The principle of natural ventilation
Air circulation, when organizing a natural type of ventilation system, occurs due to the pressure difference in the ventilation shaft, due to which there is a draft, pushing the internal air out.
The following factors influence the ventilation efficiency of a room, with this type of ventilation device:
- Pressure value on the outer and inner slice of the ventilation pipe. Traction power increases with the height of the exhaust duct.
- The temperature outside the room and inside where the ventilation is located. Cooled air is heavier, so it squeezes light air into the room from below. As a result, the used air rushes into the duct from the inside.
- Condensation level in the room. Vapors are lighter than cool air, and therefore, at a stable temperature, they rise and exit through the air ducts.
In addition to these main factors, the ability of the system to cope with maintaining a comfortable microclimate in the building is also affected by the readings of atmospheric pressure, humidity and temperature.
With the similarity of the temperature inside and outside, the draft is noticeably worse, and excessive heating of the air masses from the outside can lead to reverse thrust. In such a situation, only a large ventilation duct can save the situation.
The natural ventilation device in a wooden house, in structures built of brick or aerated concrete, and in high-rise buildings can significantly save estimates, while the efficiency of air exchange does not suffer from this.
Outlet ducts and shafts in all structures are arranged exclusively in partitions or carried out. For outdoor use, you will have to spend money on additional pipe insulation.
Advantages and disadvantages of natural ventilation
In residential construction, natural-type ventilation devices are mounted taking into account the requirements of the SNIP and the principles of modern eco-design. Despite compliance with the standards, such devices have both positive and negative properties.
The positive aspects include:
- low cost of arranging natural ventilation;
- infrequent routine maintenance of the system is normal;
- unlike forced systems, there is no noise;
- installation of ventilation devices does not cause complications even for beginners;
- in order to build a ventilation duct, it will take very little time;
- to support the functionality of the system does not require additional costs;
- the service life of the system is not limited;
- natural ventilation is not an object of increased danger and does not cause emergency situations;
- these systems can be combined with forced ventilation.
The negative points include:
- these systems are not able to regulate the speed of the exhaust flow: with increased humidity in the room, this feature causes the appearance of fungus or mold foci;
- weakly protected air intake devices do not hold dust, tiny insects and plant seeds, as a result of which it takes more effort to maintain order in the room;
- the installation of protective nets violates the normal air circulation and cannot be the solution to this problem;
- in winter, when airing the premises in a natural way, serious heat losses occur;
- dependence of hood efficiency on street temperature and wind strength.
How to calculate system performance
In order to independently calculate the required parameters for a one-story or two-story building, several factors must be taken into account:
- The area of the room.
- The multiplicity of the total exchange of air in the room in one hour.
- Standards for providing fresh air according to SANPIN per person (for normal living conditions, take into account 30 m3/hour).
The main condition for effective air circulation in the room is the equality of the volume of inflow and exhaust.
A step-by-step calculation algorithm will help determine the required air volume for further selection of suitable equipment:
- To get the full amount of air in the house, you need to add up the volume of all rooms. Focusing on the norms of air consumption in various premises of the home and the volume indicators of these premises, the average rate of the rate of total air exchange should be derived.
- Multiplying the obtained multiplicity by the total volume, we obtain the volume that is necessary for the intake and removal of air per hour.
- Based on this indicator, calculate the number and power of devices providing inflow and exhaust parameters. When calculating, it is necessary to be guided by the instructions and technical characteristics of the devices used and the type of exhaust duct.
This calculation does not take into account changes in traction power in various climatic conditions. To obtain more accurate data, more complex calculations will have to be made.
The organization of natural ventilation in a frame house is different from the equipment of buildings made of logs or beams. In chopped houses, the level of natural influx is higher than in frame houses (due to uneven shrinkage and the presence of gaps). Accordingly, to normalize the influx in frame buildings, it will be necessary to additionally use mechanical devices.
Norms of natural ventilation
Modern SNIPs regulate the ventilation standards of residential premises based on the value of the total air exchange in the building, and is measured in the number of times or cubic meters per hour.
Standards for one-story residential buildings are:
- permanent premises - 1 full exchange per hour;
- kitchen - from 60 m3/ hour (hood);
- bathroom - at least 25 3/ hour (hood);
- other premises - 0.2 full exchange per hour.
In addition to these standards, the value of the outdoor air consumption per person should be taken into account. This indicator is 30 3/hour.
Norms of natural ventilation in a multi-storey building take into account the presence of additional rooms:
- Laundry - 90 3/hour;
- gym - 80 3/hour;
- dressing room - 0.2 full exchange per hour;
- gas boiler rooms - 1 full exchange per hour + 100 3/hour.
There are special requirements and norms for ventilation equipment for basements, technical floors and attics.
Components of natural ventilation technology
Before you make natural ventilation in a private house with your own hands, you need to determine the characteristics and number of supply and exhaust elements, understand the method and places for the correct installation of these devices.
The natural ventilation system is constructed of vertical exhaust pipes (can be internal or external), devices that ensure the influx of external air and horizontal exchange ducts.
For the correct installation of devices, the calculation of ventilation standards must be carried out for each room in the building.
Supply valves
Supply air valves are used to provide outside air to the room. The choice of design of the supply equipment depends on the needs of the room. The number of devices and their performance is determined on the basis of calculations.
It is recommended to place the devices providing the inflow at a height of 1800-2000 mm from the floor. When installing the equipment, it is necessary to provide a slight slope of the valve inside the wall. The outer end of the valve should be lower than the inner. This arrangement will protect the room from precipitation inside.
Exhaust ducts
As air ducts in individual buildings, special hollow cinder blocks or plastic pipes are used. The following devices are used to regulate the exhaust air removal process:
- Adjustable louvres allowing to reduce or increase the area of the exhaust window;
- Baffles. This device, installed at the top of the ventilation duct, allows you to increase traction power;
- Traction amplifiers. It has a more complex, umbrella structure, but performs the same function as the deflector.
Ventilation ducts
Ventilation ducts are arranged to remove used air from rooms with high humidity or rooms for special purposes. Several ventilation ducts are combined in one output shaft.
Ventilation ducts are located on the inner walls. When laying the channels, it is necessary to provide unhindered passage of building structures (floors, rafters) so as not to disturb the verticality of the duct.
Recommendations
When installing natural ventilation in a private house with your own hands, it is advisable to take into account the features of a comfortable air exchange device for existing and existing buildings.
For the design of natural ventilation in a house under construction
The basic principle of drawing up a scheme of natural ventilation in a private house during the construction process is the location of the mines. They are arranged exclusively in internal partitions to ensure that the main part of the pipe is kept warm. This principle allows you to get sufficient exhaust power, especially at low temperatures of street air.
For the equipment of exhaust shafts, it is recommended to use rectangular elements. They can significantly save the internal space of the house, but in the presence of free space, you can mount round pipes that create a more intense flow.
As pipes for the duct use plastic water pipes, because when using corrugated products, there are weak, but sensed by human hearing, noises.
When ventilating pipes through the unheated attic floor to the roof, it is recommended to take care of additional insulation of the duct in this room.
When installing the exhaust pipe, it is recommended to observe verticality, if it is impossible to maintain this condition, bypass slopes should be done with a deflection angle not exceeding 30 degrees. Each transition with an offset from the main vertical axis takes about 10% of the power.
Care should be taken to the connecting nodes of the duct. Inaccurate articulation of individual elements, foreign objects, roughness - complicate the process of efficient operation of the hood.
The higher the duct pipe, the more efficient the drawing process. The removal of the ventilation fungus is recommended to be installed 500 mm above the roof ridge.
On the modernization of ventilation in an already built house
To increase traction and provide additional protection against insects and dust from entering the structure, it is advisable to install a deflector at the end of the duct. This device helps to increase power by 20%.
In rooms with high humidity, it is recommended to install exhaust fans. This measure turns the natural system into a combined one, but the dependence on weather conditions disappears. In addition, the installed devices will allow you to balance the humidity and temperature conditions in these places and prevent rotting of materials.
When the building is equipped with plastic windows and during frosty times, ventilation is rarely carried out, in order to save heat, the efficiency of air mass circulation drops sharply. In such a situation, it is recommended to equip the windows with special ventilation valves, which make it possible to organize the flow of outside air, and at the same time arbitrarily control the flow.
Natural Ventilation Tips
Each room in a suburban building or country house has features that must be considered when installing ventilation devices.
In the bathroom
For the toilet and bathroom in a suburban building, it is necessary to provide for the possibility of micro-ventilation through windows or doors.
In the bath
With ventilation equipment in the bath, it is planned to place a supply duct at the installation site of the furnace. Street air penetrates from below, gradually forcing warm air to the ceiling, heating itself. An exhaust valve in the steam room is installed under the ceiling.
If necessary, open the valve to quickly dry the steam room or washing.
In the boiler room
If a country house is heated by gas, it must provide a separate room for equipment. A gas boiler is an object of increased danger, therefore, the requirements for equipment with a boiler hood are quite serious.
The ventilation of the boiler room is mounted separately and does not crash into the common exhaust pipe, most often an external pipe is used to get rid of smoke and gas.
For the supply of outdoor air to the boiler rooms, supply devices are used. The weak point of the natural-type supply and exhaust system in boiler rooms is its dependence on wind power. In quiet, calm weather, it is impossible to provide good traction.
In living rooms
To ensure effective air circulation between individual rooms in the house, it is necessary to arrange small holes or gaps between the door leaf and the floor in the lower part of the door leaf.
On the kitchen
When installing the exhaust ventilation grille above the stove, you need to place this device at a distance of 2 meters from the floor. This position of the hood allows you to effectively remove excess heat, soot and odors, preventing them from spreading around the room.