In order for the microclimate in residential and non-residential rooms of the cottage to be favorable for humans, the ventilation system of the building must work properly and without interruption. The slightest failure in its functioning leads to a decrease in air exchange between the interior and the street. As a result, the air humidity and temperature rise inside, and the air itself becomes musty. One of the main symptoms of such a malfunction is the reverse draft of ventilation in a private house from the hoods.
The system of intra-house air exchange is usually built so that air masses from the rooms are continuously drawn into the ventilation ducts and further out. And you must admit that if air begins to blow back from the ventilation grill, then this is a sure sign of problems. It is necessary to immediately identify the root cause of this, and then somehow eliminate it, otherwise life in the cottage will become uncomfortable.
The content of the article:
- Reasons for reverse draft in ventilation
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How can you fix the problem?
- Clogged ventilation ducts of a private house
- Insufficient air flow
- Incorrectly designed ventilation
- Conclusions and useful video on the topic
Reasons for reverse draft in ventilation
A classic ventilation system in a private house is built according to a scheme with natural air movement. The latter in it moves from the rooms to the outside due to the formation of spontaneous thrust. Air masses with a high carbon dioxide content are constantly drawn into ventilation ducts from the premises, and their place is taken by fresh from the street, saturated with oxygen.
Air inflow occurs through windows, doors and special openings in the walls. At the same time, according to the laws of physics, he seeks to move where he meets the least resistance. And in the house, these are ventilation ducts that go to the attic or out to the roof. And the higher and longer such a chimney, the stronger the draft is generated in it.
The formation of natural draft in the duct occurs due to the difference in pressure and temperature of the air inside and outside a private house
Backward thrust into the hood holes occurs due to:
- clogging of ventilation shafts (narrowing their cross-section);
- decrease in air flow;
- errors in the design of the ventilation system;
- changes in the ventilation system by adding fans and hoods that were not originally foreseen.
Normal air exchange occurs only when there is 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 be simply nothing to pull out of the rooms. Even at the stage of preparing a ventilation system project, 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 indoor ventilation subject to restructuring. Initially, the channels in it were calculated for completely different parameters and volumes of air flow.
In the overwhelming majority of cases, they will be unable to work correctly in conjunction with new elements. Ideally, it will be necessary to completely re-calculate the entire air exchange system.
How can you fix the problem?
To restore the correct operation of the ventilation system, you must first identify the root cause of the failure. It's one thing when there is no normal draft in the ventilation of a private house, and another thing is when it constantly overturns (from the exhaust hole it blows back into the room). In each case, the problem will have to be solved in different ways.
To determine the presence and direction of thrust, it is recommended to use a sheet of paper or special devices - anemometers
Sometimes there are tips for checking traction with a candle or lighter. It is absolutely impossible to do so. Dust and grease from cooking on the stove gradually accumulates in the ventilation ducts. Contact with an open flame with this explosive mixture may result in fire or popping.
It is safer and most practical to independently determine the traction force in ventilation using plain paper. If you attach the sheet to the exhaust hole, then with the correct operation of the ventilation system, it should be pulled to the grate. If it is pulled back into the room, then the hood in the house is blowing incorrectly - in the opposite direction, which clearly indicates the presence of problems with traction.
Clogged ventilation ducts of a private house
Often in cottages the following situation arises - initially the ventilation worked properly, it did not changes were made and new appliances were not installed in the premises that increase consumption oxygen. However, at some point, the thrust in the system begins to fall.
The microclimate in the rooms of the house is gradually deteriorating. Moreover, this happens so unobtrusively and slowly that for the time being, none of the family members pays attention to such a problem. But then on the walls mold appearsand the air inside becomes musty.
The frequency of cleaning ventilation ducts in a private house is not regulated by laws, but it is recommended to check them once every six months, if necessary, immediately cleaning them from dust accumulations
You can clean the ventilation ducts:
- a special metal brush;
- by rinsing with water;
- industrial vacuum cleaner.
A video camera should be used to assess the degree of contamination and the quality of cleaning. Only she will allow you to see with your own eyes what is happening inside the ventilation duct.
When cleaning the ventilation, a blockage can be found both in the inner sections of the shaft and in its upper section. From above, the ventilation pipe is often clogged with snow, ice or leaves from nearby trees. This happens when there is no deflector or a cap.
They also like to arrange birds' nests inside the ventilation pipes of country cottages, heat is constantly coming from the house - what else does a feathered bird need in winter
To eliminate all blockages, it is necessary to inspect completely all existing ventilation ducts in the house from the exhaust openings in the rooms to the exit on the roof. A narrowing can form anywhere in the system.
If the ventilation pipe does not yet have a protective cap on top, then it must be installed after cleaning. It will reduce the risk of re-clogging and provide increased ventilation traction.
Insufficient air flow
Old houses used to have wooden windows and doors everywhere. Due to the low tightness, they constantly blew through, which caused a lot of trouble in winter.
However, these drafts directly participated in the air exchange. They provided the necessary air flow. At the same time, the ventilation ducts worked exclusively for the hood.
Modern double-glazed windows in a closed state completely interrupt the flow of air necessary for ventilation of premises in a private house
To ensure the proper flow of air masses, they are mounted or arranged:
- window valves;
- inlets in the walls;
- additional air ducts through the subfloor;
- mechanical fans for the organization of forced ventilation.
According to sanitary standards, the air in the living room must be completely replaced with completely fresh air at least once an hour. At the same time, in kitchens and rooms with stoves, boilers or fireplaces, air exchange should be several times higher, since they also consume more oxygen.
Incorrectly designed ventilation
If the overturning of the thrust occurs from time to time for a couple of hours, then the reason for this usually lies in a banal change in the weather. When calculating the system, the designers did not take into account something, and as a result, with a sharp cold snap, ventilation in a private house blows inward, and does not pull out, as expected.
This problem can be solved only by a complete recalculation of the ventilation system.
If a tall tree has grown next to a private house, then it can also become a causal back draft in the ventilation shaft.
Before ordering a new ventilation project, you should carefully examine all its components. It is quite possible that dirt has adhered to the ventilation grill or the blades of the duct fan. As a result, the channel narrowed quite a bit - most of the time the system works properly, but occasionally it fails. In this case, simply cleaning is sufficient.
A new tall building next to the cottage, a change in the geometry of the roof, the installation of a satellite dish - all this can lead to a decrease in thrust. If obstacles appear in the path of the wind, then in the area of the top of the ventilation pipe, the initial parameters of air pressure change. And then the speed of its movement along the ventilation ducts decreases.
In order for the draft in the ventilation pipe to be constant and sufficient, its upper point must be at a certain height relative to the roof visor
To increase traction in the ventilation shaft, a deflector should be installed on top. He creates a slight vacuum around him, as a result of which air from the house rushes into this void.
Deflectors show the greatest efficiency in windy weather. If calm is established on the street, then there will be zero sense from such a device. In such a situation, it is possible to increase traction only with the help of a mechanical impulse - a fan.
And the last point - in order to prevent the draft from overturning, the ventilation grilles on the hood in the rooms should be changed to check valves. When there is a flow of air from the ventilation into the room, they are closed, blocking the opening.
Conclusions and useful video on the topic
All the nuances of the formation of traction in the ventilation of the house:
Why reverse thrust occurs in ventilation ducts:
Backdraft formation in ventilation is rare. This is a serious and frustrating problem, but finding and fixing the cause yourself is not so difficult. It is only necessary to carefully study the entire ventilation system existing in the cottage, and, if necessary, clean or slightly modify it.
If you have a situation where the hood suddenly starts blowing in the opposite direction in the house, then share your way of solving this problem. You can also ask a question on the topic discussed in the article, and our experts will certainly help you understand all the nuances of ventilation.
