How to calculate ventilation: formulas and an example of calculating a supply and exhaust system. Calculation of the ventilation system How to correctly calculate ventilation

For selection and ordering ventilation equipment it is necessary to perform a calculation of the ventilation system. The Ecolife Company staff includes an engineering and technical department, whose specialists carry out calculations of ventilation systems of any complexity for objects of various purposes.

Ventilation design contract

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

An engineer’s visit to calculate the cost of work is free of charge.

We work with objects

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

Calculation of the ventilation system

The calculation of the ventilation system involves calculating the air exchange in each room, determining the total air flow and aerodynamic resistance of each of the ventilation systems, selecting ventilation equipment, and calculating the cross-section of ventilation ducts.
Ventilation calculations are made based on the ventilation system diagram. Based on the results of the ventilation calculation, equipment and components of the ventilation system, as well as air distributors (grills and diffusers), are selected. Ventilation calculation is one of the stages of a ventilation project.

Methodology for calculating ventilation

Exist various techniques calculation of ventilation - calculation of air exchange by people, calculation of air exchange by heat excess, calculation of air exchange by hazards.
Calculation of air exchange by people is used in most cases and involves supplying a given volume of air to each person in the room. For every permanent workplace 60 m3/h is provided, 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 provided for each athlete.
Calculation of air exchange based on excess heat 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 generates a significant amount of heat. The required supply air flow in this case is determined by the formula:
L = Q / (0.335·?t), where L is the required air flow (m3/h), Q is the heat dissipation in the room (kW), ?t is the temperature difference between the supplied and exhaust air in the room (°C).
Calculation of air exchange by hazards is relevant for production sites with emissions harmful substances. Calculation of air exchange is made based on ensuring the concentration of each of the harmful substances within the limits of maximum permissible concentrations (MPC). The MPC values ​​for each of the harmful substances are accepted 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 simultaneously in a room - people, harmful substances, and heat. In this case, each of the calculations is performed separately and the largest air flow rate obtained is selected.

Calculation of supply ventilation

Calculation supply ventilation is the main calculation when designing ventilation systems. It is the calculated air flow rate in the supply system that is taken into account when calculating exhaust systems.
Let's look at a few examples of calculating 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 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
. In the administrative building there are a total of 150 workplaces, 60 places for visitors and 4 meeting rooms with the required air exchange rate of three different ones, with a room volume of 150 m3. 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 complex - there are foyers, living rooms, corridors, reception rooms, specific rooms, such as, massage rooms, archives, warehouses, etc. To correctly calculate the supply ventilation, 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.

Calculation of exhaust ventilation

The calculation of exhaust ventilation is carried out after calculating the supply ventilation and is based on ensuring the balance of supply and exhaust air at the facility.
When calculating exhaust ventilation, rooms are identified that require separate exhaust systems. In particular, a separate hood is provided for bathrooms and showers. In this case, an exhaust amount of 50 m3/h is provided for each occupant, 25 m3/h for each urinal and 75 m3/h for each shower room.
A separate hood is also provided for kitchens and food preparation areas. The exhaust 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 suction should be provided from special kitchen equipment in accordance with the design assignment.
The calculation of exhaust ventilation for office premises is based on ensuring a positive 20% imbalance. So, if the influx into an office space for 10 workplaces and 5 visitors is 700 m3/h, then the exhaust air flow rate should be 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, contact IS “Ecolife”. Our engineers will help you do proper ventilation for objects of any type.

Calculation of natural ventilation

Natural ventilation is calculated based on the pressure difference at different atmospheric altitudes. In fact, a vertical section of the air duct connects points with different atmospheric pressure, due to which draft is naturally formed.
The moving air pressure is determined by the formula:
Р=(Рвн-Рн) h·g, where Рвн is the density of internal air (kg/m3), Рн is the density of external air (kg/m3), h is the height of natural exhaust (m), g is the acceleration of gravity, equal to 9.81 m/s2.
In fact, this pressure is equal to the aerodynamic resistance of the vertical section of the duct under consideration. Next, based on the obtained aerodynamic resistance for a given air duct, the corresponding air flow rate is determined.

Calculation of home ventilation

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

Ventilation by object:
Ventilation in the apartment
Ventilation in the house
Cottage ventilation
Office ventilation
Ventilation in production
Cafe ventilation
Restaurant ventilation
Hot shop ventilation
Basement ventilation
Ventilation in gyms
Pool ventilation
Ventilation of clean rooms ( medical institutions, laboratories)

Design and calculation of ventilation: how we work

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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 preparation of the entire package of documents.

Ventilation of any room - necessary condition, even if it is a warehouse not frequented by people. And in public and residential buildings, the ventilation system must be carefully calculated and arranged in accordance with the standards. For each enclosed space, including the attic, it is necessary to take into account an air exchange system that promotes a comfortable stay for people. In any residential building you can see ventilation holes which are responsible for the supply of fresh air. In public spaces where people are expected to be present, supply and exhaust ventilation must be installed to circulate air masses. Sanitary standards strictly regulate the design of ventilation systems, taking into account the volume of the premises and the expected number of people in it. Below we will consider the types of ventilation systems and the methodology for calculating air exchange.

Types of ventilation systems

Ventilation systems vary in the degree of complexity of their design. There are several types:

• Simple, natural, flowing clean air through channels made in the walls of the building.
• Supply and exhaust, having separate channels for air intake and air outflow.
  
  
• Supply and exhaust, forced, operating on duct fans built into the air ducts.
  
  
• Combined or complex, controlling and providing air supply and exhaust, as well as regulating temperature and humidity in the room.
  
  

From the quality of work ventilation system The comfort of people staying inside the building depends. Standards for the amount of incoming air have been developed and published by Rospotrebnadzor, which controls the operation of ventilation in public buildings.

General picture of ventilation in modern houses

What you need to know about air currents

Main stages of calculations

Natural ventilation in residential and public buildings is arranged during their construction and does not require additional calculations. Therefore, we will talk about coercive systems. The primary task for carrying out accurate calculations of ventilation systems is to take into account the microclimate of the premises.

These are permissible and standard-recommended values ​​of humidity, temperature and air circulation volumes. Depending on the types of the selected system given above, the tasks are determined - only air exchange or complex air conditioning of the room. Calculation of air flow coming from outside is the first and the most important parameter regulated by sanitary and hygienic standards. It is based on minimal volumes of air consumption and air flow due to exhaust channels and the operation of technological equipment. The determination of air exchange, which is measured in cubic meters of replaced air per hour, depends on the volume of the room and its purpose. For apartments, outside air is supplied to the rooms where, as a rule, residents are located. This is a living room and bedroom, less often an office and hallways. In corridors, kitchens and bathrooms, there is usually no air supply; only exhaust openings are installed in them. Air masses arrive naturally from the neighboring rooms where the influx is made. This scheme forces the air flow to move through the living rooms into the technical rooms, “squeezing out” the waste air-gas mixture into the exhaust ducts. At the same time, unpleasant odors are removed without spreading throughout the apartment or house.

Calculations include two air exchange values:

• In terms of productivity - based on air mass standards per person.
• By frequency - how many times the air in the room is changed in one hour.

Important! To select the performance of the planned ventilation system, the largest of the obtained values ​​is taken .

Air performance

For residential premises, the amount of air supplied must be calculated in accordance with building codes and rules (SNiP) No. 41-01-2003. The amount of consumption by one person is indicated here - 60 cubic meters per hour. This volume must be compensated by the influx of external air. For bedrooms, a smaller volume is allowed - 30 cubic meters per hour per person. When making calculations, only permanently residing people should be taken into account, i.e. The number of guests visiting the room from time to time should not be taken into account when calculating air exchange. For comfortable parties, there are systems that regulate the air flow into different rooms. Such equipment will increase the air flow into the living room by reducing it in the bedroom.

Calculations are carried out according to the formula: L = N x Ln, where: L is the estimated volume of incoming air cubic meters per hour; N - estimated number of people; Ln - standard air flow for 1 person. – for bedrooms - 30 cubic meters per hour and for other premises - 60 cubic meters per hour.

Productivity by multiple factor

Calculation of the air exchange rate in rooms should be carried out based on the parameters of the room; this will require a house or apartment plan. The plan must indicate the purpose of the room and its dimensions (height, area or length and width). For a comfortable feeling, at least one exchange of the entire volume of air is required.

It should be noted that supply ducts, as a rule, provide a volume of air for a double exchange, while exhaust ducts are designed for a single air exchange. There is no contradiction in this, since air consumption also occurs naturally - through cracks, windows and doors. After calculating the air exchange for each room, we add up the values ​​to calculate the performance of the ventilation system. After which it will be possible to correctly select the power of the supply and exhaust fans. Standard indicators The performance levels for different rooms are as follows:

• residential ventilation systems - 150-500 cubic meters per hour;
• in private houses and cottages - 550-2000 cubic meters per hour;
• in office premises - 1100-10000 cubic meters per hour.

The calculation is carried out using the formula: L = NxSxH, where: L is the estimated volume of incoming air cubic meters per hour; N is the standard air exchange rate: houses and apartments – 1-2, office premises – 2-3; S - area, sq.m; H - height, m;

Example of aerodynamic ventilation calculation

This calculator can also help you with your calculations.

The article presents an adapted method for calculating an autonomous supply and exhaust ventilation system using the example of 3 room apartment. You will learn how to calculate peak values bandwidth and learn 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. Let's look at them using the example of a three-room apartment.

Analysis of the premises and formulation of the problem for the system

Using a sheet of paper or a candle, check whether the apartment's exhaust ventilation duct, whose outlets are in the bathroom and kitchen, is working.

To determine the number and performance of air supply devices required in a particular room, you can use two options, relevant depending on the complexity of the entire system.

Option #1. Professional online engineering 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. Self-calculation, meeting the requirements of SNiP. Ventilation ordinary apartment or a small house has minimal complexity, so any home master can handle its calculations.

To independently implement a project, five indicators are required.

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

• 100 mm - for constant continuous air exchange around the clock at low power fans;
• 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 - quick ventilation 1-2 times a day for rooms with irregular or rare presence of people.

Accordingly, the diameter of the air duct in our case depends not 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”, an air exchange of at least 3 m 3 per 1 hour per 1 m 2 of living space must be ensured. In other words, the system must pass through 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, cross-section and channel walls. There are obstacles that can significantly affect system throughput:

1. Corrugated channel walls take 7-9% of the fan power. Choose smooth round pipes.
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 throughput and losses are also indicated in the factory documents.

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

Specifics of premises. You can complicate the task by calculating 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 talks about fixed norms:

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

It should be noted that these standards were developed with a huge margin, which is not implemented in practice. The problem of humidity and foreign odors is solved when necessary - during cooking or showering, the enhanced hood is turned on. To ensure fixed standards with good draft in a standard ventilation duct, it is enough to provide inflow. When installing a fan on a standard duct, the inflow must also be increased.

Calculations

Calculation of living rooms

Sum of areas: 12 + 16 + 21 = 59 m2. Air volume for exchange according to SNiP: 59 x 3 = 177 m 3.

Calculation for a bathroom or kitchen

The requirement for the hood is to ensure complete air exchange within 15 minutes. Standard kitchen volume: 9 x 7 = 27 m3, which should leave in a quarter of an hour. Accordingly, the throughput of the hood fan will be equal to at least 27 x 4 = 108 m 3 /hour during operation of the hood (40-60 min/day).

In practice, this figure for most household hoods is much higher - from 220 m 3 / hour, but in 50% of cases they run idle due to the lack of inflow.

Calculation of bathroom premises

Bathroom. Air volume: 4 x 3 = 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.

Let us recall that the calculated indicators relate to the inflow throughput, on the basis of which exhaust equipment is selected.

The obtained data can be combined into a table:

Room	Area, m2	Exchange according to SNiP norm, m 3 / hour	Optimal channel diameter, mm	Number of elbows, pcs.	Inflow source	Note
Bedroom	16	16 x 3 = 48	125	1	Window/wall valve	Periodic ventilation 10 hours a day (from 22.00 to 08.00)
Children's	12	12 x 3 = 36	100	2		Constant ventilation
Living room	21	21 x 3 = 63	125	2		Constant ventilation
Kitchen	9	90 (108 at peak)	150	3	Window/wall valve through living areas	Constant ventilation with periodic intensification (exhaust)
Bathroom	4	25 (144 at peak)	150	2
Toilet	2	30 (72 at peak)	150	-		Periodic increased ventilation

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

Answer. Connect the inlet for the bath and toilet to the combined exhaust 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 normal efficiency of the hood.

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

Based on the data provided, you can select equipment - window and wall valves, fans and hoods, ducts. 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 outlets to each room (300-700 USD), and install power controllers and switch-on timers for individual rooms (from 15 USD/piece).

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 all that remains is 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 install the system

Now, knowing what the ventilation system consists of, we can begin to assemble it. In this section we will talk about how to calculate supply ventilation for an object with an area of ​​up to 300-400 m² - an apartment, a small office or a cottage. Natural exhaust ventilation in such facilities is usually already installed at the construction stage, so it does not need to be calculated. It should be noted that in apartments and cottages, exhaust ventilation is usually designed based on a single air exchange, while supply ventilation provides, on average, a double air exchange. This is not a problem, since part of the supply air will be removed through leaks in windows and doors, without creating excess load on the exhaust system. In our practice, we have never encountered a requirement from the operation service apartment building limit the performance of the supply ventilation system (at the same time, the installation of exhaust fans in exhaust ventilation ducts is often prohibited). If you do not want to understand the calculation methods and formulas, you can use it, which will perform all the necessary calculations.

Air performance

The calculation of the ventilation system begins with determining the air productivity (air exchange), measured in cubic meters per hour. For calculations, we will need a site plan, which indicates the names (purposes) and areas of all premises.

Fresh air must only be supplied to rooms where people may be present. long time: bedrooms, living rooms, offices, etc. Air is not supplied to the corridors, but is removed from the kitchen and bathrooms through exhaust ducts. Thus, the air flow pattern will look like this: fresh air is supplied to the living quarters, from there it (already partially polluted) enters the corridor, from the corridor - into the bathrooms and into the kitchen, from where it is removed through exhaust ventilation, taking with it unpleasant odors and pollutants. This air movement pattern provides air support for “dirty” rooms, eliminating the possibility of spreading unpleasant odors by apartment or cottage.

For each living space, the amount of air supplied is determined. The calculation is usually carried out in accordance with SNiP 41-01-2003 and MGSN 3.01.01. Since SNiP sets more stringent requirements, we will be guided by this document in our calculations. It states that for residential premises without natural ventilation (that is, where windows do not open), the air flow must be at least 60 m³/h per person. For bedrooms, a lower value is sometimes used - 30 m³/h per person, since in a state of sleep a person consumes less oxygen (this is permissible according to MGSN, as well as according to SNiP for rooms with natural ventilation). The calculation takes into account only people staying in the room for a long time. For example, if a large company gathers in your living room a couple of times a year, then there is no need to increase the ventilation performance because of them. If you want your guests to feel comfortable, you can install a VAV system that allows you to regulate the air flow separately in each room. With such a system, you can increase air exchange in the living room by reducing it in the bedroom and other rooms.

After calculating the air exchange for people, we need to calculate the air exchange by frequency (this parameter shows how many times a complete change of air occurs in the room within one hour). To ensure that the air in the room does not stagnate, it is necessary to ensure at least one air exchange.

Thus, to determine the required air flow, we need to calculate two air exchange values: by number of people and by multiplicity and then choose more from these two values:

1. Calculation of air exchange by number of people:
   

   L = N * Lnorm, Where

   L

   N number of people;

   Lnorm air consumption rate per person:

   • at rest (sleep) 30 m³/h;
   • typical value (according to SNiP) 60 m³/h;
2. Calculation of air exchange by frequency:
   

   L=n*S*H, Where

   L required supply ventilation capacity, m³/h;

   n normalized air exchange rate:

   for residential premises - from 1 to 2, for offices - from 2 to 3;

   S room area, m²;

   H room height, m;

By calculating the required air exchange for each room served and adding the resulting values, we find out the overall performance of the ventilation system. For reference, typical performance values ​​of ventilation systems:

For individual rooms and apartments from 100 to 500 m³/h;

For cottages from 500 to 2000 m³/h;

For offices from 1000 to 10000 m³/h.

Air distribution network calculation

After determining the ventilation performance, you can proceed to designing the air distribution network, which consists of air ducts, fittings (adapters, splitters, turns), throttle valves and air distributors (grills or diffusers). The calculation of the air distribution network begins with drawing up a diagram of the air ducts. The circuit is designed in such a way that with minimal total length route, the ventilation system could supply the calculated amount of air to all serviced rooms. Next, according to this scheme, the dimensions of the air ducts are calculated and air distributors are selected.

Calculation of duct sizes

To calculate the dimensions (sectional area) of air ducts, we need to know the volume of air passing through the duct per unit time, as well as the maximum permissible air speed in the duct. As air speed increases, the size of the air ducts decreases, but the noise level and network resistance increase. In practice, for apartments and cottages, the air speed in air ducts is limited to 3-4 m/s, since at higher air speeds the noise from its movement in the air ducts and distributors can become too noticeable.

It should also be taken into account that it is not always possible to use “quiet” low-velocity air ducts of large cross-section, since they are difficult to place in the ceiling space. The height of the ceiling space can be reduced by using rectangular air ducts, which, with the same cross-sectional area, have a smaller height than round ones (for example, a round air duct with a diameter of 160 mm has the same cross-sectional area as a rectangular one with a size of 200×100 mm). At the same time, installing a network of round flexible air ducts is easier and faster.

So, the calculated cross-sectional area of ​​the air duct is determined by the formula:

Sc = L * 2.778 / V, Where

Sс— calculated cross-sectional area of ​​the air duct, cm²;

L— air flow through the air duct, m³/h;

V— air speed in the duct, m/s;

2,778 — coefficient for coordinating different dimensions (hours and seconds, meters and centimeters).

We get the final result in square centimeters, since in such units of measurement it is more convenient for perception.

The actual cross-sectional area of ​​the duct is determined by the formula:

S = π * D² / 400- for round air ducts,

S = A * B / 100- for rectangular air ducts, where

S— actual cross-sectional area of ​​the air duct, cm²;

D— diameter of the round air duct, mm;

A And B— width and height of the rectangular air duct, mm.

The table shows data on air consumption in round and rectangular air ducts at different air speeds.

Table 1. Air flow in air ducts

Duct parameters			Air flow (m³/h) at air speed:
Diameter round air duct	Dimensions rectangular air duct	Square sections air duct	2 m/s	3 m/s	4 m/s	5 m/s	6 m/s
	80×90 mm	72 cm²	52	78	104	130	156
Ø 100 mm	63×125 mm	79 cm²	57	85	113	142	170
	63×140 mm	88 cm²	63	95	127	159	190
Ø 110 mm	90×100 mm	90 cm²	65	97	130	162	194
	80×140 mm	112 cm²	81	121	161	202	242
Ø 125 mm	100×125 mm	125 cm²	90	135	180	225	270
	100×140 mm	140 cm²	101	151	202	252	302
Ø 140 mm	125×125 mm	156 cm²	112	169	225	281	337
	90×200 mm	180 cm²	130	194	259	324	389
Ø 160 mm	100×200 mm	200 cm²	144	216	288	360	432
	90×250 mm	225 cm²	162	243	324	405	486
Ø 180 mm	160×160 mm	256 cm²	184	276	369	461	553
	90×315 mm	283 cm²	204	306	408	510	612
Ø 200 mm	100×315 mm	315 cm²	227	340	454	567	680
	100×355 mm	355 cm²	256	383	511	639	767
Ø 225 mm	160×250 mm	400 cm²	288	432	576	720	864
	125×355 mm	443 cm²	319	479	639	799	958
Ø 250 mm	125×400 mm	500 cm²	360	540	720	900	1080
	200×315 mm	630 cm²	454	680	907	1134	1361
Ø 300 mm	200×355 mm	710 cm²	511	767	1022	1278	1533
	160×450 mm	720 cm²	518	778	1037	1296	1555
Ø 315 mm	250×315 mm	787 cm²	567	850	1134	1417	1701
	250×355 mm	887 cm²	639	958	1278	1597	1917
Ø 350 mm	200×500 mm	1000 cm²	720	1080	1440	1800	2160
	250×450 mm	1125 cm²	810	1215	1620	2025	2430
Ø 400 mm	250×500 mm	1250 cm²	900	1350	1800	2250	2700

The size of the air duct is calculated separately for each branch, starting with the main duct to which the ventilation unit is connected. Note that the air speed at its outlet can reach 6-8 m/s, since the dimensions of the connecting flange of the ventilation unit are limited by the size of its body (the noise arising inside it is damped by a silencer). To reduce air speed and reduce noise levels, the dimensions of the main air duct are often chosen more sizes flange of the ventilation unit. In this case, the connection of the main air duct to the ventilation unit is made through an adapter.

Domestic ventilation systems usually use round ducts with a diameter of 100 to 250 mm or rectangular ducts of equivalent cross-section.

Selection of air distributors

Knowing the air flow, you can select air distributors from the catalog, taking into account the ratio of their size and noise level (the cross-sectional area of ​​the air distributor is, as a rule, 1.5-2 times larger than the cross-sectional area of ​​the air duct). For example, consider the parameters of popular air distribution grilles Arktos series AMN, ADN, AMP, ADR:

Selecting an air handling unit

To select an air handling unit, we will need the values ​​of three parameters: overall performance, heater power and air network resistance. We have already calculated the performance and power of the heater. The network resistance can be found using or, during manual calculation, taken equal to the typical value (see section).

For selection suitable model we need to select ventilation units whose maximum performance is slightly greater than the calculated value. After this, using the ventilation characteristic, we determine the system performance at a given network resistance. If the obtained value is slightly higher than the required performance of the ventilation system, then the selected model is suitable for us.

As an example, let’s check whether a ventilation unit with the ventilation characteristics shown in the figure is suitable for a cottage with an area of ​​200 m².

The estimated productivity is 450 m³/h. Let us take the network resistance to be 120 Pa. To determine the actual performance, we must draw a horizontal line from the value of 120 Pa, and then draw a vertical line down from the point of its intersection with the graph. The intersection point of this line with the “Performance” axis will give us the desired value - about 480 m³/h, which is slightly more than the calculated value. So this model suits us.

Note that many modern fans have flat ventilation characteristics. It means that possible mistakes in determining network resistance have almost no effect on the actual performance of the ventilation system. If in our example we had made a mistake in determining the resistance of the air supply network by 50 Pa (that is, the actual network resistance would not have been 120, but 180 Pa), the system performance would have dropped by only 20 m³/h to 460 m³/h, which had no effect would be the result of our choice.

After choosing an air handling unit (or a fan, if a dial system is used), it may turn out that its actual performance is noticeably higher than the calculated one, and the previous model of the air handling unit is not suitable because its performance is not enough. In this case we have several options:

1. Leave everything as is, but the actual ventilation performance will be higher than the calculated one. This will lead to increased energy consumption spent on heating the air during the cold season.
2. “Strangle” the ventilation unit using balancing throttle valves, closing them until the air flow in each room drops to the calculated level. This will also lead to excessive energy consumption (although not as much as in the first option), since the fan will work with excess load, overcoming the increased network resistance.
3. Do not turn on maximum speed. This will help if the ventilation unit has 5-8 fan speeds (or smooth speed control). However, most budget ventilation units have only 3-step speed control, which most likely will not allow you to accurately select the desired performance.
4. Reduce the maximum productivity of the air handling unit exactly to a specified level. This is possible if the automatic ventilation unit allows you to adjust the maximum fan rotation speed.

Do I need to rely on SNiP?

In all calculations that we carried out, the recommendations of SNiP and MGSN were used. This regulatory documentation allows you to determine the minimum permissible ventilation performance that ensures a comfortable stay for people in the room. In other words, SNiP requirements are aimed primarily at minimizing the cost of the ventilation system and the costs of its operation, which is important when designing ventilation systems for administrative and public buildings.

In apartments and cottages the situation is different, because you are designing ventilation for yourself, and not for the average resident, and no one forces you to adhere to the recommendations of SNiP. For this reason, system performance can be either higher than the design value (for greater comfort) or lower (to reduce energy consumption and system cost). In addition, everyone’s subjective feeling of comfort is different: for some, 30-40 m³/h per person is enough, but for others, 60 m³/h will not be enough.

However, if you do not know what air exchange you need to feel comfortable, it is better to follow the recommendations of SNiP. Since modern air handling units allow you to adjust the performance from the control panel, you can find a compromise between comfort and savings already during the operation of the ventilation system.

Ventilation system noise level

How to make a “quiet” ventilation system that will not disturb your sleep at night is described in the section.

Ventilation system design

For accurate calculation of ventilation system parameters and project development, please contact. You can also calculate the approximate value using a calculator.

Ventilation in a room, especially in a residential or industrial one, must function 100%. Of course, many may say that you can simply open a window or door to ventilate. But this option can only work in summer or spring. But what to do in winter, when it’s cold outside?

Need for ventilation

Firstly, it is immediately worth noting that without fresh air, a person’s lungs begin to function worse. It is also possible that a variety of diseases will appear, which with a high percentage of probability will develop into chronic ones. Secondly, if the building is a residential building in which there are children, then the need for ventilation increases even more, since some ailments that can infect a child will most likely remain with him for life. In order to avoid such problems, it is best to arrange ventilation. There are several options worth considering. For example, you can start calculating the supply ventilation system and installing it. It is also worth adding that diseases are not the only problem.

In a room or building where there is no constant exchange of air, all furniture and walls will become covered with a coating from any substance that is sprayed into the air. Let's say, if this is a kitchen, then everything that is fried, boiled, etc. will leave its sediment. In addition, dust is a terrible enemy. Even cleaning products that are designed to clean will still leave a residue that will negatively impact the occupants.

Type of ventilation system

Of course, before you start designing, calculating a ventilation system or installing it, you need to decide on the type of network that is best suited. Currently, there are three main distinctions: different types, the main difference between them is in their functioning.

The second group is the exhaust group. In other words, this is a regular hood, which is most often installed in the kitchen areas of a building. The main task of ventilation is to extract air from the room to the outside.

Recirculation. Such a system is perhaps the most effective, since it simultaneously pumps air out of the room and at the same time supplies fresh air from the street.

The only question that everyone has next is how the ventilation system works, why does the air move in one direction or another? For this, two types of sources of awakening the air mass are used. They can be natural or mechanical, that is, artificial. To ensure their normal operation, it is necessary to correctly calculate the ventilation system.

General network calculation

As mentioned above, just select and install certain type there won't be enough. It is necessary to clearly determine exactly how much air needs to be removed from the room and how much needs to be pumped back in. Experts call this air exchange, which needs to be calculated. Depending on the data obtained when calculating the ventilation system, it is necessary to make a starting point when choosing the type of device.

Today it is known a large number of various calculation methods. They are aimed at determining various parameters. For some systems, calculations are carried out to find out how much warm air or evaporation needs to be removed. Some are carried out in order to find out how much air is needed to dilute contaminants, if this industrial building. However, the disadvantage of all these methods is the requirement of professional knowledge and skills.

What to do if it is necessary to calculate the ventilation system, but there is no such experience? The very first thing that is recommended to do is to familiarize yourself with the various regulatory documents available in each state or even region (GOST, SNiP, etc.) These papers contain all the indications that any type of system must comply with.

Multiple calculation

One example of ventilation can be calculation by multiples. This method is quite complicated. However, it is quite feasible and will give good results.

The first thing you need to understand is what multiplicity is. A similar term describes how many times the air in a room is changed to fresh in 1 hour. This parameter depends on two components - the specifics of the structure and its area. For a clear demonstration, a calculation using the formula for a building with a single air exchange will be shown. This indicates that a certain amount of air was removed from the room and at the same time an amount of fresh air was introduced that corresponded to the volume of the same building.

The formula for calculation is: L = n * V.

Measurement is carried out in cubic meters/hour. V is the volume of the room, and n is the multiplicity value, which is taken from the table.

If you are calculating a system with several rooms, then the formula must take into account the volume of the entire building without walls. In other words, you must first calculate the volume of each room, then add up all the available results, and substitute the final value into the formula.

Ventilation with mechanical type device

Calculation of the mechanical ventilation system and its installation must take place according to a specific plan.

The first stage is to determine the numerical value of air exchange. It is necessary to determine the amount of substance that must enter the structure in order to meet the requirements.

The second stage is determining the minimum dimensions of the air duct. It is very important to choose correct section devices, since such things as the cleanliness and freshness of the incoming air depend on it.

The third stage is the selection of the type of system for installation. This is an important point.

The fourth stage is the design of the ventilation system. It is important to clearly draw up a plan according to which the installation will be carried out.

Need for mechanical ventilation occurs only if the natural influx fails to cope. Any of the networks is calculated on such parameters as its air volume and the speed of this flow. For mechanical systems this figure can reach 5 m 3 / h.

For example, if it is necessary to provide natural ventilation area of ​​300 m 3 / h, then you will need a 350 mm caliber. If a mechanical system is installed, the volume can be reduced by 1.5-2 times.

Exhaust ventilation

The calculation, like any other, must begin with the fact that productivity is determined. The units of measurement for this parameter for the network are m 3 /h.

To carry out an effective calculation, you need to know three things: the height and area of ​​the rooms, the main purpose of each room, the average number of people who will be in each room at the same time.

In order to begin calculating a ventilation and air conditioning system of this type, it is necessary to determine the multiplicity. The numerical value of this parameter is set by SNiP. It is important to know here that the parameter for residential, commercial or industrial premises will be different.

If calculations are carried out for a domestic building, then the multiplicity is 1. If we are talking about installing ventilation in an administrative building, then the indicator is 2-3. It depends on some other conditions. To successfully carry out the calculation, you need to know the amount of exchange by multiplicity, as well as by the number of people. Must be taken highest value flow rate to determine the required system power.

To find out the air exchange rate, you need to multiply the area of ​​the room by its height, and then by the value of the rate (1 for domestic, 2-3 for others).

In order to calculate the ventilation and air conditioning system per person, it is necessary to know the amount of air consumed by one person and multiply this value by the number of people. On average, with minimal activity, one person consumes about 20 m 3 / h; with average activity, the figure increases to 40 m 3 / h; with intense physical activity the volume increases to 60 m 3 / h.

Acoustic calculation of the ventilation system

Acoustic calculation is a mandatory operation that is attached to the calculation of any room ventilation system. This operation is carried out in order to perform several specific tasks:

• determine the octave spectrum of airborne and structural ventilation noise at design points;
• compare the existing noise with the permissible noise according to hygienic standards;
• determine a way to reduce noise.

All calculations must be carried out at strictly established design points.

After all measures have been selected according to building and acoustic standards, which are designed to eliminate excess noise in the room, a verification calculation of the entire system is carried out at the same points that were determined earlier. However, the effective values ​​obtained during this noise reduction measure must also be added to this.

To carry out calculations, certain initial data are needed. They became the noise characteristics of the equipment, which were called sound power levels (SPL). For calculations, geometric mean frequencies in Hz are used. If an approximate calculation is carried out, then correction noise levels in dBA can be used.

If we talk about design points, they are located in human habitats, as well as in places where the fan is installed.

Aerodynamic calculation of the ventilation system

This calculation process is performed only after the air exchange calculation for the building has already been carried out, and a decision has been made on the routing of air ducts and channels. In order to successfully carry out these calculations, it is necessary to create a ventilation system, in which it is necessary to highlight such parts as the fittings of all air ducts.

Using information and plans, you need to determine the length of individual branches of the ventilation network. It is important to understand here that the calculation of such a system can be carried out to solve two different problems - direct or inverse. The purpose of the calculations depends on the type of task at hand:

• straight - it is necessary to determine the cross-sectional dimensions for all sections of the system, while setting a certain level of air flow that will pass through them;
• the reverse is to determine the air flow by setting a certain cross-section for all ventilation sections.

In order to carry out calculations of this type, it is necessary to divide the entire system into several separate sections. The main characteristic of each selected fragment is constant flow air.

Calculation programs

Since carrying out calculations and building a ventilation scheme manually is a very labor-intensive and time-consuming process, simple programs have been developed that can do all the actions independently. Let's look at a few. One such ventilation system calculation program is Vent-Clac. Why is she so good?

A similar program for calculations and network design is considered one of the most convenient and effective. The operating algorithm of this application is based on the use of the Altschul formula. The peculiarity of the program is that it copes well with both ventilation calculations natural type, and mechanical type.

Since the software is constantly updated, it is worth noting that the latest version of the application is also capable of carrying out such work as aerodynamic calculations of the resistance of the entire ventilation system. Also can effectively calculate other Extra options, which will help in the selection of preliminary equipment. In order to make these calculations, the program will need data such as air flow at the beginning and end of the system, as well as the length of the main air duct of the room.

Since manually calculating all this takes a long time and you have to break the calculations into stages, this application will provide significant support and save a lot of time.

Sanitary standards

Another option for calculating ventilation is according to sanitary standards. Similar calculations are carried out for public and administrative facilities. To make correct calculations, you need to know the average number of people who will constantly be inside the building. If we talk about regular consumers of indoor air, they need about 60 cubic meters per hour per person. But since public facilities are also visited by temporary persons, they must also be taken into account. The amount of air consumed by such a person is about 20 cubic meters per hour.

If you carry out all the calculations based on the initial data from the tables, then when you receive the final results, it will become clearly visible that the amount of air coming from the street is much greater than that consumed inside the building. In such situations, they most often resort to the simplest solution - hoods of approximately 195 cubic meters per hour. In most cases, adding such a network will create an acceptable balance for the existence of the entire ventilation system.