a higher building.

If it was not possible to find a solution to the problem of the lack of draft inside the chimney channel on your own, seek advice from an experienced stove-maker who will tell you what to do and correct the defect in the most rational way.

Effective ways to increase chimney draft Effective ways to increase chimney draft. Common causes of reduced draft in the chimney and methods and devices for their elimination.

Perhaps "guilty" plastic windows

Forced ventilation is shown in rooms with plastic windows.

During construction, apartment buildings are equipped with a natural supply and exhaust ventilation system (exhaust air masses exit through special openings in the sanitary room and in the kitchen). This is provided for by SNiP 2.08.01-89 "Residential buildings". He must enter the living quarters through windows, vents, doors, natural cracks. But, modern civil engineering provides for the installation of metal-plastic windows in apartments. They are sealed and do not allow air to freely enter the apartment, which contradicts the natural ventilation device.

The reason why the exhaust air blows from the ventilation is metal-plastic windows and doors with a seal. How does this process take place? Kitchen hoods during operation are able to absorb not only fumes and smells of food, they “pull” air from the entire apartment. This leads to reverse draft in the ventilation duct.That is, fresh air from the street does not enter due to the sealing of the room, and uncleaned air masses from the ventilation take its place.

Air regulation optimization

To understand why reverse thrust occurs, it is necessary to analyze all the components. Such environmental factors as atmospheric pressure, humidity, activity of convective currents, the presence of isotherm and inversion can disturb 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 - with the help of it, the reverse draft is regulated. Usually they are installed in the chimney channel and in the oven door. Sometimes the issue is solved very simply - just open the doors and ventilate the room.

This problem often occurs when oven or fireplace haven't 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 chimney draft stabilizer will help to cope with it - it optimizes the movement of air in the ventilation. Safety valve protects against sudden pressure drops.

As a preventive measure, it is necessary to clean the chimney from time to time and install a special tee for cleaning. Use the following troubleshooting steps to troubleshoot:

1. Removing the pipe above the wind shadow zone.
2. Repair, if necessary, of the ventilation structure.
3. Creating an influx of fresh air currents.
4. Channel cleaning.
5. Clearing frozen areas from snow and ice.
6. Changing the layout of the room, creating organized flows and installing doors.

Supply valve

On plastic windows you need to install a supply valve

If you live in an apartment where there is no air flow through windows and doors, it must be provided. To do this, you can use a simple window inlet valve, through which fresh air will flow even when windows and doors are closed. Simply install it on a plastic window. It is adjustable so you can control the flow of air into the apartment. It will take very little time to install.

Supply valve diagram

There is a model that is mounted on the wall. It consists of a round pipe passing through the wall through. It is covered with bars on both sides. There is also a filter that does not allow dust and other unwanted particles from the street to enter the house. The grate inside can be adjusted so you can open and close the valve. For convenience, such a wall valve is installed near the window, then the air will heat up. Installing such a valve will cost more, but the result will also please you. Thanks to such simple methods, you can get rid of problems with ventilation.

Why is there a back draft in the chimney

This process is influenced by a large number of factors. The main one is the incorrect design of the chimney at the construction stage. In order not to face the problem of insufficient or incorrect traction in the future, it is necessary to correctly calculate in advance:

• chimney section size;
• its location;
• material of manufacture;
• form;
• pipe height;
• the presence of additional devices that increase traction.

The number of people or devices consuming oxygen in the room also affects the quality of air movement. The latter include heaters, irons, stoves and so on.

It is important for proper operation and regular ventilation of the room

Additional Information

The principle of operation of the fire damper is also completely determined at the design stage. In this case, the static method is simpler than dynamic isolation. In the first case, the operation of the ventilation system simply stops. Because of this, the smoke cannot reach neighboring rooms, and that part of it that has already penetrated the outside gradually dissipates and does not pose a particular threat. At the same time, blocking the oxygen supply to the flame from the outside slows down the growth of the fire.

In dynamic systems, valves are assisted by fans that turn on at the command of sensors. With the natural method of removing burning, smoke is drawn out through the lanterns and smoke hatches

Attention: according to official requirements, smoke can only be removed from one source, that is, valves in other rooms will remain in their original position

The valve itself is not very complex. A shutter is hidden in the metal case, blocking the clearance if necessary. Its start is carried out using the drive. As for the grilles that some models are equipped with, their role is limited to just external design. Valves are divided into those mounted inside the wall, as well as duct valves, which are placed in the ventilation shaft.

Drives are varied in execution.In addition to electromagnetic and electromechanical devices, standard solutions based on spring action are often used. After connecting the installed valves, it is mandatory to check the performance of the system as a whole. Commissioning work is completed by aerodynamic tests, the results of which are recorded in a protocol drawn up in a special form. It is quite reasonable to combine such tests with a fire drill.

Depending on the design, the type of drive used also differs. So, with a reversible electric drive, flange devices that remove smoke are usually supplied. But the systems that restrain the spread of fire are for the most part equipped with return springs. When selecting engines for torque, it is necessary to focus on the area that the air damper has according to the standard. Most developers prefer to make the voltage disappearance as a control signal, which provokes the movement of the shutter of the electromechanical apparatus from the initial state to the working position.

To hold the sash in its initial position, very little electricity is consumed. For your information: some of the actuators are equipped with thermal indicators, due to which the system is triggered if the heating inside the valve has reached a critical value. And in reversible models, the movement of the valves occurs due to changes in the circuit of the supply circuit. The undoubted superiority of reversible systems is due to the fact that they cannot accidentally work if the power is suddenly turned off for any reason. That is why such blocks are recommended for supply and exhaust devices.

A visual demonstration of the operation of the smoke exhaust valve is in the video below.

Reasons for the formation of reverse thrust

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

If the initial inspection did not give tangible results, it is necessary to look for the reasons for the incorrect operation of the system inside the apartment.

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

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

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

Also an important factor in the violation of the correct 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. m3 of air per hour. Neither chimney nets nor the air duct can cope with such a volume.

Common causes of reverse ventilation ducts in the apartment:

• Features of the location of the pipe on the roof. There is a possibility of finding a pipe in the area of ​​the so-called. "wind shadow" when the protruding parts of the house close the air flow. Also, the wind can blow in the opposite direction, preventing the movement of air into the pipe.
• Clogged ventilation ducts. Various debris, ice and snow, soot and the consequences of the life of birds living on the roof get into them.
• Accumulation in the channels of a large volume of steam or cold air, which prevents the movement of air.
• Incorrect operation of hoods, compressors and fans. A similar problem occurs due to drafts that blow in large rooms that do not have partitions. In multi-apartment buildings, a situation is often encountered when intensive removal of air from one apartment leads to a reverse draft in another.

Reverse thrust elimination

So, how to get rid of reverse draft in the chimney? In most cases, this problem can be solved independently. To eliminate a short-term lack of draft in the furnace firebox, you should burn a couple of newspapers to warm the air in the pipe, but most often the chimneys just need to be cleaned.If the draft disappeared after the repair or did not appear at all, then an error in the calculations was probably made, and additional devices would need to be installed in the room.

The lack of traction is dangerous not only for the functioning of the appliances, but also for the health of the residents themselves, therefore, in such situations, it is forbidden to use heating appliances until the troubleshooting.

Eliminate causes of reverse thrust

Poor chimney draft requires immediate elimination of this problem, which is why many people often resort to using a special regulator. With it, it is easy to control the flow level, as well as create it if necessary. The automatic chimney draft regulator is produced in several variations. It can be a chimney stabilizer or a ventilation stabilizer.

Of course, the device for the chimney is aimed at regulating air flows. At the same time, it is characterized by increased economy, which cannot but rejoice. In addition, savings are also achieved by controlling fuel consumption. Such a device guarantees the accurate functioning of the chimney, and therefore the appearance of combustion products in the room will be impossible.

The ventilation stabilizer provides the room and the stove with the necessary air exchange. The stabilizer is produced in the form of an aerodynamic design, and it has two types of installation - at home or on the street as a stand-alone device. Thanks to the use of this device in the room, the appearance of any odors or unpleasant blowing will be excluded.

Also, this device helps to reduce the development of mold and other harmful fungi. It is extremely convenient to use in combination with a chimney stabilizer.In addition to these devices, checking the draft in the chimney will identify the reasons for its absence, after the elimination of which, the pipe's performance will again be at its best.

System check

An air sample is taken to check ventilation

An inspection is carried out to identify problems and troubleshoot. It consists of the following steps:

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

Based on the inspection carried out, experts decide how to eliminate back draft.

Causes of reverse draft in ventilation

The classic ventilation system in a private house is built according to the scheme with natural air movement. The latter in it moves from the rooms to the outside due to the formation of spontaneous traction. Air masses with a high content of carbon dioxide are constantly drawn into the ventilation ducts from the premises, and their place is taken by fresh ones from the street, saturated with oxygen.

Air flow occurs through windows, doors and special openings in the walls. At the same time, according to the laws of physics, he tends to move to where he encounters the least resistance. And in the house, these are ventilation ducts that go to the attic or out onto the roof. And the higher such an exhaust pipe and longer, the stronger the draft is formed in it.

Back draft into the hood openings occurs due to:

clogging of ventilation shafts (narrowing of their cross section);
decrease in air flow;
errors in the design of the ventilation system;
changes in the device of the ventilation system by adding fans and hoods that were not originally intended.

Normal air exchange occurs only with sufficient air flow into the premises of the house. If the windows and doors are airtight, and the air inlets are closed or small, then there will simply be nothing to pull out of the rooms. Even at the stage of preparing the project of the ventilation system, all these nuances are taken into account in order to ensure the proper flow of air masses.

If a few years after the construction of the house, a mechanical hood is installed in the kitchen or a gas boiler is installed, then the house ventilation must be rebuilt. Initially, the channels in it were calculated for completely different parameters and volumes of air inflow.

In the vast majority of cases, they will not be able to work correctly in conjunction with new elements. Ideally, it will be necessary to completely recalculate the entire air exchange system.

Advantages and design features

Manufacturers of ventilation valves call their devices ideal. This is due to the fact that the ventilation valves provide the room with good ventilation, but at the same time they do not create drafts and do not reduce the temperature. Also, ventilation valves do not violate one of the most important properties of plastic windows - sound insulation. In addition, in the room where the ventilation valve is installed, there will always be a good microclimate. When airing, it will not be possible to achieve a normal microclimate, since the temperature inside the room will constantly jump.

Externally, the ventilation valve is an oblong plastic element.Due to the fact that all the incoming air is directed upwards, there will never be drafts in the room where the device is installed. Installation of the ventilation valve will be an excellent solution for owners of premises with a large number of plants who need a good microclimate.