Nowadays, ventilation is an integral system of comfortable and energy-efficient accommodation. Modern houses have high thermal insulation characteristics (high-quality double-glazed windows and insulated external structures). As a result, fresh air flows do not get inside.

Excess CO2 negatively affects the human condition and may cause headaches, insomnia, decreased productivity, etc. When windows are open, unpurified cold air will enter the room, and this will reduce comfort and increase the load on the heating system as well. Therefore, forced ventilation is needed in the apartment.

Therefore, ventilation is a must. The best solution is to install a supply and exhaust system with recuperation, which will accomplish several objectives at once:

Supply and exhaust ventilation with heat and moisture recovery is a rational use of energy resources. 

Before we start discussing the features, it is necessary to understand the concept of supply and exhaust ventilation.

THE OPERATION PRINCIPLE OF THE SUPPLY AND EXHAUST VENTILATION SYSTEM

Supply and exhaust ventilation is a system that provides the flow of air from outdoors into the room, as well as the extraction of already exhausted air. The key element of supply and exhaust ventilation, which is responsible for maintaining of air exchange, is an air handling unit. 

The air-handling unit is a mono-block device that contains in its casing all the main components for organizing ventilation.

The supply and exhaust ventilation system consists of:

In addition to basic functions (air supply and exhaust), the equipment also performs additional functions, for example: air filtration, heating, cooling and humidification.

Main principles of system operation

Firstly, the living area is divided into two areas – “clean” and “dirty”.

“Clean area” is the premises where residents spend a lot of time (a living room, a bedroom, children's room). The “dirty area” includes: a bathroom, a shower room, a dressing room, a laundry room, a kitchen, etc.

Thus, the supply of clean air is carried out in the key premises – the “clean area”, and the intake of exhaust air in the secondary ones – in the “dirty area”.

In order for the air exchange to be correct, the system must be in balance. This means that when supplying 100 cubic meters of air, the unit must intake 100 cubic meters. If the balance of the system is not maintained, then the efficiency of the recuperation process will decrease.

So, the first basic principle of the supply and exhaust ventilation device is to supply in the “clean area” and intake in the “dirty” one.

The second basic principle is the balance of the system.

SUPPLY AND EXHAUST VENTILATION: KEY FEATURES

The engineering of supply and exhaust ventilation is a very painstaking process that requires compliance with many rules and nuances.

We already know that the air supply is carried out in the “clean area”, and the intake – in the “dirty” one. However, to organize proper air exchange, the following recommendations must be observed.

In order to avoid trouble, four silencers (at the outlet of the unit) are installed on each of the air ducts. These silencers perform the following functions:

In addition, the wrong selection of air ducts contributes to the appearance of noise. It is necessary to calculate the required cross section so that the air speed is within the normal range and does not create noise.

 In winter, there is a sharp temperature drop, which leads to condensation on the outside of the air ducts.

To avoid the above-mentioned problems, 2 cm thick rubber is used for thermal insulation of air ducts.

Various filters are used to filter the air, these can be:

ADVANTAGES OF SUPPLY AND EXHAUST SYSTEMS

Supply and exhaust ventilation has a number of advantages:

DISADVANTAGES OF SUPPLY AND EXHAUST VENTILATION

Supply and exhaust ventilation systems have almost no drawbacks.

Before installing the system, it is necessary to take into account the lowering of the ceilings, which is 17 cm clean (without false ceiling, etc.).

SUPPLY AND EXHAUST VENTILATION SYSTEM WITH HEAT AND MOISTURE RECOVERY

The process of heat and moisture recovery is the main advantage of the air handling unit. This function allows you to regenerate the heat and moisture of the exhaust air, significantly reducing the p pressure on the heating system and reducing the cost of heating the supply air using a special heat exchanger – recuperator.

When using a conventional exhaust system (for example: a kitchen hood or an exhaust fan in a bathroom, etc.), heated air (heat) is removed to the outdoors.

The air handling unit with recuperation is an energy-efficient equipment, and will allow heating the supply air using the thermal energy of the exhaust air.

A recuperator is an energy-saving element of the ventilation system, the main task of which is to transfer heat from the exhaust air to the supply air.

The main types of recuperators:

Heat exchange between exhaust and supply air occurs due to the intersection of air flows. Since the recuperator consists of plates, the air flows do not intersect. Thus, clean, but already heated air is supplied to the “clean areas”.

The main difference from the classic heat recuperator is that this unit returns both heat and moisture to the room. However, the main disadvantage is rapid wear. The enthalpy recuperator is recommended to be used during the winter period. In winter, the humidity of the outdoor air drops significantly.

A rotary recuperator is a heat exchanger similar to a drum, which, due to a special element – a rotor, rotates and heats the supply air.

Rotary recuperators are not used in the household segment, as they are designed for high airflow rate.

 You can additionally find more detailed information about recuperators in our article “Air recovery system in a house or apartment”.

CALCULATION OF SUPPLY AND EXHAUST VENTILATION

Supply and exhaust ventilation schemes Implements based on air exchange calculations.

There are three main methods of the air exchange calculation:

BASED ON AIR EXCHANGE RATE

The air exchange rate directly depends on the volume of the room (ceiling height and area). It makes it clear how much air is replaced per unit of time. The air exchange rate is regulated by Construction Norms & Regulations and depends on the type of premises.

Thus, knowing the air exchange rate for optimal conditions of 0.6 (according to Construction Norms & Regulations), the volume of the room (ceiling height × area), and multiplying these values, you can find out the required amount of air in m³/ h.

BASED ON THE NUMBER OF PEOPLE

According to Construction Norms & Regulations, the following rates of the amount of air per person are accepted:

This calculation considers the number of people living in the house. Thus, for each room (clean area) a calculation is made. For example, if two people live in a bedroom, then the amount of air supplied is 72 m³/hour (for increased comfort). However, the living room will consider the total number of occupants, as this is the place where the whole family gathers.

BASED ON THE AMOUNT OF CO2

Such a calculation is made when arranging a variable ventilation system, and not a constant one, as in the two previous cases.

In this case, 60 m³/h per person is applied. This is how much air is needed in order to remove the CO2 that our body produces. The calculation method does not differ from the previous version (calculation based on the number of people).

To organize variable air supply, Alter Air uses innovative equipment from the Czech manufacturer Jablotron, which has no analogues in Ukraine.

AERODYNAMIC CALCULATION

When the engineer has already developed an air duct scheme, an aerodynamic calculation is performed. This calculation is very important. In the case of an incorrect calculation, the following problems may arise:

To select equipment, the resistance in the system is calculated, which considers the pressure of the air ducts themselves and local resistances (valves, air distributor units, air supply boxes, etc.).

To avoid noise in the air duct system, the air speed must not exceed 3 m/s. To achieve the required speed, it is necessary to choose the right cross-sections of the air ducts.

To ensure comfortable air distribution, the air speed at the outlet of the system should not exceed 2.5 m/s. The air speed depends on the size of the air distributor; it can be a diffuser, anemostat or a grid. It is also important that the speed is not lower than 2 m/s. If lower, fresh air will not enter the working area (where the person is), since in most cases the air supply is implemented from the ceiling.

SUPPLY AND EXHAUST VENTILATION: INSTALLATION DIAGRAM

Equipment for supply and exhaust ventilation

Supply and exhaust ventilation systems can be implemented not only with the help of an air handling unit, but also with the help of other devices that are cheaper.

For air supply, you can use:

For air extraction in the supply and exhaust system, the following are used:

Types of exhaust fans, depending on the principle of operation:

Alter Air prefers the following manufacturers of exhaust fans:

The main disadvantage of the above-mentioned exhaust systems is that warm air is extracted to outdoors. While the supply and exhaust system performs the recovery process and uses the energy of the exhaust air to heat the supply air.

Decentralized supply and exhaust system

Decentralized ventilation is implemented by using household recuperators.

A household recuperator is a compact system for organizing local air exchange. This device is equipped with a recuperator, which allows you to heat the supply air without significant electricity costs, as well as humidify when buying an enthalpy recuperator.

Manufacturers of household recuperators:

We will take a look at two air handling units from the German brand Meltem:

Meltem M-WRG does not differ much from the newer model, the difference is only in the efficiency (coefficient of performance) of the recovery of 76%, in the level of soundproofing (up to 56 dB) and in the filtering system (two G4 filters).

The Meltem unit generates 100 m³/hour, which allows you to supply 100 cubic meters of clean air and remove the same amount of polluted air. One unit is able to organize high-quality air exchange in several rooms at once. For example, supply 50 m³/hour to the bedroom and 50 m³/hour to the children’s room. According to Construction Norms & Regulations, 50 m³/hour is enough for optimal comfort of 2 people. Air extraction is carried out in two “dirty areas”.

Additional CO2 sensors and humidity sensors can be purchased for better adjustment of the system.

The filtration system is represented by two filters:

System installation options:

Conventional air handling units are not designed for extraction of air from the kitchen. However, our company works with leaders in the ventilation industry, Jablotron and Faber. These manufacturers, together, have created a unique supply and exhaust system that can also remove polluted air from the kitchen and use more heat to heat the supply air.

Centralized supply and exhaust ventilation

The best solution for high-quality ventilation is a VAV system (system with variable air supply) based on Czech equipment Jablotron (Futura L or Futura M).

The air supply to the premises is carried out based on CO2 indicators for the rooms. Sensors that are installed in each “clean area” monitor the amount of carbon dioxide.

In the case when there is no one in the house, the air handling unit operates at a minimum speed and supplies air in small quantities. With an increase in CO2, which indicates that there is a person in the room, the unit gradually increases the air supply to the desired room, reducing the airflow in rooms where there is nobody. It is worth noting that the system also operates at minimum speed. If the amount of CO2 continues to increase, then the efficiency of the unit increases until the level of carbon dioxide is normal.

The principle of variable air supply allows the rational use of energy resources and reduces the cost of operating the device. While with a constant air supply, the entire area of accommodation is ventilated and the unit operates at full capacity, using a lot of energy.

Because the system supplies air to the premises where it is needed, analyzing the information from the CO2 sensors in the rooms, this principle of operation allows you to increase the amount of air supplied by 2 times, using a unit of the same power. Instead of 36 cubic meters of air, 60 cubic meters will be supplied, which will significantly increase indoor comfort.

The innovative VarioBreeze VAV valves from Jablotron are used to regulate air exchange. The valves are installed on supply and exhaust air ducts. The cross-sections of the supply VAV valves are regulated depending on the CO2 indicators. With an increase in carbon dioxide, the valves open slightly and with a decrease, they close slightly.

Exhaust VAV valves work depending on the flow valves. This implies that the system is in balance (supply air = exhaust air).

For enhanced air extraction in bathrooms and showers, “Boost Button” is used. This device is mounted in a light switch and unnoticeable in the interior. Thus, when the light turns on, there is an increased air extraction. This mode is configured individually, depending on the needs of the customer.

Faber's equipment is used for the kitchen hood, which interacts with the Jablotron air handling units. This implies that the air extraction is carried out through the ventilation unit. Thus, a large amount of warm air energy is sent to the recuperator to supply heating, and is not discharged to the outdoors as in conventional exhaust systems.

Optionally, you can purchase CoolBreeze.

CoolBreeze is an air-to-air heat pump that can be used to heat or cool air during the off-season.

In the case when the recuperator no longer heats the supply air to a comfortable temperature in winter, an additional module, CoolBreeze, is installed on the air duct through which the exhaust air moves. In this way, the temperature of the exhaust air rises, and since the exhaust air passes through the plate recuperator, the temperature of the supply air also rises. By the same principle, the device works for cooling.

CoolBreeze is ideal for demi-season and nighttime when there is no active heat. In the summer, this device is no longer enough, and it is necessary to install an additional air conditioning system for a comfortable microclimate.

Using the Jablotron climate system is an excellent combination of price and quality.

Currently, there are no analogues of the innovative variable air supply system in Ukraine.

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