An example of calculating ventilation using a calculator

In this example, we will show how to calculate the supply ventilation for a 3-room apartment in which a family of three lives (two adults and a child). During the day, relatives sometimes come to them, so up to 5 people can stay in the living room for a long time. The ceiling height of the apartment is 2.8 meters. Room options:

We will set the consumption rates for the bedroom and the nursery in accordance with the recommendations of SNiP - 60 m³ / h per person. For the living room, we will limit ourselves to 30 m³ / h, since a large number of people in this room are infrequent. According to SNiP, such air flow is acceptable for rooms with natural ventilation (you can open a window for ventilation). If we also set an air flow rate of 60 m³/h per person for the living room, then the required performance for this room would be 300 m³/h. The cost of electricity to heat this amount of air would be very high, so we made a compromise between comfort and economy. To calculate the air exchange by the multiplicity for all rooms, we will choose a comfortable double air exchange.

The main air duct will be rectangular rigid, the branches will be flexible and soundproof (this combination of duct types is not the most common, but we chose it for demonstration purposes). For additional cleaning of the supply air, a carbon-dust fine filter of the EU5 class will be installed (we will calculate the network resistance with dirty filters). The air velocities in the air ducts and the permissible noise level on the gratings will be left equal to the recommended values ​​that are set by default.

Let's start the calculation by drawing up a diagram of the air distribution network. This scheme will allow us to determine the length of the ducts and the number of turns that can be both in the horizontal and vertical plane (we need to count all the turns at a right angle). So our schema is:

The resistance of the air distribution network is equal to the resistance of the longest section. This section can be divided into two parts: the main duct and the longest branch. If you have two branches of approximately the same length, then you need to determine which one has more resistance. To do this, we can assume that the resistance of one turn is equal to the resistance of 2.5 meters of the duct, then the branch with the maximum value (2.5 * number of turns + duct length) will have the greatest resistance. It is necessary to select two parts from the route in order to be able to set different types of air ducts and different air speeds for the main section and branches.

In our system, balancing throttle valves are installed on all branches, allowing you to adjust the air flow in each room in accordance with the project. Their resistance (in the open state) has already been taken into account, since this is a standard element of the ventilation system.

The length of the main air duct (from the air intake grille to the branch to room No. 1) is 15 meters, there are 4 right-angle turns in this section. The length of the supply unit and the air filter can be ignored (their resistance will be taken into account separately), and the silencer resistance can be taken equal to the resistance of an air duct of the same length, that is, simply consider it a part of the main air duct. The longest branch is 7 meters long and has 3 right angle bends (one at the branch, one at the duct and one at the adapter). Thus, we have set all the necessary initial data and now we can proceed to the calculations (screenshot). The calculation results are summarized in tables:

How the parameters of ventilation systems are calculated. Features and procedure for calculating exhaust and supply ventilation Ready-made calculation of local exhaust ventilation The air environment inside industrial buildings is polluted much more intensively than in apartments and private houses. The types and amount of harmful emissions depend on many factors - the industry, the type of raw materials, the technological equipment used, and so on. It is quite difficult to calculate and design ventilation of industrial premises that removes all harmful substances. We will try in an accessible language to state the calculation methods prescribed in the regulatory documents. Design Algorithm The organization of air exchange inside a public building or in production is carried out in several stages: Collection of initial data - the characteristics of the structure, the number of workers and the severity of labor, the variety and amount of harmful substances formed, the localization of places of release. It is very useful to understand the essence of the technological process. Choosing a ventilation system for a workshop or office, developing schemes. There are 3 main requirements for design solutions - efficiency, compliance with SNiP (SanPin) standards and economic feasibility. Calculation of air exchange - determination of the volume of supply and exhaust air for each room. Aerodynamic calculation of air ducts (if any), selection and placement of ventilation equipment. Refinement of schemes for supplying inflow and removal of polluted air. Installation of ventilation according to the project, start-up, further operation and maintenance. Note. For a better understanding of the process, the list of works is greatly simplified. At all stages of documentation development, various approvals, clarifications and additional surveys are required. The design engineer constantly works in conjunction with the technologists of the enterprise. We are interested in points No. 2 and 3 - the choice of the optimal air exchange scheme and the determination of air flow rates. Aerodynamics, installation of ventilation ducts and equipment are extensive topics of other publications. Types of ventilation systems To properly organize the renewal of the indoor air environment, you need to choose the best ventilation method or a combination of several options. The block diagram below shows a simplified classification of existing ventilation systems installed in production. Let's explain each type of air exchange in more detail: Unorganized natural ventilation includes ventilation and infiltration - the penetration of air through door porches and other gaps. Organized supply - aeration - is carried out from the windows by means of exhaust vents and skylights. Auxiliary roof and ceiling fans increase the intensity of exchange during the natural movement of air masses. The mechanical system implies the forced distribution and extraction of air by fans through air ducts. This also includes emergency ventilation and various local exhausts - umbrellas, panels, shelters, laboratory fume hoods. Air conditioning - bringing the air environment of a workshop or office to the required condition. Before entering the working area, the air is cleaned by filters, / dried, heated or. Heating / cooling of air with the help of heat exchangers - heaters Reference. According to the regulatory documentation, the serviced (working) area includes the lower part of the workshop volume 2 meters high from the floor, where people are constantly located. Often, mechanical supply ventilation is combined with air ventilation - in winter, the street flow is heated to the optimum temperature, water radiators are not installed. Polluted hot air is sent to the heat exchanger, where it gives off 50-70% of the heat to the inflow. To achieve maximum efficiency at a moderate price of equipment allows a combination of these options. Example: in a welding shop, it is allowed to design natural aeration, provided that each post is equipped with a forced local exhaust. Scheme of flow movement under natural aeration Direct instructions for the development of air exchange schemes are given by sanitary and industry standards, there is no need to invent or invent anything. Documents have been developed separately for public buildings and various industries - metallurgical, chemical, catering and so on. Example. When developing the ventilation of a hot welding shop, we find the document “Sanitary rules for welding, surfacing and cutting metals”, read section 3, paragraphs 41-60. It sets out all the requirements for local and general ventilation, depending on the number of workers and the consumption of materials. Supply and exhaust ventilation of industrial premises is selected depending on the purpose, economic feasibility and in accordance with applicable standards: In office buildings, it is customary to do natural air exchange - aeration, ventilation. With an increased crowding of people, it is planned to install auxiliary fans or organize air exchange with mechanical stimulation. In machine-building, repair and rolling shops of large sizes, it will be too expensive to arrange forced ventilation. The generally accepted scheme: natural exhaust through skylights or deflectors, the inflow is organized from openable transoms. Moreover, the upper windows (height - 4 m) swing open in winter, and the lower ones in summer. When toxic, dangerous and unhealthy vapors are released, aeration and ventilation are not allowed. At workplaces next to heated equipment, it is easier and more correct to organize the showering of people with fresh air than to constantly renew the entire volume of the workshop. In small industries with a small number of sources of pollution, it is better to install local exhausts in the form of umbrellas or panels, and provide general ventilation with natural ventilation. In industrial buildings with a large number of jobs and sources of harmful emissions, powerful forced air exchange should be done. It is not advisable to fence 50 or more local hoods, unless such events are dictated by the norms. In laboratories and working rooms of chemical plants, all ventilation is mechanical, and recirculation is prohibited. The project of general exchange forced ventilation of a three-story building with the use of a central air conditioner (longitudinal section) Note. Recirculation - the return of part of the selected air back to the workshop in order to save heat (in summer - cold) spent on heating. After filtering, this part is mixed with the fresh street stream in various proportions. Since it is unrealistic to consider all types of industries within the framework of one publication, we have outlined the general principles of air exchange planning. A more detailed description is presented in the relevant technical literature, for example, the textbook by O. D. Volkov “Designing the ventilation of an industrial building”. The second reliable source is the ABOK engineers forum (http://forum.abok.ru). Methods for calculating air exchange The purpose of the calculations is to determine the flow rate of the supplied supply air. If spot hoods are used in production, then the amount of air mixture removed by umbrellas is added to the resulting inflow volume. For reference. Exhaust devices have very little effect on the movement of flows inside the building. Supply jets help to tell them the right direction. According to SNiP, the calculation of the ventilation of the industrial premises is done according to the following indicators: excess heat emanating from heated equipment and products; water vapor saturating the shop air; harmful (toxic) emissions in the form of gases, dust and aerosols; the number of employees of the enterprise. An important point. In utility and various household rooms, the regulatory framework also provides for the calculation of the frequency of exchange. You can familiarize yourself with the methodology and use the online calculator. An example of a local suction system operating from a single fan. Dust collection with scrubber and additional filter Ideally, the inflow rate is considered for all indicators. The largest of the obtained results is accepted for the subsequent development of the system. One caveat: if 2 types of dangerous gases are released that interact with each other, the inflow is calculated for each of them, and the results are summed up. We calculate the consumption by heat release Before undertaking calculations, it is necessary to carry out preparatory work to collect the initial data: find out the areas of all hot surfaces; find out the heating temperature; calculate the amount of heat released; determine the temperature of the air in the working area and beyond (above 2 m above the floors). In practice, the task is solved together with the process engineer of the enterprise, who provides information about the production equipment, product characteristics and the intricacies of the manufacturing process. Knowing the specified parameters, perform the calculation according to the formula: Explanation of designations: · L - the desired volume of air supplied by supply units or penetrating through the transoms, m³ / h; Lwz is the amount of air taken from the serviced area by point suctions, m³/h; Q is the amount of heat release, W; c is the heat capacity of the air mixture, taken equal to 1.006 kJ/(kg °C); Tin is the temperature of the mixture supplied to the workshop; Tl, Twz - air temperatures above the working area and within it. The calculation seems cumbersome, but if the data is available, it is performed without problems. Example: indoor heat flow Q is 20000 W, exhaust panels remove 2000 m³/h (Lwz) outdoor temperature + 20 °C, inside - plus 30 and 25 respectively. We consider: L \u003d 2000 + \u003d 8157 m³ / h. Excess water vapor The following formula practically repeats the previous one, only the heat parameters are replaced by humidity notation: W is the amount of water vapor coming from sources per unit of time, gram/hour; Din is the moisture content in the inflow, g/kg; Dwz, Dl - moisture content of the air in the working area and the upper part of the room, respectively; the rest of the designations are the same as in the previous formula. The complexity of the technique lies in obtaining the initial data. When the facility is built and the production is running, it is not difficult to determine the humidity indicators. Another issue is to calculate the vapor emissions inside the workshop at the design stage. Development should be carried out by 2 specialists - a process engineer and a designer of ventilation systems. Emissions of dust and harmful substances In this case, it is important to study the subtleties of the technological process well. The task is to compile a list of hazards, determine their concentration and calculate the flow rate of supplied clean air. Calculation formula: Mpo is the mass of a harmful substance or dust emitted per unit of time, mg/hour; Qin is the content of this substance in the outdoor air, mg/m³; Qwz is the maximum permissible concentration (MPC) of harmfulness in the volume of the serviced area, mg/m³; Ql is the concentration of aerosol or dust in the rest of the workshop; the interpretation of the designations L and Lwz is given in the first formula. The ventilation algorithm is as follows. A calculated amount of inflow is sent to the room, diluting the indoor air and lowering the concentration of pollutants. The lion's share of harmful and volatile substances is drawn in by local umbrellas located above the sources, the mixture of gases is removed by mechanical exhaust. Number of working people The methodology is applied to calculate the inflow to office and other public buildings where there are no industrial pollutants. You need to find out the number of permanent jobs (denoted by the Latin letter N) and use the formula: Parameter m shows the volume of clean air mixture allocated to 1 workplace. In ventilated offices, the value of m is assumed to be 30 m³/h, in fully closed offices - 60 m³/h. Comment. Only permanent jobs are taken into account, where employees stay at least 2 hours a day. The number of visitors does not matter. Calculation of the local exhaust hood The task of local suction is to remove harmful gas and dust at the stage of isolation, directly from the source. To achieve maximum efficiency, you need to choose the right size of the umbrella, depending on the dimensions of the source and the height of the suspension. It is more convenient to consider the calculation method with reference to the suction drawing. Let's decipher the lettering in the diagram: A, B - the desired dimensions of the umbrella in terms of; h is the distance from the lower edge of the retractor to the surface of the ejection center; a, b - the dimensions of the overlapped equipment; D is the diameter of the ventilation duct; H - suspension height, taken no more than 1.8 ... 2 m; α (alpha) - the opening angle of the umbrella, ideally does not exceed 60 °. First of all, we calculate the dimensions of the suction in terms of simple formulas: F - the area of ​​​​the wide part of the umbrella, calculated as A x B; ʋ - air flow velocity in the duct section, for non-toxic gases and dust we take 0.15 ... 0.25 m / s. Note. If it is necessary to suck out toxic hazards, the standards require an increase in the exhaust flow rate to 0.75 ... 1.05 m / s. Knowing the amount of bleed air, it is not difficult to choose a duct fan of the required performance. The cross section and diameter of the exhaust duct is determined by the inverse formula: Conclusion Designing ventilation networks is the task of experienced engineers. Therefore, our publication is for informational purposes, explanations and calculation algorithms are somewhat simplified. If you want to thoroughly understand the issues of ventilation of premises in production, we recommend that you study the relevant technical literature, there is no other way. Finally - a method for calculating air heating in the framework of the video. The performance of a system serving up to 4 rooms. Dimensions of air ducts and air distribution grilles. Air line resistance. Heater power and estimated electricity costs (when using an electric heater). If you need to choose a model with humidification, cooling or recuperation, use the calculator on the Breezart website.

Calculation of the air duct network

• For each room (subsection 1.2), the performance is calculated, the cross-section of the duct is determined, and a suitable duct of standard diameter is selected. According to the Arktos catalog, the dimensions of distribution grids with a given noise level are determined (data for the AMN, ADN, AMR, ADR series are used). You can use other gratings with the same dimensions - in this case, there may be a slight change in the noise level and network resistance. In our case, the grilles for all rooms turned out to be the same, since at a noise level of 25 dB(A) the allowable air flow through them is 180 m³/h (there are no smaller grilles in these series).
• The sum of the air flow rates for all three rooms gives us the total system performance (subsection 1.3). When using a VAV system, the system performance will be one third lower due to the separate adjustment of the air flow in each room. Next, the section of the main air duct is calculated (in the right column - for the VAV system) and suitable rectangular air ducts are selected (usually several options are given with different aspect ratios). At the end of the section, the resistance of the air duct network is calculated, which turned out to be very large - this is due to the use of a fine filter in the ventilation system, which has a high resistance.
• We have received all the necessary data to complete the air distribution network, with the exception of the size of the main air duct between branches 1 and 3 (this parameter is not calculated in the calculator, since the network configuration is not known in advance). However, the cross-sectional area of ​​this section can be easily calculated manually: from the cross-sectional area of ​​the main duct, you need to subtract the cross-sectional area of ​​\u200b\u200bbranch No. 3. Having obtained the cross-sectional area of ​​\u200b\u200bthe duct, its size can be determined by.

Calculation of heater power and selection of air handling unit

The recommended Breezart 550 Lux model has programmable parameters (capacity and power of the heater), therefore, the performance that should be selected when setting up the remote control is indicated in brackets. It can be seen that the maximum possible power of the heater of this launcher is 11% lower than the calculated value. The lack of power will be noticeable only at outdoor temperatures below -22 ° C, and this does not happen often. In such cases, the air handling unit will automatically switch to a lower speed to maintain the set outlet temperature (Comfort function).

In the calculation results, in addition to the required performance of the ventilation system, the maximum performance of the PU at a given network resistance is indicated. If this performance turns out to be noticeably higher than the required value, you can take advantage of the possibility of programmatically limiting the maximum performance, which is available for all Breezart ventilation units. For a VAV system, the maximum performance is indicated for reference, since its performance is adjusted automatically during the operation of the system.

Calculation of the cost of operation

This section calculates the cost of electricity used to heat the air during the cold season. The costs for a VAV system depend on its configuration and mode of operation, so they are assumed to be equal to the average value: 60% of the costs of a conventional ventilation system. In our case, you can save money by reducing the air consumption at night in the living room, and during the day in the bedroom.

To select and order ventilation equipment, it is required to calculate the ventilation system. The staff of Ecolife Company has an engineering and technical department, whose specialists perform the calculation of ventilation systems of any complexity for objects of various purposes.

Ventilation design contract

Our company works with legal entities and individuals. We conclude a contract for the design of ventilation, which is a document that clearly defines the cost and timing of the work. Pre-negotiated terms reduce the risks for both parties, as well as ensure the benefits of the transaction for the seller and the buyer.
The signing of acts of work performed and the acceptance and transfer of equipment means the successful completion of work. We provide a full package of documents, including invoices, acts, invoices and cash receipts when paying in cash, commissioning reports, system settings.
After completing the work, we continue to work with you as a consultant and service organization.

Departure of an engineer to calculate the cost of work is free of charge.

We work with objects

* Manufacturing plants, factories, shopping malls
* Restaurants, cafes, and all catering establishments
* Multi-storey and private residential buildings, office complexes
* Polyclinics, hospitals, schools, educational institutions
* Airports, train stations and all government agencies.

Calculation of the ventilation system

The calculation of the ventilation system provides for the calculation of air exchange in each room, the determination of the total air flow and the aerodynamic resistance of each of the ventilation systems, the selection of ventilation equipment, the calculation of the cross section of ventilation ducts.
The ventilation calculation is based on the scheme of the ventilation system. Based on the results of the ventilation calculation, the equipment and components of the ventilation system, as well as air distributors (grilles and diffusers) are selected. Calculation of ventilation is one of the stages of the implementation of the project for ventilation.

Ventilation calculation method

There are various methods for calculating ventilation - calculation of air exchange by people, calculation of air exchange by heat excess, calculation of air exchange by hazards.
The calculation of air exchange by people is used in most cases and involves the supply of a given volume of air for each person in the room. 60 m3/h is provided for each permanent workplace, and 20 m3/h is provided for each visitor. If we are talking about a gym, swimming pool, fitness center or dance hall, then 80 m3 / h of fresh air is laid for each athlete.
Calculation of air exchange by heat excess is used in rooms with a large number of people (for example, concert halls, cinema halls, indoor stadiums, discos) or in industrial premises with technological equipment that emits a significant amount of heat. The required supply air flow in this case is determined by the formula:
L \u003d Q / (0.335 ?t), where L is the desired air flow (m3 / h), Q is the heat release in the room (kW), ?t is the temperature difference between the supply and exhaust air in the room (°С).
The calculation of air exchange by hazards is relevant for production sites with emissions of harmful substances. Air exchange is calculated on the basis of ensuring the concentration of each of the harmful substances within the maximum allowable concentrations (MAC). MPC values ​​for each of the harmful substances are taken in accordance with the Hygienic Standards GN 2.2.5.1313-03 "Maximum Permissible Concentrations (MAC) of harmful substances in the air of the working area."
In some cases, several factors act at once in the room - people, hazards, and heat. In this case, each of the calculations is made separately and the largest of the obtained air flow rates is selected.

Supply ventilation calculation

The calculation of supply ventilation is the main calculation in the design of ventilation systems. It is from the calculated air flow in the supply system that they are repelled when calculating exhaust systems.
Consider a few examples of calculating the supply ventilation:
. The office has three rooms - for 4 workplaces and 4 visitors, for 5 workplaces and 5 visitors and a secretariat with one workplace and two chairs for visitors.
The required supply air flow rate is determined as follows:
L = 4 60+4 20+5 60+5 20+1 60+2 20 = 820 m3/h
. The dance studio has a hall for 20 people and a living room with one workplace and 5 chairs for visitors. The required supply air flow is:
L = 20 80+1 60+5 20 = 1760 m3/h
. The administrative building has a total of 150 workplaces, 60 places for visitors and 4 meeting rooms with the required air exchange rate, three different, with a room volume of 150m3. The required supply air flow will be:
L = 150 60+60 20+4 3 150 = 12000 m3/h
However, in practice, the situations turn out to be more complicated - there are foyers, living rooms, corridors, reception rooms, specific rooms, such as massage rooms, archives, warehouses, etc. For the correct calculation of supply ventilation, please contact the engineers of the Ecolife Group of Companies. We will answer all your questions, advise on the operation and installation of ventilation systems, design ventilation systems, as well as supply equipment and install ventilation at your facility.

Exhaust ventilation calculation

The calculation of exhaust ventilation is performed after the calculation of supply ventilation and is based on ensuring the balance of supply and exhaust air at the facility.
When calculating exhaust ventilation, rooms are distinguished that require separate exhaust systems. In particular, a separate hood is provided for bathrooms and showers. At the same time, an exhaust hood is laid in the amount of 50 m3/h for each dead person, 25 m3/h for each urinal and 75 m3/h for each shower room.
Also, a separate hood is provided for kitchens and rooms for cooking. The extract from kitchens depends on the type of stove and is usually 90 m3/h. If we are talking about the kitchen premises of cafes and restaurants, then local exhausts should be provided from special kitchen equipment in accordance with the design assignment.
The calculation of the exhaust ventilation of office premises is based on the provision of a positive 20% imbalance. So, if the inflow into an office space for 10 workplaces and 5 visitors is 700 m3/h, then the exhaust air flow rate should be taken as 560 m3/h.
A separate task is to reduce the costs of supply and exhaust ventilation systems and ensure their equality for the facility as a whole. To calculate and design ventilation for specific objects, please contact IS Ecolife. Our engineers will help you make the right ventilation for any type of facility.

Calculation of natural ventilation

The calculation of natural ventilation is based on the pressure difference at different altitudes of the atmosphere. In fact, the vertical section of the duct connects points with different atmospheric pressure, due to which draft is naturally formed.
The air-moving pressure is determined by the formula:
Р=(Рвн-Рн) h g, where Рвн is the density of the indoor air (kg/m3), Рн is the density of the outdoor air (kg/m3), h is the height of the natural draft (m), g is the free fall acceleration, equal to 9.81 m/s2.
In fact, this pressure is equated to the aerodynamic resistance of the considered vertical section of the duct. Further, according to the obtained aerodynamic resistance for a given duct, the corresponding air flow is determined.

Calculation of ventilation at home

When calculating the ventilation of a house, the number of people, sleeping places, and living room areas are taken into account.
As a rule, a supply air flow rate of 120 m3/h is assumed for bedrooms. The influx to offices and children's rooms - according to the number of permanent and temporary people arriving in them. The living rooms are provided with double air exchange. Extraction from bathrooms and kitchens is carried out according to general rules.
For a more complete and accurate calculation of ventilation at home, please contact the specialists of the Ecolife Group of Companies. We have significant experience in the design and installation of cottage ventilation.
Calculation of the ventilation section
The cross section of the air ducts is determined by the air flow. From an aerodynamic point of view, round ducts have advantages over rectangular ones. Therefore, for small and medium air flow rates, air ducts of circular cross section are mainly used.
As you know, the air flow through a certain section is equal to the product of the air velocity and the cross-sectional area of ​​\u200b\u200bthe duct. Accordingly, the cross-sectional area is determined by the formula:
S = G / (3600 v), where S is the cross-sectional area (m2), G is the air flow rate (m3/h), v is the air velocity (m/s).
The determination of the diameter of round ducts is carried out according to the formula:
D 2 \u003d 4πS, where D is the diameter of the duct, m, π is the number of pi (approximately equal to 3.1415), S is the cross-sectional area (m2)
D=√D2
It is recommended to take the speed in air ducts no more than 4 m/s, for large air ducts (more than 600x300) it is permissible to slightly increase this value.

Ventilation by objects:
Ventilation in the apartment
Ventilation in the house
Cottage ventilation
Office ventilation
Industrial ventilation
Cafe ventilation
Restaurant ventilation
Hot shop ventilation
Basement ventilation
Ventilation in sports halls
Pool ventilation
Ventilation of clean rooms (medical facilities, laboratories)

Design and calculation of ventilation: how we work

Why is it profitable to order ventilation design in IS Ecolife

The Ecolife Engineering Systems Company is a team of experienced and licensed specialists in the installation and maintenance of all types of engineering systems with the subsequent execution of the entire package of documents.

The task of organized air exchange in the rooms of a residential building or apartment is to remove excess moisture and exhaust gases, replacing them with fresh air. Accordingly, for the exhaust and inflow device, it is necessary to determine the amount of air masses to be removed - to calculate the ventilation separately for each room. Calculation methods and air flow rates are accepted exclusively according to SNiP.

Sanitary requirements of regulatory documents

The minimum amount of air supplied to and removed from the cottage rooms by the ventilation system is regulated by two main documents:

1. "Residential multi-apartment buildings" - SNiP 31-01-2003, paragraph 9.
2. "Heating, ventilation and air conditioning" - SP 60.13330.2012, mandatory Appendix "K".

The first document sets out the sanitary and hygienic requirements for air exchange in residential premises of apartment buildings. On these data, the calculation of ventilation should be based. 2 types of dimensions are used - air mass flow rate by volume per unit of time (m³ / h) and hourly multiplicity.

Reference. The air exchange rate is expressed as a figure indicating how many times within 1 hour the air environment of the room is completely updated.

Depending on the purpose of the room, supply and exhaust ventilation should provide the following flow rate or the number of updates of the air mixture (multiplicity):

• living room, nursery, bedroom - 1 time per hour;
• kitchen with electric stove - 60 m³/h;
• bathroom, bathroom, toilet - 25 m³ / h;
• for and a kitchen with a gas stove, a multiplicity of 1 plus 100 m³ / h is required during the operation of the equipment;
• , burning natural gas - three times the renewal plus the volume of air required for combustion;
• pantry, dressing room and other utility rooms - multiplicity 0.2;
• drying or laundry room - 90 m³ / h;
• library, office - 0.5 times per hour.

Note. SNiP provides for a reduction in the load on general ventilation when the equipment is not working or there are no people. In residential premises, the multiplicity decreases to 0.2, technical - to 0.5. The requirement for rooms where gas-using installations are located remains unchanged - an hourly one-time renewal of the air environment.

Clause 9 of the document implies that the volume of the extract is equal to the amount of inflow. The requirements of SP 60.13330.2012 are somewhat simpler and depend on the number of people in the room for 2 hours or more:

1. If 1 resident has 20 m² or more of the area of ​​​​the apartment, a fresh influx of 30 m³ / h per 1 person is provided to the rooms.
2. The volume of supply air is calculated by area when there are less than 20 squares per 1 tenant. The ratio is as follows: 3 m³ of inflow is supplied per 1 m² of housing.
3. If the apartment does not provide ventilation (there are no vents and windows that open), 60 m³ / h of a clean mixture must be applied to each resident, regardless of the quadrature.

The listed normative requirements of two different documents do not contradict each other at all. Initially, the performance of the ventilation general exchange system is calculated according to SNiP 31-01-2003 "Residential buildings".

The results are checked against the requirements of the Code of Rules "Ventilation and Air Conditioning" and, if necessary, corrected. Below we will analyze the calculation algorithm using the example of a one-story house shown in the drawing.

Determination of air consumption by multiplicity

This typical calculation of supply and exhaust ventilation is performed separately for each room of an apartment or a country cottage. To find out the flow of air masses in the building as a whole, the results obtained are summarized. A fairly simple formula is used:

Explanation of designations:

• L is the desired volume of supply and exhaust air, m³/h;
• S is the quadrature of the room where ventilation is calculated, m²;
• h - ceiling height, m;
• n is the number of room air updates within 1 hour (regulated by SNiP).

Calculation example. The area of ​​the living room of a one-story building with a ceiling height of 3 m is 15.75 m². According to the requirements of SNiP 31-01-2003, the multiplicity n for residential premises is equal to one. Then the hourly flow rate of the air mixture will be L = 15.75 x 3 x 1 = 47.25 m³/h.

An important point. Determination of the volume of air mixture removed from the kitchen with a gas stove depends on the installed ventilation equipment. A common scheme looks like this: a single exchange according to the standards is provided by a natural ventilation system, and an additional 100 m³ / h is emitted by a household one.

Similar calculations are made for all other rooms, a scheme for organizing air exchange (natural or forced) is developed and the dimensions of the ventilation ducts are determined (see the example below). A calculation program will help automate and speed up the process.

Online calculator to help

The program calculates the required amount of air according to the multiplicity regulated by SNiP. Just select the type of room and enter its dimensions.

The article presents an adapted method for calculating an autonomous system of supply and exhaust ventilation using the example of a 3-room apartment. You will learn how to calculate peak throughput values ​​and how to choose the right equipment based on the needs of the apartment.

Like any work related to the installation of engineering equipment, ventilation installation consists of several stages. Consider them on the example of a three-room apartment.

Room analysis and problem setting for the system

Use a sheet of paper or a candle to check if the apartment's exhaust ventilation duct is working, the outlets of which are located in the bathroom and in the kitchen.

To determine the number and performance of air handling units needed in a particular room, you can use two options that are relevant depending on the complexity of the entire system.

Option number 1. Professional engineering online calculator. This method is filled with rather complex terms and formulations and is more suitable for complex layouts with many rooms that have different air exchange requirements. Full use requires knowledge and professional experience.

Option number 2. Independent calculation, suitable for the requirements of SNiP. The ventilation of an ordinary apartment or a small house has minimal complexity, so any home master can handle its calculation.

Five indicators are necessary for the independent implementation of the project.

Air duct diameter. A complex calculation based on SNiP data, the number of people, room functions at different times of the day, etc. However, from experience it is known that it all comes down to three popular channel diameters (sections) - 100, 125 and 150 mm. Respectively:

• 100 mm - for constant continuous air exchange around the clock with low fan power;
• 125 mm - periodic ventilation while people are in the room (for example, from 18.00 to 8.00) at low and medium power;
• 150 mm - fast ventilation 1-2 times a day for rooms with irregular or rare presence of people.

Accordingly, the diameter of the duct in our case does not depend on the power of the devices, but on the requirements for the room.

Fan performance. Measured in m 3 / hour. According to SNiP 41-01-2003 "Heating, ventilation and air conditioning", air exchange should be provided at least 3 m 3 per 1 hour per 1 m 2 of living space. In other words, the system must pass through itself the entire volume of air in the room in 1 hour. Please note that supply ventilation provides air flow from 5 to 40 m 3 / hour, depending on the set mode.

Shape, section and walls of the channel. There are obstacles that can significantly affect the throughput of the system:

1. The corrugated walls of the channel take 7-9% of the fan power. Choose smooth round tubes.
2. Right angles (90°) of the channel - each angle takes 2-3% of the fan power. Design the channel with a minimum number of corners.
3. Filters and noise absorbers. Their bandwidth and losses are also indicated in the factory documents.

Performance of supply devices. It must be equal to the performance of the exhaust system, otherwise the exhaust fans will work with a load and without the proper result. The numbers of this main indicator are always in the instructions for the air handling units.

Room specifics. You can complicate the task by applying the calculation of air per person or by the frequency of exchange, but in practice there is enough information from the SNiP norm - 3 m 3 per 1 m 2 for bedrooms, living rooms, children's rooms. The same document speaks of fixed norms:

1. For the kitchen - 90 m 3 / hour.
2. For the bathroom - 25 m 3 / hour.
3. For a toilet - 30 m 3 / hour.
4. For a combined bathroom - 35 m 3 / hour.

It should be noted that these norms are developed with a huge margin, which is not implemented in practice. The problem of humidity and extraneous odors is solved if necessary - during cooking or a shower, an enhanced hood is turned on. To ensure fixed norms with good draft in a regular ventilation duct, it is enough to provide an inflow. When installing a fan on a regular channel, the inflow must also be increased.

Calculations

Calculation of living rooms

Amount of areas: 12 + 16 + 21 \u003d 59 m 2. Air volume for exchange according to SNiP: 59 x 3 = 177 m 3.

Calculation for bathroom or kitchen

The requirement for the hood is to ensure complete air exchange within 15 minutes. The volume of the kitchen according to the norm: 9 x 7 = 27 m 3, which should be removed in a quarter of an hour. Accordingly, the throughput of the exhaust fan will be equal to at least 27 x 4 \u003d 108 m 3 / hour while the hood is running (40-60 min/day).

In practice, this indicator for most household hoods is much higher - from 220 m 3 / h, however, in 50% of cases they are idle due to the lack of inflow.

Calculation of the bathrooms

Bathroom. Air volume: 4 x 3 \u003d 12 m 3 / hour. Complete air exchange in 5 minutes (1/12 hour). Bandwidth - 12 x 12 = 144 m 3 / hour.

Toilet. Air volume: 2 x 3 = 6 m 3 / hour. Complete exchange in 5 minutes (1/12 hour). System throughput — 6 x 12 = 72 m 3 / hour.

Recall that the calculated indicators refer to the throughput of the inflow, on the basis of which the exhaust equipment is selected.

The resulting data can be combined into a table:

Question. How to ensure an inflow of 144 m 3 / h into the bathroom if the maximum capacity of the supply valves is 40 m 3 / h?

Answer. Connect the bath and toilet inlet to the combined extract from the living rooms. The air quality is quite suitable for enhanced ventilation, and a total of 120 m 3 / hour of inflow will ensure the normal efficiency of the hood.

The number of elbows is an indicator of the power loss of the exhaust fan (2% per elbow), take this into account when selecting equipment.

Based on the given data, it is possible to select equipment - window and wall valves, fans and hoods, channels. The main thing is to follow the rule - the volume of inflow must be equal to the volume of air exhaust. It is advisable to use a centralized multi-channel system with taps to each room (300-700 cu), and install power controllers and turn-on timers (from 15 cu/piece) to separate rooms.

Using the adapted methodology given in the article, you can save on the services of professionals. This is quite acceptable, given the low complexity. Now it remains to choose equipment, the price of which will depend only on the quality of the product and the noise level. We will tell you how to mount the system