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

In order for the microclimate in the residential and non-residential rooms of the cottage to be favorable for humans, the ventilation system of the building must work properly and without fail. The slightest malfunction in its functioning leads to a decrease in air exchange between the interior and the street. As a result, humidity and temperature rises inside, and it becomes musty. One of the main symptoms of such a malfunction is the reverse draft of ventilation in a private house from the exhaust openings.

The system of intra-house air exchange is usually built so that the air masses from the rooms are continuously drawn into the ventilation ducts and further out. And you must admit, if air starts 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.

Reasons for back draft in ventilation

The classic ventilation system in a private house is built according to the scheme with the natural movement of air. The latter in it moves from rooms outwards due to the formation of spontaneous traction. Carbon dioxide-rich air is constantly drawn into ventilation ducts from the premises, and their place is occupied by fresh from the street, saturated with oxygen.

Air flows through windows, doors and special openings in the walls. Moreover, according to the laws of physics, he seeks to move to the place 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 a chimney 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 the private house

The reverse draft in the exhaust openings is due to:

• clogging of ventilation shafts (narrowing of their section);
• reduce air flow;
• errors in the design of the ventilation system;
• changes in the ventilation system device by adding initially unforeseen fans and hoods.

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

If a few years after the construction of the house in the kitchen, a mechanical hood is installed or a gas boiler is mounted, then house ventilation subject to restructuring. Initially, the channels in it were calculated for completely different parameters and volumes of air flow.

In the vast majority of cases, they will be unable to work correctly in conjunction with new elements. Ideally, it will be necessary to fully calculate the entire air exchange system again.

How can I fix the problem?

To restore the correct operation of the ventilation system, you must first identify the root cause of the failure. It is one thing when there is no normal draft in the ventilation of a private house, and another when it constantly capsizes (it blows back from the exhaust outlet into the room). In each case, the problem will have to be solved in different ways.

To determine the presence and direction of traction, it is recommended to use a sheet of paper or special instruments - anemometers

Sometimes there are tips for checking traction with a candle or lighter. You can’t do this categorically. Dust and grease gradually accumulate in the ventilation ducts from cooking on the stove. Contact with an open flame with this explosive mixture may result in fire or cotton.

Independently determine the traction in ventilation is the safest and most practical way with ordinary paper. If you attach the sheet to the exhaust hole, then with the correct operation of the ventilation system, it should be attracted to the grate. If it pulls back into the room, then the hood in the house blows incorrectly - in the opposite direction, which clearly indicates the presence of problems with traction.

Clogged ventilation ducts of a private house

Often the following situation arises in cottages - initially the ventilation worked properly, no changes were made to it, and new devices that increased oxygen consumption were not installed in the rooms. 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 inconspicuously and slowly that for the time being, none of the family members pays attention to such a problem. But then on the walls mold appears, and the air inside becomes stale.

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 from dust accumulations

You can clear ventilation ducts:

• special metal brush;
• by washing with water;
• industrial vacuum cleaner.

To assess the degree of contamination and the quality of cleaning, use a video camera. Only it will allow you to see firsthand what is happening inside the ventilation duct.

When cleaning ventilation, blockages can be detected both in the interior of the shaft and in its upper section. Above, the ventilation pipe is often clogged with snow, ice or leaves with nearby trees. This happens when it is not on deflector or cap.

Inside the ventilation pipes of suburban cottages, they also like to arrange bird nests for themselves, it is always warm from the house - what else is needed for a feathered 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 to the roof. Narrowing can form on any part of the system.

If the ventilation pipe on top does not yet have a protective cap, then it must be installed after cleaning.It will reduce the risk of re-blockage and increase traction in ventilation.

Insufficient air supply

Old houses used to have wooden windows and doors everywhere. Due to the low tightness, it constantly blew through them, which caused a lot of trouble in the winter.

However, these drafts were directly involved in air exchange. They provided the necessary air flow. At the same time, ventilation ducts worked exclusively for the hood.

Modern double-glazed windows in a closed state completely interrupt the flow of air necessary for ventilating rooms in a private house

To ensure the proper flow of air masses, they are mounted or arranged:

• window valves;
• air inlets in the walls;
• additional ducts through the subfloor;
• mechanical fans for organizing forced ventilation.

According to sanitary standards, the air in the living room should be completely replaced completely fresh at least once an hour. Moreover, in kitchens and rooms with stoves, boilers or fireplaces, air exchange should be several times higher, since they also have more oxygen consumption.

Improper ventilation

If traction tipping occurs from time to time for a couple of hours, then the reason for this usually lies in the banal change in the weather. When calculating the system, the designers did not take into account something, and as a result, during a sharp cooling, ventilation in a private house blows in, and does not stretch as it should.

This problem can only be solved by a complete recalculation of the ventilation system.

If a tall tree has grown near a private house, it can also become a causal back draft in the ventilation shaft.

Before ordering a new ventilation project, you should carefully examine all of its components. It is quite possible that dirt has adhered to the ventilation grille or duct fan blades. As a result, the channel narrowed quite a bit - most of the time the system works properly, but occasionally crashes. In this case, just cleaning is enough.

A new tall building near the cottage, a change in the geometry of the roof, the installation of a dish of satellite dishes - all this can lead to reduced traction. If obstacles appear in the way of the wind, then in the region of the top of the ventilation pipe, the initial parameters of the air pressure change. And then the speed of its movement along the ventilation channels drops.

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. It creates a small pressure around itself, as a result of which air from the house rushes into this void.

The most effective deflectors show in windy weather. If the street is calm, then the sense of such a device will be zero. In a similar situation, traction can be strengthened only with the help of mechanical motivation - a fan.

And the last moment - in order to avoid tipping over the draft, 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 to the room, they close, blocking the hole.

Conclusions and useful video on the topic

All the nuances of traction in ventilation at home:

Why there is a reverse thrust in ventilation ducts:

The formation of back draft in ventilation is rare. This is a serious and unpleasant problem, but finding and eliminating the cause of it yourself is not so difficult. It is only necessary to carefully examine the entire ventilation system in the cottage, and, if necessary, clean or slightly modify it.

If you have a situation where the hood in your house suddenly starts to blow in the opposite direction, then share your way to solve this problem. You can also ask a question on the topic discussed in the article, and our experts will surely help you understand all the nuances of the ventilation.