Ventilation in the cellar: the technology of the device proper ventilation system
On how well the ventilation functions in the cellar, depends on the safety of the objects placed there, and sometimes the state of health and health of the owners.
To create a properly functioning air exchange system, an understanding of some physical processes and knowledge of the technology of ducting equipment for underground premises are necessary.
The task of ventilation of underground rooms
Cellars are used for long-term storage of items with special requirements to environmental conditions. The temperature in enclosed premises is almost always kept in the range from +5 to + 12 degrees Celsius.
Humidity indicators can vary significantly depending, as a rule, from external conditions. With the help of ventilation it is possible to regulate these parameters to the required values.
Compliance with temperature
The temperature regime of a properly constructed and insulated cellar is formed by heat exchange between the walls, the floor and the air in it. The ceiling is usually insulated, so its effect on the temperature change inside the structure is minimal.
Seasonal variations in the temperature of the soil are much less than atmospheric, which makes it possible to establish a constant microclimate in the room. Heating or cooling of the air inside the cellar is slow due to the low thermal conductivity of the earth.
If necessary, you can use ventilation to change the temperature.Considering that the building is underground, the natural movement of air is sufficient for cooling the cellar in winter, whereas in the summer time it is better to stimulate the air flow by using fans.
The solution to the problem of excess moisture
The most common problem of the microclimate of the cellar is an excessive amount of moisture. Its evaporation using solar radiation or wind exposure is impossible; therefore, ventilation is the main method of draining rooms buried in the ground.
Ways of moisture can be divided into three types:
- Moisture can get into the cellar in the form of water through the walls, floor or ceiling in the absence or violation of the waterproofing layer. Most often this occurs in the spring during the thawing of snow.
- The internal source of moisture can be objects or products located in the room. Vegetables and fruits, especially in the initial stage of the storage process, emit evaporation. Also, air humidification occurs during the fermentation process, during the bees breathing, if the cellar is used as omshanik and in many other cases.
- In the spring and autumn period of time, when the temperature in the cellar is much lower than the street one, the source of moisture is condensate.Therefore, for the proper use of ventilation, knowledge of the physical laws of condensation and evaporation is necessary.
The process of removing moisture through ventilation is slow. Therefore, before starting this procedure, it is necessary to determine the cause of the increase in the humidity of the cellar and, if possible, eliminate it.
Reducing the concentration of hazardous gases
Another reason for ventilation is the need to change the chemical composition of the air. So, as a result of storage of agricultural products, all kinds of odors are released, and when it decays, as well as when bees or fermentation tanks are kept in the cellar, carbon dioxide is abundantly released, replacing oxygen. In poorly ventilated cellars, gas may have a different origin.
Excessive concentration of carbon dioxide (CO2), methane, carbon monoxide (CO) or hydrogen sulfide can cause a person to lack oxygen in the blood, suffocation and, as a result, loss of consciousness.In case of failure to provide immediate assistance, death is possible.
In the absence of internal air circulation, the concentration of hazardous heavy gases occurs at the lowest point of the cellar. Therefore, if simple airing is enough to remove odors, then to reduce the concentration of gases, whose specific weight with respect to atmospheric air is greater than one, ventilation is necessary with the location of the air intake aperture a short distance from the floor.
If there are prerequisites for excessive concentration of heavy gases in the cellar, it is necessary either to conduct mandatory ventilation of the room before visiting it, or use sensors or gas analyzers to determine the need for ventilation.
Theoretical basis of moisture removal
In the event that the main purpose of air exchange is to dry the room,then from the standpoint of physics, the problem can be formulated as follows: it is necessary to perform a ventilation device in the cellar in such a way that the absolute mass of moisture entering the inside is less than that going out.
Physical description of condensation and evaporation
There are three main terms, the essence of which must be understood in order to understand the nature of condensation and evaporation of moisture from the air:
- Absolute humidity shows the mass of water vapor contained in one cubic meter of air. This value is expressed in g / m 3.
- Relative humidity shows the ratio of the current mass of water vapor to the maximum possible, at constant pressure and temperature. It is expressed as a percentage.
- The dew point temperature indicates the temperature, when it is lowered to which the water vapor in the air reaches a saturation state and the process of condensation begins.
With reference to the cellar, the condensation process can be described as follows. At a certain temperature, the air has some values of absolute and relative humidity. With a decrease in temperature, the value of absolute humidity remains unchanged, while relative humidity increases.When the relative humidity reaches a value of 100%, the dew point sets in and moisture is discharged in the form of condensate.
The evaporation process is as follows: upon contact of air, whose relative humidity is less than 100%, it is saturated with water with water, which can continue until the relative humidity reaches 100%. The higher the temperature of the air, the greater the amount of moisture it can absorb during the evaporation process.
Drainage of underground premises in summer
In dry and hot weather there is a temptation to open the wet cellar for a while and run warm dry air into it to remove condensate. This is one of the most common mistakes that lead to the opposite effect - the flow of moisture from the atmosphere into the dungeon.
For example, during the day with anticyclone and air temperature reading +32 degrees Celsius and a relative humidity of 40% there is a feeling of dry air. In the cellar with a temperature of +12 degrees and relative humidity of 100% there is a feeling of dampness.However, the absolute humidity on the street with such parameters will be greater than in the room.
When ingested, the warm air will begin to cool. The dew point temperature at the above parameters of outdoor air will be equal to 16 degrees. Consequently, in the period of lowering the temperature from 16 degrees to 12 there will be condensation of moisture, and the relative humidity of the air will be equal to 100%.
Drainage of underground premises due to ventilation to properly produce for a long time. At the same time, the volume of air passing through the premises must ensure minimum indicators of the temperature drop, so that at low values of its relative humidity the evaporation process takes place.
However, after the end of the ventilation period, heat exchange with the walls and the floor will result in a gradual decrease in temperature and condensation of the air in the air. Therefore, temporary removal of moisture using ventilation in the warm period of the year is produced in the following cases:
- the amount of moisture in the cellar clearly exceeds the volume that will be there after the condensation of water from atmospheric air;
- it is necessary to create conditions for the cessation of intensive processes of decay, the spread of mold and fungus;
- It is necessary to conduct antifungal treatment, which is most effective when applying an antiseptic on dry surfaces.
Removal of condensate from the cellar in the warm season is carried out by alternative methods. You can use moisture collection with substances that have good hygroscopic (water-absorbing) properties, such as ash or sawdust. At the same time, if possible, it is necessary to exclude external air exchange, if this does not contradict the observance of other parameters of the microclimate of the room.
Freezing moisture in winter
At negative temperatures, the absolute humidity of the air is small. Therefore, the most effective method of removing moisture through ventilation, which is not quite rightly called “freezing,” is to ensure the flow of frosty air into the cellar.
So, even if at a temperature of -10 degrees Celsius, the air has the maximum possible humidity (2.36 g / cubic meter), then after it is heated in the room to values of +5 degrees, the value of relative humidity will be only 30%. One cubic meter of such air will be able to evaporate 4.5 grams of water in the cellar.
Since it is undesirable for almost any cellar to lower the temperature to negative values, the flow of frosty air should be carried out in small portions. It displaces humid air from the room and mixes with the rest. Then you need to wait for the temperature to rise to normal values and you can again carry out this procedure.
This method is effectively used in the fall after the laying of the crop, opening up ventilation for some time at night.
Technical points of the ventilation device
Technically correct implementation of the ventilation system for the cellar, along with an understanding of the rules for its use, will ensure the necessary microclimate in the room.For small structures, you can do all the work yourself, possessing basic skills in the field of construction.
Placement of air ducts and their maintenance
As ducting is usually used plastic or metal pipes. To plastic impose a requirement for resistance to low temperatures. This is necessary in order to avoid breakdowns in the winter during mechanical stress, such as cleaning from the coaster.
Usually, for the purpose of ventilation of underground premises, two pipes are used, one of which works for air flow, and the second for exhaust. The use of a single pipe leads to a much smaller volume of circulating air.
Places exit pipes preferably located at different ends of the cellar. In this case, there is a uniform airing of the entire area of the room, without the formation of zones of air stagnation.
The place of entry of ventilation is usually located near the floor of the room, and the place of air intake is closer to the ceiling. This is necessary to comply with the physical laws of the functioning of the natural air circulation. An exception is the placement of the entrance to the exhaust pipe near the floor for more efficient outflow of dangerous heavy gases.
When placing outdoor exits near the ground, it is necessary to monitor the level of snow, since the formation of a snowdrift above the level of the pipe can cause the termination of ventilation. Humid air escaping from the room causes a cobble to form in the exhaust pipe, which can reduce the speed of air movement or even cause ventilation to stop.
Purging the burr is sometimes a difficult task due to the presence of ice or deposits of increased density.To simplify the work, you can insert a rigid metal rod with a diameter of 8-12 mm into the pipe in the fall. In the case of complete closure of the pipe section by the chiller, translational movements and rotation of the rod, you can begin the procedure of cleaning the hood.
If the exhaust pipe is positioned vertically, then under its end located in the cellar it is necessary to put a container into which condensate and fragments of snow and ice will fall, crumbling when cleaning the pipe.
Natural and forced air circulation
In the overwhelming majority of cases, natural ventilation of small underground rooms is used. In winter, the physics of the air mass turnover process is based on the difference in density between cold and warm air. To do this, the outlet from the inlet pipe is placed closer to the floor, and the entrance to the exhaust pipe is located under the ceiling.
The cross-sectional area of the air ducts is calculated based on the indicator of the volume of air circulation required for a particular room and the estimated speed of its movement through the pipes.To adjust the volume of ventilation, it is better to use a section of the pipe slightly larger than that calculated with the valve. It can be installed both on the intake pipe and on the exhaust pipe.
Natural ventilation does not work well in the summer, and also removes gases for a long time, with a specific mass greater than that of ordinary air. In this case, fans are used to create air pressure, as a rule, with a blade principle of operation.
You can install the fans on the exhaust and intake pipes, as well as on both at once. In case of high humidity in the cellar, it is recommended not to install the fan on the exhaust pipe due to possible rapid breakage due to moisture.
Moisture removal with condensation zones
There is a way to remove moisture from the cellar in the winter, which does not require pipes and holes for air intake and outflow. It consists in the formation of zones for condensation of moisture and its subsequent removal. This method does not apply to ventilation, but to circulation, since there is no air exchange between the room and the atmosphere.
The most elementary implementation of this method is to use the canopy outside the ajar cellar door. Warm air, penetrating from the cellar through a small hole, is cooled, coming into contact with the cold canopy, on which the condensate in the form of frost and kuzhak remains. Cold dry air returns to the room.
When applying such a method, it will be periodically necessary to move the canopy back, close the door, knock down the cuff and remove it to the street. As a canopy it is necessary to use a dense rag capable of supporting a weight of up to 20 kg of adhering snow per 1 square meter of its area.
Conclusions and useful video on the topic
The problem of moisture condensation in summer and methods for its elimination:
Assembly and installation of the fan on the exhaust pipe:
For the quality of the ventilation system, it is necessary to carefully approach the issue of studying the physical principles of air circulation, as well as its condensation and evaporation.The technological air exchange device is not complicated and for small rooms its implementation is possible on its own.