The Most Commonly Used Types of Ventilation Systems

Not all ventilation systems are the same. Some are more suitable for residential spaces, others for commercial facilities, while others are designed for installation in industrial plants. In addition, they offer different levels of intelligent control and heat recovery devices for energy savings. These are two very important factors for increasing energy efficiency.

They are also classified into single-airflow and double-airflow systems. In tertiary sector buildings, the use of the latter is mandatory, as they are more efficient.

Types of Ventilation Systems

Air Handling Units (AHUs)
These are configurable, box-shaped modular units. They are installed on the roofs of buildings, facilities, or industrial sites. This type of system is characterized by the continuous renewal of indoor air, which improves its quality, maintains temperature control to regulate HVAC, and monitors relative humidity. In these units, heat is recovered from the exhaust air, and because they are optimized for large buildings and typically use rotary heat exchangers, they are considered the most energy-efficient option.

Heat Recovery Units
These are generally more compact ventilation systems installed in suspended ceilings, which operate mechanically and in a controlled manner mainly to eliminate or reduce heat losses, as well as to renew the air. Like AHUs, they exchange heat between supply and exhaust air: they remove polluted air from the room and use its heat to temper the fresh air supplied from outside. Their design is more compact and simpler compared to AHUs; they use cross-flow heat exchangers, which are less efficient than rotary ones.

Rooftop
This is fully integrated equipment with direct expansion air conditioning and ventilation. It is installed on the roof, has a lightweight and compact design, and is easy to install. It is ideal for conditioning large volumes of air in a single space (large stores, supermarkets, etc.). It allows customization of the supply and return air configuration and is responsible for producing heating or cooling to treat the mixture of outdoor and recirculated air.

Components of a Ventilation System

• Filters. They are necessary to prevent dust, dirt, insects, and other particles from entering the room.

• Heat exchanger, acts as the most energy-efficient method of air treatment. Using the thermal gradient of conditioned indoor air, it cools the incoming outdoor air.

• Electric heaters or hot water coils, are useful in ventilation systems to prevent very cold air from entering indoor spaces.

• Cooling coils, perform the opposite function, cooling the incoming outdoor air to the required temperature.

• Humidifiers, may or may not be present. They control the humidity level in the environment — either increasing or decreasing it.

In addition to complying with current regulations, ventilation and exhaust systems can help earn points under sustainability certifications such as LEED, BREEAM, or WELL. These certifications assess health, sustainability, and energy efficiency in newly built or existing buildings. The conditions for the three most common certifications are outlined below:

Certification Requirements:

LEED
A method for monitoring the outdoor air supply flow rate is mandatory, as well as compliance with the UNE EN 15251 and RITE standards. Therefore, flow meters must be installed for measurements, with an accuracy better than 10% of the minimum design flow rate. There must also be an alarm that is triggered when the specified flow value deviates by more than 15%.

In addition, the ASHRAE 90.1-2010 standard, which is mandatory for LEED certification, requires ventilation systems in stairwells and elevator shafts to be equipped with motorized dampers that automatically close and open in the event of a fire.

All outdoor air intakes and exhaust systems must also be equipped with motorized dampers that automatically close when not in use.

For spaces with high occupancy (more than 40 people per 100 m², such as auditoriums), the system must operate on demand. For example, the unit should start when a high CO₂ concentration is detected based on sensor readings.

Other common point-earning aspects include: the presence of F7-class or higher filters in supply systems; or increasing the outdoor air flow by 30% compared to regulatory requirements to improve indoor air quality.

BREEAM
This certification is adapted to government regulations and does not contain mandatory requirements for ventilation systems. However, there are conditions that help achieve a higher score. For example, in the “Health and Wellbeing” category, the placement of air conditioning equipment, air intakes, and exhaust outlets at a distance of more than 10 meters from each other to prevent recirculation is evaluated. It is also required that air intakes be located at least 20 meters away from any sources of pollution.

As with LEED, the presence of air quality sensors (for example, CO₂ probes) that regulate the operation of the ventilation system in areas of the building exposed to high or variable occupancy is also assessed.

WELL
Finally, the WELL standard places great emphasis on air quality and analyzes the concentrations of pollutants such as carbon monoxide, ozone, volatile organic compounds, or particulate matter through on-site testing in accredited laboratories.

Therefore, the ventilation system and especially the filters used play a key role.

Although compliance with the limit values for these pollutants is mandatory, further improvement of these indicators can be decisive in obtaining a higher score under the WELL standard.

Compared to regulatory standards, increasing outdoor air flow rates or controlling the ventilation system using a carbon dioxide sensor that maintains indoor concentrations below specified quality limits are considered effective strategies and earn a significant number of points.

The use of filters of a higher class than required by the standard is considered important for optimization; this not only earns points under WELL, but also improves the capture of particles and pollutants.

In systems using air recirculation, it is recommended to clean the recirculated air using activated carbon filters (at least F8 class) or ultraviolet treatment.

The Importance of Commissioning

To verify whether these requirements are met, commissioning plays a very important role. It is a comprehensive process that acts as an external audit for systems that are already in operation or about to be commissioned.

It takes specific requirements into account and often makes it possible to identify easily correctable faults through testing and measurements, checking whether the elements are in good condition and demonstrate the expected performance.

Commissioning of the Ventilation System

Now that you know more about ventilation systems, their types, and components, we remind you that Caspian-klima offers you its services for inspecting the main engineering systems of buildings with the help of our professional teams. We confirm their compliance with the requirements of the mentioned sustainability certifications LEED, BREEAM, and WELL, as well as others.