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Ventilation systems in comparison - the inVENTer-Check

Advantages and disadvantages of the ventilation systems at a glance

With the current Energy Saving Ordinance (EnEV), the federal government requires a minimum air exchange in living spaces in accordance with DIN 1946-6. Minimum air exchange is understood to mean the exchange of air in rooms and buildings in terms of the indoor climate and building protection. The air exchange limits increased substance concentrations and moisture in the buildings. The main reason for the regulation are building envelopes that are becoming more and more airtight (for example through insulated facades or triple-glazed windows), which serve to keep energy and heat losses as low as possible. Due to the sealed envelope, the necessary air exchange via natural joint ventilation (natural air flow through leaky windows and doors or other gaps and joints) is no longer given. Nevertheless, a way must be created to exchange stale room air and high humidity, as these promote the growth of mold, for example.

Classic window ventilation also reaches its limits here, as repeated, continuous push ventilation by the residents (even at night and during work days) becomes unreasonable. The required minimum air exchange can be guaranteed by various ventilation systems. A distinction must be made here between mechanical ventilation, which is supported by a fan, and so-called free ventilation, which works without a fan. In the case of mechanical ventilation systems, a distinction is made between central and decentralized ventilation in the supply and exhaust air systems category. Central ventilation systems consist of a single large device with an air duct system that enables centrally controlled living space ventilation. Decentralized ventilation systems are made up of several, specifically arranged ventilation devices in the outer walls, which enables individual ventilation of individual rooms or living areas.

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The devices require balanced air volume flows, which are usually implemented in pairs. The used warm room air is discharged via one of the devices. At the same time, fresh air is supplied from outside via the other device. After a certain time interval, the roles are then swapped so that there is a periodic change between exhaust and supply air mode. Free ventilation includes, for example, window rebate ventilation, which consists of simple ventilation slots that are inserted in the window frame. When choosing a ventilation option, we recommend well-thought-out planning at the beginning of the construction or renovation work. The advantages and disadvantages of ventilation systems will be considered below.

Vorteile beim Wohnen mit einer Lüftungsanlage

The ventilation systems in comparison

Controlled ventilation test

Installation & planning
Window rebate ventilation / window ventilation

1. Installation & assembly

How easily can the ventilation be installed?

+ flexible system
+ installation in sections
– Cabling and core hole drilling necessary

– all in one step
– complex pipe system
– The installation site must be available

+ no electrical connection
+ easy installation

2. Ventilation planning
What do I have to consider when planning my ventilation?

+ flexible installation location
+Air flows (AF) can be calculated

– restricted installation location
– Planning of complex pipe systems
+ AF predictable

– low air flows
– Air flow depending on other influences (e.g. wind)
+ / – depending on the number of windows

3. Eligibility
Which ventilation is promoted?

+ eligible e.g. KfW

+ eligible e.g. KfW

– not eligible

4. Required expertise
What technical support do I need?

– Electrical connection necessary
– Wiring of the devices

– several trades necessary
– Commissioning necessary

+ no expertise

5. Acquisition costs
What does the ventilation cost me?

– medium acquisition cost

– High acquisition costs

+ low acquisition costs

Window rebate ventilation / window ventilation

1. Energy efficiency (heat recovery)
Where can I save the most?

– low operating costs
+ high heat recovery

– high operating costs
+ high heat recovery

– 100% heat loss
+ No operating cost

2. Moisture recovery
Which ventilation maintains healthy air humidity?

+ is possible

– / + only possible with a special heat exchanger

– Indoor moisture is lost

3. Sound & noise development
How quiet is my ventilation?

– direct sound transmission
+ Soundproof accessories available

+ no direct sound transmission
– Telephony sound possible

– direct sound transmission
– no sound insulation

4. Frost protection
How does my ventilation react to frost?

+ Frost protection through reversing operation (regenerative)
+ Temperature monitoring possible

– / + complex frost protection (heating register / shutdown)
+ Temperature monitoring possible

– no frost protection (risk of mold from cooling down)

5. Sensor technology
How adaptable is my ventilation?

+ Sensors available
+ demand-based ventilation (CO2, humidity, VOC)

+ Sensors available
+ demand-based ventilation (CO2, humidity, VOC)

– no sensors
– no demand-driven ventilation

6. Areas of application: ventilation
Where can my ventilation be used?

+ continuance
+ New building

– continuance
+ New building

– fixed installation locations
(Cooling down of window soffit)
+ continuance
+ New building

Practical use
Window rebate ventilation / window ventilation

1. Filtering
What protection does the ventilation offer me against pollen, dust, odors and pollutants?

– diverse filters
– high filter classes
– Loss of air flow possible

– diverse filters
– high filter classes
– low loss of air flow

– no filters

2. Control options (automation)
How flexibly can my ventilation be controlled?

+ individual ventilation control
+ Define ventilation zones

+ individual ventilation control
– fixed room layout

– no control possible

3. Follow-up costs
How much does ongoing operations cost me?

+ hardly any operating costs

– high electricity costs

+ no operating cost

4. Cleaning & maintenance
How do I keep my ventilation clean?

+Maintenance by user possible
+ quick cleaning
+ Reminder function possible

+ individual ventilation control
– fixed room layout

– no control possible

Legend in the form of stars

very good (green)

good (yellow)

satisfactory (red)

The advantages and disadvantages of the ventilation systems summarized

Advantages and disadvantages of window rebate ventilation

Window rebate ventilation is inexpensive, easy to assemble and easy to clean. Without special filter systems or power lines, the simple ventilation slots in the window frame provide fresh air in the house and prevent mold. For window rebate ventilation, part of the seal is replaced by simple ventilation gaps in the window frame. In retrospect, tight windows are deliberately made leaky again.

In order for the window rebate ventilation to work, there must be an air flow between building fronts that are parallel to each other, which is rarely the case in practice. In addition, the principle with the openings in the window frame does not allow any heat recovery. The rooms are continuously cooled and mold growth can be encouraged at critical points, even if there is fundamentally an exchange of fresh air.

Vorteile und Nachteile von Fensterfalzlüftung
Vorteile und Nachteile einer zentralen Lüftung

Advantages and disadvantages of central ventilation systems

Fresh air is fed centrally into the living room, bedroom and children’s room via the air duct system and exhaust air is extracted from the kitchen, bathroom and toilet. The heat from the exhaust air is returned to the supply air in the heat exchanger. Air silencers in the pipe network suppress the running noise of the fan motors and the transmission of sound from room to room.

Particle filters remove dust, soot or pollen from the supply air. Central ventilation systems are quite expensive to purchase and are only suitable for new buildings. A subsequent installation in the old building is associated with great structural and financial effort. In addition, for hygienic reasons, the built-in air ducts have to be cleaned regularly by a specialist company, a (financial) expense that is often avoided in practice.

Advantages and disadvantages of decentralized ventilation systems

Decentralized ventilation systems in the house enable fresh air to be supplied with heat recovery: a ceramic heat accumulator inside absorbs the heat from the used room air and releases it into the fresh air. An important advantage of decentralized ventilation systems is their high energy efficiency, which is due on the one hand to the heat recovery and on the other hand to the low power consumption.

In addition, they are usually cheaper to buy and quick to install – both in new and old buildings. The user can easily carry out maintenance and cleaning himself. The only disadvantage of decentralized living space ventilation systems: Noise is generated by external and internal noise, but this can be absorbed with increasingly better sound insulation solutions on the market.

Dezentrale Lüftungsanlage Nachteile und Vorteile

Conclusion - the advantages of decentralized living space ventilation predominate

In comparison to window rebate ventilation and the central systems, decentralized living space ventilation scores with greater advantages. End users also know this: the demand for decentralized living space ventilation systems has risen sharply over the past few years. Nevertheless, it should be said: There is no blanket right or wrong. The decision for a ventilation solution always depends on the individual needs and the building project.

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