What is ventilation?

Ventilation system

Ventilation is a process of removing polluted air from a room and supplying fresh air from the outside. This is an essential mechanism because the air is constantly being polluted. Functional and efficient ventilation is currently one of the key criteria to be taken into account when designing residential and public buildings. Adequate air change is necessary for breathing and for the safe operation of air-consuming equipment.

Ventilation is particularly important when additional pollutants are present in the air, such as cigarette smoke, chemical vapors and various types of dust. Thanks to ventilation systems, appropriate indoor air parameters are maintained so as to meet the established hygienic standards and technical requirements.

What is the purpose of ventilation?

Effective ventilation guarantees constant supply of appropriate indoor air quality. If this important process did not occur, the level of carbon dioxide and steam would increase, which is a particularly disadvantageous situation. Carbon dioxide is present not only in the air breathed out by people, but is also created as a result of operation of stoves, fireplaces, boilers and furnaces. In case of air shortage, the combustion results in fatally hazardous carbon monoxide. The excess of water vapor may lead to dampness of walls, which will contribute to the formation of fungi or mold.

Additionally, damp thermal insulation has worse parameters of thermal protection. If windows and mirrors at home are constantly covered with vapor and water accumulates on them, this is often an indication of too much water vapor in the air. This also proves that ventilation system in the building does not function properly. Due to the hazards that may occur in the event of ineffective ventilation, ensuring continuous air circulation is a very important aspect. A properly installed ventilation system allows you to enjoy fresh air without unpleasant air drafts.

What are the types of ventilation available?

There are two basic types of ventilation: natural (gravity) and mechanical. Gravity ventilation is one of the simplest and oldest mechanisms of air circulation. This method consists of vertical ventilation ducts which are responsible for extraction of warm air from the upper parts of rooms to the outside. By means of pressure difference which, under suitable conditions, is formed in the ventilation stack, air line is formed which allows the air to be pushed through the gravity ventilation duct up the stack. However, favorable conditions must be maintained for this to happen.

The advantages of gravity ventilation:

  • no need to install a mechanical device for gravity ventilation to operate;
  • it is not necessary to install a ventilation system throughout the building;
  • silent operation;
  • maintenance-free operation.

The disadvantages of gravity ventilation:

  • the necessity to use trickle ventilation through open air trickle vents or slightly open windows,
  • it is not possible to control the amount of extracted and supplied air and ventilation intensity,
  • it is completely dependent on weather conditions (temperature and pressure),
  • large energy losses of the building (inability to use any kind of energy recovery),
  • inversion, i.e. change of airflow direction in exhaust ducts.

The second type of ventilation is mechanical ventilation – otherwise referred to as heat recovery ventilation, which ensures a constant exchange of stale air for fresh air. This is the most energy-efficient way of ventilating as it guarantees a constant air exchange with simultaneous heat recovery. The supplied air is also filtered.

In mechanical ventilation, the essential element is the air handling unit commonly referred to as a heat recovery unit (HRV). The most important part of the heat recovery unit is the heat exchanger where energy is transferred between the supply and exhaust air streams.

The advantages of mechanical ventilation:

  • constant air circulation independent of ambient conditions, which is additionally fully controlled,
  • very high savings on heating (up to 50%),
  • supply air filtration, thus limiting contact with smog and allergens present in the air,
  • high climate comfort in ventilated rooms,
  • possibility of using energy from the ground (a ground exchanger).

The disadvantages of using recuperation systems:

  • costs of the installation are higher than the costs of gravity ventilation,
  • operating costs related to servicing, filter replacement, and electricity consumption,
  • possibility of heat recovery ventilator's failure.

Each type of ventilation has its own advantages and disadvantages, and you need to decide, which option will work better.

Hybrid ventilation – what is it?

Hybrid ventilation consists of alternating mechanical and natural ventilation or operation of both systems which complement each other. It is possible because hybrid ventilation uses components that control the operation of both systems by monitoring ambient conditions and operating parameters of the ventilation system.

Therefore, hybrid ventilation operates as natural ventilation when outside and inside conditions are favorable, and when they are not sufficient for efficient air exchange – it starts to operate mechanically. Obviously, this also works in the opposite direction, i.e. the mechanical operation is assisted or replaced by natural air exchange, whenever possible. The purpose of the hybrid ventilation is to ensure the required air exchange in rooms, while minimizing the energy consumption that is necessary for the operation of the system.

What ventilation system should I choose for my home?

A few years ago, natural ventilation could have been found in the vast majority of houses. However, more and more people have recently chosen mechanical ventilation. It is often not easy to choose suitable ventilation. The decision is influenced by individual needs as well as costs. There are several issues that need to be addressed when choosing the type of ventilation for your home. A huge advantage of gravitational ventilation lies in its simplicity, therefore it is characterized by low price.

However, experts draw attention to the very important disadvantage of this type of ventilation – the lack of possibility of full control over the exchange of air at home, which in the long term may turn out to be a burdensome feature. Therefore, it will be better to invest in mechanical ventilation, i.e. the one containing a heat recovery ventilator. The most important advantage of this system is its independence from weather conditions.

Another aspect is the full possibility of controlling the volume of cycled air, which results in significant savings on heating. An additional advantage of mechanical ventilation is the filtration of air that enters the house and the reduction of harmful substances such as smog particles and allergens.

Gravity ventilation does not work with tightly sealed windows – why is that?

The driving force of the gravity ventilation system is the difference in the density of cold air (i.e. outside) and warm air (inside the rooms). Thanks to this phenomenon, lighter, heated air will rise and then escape outside through ventilation stacks. The inlets to ventilation stacks equipped with grates are located in rooms which are defined as the dirtiest ones or wet rooms, i.e. kitchen and bathroom.

Fresh air comes from outside and replaces stale air. If the temperature difference between outside and inside is small, the draft force in ventilation ducts may be too small to effectively remove the stale air from the rooms. Air from outside enters flats or houses by leaky windows. For this reason, gravity ventilation can't operate with tightly sealed windows.

What are the costs of mechanical ventilation?

If you are considering a ventilation system that is equipped with a heat recovery unit, you should consider it even before you start building your house. Otherwise it will be necessary to cut into walls and floors. When designing the ventilation system, the amount of air to be exchanged should be taken into account, depending on room dimensions.

Law regulations impose the number of cubic meters of air to be removed from a room. The price of a mechanical ventilation system is influenced by several factors. Firstly, different costs of hiring professionals. Another aspect is the price of materials of the ventilation system and a heat recovery ventilator. Another issue is the labor cost, which is not always included in the project quotation, so it is worth asking for this information at the source.

At first, you may be concerned about the price of the MVHR system, but the advantages of the system mentioned above must also be taken into account. The installation of gravity ventilation also generates costs, although they are smaller when compared to a mechanical ventilation system, but in the long run the choice of the latter will turn out to be a better investment. During the construction of a new house, masonry/prefabricated ducts may be avoided, which indirectly reduces the cost of heat recovery ventilation. Ventilation with a heat recovery additionally allows significant savings in heating.

Can heat recovery unit be installed in any house?

A ventilation system with an MVHR unit can be installed in any type of house as its main task is to ensure the highest quality of indoor air without the need for ventilation. In addition, heat from the ventilated area is recovered by means of a heat recovery unit because the it is equipped with a heat exchanger, thanks to which the extracted air from the house, which is warmer, heats up the colder air from the outside. This is a great solution for those who draw attention to ecological issues and want their homes to be friendlier for our planet.

An additional advantage of a heat recovery ventilation system is that rooms are not cooled down in winter or overheated in summer. It is true that mechanical ventilation with heat recovery is an ideal solution for any house or apartment whose residents want to enjoy fresh and healthy air. Ventilation with a heat recovery unit can be installed in a detached house, an apartment, a tenement house or a wooden cottage.

Does mechanical ventilation guarantee that air in the house will be clean, without smog and viruses?

At present, when air pollution is extremely high, more and more people want to know not only how to reduce emissions of harmful substances, but also how to protect homes and families from huge amounts smog, allergens and viruses.

Many people buy air purifiers, but it is worth knowing that mechanical ventilation also provides protection against harmful particles. Filters are located inside the heat recovery unit at the heat exchanger.

MVHR filter

The classification marked on the filter indicates the amount of impurities that can be filtered out. Larger particles, such as insects, sand and dust, are also filtered out due to the use of an appropriate filter type. The most important, in terms of health protection, is the removal of smog and viruses from the air.

Pay attention to the filter class, as each manufacturer gives information on which type of particles the product is able to remove. As the heat recovery unit consists of two fans that respectively extract and supply air, this system provides sufficient air exchange to enjoy clean and healthy air at home.

Is ventilation necessary? Why should rooms be ventilated?

Ventilation of a house or an apartment is of utmost importance as it directly affects health. As a result of the lack of air ventilation, high carbon dioxide and steam content accumulates, which reduces the oxygen content and thus contributes to the feeling of sleepiness and headaches, and problems with concentration.

On the one hand, when air becomes too dry (i.e. humidity drops below 40%), mucous membranes are overdried and some bacteria and viruses develop, which contributes to upper respiratory problems.

On the other hand, in too humid air (humidity above 60%), various types of fungi and mold, which are harmful to health and furniture, develop at a very fast rate. Ventilation of rooms with gas stoves, fireplaces or central heating boilers is particularly important for safety reasons.

What ventilation should be selected for kitchens?

Adequate ventilation in the kitchen is very important, as this will remove hazardous gas that may escape from a gas stove. In addition, it helps to remove unpleasant odors after cooking and excess moisture.

For safety reasons, mechanical ventilation is the best choice in kitchens as gravity ventilation depends on weather conditions and does not always work efficiently. A kitchen hood is an additional element supporting ventilation. It is a good idea to connect a hood to the heat recovery unit automation system, even in the simplest way, in order to balance the amount of air during hood operation.

Often, the capacity (in m3/h) of the hood is at least equal to or greater than the total capacity of the unit. It is useful during cooking as it removes not only odors but also accumulated vapor. Apart from individual preferences, kitchen ventilation is somewhat imposed on in the PN-83/B-03430 standard. In accordance with this standard, it is assumed that the volume flow rate of ventilation air for flats is the sum of fluxes removed from the kitchen. Therefore, the aforementioned fluxes should amount to:

  • for a kitchen with an external window, which is equipped with a gas or coal stove – 70 m3/h,
  • for a kitchen with an external window, which is equipped with an electric stove – 30 m3/h (without a window – 50 m3/h),
  • kitchens without an external window, equipped with a gas stove, should have mechanical exhaust ventilation, and the removed air flux should amount to 70 m3/h.

Apart from the above-mentioned issues, it is worth noting that kitchen doors must have either small openings at the bottom or must be shorter by several centimeters, as they cannot be completely tight.

What ventilation should be selected for a bathroom without a window?

If the bathroom towels don' dry and the mirrors are covered with vapor all the time – these are the most common signs of poor ventilation in this room. Gravity ventilation is the most common type of ventilation in bathrooms, which is additionally supported by air supply vents and doors with openings at the bottom.

However, in the case of a bathroom which does not have windows, it is worth considering a mechanical ventilation system. It operates continuously or only when the light in the bathroom is switched on. This is a very convenient solution because modern fans are equipped with sensors of humidity level in the room, as well as motion or light sensors and thus they start operating on their own.

The installation location of a fan is important. It should preferably be away from the door so that fresh air flows through the entire bathroom. The best place for the fan is directly above the steam source, for example, above the shower cabin. Obviously, in the case of a central ventilation system, the vents from bathrooms and toilets should be connected to the system.

What ventilation should be selected for a boiler house?

Ventilation in rooms such as boiler houses is designed to provide an adequate amount of fresh air necessary for the combustion process and to ensure proper air exchange. The requirements to be met by the rooms in which heating boilers are located are specified in legal regulations.

A very important aspect of ventilation in boiler houses is the removal of harmful gases which are released during combustion. Depending on the boiler type, there are different ventilation systems used in the boiler house. In rooms where solid fuel or fuel oil boilers are located, it is necessary to ensure sufficient air draft for the correct operation of boilers and, additionally, supply and extract air for boiler house ventilation.

On the other hand, if a solid or liquid fuel furnace, or gas equipment is installed in a boiler house, it draws combustion air from the room. It is forbidden to use mechanical exhaust ventilation in such a place. The type of ventilation chosen for a boiler house depends on the equipment found in this room.

Depending on the boiler type, gravity ventilation or mechanical ventilation may be installed. In modern buildings, the function of the boiler house is taken over by process rooms where heat pumps, recuperators and other equipment (not boilers!) are installed. Very often these rooms play an additional function of a laundry/drying room, and can then be connected to the heat recovery system.

Would you like to know more? Read other articles on heat recovery ventilation:

  1. How can You install heat recovery unit in the ready-built house?  - the article about decentralized heat recovery systems.
  2. What is an Electrostatic Precipitator and how does it work? - the article about highest filtration efficiency solutions.
  3. 14 Things You Need to Know about PremAIR - pretty self-explanatory title about the best HRU for clients looking for "premium" solutions. 
  4. Air distribution system for the MVHR - overview of FLX-REKU system: radial, semi-rigid ducting, plenum and distribution boxes, etc.
Alnor Ventilation Systems
Krakowska 10 Avenue
05-552 Wola Mrokowska

tel. +48 22 737 40 00