The heaviness that sets in during the afternoon in offices, the stuffiness in meeting rooms, or condensation and mold in a home are often signs of inadequate ventilation. In this article we explain how ventilation systems work, their types, heat recovery technologies, and the main brands in the industry.
What is the difference between ventilation and air conditioning?
An air conditioner takes the air in the space, cools or heats it, and returns the same air; ventilation, on the other hand, replaces the air in the space. Split air conditioners, cassette units, and most VRF indoor units do not bring in fresh air. That is why buildings with a lot of occupants need a separate fresh air system in addition to the air conditioning system.
What are the types of ventilation systems?
| System | How it works | Typical use |
|---|---|---|
| Natural ventilation | Air exchange through windows, chimneys, and pressure differences | Homes, small buildings |
| Mechanical exhaust | Dirty air is expelled with an extractor fan, and fresh air enters on its own | Toilets, kitchens, storage rooms |
| Mechanical supply | Filtered fresh air is supplied by a fan | Clean room entrances, pressurization |
| Balanced ventilation | Supply and exhaust fans work together | Offices, schools, hospitals |
| Heat recovery (HRV/ERV) | The heat (and moisture) of the exhausted air is transferred to the fresh air | Offices, homes, hotels |
| Air handling unit (AHU) | Filters fresh air, heats/cools it, humidifies it | Hospitals, shopping malls, factories, large offices |
| Parking garage jet fan | Jet fans push air toward the exhaust point and remove smoke in a fire | Enclosed parking garages |
How do heat recovery units work?
A heat recovery unit passes the air exhausted from the building and the incoming fresh air through an exchanger without mixing them; in winter the heat of the exhausted warm air is transferred to the fresh air, and in summer the heat of the fresh air is transferred to the exhausted air. This greatly reduces the energy loss caused by ventilation.
| Heat exchanger type | Feature |
|---|---|
| Plate (cross-flow or counter-flow) | The air streams are completely separate; easy to maintain, suitable for hygienic applications |
| Rotary (rotating drum) | Can transfer moisture along with heat; high efficiency, a small amount of air leakage may occur |
| Enthalpy (membrane, ERV) | Transfers heat and moisture; helps balance winter humidity in homes and offices |
| Glycol loop (run-around) | When supply and exhaust are far apart, glycol water circulates between two coils |
| Heat pipe | No moving parts; medium efficiency, simple maintenance |
According to manufacturer data, the thermal efficiency of plate and rotary exchangers is generally between 70 and 90 percent. Actual efficiency depends on airflow, outdoor temperature, and how clean the exchanger is.
What are the main parts of a ventilation system?
01Fans
Duct systems mostly use radial (centrifugal) fans, and axial fans are used for high airflow at low pressure. In new systems, fans with EC motors whose speed can be adjusted steplessly significantly reduce energy consumption.
02Filters
Filters are divided into ePM1, ePM2.5, ePM10, and coarse dust classes according to the ISO 16890 standard; the old G4, F7, and F9 classification is still widely used. HEPA filters are required in hospitals and clean rooms. Details are on our HVAC filters page.
03Ducts, grilles, and dampers
Air ducts, grilles, diffusers, control and fire dampers, and silencers ensure that air is distributed in the right amount and quietly. If the duct size is chosen incorrectly, noise and fan energy increase. For a preliminary calculation, you can use our airflow and duct sizing calculator.
04Controls and sensors
Demand-controlled ventilation with a CO2 sensor saves energy by reducing fan speed in empty or lightly occupied spaces. In parking garages, CO and NO2 sensors activate the jet fans.
How much fresh air is needed?
The required amount of fresh air is calculated according to the intended use of the space, the number of people, and the floor area. Standards such as EN 16798-1 in Europe and ASHRAE 62.1 in the US form the basis of this calculation. For areas such as hospitals, laboratories, and kitchens, special regulations and specifications also apply.
Is your building's ventilation adequate?
Let us measure the fresh air flow, filters, and fan performance, and present our improvement recommendations in writing.
How does parking garage ventilation work?
In enclosed parking garages, jet fans hung from the ceiling push air toward the exhaust shafts instead of using ducts. In normal operation they run at low speed with CO and NO2 sensors, and in a fire they run at high speed to remove smoke. Details are on our parking garage jet fan page.
Which brands stand out in the ventilation industry?
| Brand | Notable products |
|---|---|
| Systemair (Sweden) | Fans, heat recovery units, air handling units |
| Swegon (Sweden) | Air handling units, heat recovery, indoor air quality solutions |
| FläktGroup (Germany) | Air handling units and fans; part of Samsung since November 2025 |
| Trox (Germany) | Grilles, diffusers, dampers, fire dampers, air handling units |
| Soler & Palau (Spain) | Extractor fans, duct fans, jet fans |
| ebm-papst and Ziehl-Abegg (Germany) | Fans with EC motors; they supply fans to many equipment manufacturers |
| Daikin | Heat recovery ventilation units and air handling units |
| Domestic manufacturers: Üntes, Aldağ, Alarko Carrier | Air handling units, heat recovery, fans |
Why is maintenance important in ventilation systems?
A clogged filter, a loose belt, or a dirty exchanger reduces the amount of fresh air, raises fan energy use, and degrades indoor air quality. Filter replacement, fan and belt checks, exchanger and drain cleaning, and damper checks should be done regularly. For a checklist, see our air handling unit maintenance checklist article.
Brand names belong to their owners. YOİ Mühendislik is an authorized service and sales point for LG; for other brands it provides maintenance, fault, and repair services as an independent technical service. Model and serial information may vary by manufacturer and market; for current information, refer to the manufacturer's Türkiye sources.
Frequently asked questions
Does a heat recovery unit replace an air conditioner?
No. A heat recovery unit provides fresh air and reduces the energy loss of ventilation, but its heating and cooling capacity is limited. In most buildings it is used together with an air conditioner or a heating system.
Is mechanical ventilation needed in a home?
In new homes that are well insulated and have airtight windows, heat recovery mechanical ventilation can help prevent humidity, odor, and mold problems.
Which is better, rotary or plate heat recovery?
Rotary exchangers can also transfer moisture and are highly efficient; plate exchangers keep the air streams completely separate, so they are preferred in hygienic applications. The choice is made according to the intended use.
How often should a ventilation filter be changed?
It depends on how intensively it is used and how polluted the outdoor air is. The replacement time should be determined by measuring the filter differential pressure; details are in our air handling unit filter article.