Ventilation systems are systems for controlled home ventilation, which have a multi-stage control system and which supply fresh outer air to living rooms.
Ventilation systems combine multiple functions: They ensure the required hygienic air exchange by replacing the exhaust air containing unpleasant smells and vapours with fresh air. Thus, ventilation heat losses are reduced particularly in reconstructions and new constructions. Ventilation systems reduce the moisture content and the CO2 and VOC content in the air. Volatile organic compounds, VOC in short, are chemical substances, which are e.g. released from building materials, adhesives and paints and also found in tobacco smoke and car exhausts and which pollute the indoor air. By using ventilation systems, the quality of air is improved and the moisture in the ambient air reduced. Thus, the formation of moulds is avoided and the structure of the building protected.
Besides, these systems offer an effective protection against smells and outside noise. The fresh air can also be purified by passing it through a pollen filter, so that the amount of pollens and allergens in the air is kept to a minimum. A ventilation system also restricts the multiplication of house dust mites, which are the most frequent causes of allergy indoors. Thanks to its versatile options, a tailor-made ventilation solution can be found for every individual requirement.

Ventilation is essential, but is always coupled with thermal loss, because the outer air must flow into the building. Only automatically operated ventilation systems are able to strike the right balance between fresh air supply and minimising the thermal loss. If the energy from the hot exhaust air is utilised for pre-heating the incoming cooler fresh air (heat recovery), the user will save maximum energy, maintain excellent air hygiene and enjoy maximum comfort. A significant advantage of such systems is using the exhaust heat in the outgoing air flow, this way up to 90 % of the ventilation heat losses can be recovered. Plate heat exchangers, liquid cooling systems, rotary heat exchangers and counter-current heat exchangers as well as exhaust air heat pumps can be used for an effective heat recovery. The requirements for modern ventilation systems with heat recovery are – ensuring the essential minimum air exchange, an efficient heat transfer of at least 75 %, electrical efficiency of less than 0.45 Wh/m3, availability of an exhaust air and fresh air filter for ensuring hygienic conditions, condensate drain and the overflow orifice between the fresh air and exhaust air areas.

In ventilation systems with heat recovery, the moisture in the exhaust air condenses and precipitates as condensed water. The condensate must be drained in an appropriate manner. Besides, the heat transfer devices must be protected against frost. The heat transfer device can be kept frost-free using different preheaters, e.g. air-to-brine heat exchanger or ground-air heat exchanger. This will help reduce the heat demand and thereby the consumption of precious fuel. Geothermal heat exchangers can maintain the right air temperature in summer and winter.

As regards mechanical ventilation systems, we can differentiate between decentralised and centralised ventilation systems.

Decentralised ventilation of individual rooms

Decentralised ventilation systems allow particularly flexible ventilation. For this, multiple devices are required per housing unit; an air distribution system is not necessary.

Exhaust air is sucked out with a central fan. The cold supply air flows into the outer wall through fresh air valves. The direction of flow starts from the living room, bedroom, children’s room and then leads into the humid rooms such as the kitchen, bathroom and WC. The fresh air that is supplied is heated with the existing heating systems.

Centralised ventilation systems function with an air distribution system. One fan directs the outer air into the building, whereas another fan sucks out the exhaust air from the rooms. A major part of the heat content in the exhaust air is transferred to the supply air by a heat exchanger. Up to 90 % of the heat from the exhaust air can be recovered and used for heating up the supply air. In this process, up to 50 % of the heat energy is saved.

An exhaust air system with service water heat pump is based on a ventilation system, which is combined with a heat pump for heating and providing hot water. In a centralised exhaust air system with service water heat pump, the air is routed through a heat pump. A refrigerant removes the thermal energy from the exhaust air current and evaporates in this process. Then, the refrigerant is compressed in a compressor and the stored thermal energy is released into the service water.

The total heat demand in a low-energy house is lesser than in a standard house. During autumn, the heating system is started late and during spring, it is switched off early. A great deal of importance is given to the ventilation system at the time of restructuring and new construction. Since the building shell is becoming more and more impermeably, the moisture cannot escape naturally. Ventilation systems not only ensure sufficient air exchange, but also reduce the energy consumption. A centralised ventilation system, coupled with a heat pump, can cover the heat demand of the entire house.

At the time of planning or modernisation of a building, building and house owners should gather information about modern and reliable ventilation systems at an early stage, so that energy-saving potentials are optimally utilised and the expenses minimised.

Besides saving energy and costs, the users of ventilation systems can enjoy more comfort: These systems offer optimum air quality and a comfortable indoor climate as well as excellent sound insulation. Another advantage of this system is all-round hygiene, reduction of pollutants and protection against pollens, mites and mould formation. Moreover, a professional ventilation system protects the building structure.