Reverse draft in the ventilation of a private house: why ventilation works in the opposite direction and how to fix it

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.

The formation of natural draft in the duct occurs due to the difference in pressure and air temperature inside and outside a private house

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.

Causes of violation of air circulation

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

1. There is no supply ventilation.
2. The indoor temperature is lower than outside. This usually happens in the summer when it's hot.

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

Other causes of traction disturbance and reverse flow include:

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

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 draft ventilation in an 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.

Possible causes of reverse thrust

So, there are several reasons for the fact that in a private house or apartment there is a violation of draft in ventilation. Let's look at a few common problems:

1. The problem may be the incorrect installation of the ventilation pipe. That is, the pipe with the outlet of the exhaust air is located incorrectly in relation to the wind flows. As a result, the wind will blow into the ventilation and the air in it will form a reverse draft.
2. Also, the reason may be the formation of a blockage in the ventilation duct. How does this happen? Cold air and steam mix with each other. As a result, the ventilation process is disrupted.
3. The reason for the violation of draft may be a physical clogging of the ventilation system, for example, accumulated dirt, bird nests, and the like. Therefore, if reverse thrust is observed, then this moment is immediately checked. It is best to periodically check the ventilation duct for clogging. Due to this, air exchange will not be disturbed.
4. If inside a private house or apartment the rooms are too large and there is a draft in them, this can lead to incorrect ventilation.
5. Use of modern powerful exhaust units. They also create an imbalance in the ventilation system.

Often the problem comes down to the fact that in an old house wooden windows are replaced with plastic ones. This is especially true in situations where ventilation was designed taking into account the penetration of air through the cracks of wooden windows. Therefore, the installation of plastic windows can create a problem for air exchange. Worst of all, the formation of a traction disturbance in an apartment building can be the wrong redevelopment of your neighbors.

So, as you can see, there are many reasons for reverse thrust in a multi-storey building and a private building. First of all, you should look for the reasons in your apartment. If you have not found them, then you should look for them from the outside. In this case, you will have to connect ingenuity and logic in order to understand the entire ventilation system.

Possible causes of problems

As for the reasons, there are quite a lot of them for the occurrence of reverse thrust. For example, they might be:

incorrect installation

When arranging the ventilation system, it is important to foresee quite a few important nuances - in particular, the location of the pipe going out in relation to wind flows. If it is installed incorrectly, then the wind can blow into it in the most usual way, thereby provoking the exit of air into the room; airlock

airlock

It can occur as a result of mixing cold air and steam. Such a blockage prevents the normal outflow of air masses;

channel blockage. As mentioned above, they can get bird nests or the birds themselves - for example, pigeons that love to nest on roofs and attics. There were cases when specialists in cleaning ventilation pulled out huge clods of caked straw and feathers from it.Oddly enough, garbage can be household. For example, if there is free access to the roof of an apartment building, then teenagers or other people can gather there. As a result, various objects that should not be there get into the ventilation shaft. Accordingly, all this greatly interferes with the normal outflow of air from the premises;

drafts in the room. This is typical, first of all, of large-sized dwellings. If there are no walls or partitions on a large area, then under such conditions quite strong drafts can occur - that is, air flows, the power of which negatively affects the suction capacity of the ventilation system;

availability of forced-air supply equipment. We are talking about various fans and similar devices that pump air into the room. With their excessive power, ventilation simply will not have time to cope with the incoming volumes of air masses. This point must be taken into account when purchasing supply equipment;

chimney problems. This point is relevant in cases where it is a private house. If the chimney is out of order, this can affect the outflow of air and smoke from the room;

• insufficient supply of fresh air. Like an excessively powerful intake of air masses, their shortage can affect the route of the flows. In the modern world, this reason is becoming more and more relevant, since plastic double-glazed windows have been installed almost everywhere. Previously, window frames were wooden. This material itself is not bad for passing air, and the cracks that formed over time contributed to fresh receipts.Now, window and balcony openings are hermetically sealed, and air masses can enter the room only when the door is opened or when airing. Naturally, this volume is not enough for high-quality air exchange. Therefore, it is necessary to provide for the presence of a special valve or other supply equipment;
• improper redevelopment in a neighboring apartment. If we are talking about an apartment building, it often happens that during a major overhaul, neighbors in one way or another affect the operation of ventilation ducts. If you have already ruled out all other possible causes of problems, then this factor should also be checked.

How to determine that ventilation is not working properly?

There are several main factors by which you can determine that the ventilation system is faulty:

• extraneous odors appear from the ventilation hole;
• windows fog up in the apartment;
• mold has appeared in the room;
• there is a draft with closed windows and doors;
• during frosts in a room with a hood it becomes very cold.

If the ventilation system is faulty, windows fog up in the apartment

If you suspect that there is a malfunction in the ventilation system, a small test can be performed. You will need a sheet of paper that can completely cover the vent. It is necessary to create a draft - open all the doors and windows in the apartment. After that, it is worth attaching a sheet of paper to the hood. If the grate holds the sheet tightly, there is no problem with ventilation. In the event that the paper flies off the grate, there is a reverse thrust. This suggests that polluted air enters the apartment, and not vice versa.

Another way to check draft in the kitchen is to use a candle.First of all, it is necessary to create natural ventilation. To do this, open the window in the kitchen and the door to the bathroom. A candle is lit. Ventilation works properly if the flame deviates towards the hood. If it slopes in the opposite direction, it is necessary to clean the air duct. An important condition for this check is to turn off the electric cooker hood, as it creates artificial draft.

Reverse thrust elimination

In some cases, when the reverse draft is in the chimney, elimination can be done by hand.

• This applies to cleaning the chimney from soot and removing foreign objects. You will need a ruff and a weight with a cable.
• If there is a lack of air, you need to open the window for 10 minutes to ventilate.
• Chimneys in the outer wall or remote need to be insulated.
• Sometimes in wet weather or after a long break in the operation of the heater, it is enough to burn a piece of newspaper in the firebox to resume traction.

A good means of eliminating the possibility of reverse thrust is the use of various devices. These can be gate valves, deflectors (pictured), chimney weathercocks, smoke fans.

The deflector is always available for sale. The price ranges from 550 to 3800 rubles. The manufacturer provides instructions for use.

Safe and efficient operation of heating units is possible if there is draft in the chimney. At the first sign of back draft formation, it is necessary to check the chimney and ventilation ducts. The entry of combustion products into the home is fraught with health risks and can threaten people's lives.

Stabilizers

During the existence of heating, many devices have been invented that improve the flow of gases in the chimney (see photo):

rotary turbines - consists of a nozzle and a housing mounted on the chimney head. Under the influence of wind, the nozzle rotates and creates an increase in the flow of exhaust gases due to the created rarefaction;

electric smoke exhauster, or smoke fan. With forced draft, you don’t have to worry about tipping over - this is an almost ideal smoke outflow regulator, however, maintenance of the device on the roof is quite difficult, and the installation of such a design should be calculated even at the drawing stage;

all kinds of caps are also able to slightly improve the outflow;

chimney weathercocks, often mounted on wood-burning stoves.

Gate manipulations

Shiber - a damper that affects the strength and direction of thrust. Usually, during the construction of a stove or fireplace, two gates are installed. One is in the chimney, the second is in the stove or in its door. "Play" with the position of these flaps, often this increases traction, and the problem is solved by itself.

Using a draft regulator (stabilizer)

This is a special device that creates air currents in the chimney and controls their strength. It stabilizes draft and, among other things, contributes to fuel economy, and also prevents combustion products from entering the room.

Ventilation system

Often a situation arises when everything is fine with the chimney, but there is still a reverse draft in the chimney, what to do then? What is the reason? Most likely, the matter is in the ventilation system, which works according to certain natural patterns.

The density of warm air flows is significantly lower than the cold masses, so warm air rushes up.If at this time the doors or windows are open in the room, then the air masses will go exactly into the open openings, and not into the chimney of the heater. Therefore, you need to ensure that when you turn on the device, all doors and windows to the street are closed.

Also, the internal architecture of the structure has a huge impact on traction. If there are many doors or windows in the building, there is a passage to a balcony or stairs to another level, then a draft will certainly occur. Therefore, it is impossible to keep open windows and doors located above the level of the combustion chamber.

It often happens that all openings are locked, but when the heating device is kindled, the low-pressure zones attract fresh air flows from the chimney, and as a result, the thrust is overturned. You can solve the problem by creating the necessary air circulation.

For this you need:

• install in-wall supply valves;
• equip windows with supply valves;
• install a forced ventilation device in the window glass;
• slightly open the door, window or window.

The implementation of one of the proposed measures will lead to a decrease in atmospheric pressure in the room and, accordingly, the disappearance of reverse thrust.

If a gas column is used as a heating device, then there are some nuances:

• the combustion chamber draws air flows from the room;
• oxygen deficiency begins to be felt in a fairly short time;
• air from the chimney will begin to flow back, which will lead to the extinction of the flame and smoke.

In this case, it is worth carefully checking the efficiency of the ventilation system.

Reverse draft in the chimney: what to do

In case of insufficient draft, first of all, it is necessary to check the entire structure of the chimney and eliminate the detected malfunctions. Most often, it is possible to establish the presence of contamination or clogging of the channel. It can be garbage brought into the chimney by the wind and even bird nests built during an unheated period. But most often the cause of insufficient traction is the deposition of soot on the walls of the chimney. To eliminate it is necessary:

Cut a bucket of potatoes into small pieces and burn the root crops in a firebox in small portions. The released starch softens the soot coating, and it falls in pieces into the furnace. At the end of the firebox, they must be removed. The same effect can be achieved by burning potato peels.
Firebox with aspen wood. When such fuel is burned, a large amount of heat is released, but there should be no more than 2–3 logs in the bookmark

When using this method, special care must be taken, since soot can ignite, which will lead to a fire.
Salt rock, periodically added to the firebox. Its vapors clean the walls of the chimney. Used as a prophylactic.
Pipe brush in the form of a brush for mechanical cleaning of pipes.
Installing a deflector always creates additional draft in the direction of the chimney.

Used as a prophylactic.
Pipe brush in the form of a brush for mechanical cleaning of pipes.
Installing a deflector always creates additional draft in the direction of the chimney.

Mandatory maintenance of the chimney must be carried out annually before the start of the heating season.

Individual heating of a country house with any type of fuel can be safe if, during the construction and installation of chimneys, all devices are provided to ensure normal draft and preventive maintenance is regularly carried out.

Traction and possible accidents

First, about traction, and about those processes with which many owners of heating appliances may be familiar firsthand.

What is traction?

Air circulation is a natural process that allows oxygen to enter the combustion chamber, and then the exhaust gases to be expelled through the pipe. The movement of air and gases in the chimney is due to the lower density of the heated air. For this reason, there is a pressure difference in the lower and upper parts of the channel.

The draft in the chimney is a natural ventilation, consisting of an exhaust and an inflow. Hot gas, having excess pressure and lower density, tends to the area where it is lowered - up. Cold air coming from the street occupies the vacated space. Combustion in the furnace provides air that continuously enters the chamber from the room, and then "travels" through the chimney and goes outside.

Reverse thrust

Reverse thrust is a similar process, but the movement of gases or air is exactly the opposite. This situation occurs when the pressure at the top of the channel is higher than at the bottom. Reverse draft - stable, but reverse circulation: in this case, the flue gases return to the room along with the air that enters the chimney from the street. There are a lot of reverse thrust provocateurs. These include:

• discrepancy between the elements of the system - the height, diameter of the vertical part of the chimney and the parameters of the heater;
• errors in the design of the chimney: low vertical height, incorrectly selected section, the presence of horizontal or inclined sections, uneven walls;
• violation of tightness, narrowing of the channel due to soot, some kind of obstacle near the chimney;
• problems with the exhaust hood in the room, or with the general inflow;
• channel freezing.

Thrust overturning

This is another possible occurrence. When the flow of gases decreases, the draft in the channel also weakens. Burning during this period of time slows down, the flame darkens. At the moment when the circulation stops, there is a "thrust rollover". This is the name given to the sudden release of smoke into a room. As a rule, it is one-time.

The reasons for the unusual situation are the mistakes made during the construction of the appliance or chimney, the quality of the firewood and external factors: these include an increase in humidity, a change in atmospheric pressure, or strength, wind direction. Such "tilting whims" are characteristic of fireplaces that have large, open fireboxes. These fumes may occur intermittently, but they are not extreme events.

Installation of supply channels

Supply valves are through holes in the wall that goes outside. They provide an additional flow of fresh air in the room. Such valves are installed with two gate valves. This allows you to fully open or close the holes or slightly open them. Do not forget about double-glazed windows, the design of which already includes valves. This simultaneously ensures air circulation and tightness.

A grill is mounted inside each valve, which protects against dust, dirt and debris, moisture from entering the devices and the apartment. And to protect the room from excess sound, a soundproof box is installed on the inside of the holes.

It is important to choose reliable valves, as low-quality models will only work effectively with a large temperature difference. In addition, it can blow through the holes even when the shutter is closed.

To improve the indoor climate, control humidity and air temperature, you can install special cleaning filters, ionizers and humidifiers, install a climate control system. Then you will forget about the problems of the microclimate in the apartment, get rid of bacteria, allergens, dust and unpleasant odors forever.

How should proper ventilation work in an apartment?

If the ventilation in your apartment does not work, of course the Internet will tell you where to turn. But how to understand whether the air exchange system is working or not? Consider the standard ventilation scheme for an ordinary apartment in a multi-storey building. It consists of two systems, supply and exhaust. Let's try to understand how the functionality of each is implemented:

• The basics of the MKD exhaust system are determined by the calculations and the construction project. Each house has ventilation ducts arranged next to the kitchen and bathroom. They go up to the roof of the house. In low-rise buildings, each kitchen and bathroom has its own ducts. In high-rise buildings, apartment ventilation ducts-satellites are connected to common house ventilation shafts. In serviceable channels, natural draft is formed due to the rise of warm air and pressure difference. On the lower floors, the traction should be excellent, on the upper floors in the summer heat, there may be problems with it.They check the draft with a special device - an anemometer, but only specialists from the operating services use it. In everyday life, you can make sure that there is a draft by blowing cigarette smoke into the hood or by attaching a piece of thin paper to the ventilation grille. If it sticks to the grate, the system is working;
• Builders often forget about forced ventilation. 3-4 years have passed since the most advanced of the developers began to install supply valves in the apartments. In the last century, the inflow function was carried out through loose porches and defects in the wooden bindings of window fillings. A fresh supply was drawn into the apartment, displacing the exhaust air into the toilet and into the kitchen. Plastic windows block this inflow option. The owners will have to regularly open windows for ventilation, or install a supply unit in the apartment. They select it according to performance, having calculated the required volume of inflow for your family according to the standards. A good ventilation system implies a slight excess of the inflow volume over the capabilities of the exhaust system.

Ventilation problems in multi-apartment buildings

In multi-apartment buildings, the failure of ventilation, and in particular the formation of back draft, leads to a number of problems. Residents of apartments in this case complain about fogging of windows, humid air, increased mold formation.

All this provokes the development of dangerous diseases of the respiratory system, such as bronchial asthma.

If there is a suspicion that the air exchange in the room is disturbed, first of all you need to check it yourself. If the suspicion is confirmed, you should contact the house management company to resolve this problem.

It is forbidden to take any measures on your own in this case.The only thing that can be done is to clean the ventilation grill at the entrance to the apartment.

One of the most common causes of reverse draft, causing a malfunction of ventilation in an apartment building, is the redevelopment of the premises of the neighbors, which is not coordinated with the competent organizations.

In this case, both part and the entire ventilation duct can be dismantled.

If the violation of air exchange is caused by the installation of plastic windows and doors, a supply fan can solve the problem.

At the same time, it is important to follow the rules for installing the device in apartment buildings and ensure silence for residents of neighboring apartments.

Also in large houses there is often a problem on the upper floors. This is due to the peculiarities of the operation of the ventilation system itself.

In order for everything to work properly, there must be at least 2 meters from the last vent to the outlet on the roof. In modern buildings, this is difficult to implement.

To solve this problem, additional devices are installed that bring air outside, or the ventilation ducts are expanded.

The quality of ventilation is an important element for maintaining a favorable microclimate in the apartment.

The difficulty of living in apartment buildings is due to the fact that ventilation problems can begin with one of the neighbors, and all residents of the house will suffer.

That is why, if there are problems with traction, you should definitely contact specialists who can conduct a comprehensive check and identify the cause of the violation of air exchange.