Types of Ventilation Systems
Ventilation is the process of maintaining and improving indoor air quality by replacing stale indoor air with fresh outdoor air. A well-functioning ventilation system supplies fresh, filtered air to living spaces while removing moisture and indoor pollutants generated within the building.
There are several types of ventilation systems. Regardless of the system, the basic principle remains the same: fresh supply air is delivered to living areas, such as living rooms and bedrooms, while stale air is extracted from so-called wet or service areas, including bathrooms, toilets, utility rooms, and kitchens.
Natural Ventilation
In a natural ventilation system, air movement is driven by the temperature difference between indoor and outdoor air, together with pressure differences created by the wind. Fresh air enters the building through fresh air valves located in the external walls of living spaces, ventilation hatches, or wooden ventilation windows. Stale air is extracted through exhaust vents located in so-called wet or service areas, such as toilets, bathrooms, and walk-in closets.
For a natural ventilation system to function properly, fresh air valves must be installed in all living areas. Without them, the building does not have a true natural ventilation system but relies instead on uncontrolled air infiltration.
The height of the exhaust flue has a significant impact on the performance of natural ventilation. The taller the flue, the stronger the natural stack effect and the more efficient the ventilation. Natural ventilation can also be enhanced by installing wind-driven chimney cowls at the top of the flue to improve draft.
Mechanical Exhaust Ventilation
In a mechanical exhaust ventilation system, air extraction is assisted by an exhaust fan. The roof-mounted exhaust fan removes stale indoor air through a network of ducts and discharges it outdoors. Fresh replacement air enters living rooms and bedrooms through fresh air valves installed in exterior walls, ventilation hatches, or wooden ventilation windows. Exhaust vents are located in so-called wet or service areas, such as toilets, bathrooms, and walk-in closets.
An adequate supply of fresh air is essential for the proper operation of a mechanical exhaust ventilation system. One of the most common problems is insufficient replacement air. If fresh air valves are not installed, they should be added. Without dedicated valves, the exhaust system draws air through gaps and joints in the building structure, allowing harmful pollutants to enter the indoor environment. Fresh air should always be supplied in a controlled manner through fresh air valves. The best solution is to install the valves in exterior walls or wooden ventilation windows and equip them with high-quality air filters.
Uncontrolled Ventilation
Air is extracted from the building either naturally or mechanically, but the living rooms and bedrooms lack fresh air valves to provide replacement air. As a result, the building does not have a properly functioning ventilation system. Instead, replacement air enters the building through uncontrolled and unfiltered leakage paths, carrying dust, pollutants, and other contaminants into the indoor environment. Typical air leakage routes include gaps in the building envelope, openings around doors and windows, and service penetrations such as drainage and utility shafts.
When air is extracted mechanically without an adequate supply of replacement air, excessive negative pressure can develop inside the building. This is one of the most common causes of indoor air quality problems, as it draws contaminants from building structures and other unintended air leakage paths.
Mechanical Supply and Exhaust Ventilation
In a mechanical supply and exhaust ventilation system, both the supply air and the exhaust air are handled mechanically. The system may be apartment-specific, with the ventilation unit located inside the dwelling, or centralized, with the main ventilation equipment serving the entire building and typically located on the roof or in a dedicated plant room.
