Home ventilation - central or decentralized?

Both central and decentralized systems ensure a consistently good indoor climate. They also prevent mold growth and moisture damage by removing moisture. Heat recovery systems also utilize heat efficiently. This, on the one hand, saves homeowners on heating costs and, on the other, reduces the environmental impact. However, there are some differences between centralized and decentralized ventilation systems.

Design and function as important distinguishing features

When comparing centralized and decentralized ventilation systems, it’s important to distinguish between design and functionality. This is because both characteristics influence the area of ​​application and are therefore also important criteria for homeowners.

Building ventilation through an air distribution system

The central ventilation system consists of a ventilation unit with fans and a heat exchanger, along with a corresponding air distribution system. It ventilates the entire building. The ventilation unit draws fresh outside air and transfers it to the supply ventilation zones (living rooms, bedrooms, or children’s rooms) through a built-in heat exchanger and supply air ducts. At the same time, warm exhaust air from the exhaust zones (bathrooms, kitchens, or toilets) enters the ventilation unit through exhaust ducts and also passes through the heat exchanger. The heat from the exhaust air is transferred to the supply air, thereby being recovered. Cool exhaust air is expelled outside through the exhaust ducts.

Ventilation of individual rooms

The main difference between central and decentralized ventilation systems is that the latter typically lack ductwork. The units are mounted directly in the exterior walls of individual rooms. Like central systems, Viessmann decentralized ventilation systems are also equipped with a heat exchanger and can extract heat from exhaust air. There are two types of units.

Constant fan : units with a built-in cross-flow heat exchanger. Two fans operate continuously. One fan always supplies fresh outside air to the room, while the other removes exhaust air.

Pendulum fan : These systems use only one fan and one heat accumulator. The two units communicate with each other based on air exchange rates. One unit draws warm indoor air through the heat accumulator and expels it outside. The second unit draws fresh outdoor air and directs it into the room through the previously heated heat accumulator. After approximately 70 seconds, the process reverses.

The section on decentralized mechanical ventilation explains what is important when using such a system.

Moderate heating option as a distinctive feature

Unlike decentralized mechanical ventilation, the centralized option offers the option of moderate heating of the room. All Viessmann central ventilation units are equipped with an automatic summer bypass. It bypasses the heat exchanger during warm summer nights. This allows fresh night air to enter the room and cool it to some extent.

The characteristics of the building dictate the need for different areas of application

The choice of ventilation system installation—central or decentral—depends largely on the building’s characteristics. Due to its nearly invisible installation and the associated high design complexity, the central option is most often used in energy-efficient new buildings. Suitable locations for installation include utility rooms, basements, or well-insulated attics.

Since an air distribution system is not required, decentralized systems, on the other hand, can also be easily retrofitted. Depending on the system type, only a hole in the exterior wall is required. This feature makes decentralized ventilation systems very attractive for retrofitting both older and existing buildings. Furthermore, units can be installed specifically in individual rooms where, for example, humidity is a problem. However, decentralized units can also ventilate entire residential buildings. A wide range of possible applications and relatively simple installation are two decisive advantages of decentralized mechanical ventilation.

Central systems can also be upgraded

Depending on the building’s characteristics, a central mechanical ventilation system can also be upgraded. This typically requires lowering the ceiling. Ceiling-mounted or wall-mounted flat-panel ventilation units, such as the Vitovent 200-C or Vitovent 300-C , are designed to maintain a low overall height.