To create the right microclimate in the house, you need to equip it with an air circulation system. To ensure its efficient operation, it is required to perform the correct calculation of the length and diameter of the pipe that removes air from the house. Calculations are performed using different methods, depending on what type of ventilation system is installed in the house.
The wrong height of the pipe above the roof contributes to the occurrence of oxygen deficiency in the house and exceeding the permissible humidity. If an error was made in the design of the hood, soot and fungus will appear on the walls and furniture, and the windows will be constantly covered with perspiration.
Ventilation calculation
Ventilation usually consists of round or square ventilation ducts. If special devices are not used to remove air, then the best option would be to install round air ducts. They, in comparison with square ones, are distinguished by higher strength, tightness and better aerodynamic performance. If the room is equipped with forced ventilation, then in this case, you can install square pipes.
Volume of inflowing air
As a rule, residential buildings are equipped with natural air circulation. Outside air can be supplied through a window or a special valve. The outflow occurs through the ventilation duct. It can be located inside a wall or designed as an extension. It is impossible to equip the vent channel in the outer wall, since in this case condensation may form on the surface, which will damage the structure. Also, due to cooling, the speed of air movement may decrease.
Values for ventilation pipes in residential buildings are determined by the established requirements, which are regulated by SNiP. Of no small importance is the frequency of exchange, which reflects the quality of the ventilation system. So, the volume of air flowing into the room should have the following values:
- in a residential building - 3 m³ per hour per square meter of area. Moreover, this indicator does not depend on how many people are in the room. Sanitary standards establish that for temporarily staying people in the building, 20 m³ per hour of fresh air is enough, and permanent residents need 60 m³;
- in an auxiliary building (for example, in a garage) - at least 180 m³ of air per hour.
To calculate the diameter of the vent pipes, a system is used in which only natural air inflow is present, without installed compulsory devices. The simplest method of calculation is the ratio of the area of the room to the cross-section of the vent channel opening.
For a living space per square meter, 5.4 m² of the duct cross-section is required, and for a utility room - 17.6 m². With a diameter of 15 m², sufficient air circulation will not be ensured. To obtain more accurate figures, complex calculations must be used.
Pipe length
All the channels in the building are connected to the vent pipe, through which the air moves out through the pipe to the street.
To calculate the height of this pipe, you need to know its diameter and have a special table. The cells in the tables contain the values of the duct cross-sections, and the left column indicates the width of the pipes. The top line shows how high the pipe should be for a certain diameter in millimeters.
It is necessary to take into account the following norms of SNiP:
- When the chimney and ventilation pipes are located next to them, their height should be the same. If this requirement is not observed, smoke from the heating unit may penetrate into the room.
- If the air duct is located no more than 1.5 m from the ridge, then its height should not exceed 0.5 m. If the pipe is at a distance of 1.5-3 m from the ridge, it should not be located below it.
- If the roof is flat, then the pipe should be at least half a meter.
When choosing a ventilation pipe and determining its location, it should be borne in mind that it must have sufficient wind resistance. So, the pipe must withstand a 10-point storm, and for this its weight must be about 50 kg per 1 square meter of surface. The picture shows how the height of the ventilation pipe above the roof is calculated.
You can also use special programs to determine natural ventilation. In this case, the calculation process is greatly facilitated. To do this, it is necessary to determine the optimal amount of air supplied to the living or utility room, respectively. The program also determines the following data:
- average outdoor and indoor temperature;
- the shape of the air pipe;
- the degree of roughness of the walls inside the duct;
- resistance that forms when air moves.
As a result, the program determines how long the vent pipe should be to ensure optimal air movement under the given conditions.
When calculating the values for the duct, it is necessary to take into account the resistance indicators when moving air flows. Resistance is influenced by meshes, gratings and other structural details.
Pipe diameter
To calculate the values of ventilation pipes based on the frequency of air exchange, the SNiP table is used. The rate of air exchange is understood as an indicator that determines how many times the air in the room changes in one hour. Before calculating the diameter of the vent pipe, you need to do the following:
- Calculate the volume of each of the available rooms.
- Determine the volume of air required for normal circulation. For this, the formula is used:
Using the above formula, the volume is calculated separately for each room.
- As a rule, for premises rationing of the exhaust or inflow is used. Sometimes in the rooms it is necessary to organize not only the flow of air, but also its effective outflow.
- When making calculations, keep in mind that the L value should be rounded up. After rounding, the resulting value must be divisible by 5.
- After determining the required air volume for the entire housing area, a special diagram is used to calculate the pipe diameter. In this case, you should know that in the central ventilation pipe the speed should be no more than 5 m / s, and in its branches - no more than 3 m / s.
SNiP requirements for air ducts
SNiP requirements provide for checking and cleaning the chimney and vent pipes:
- before the onset of the heating season;
- at least once every 3 months (for combined and brick canals);
- at least once every 12 months (for asbestos-cement ducts and chimneys, as well as for pottery pipes and pipes made of heat-resistant concrete).
During the initial check of the ventilation ducts and chimneys, the materials from which they were made, the presence of blockages in the ducts, the presence of separate smoke and ventilation ducts are checked. SNiP norms categorically prohibit the withdrawal of waste combustion products through the ventilation duct.
The owner of the home has the right to clean the ventilation ducts only after passing the briefing and with the corresponding document on the completed briefing. When starting the construction of a ventilation pipe, the owner is obliged to notify the operating organization that is the owner of the house. Upon completion of the work, the same organization must check and give permission for the operation of the duct.
Building a quality system that allows you to control moisture levels and provides the best living conditions is a feasible task. To do this, you just need to correctly calculate the parameters of the vent pipe.
