Exhaust air heat pumps

Ventilation, which means totally hygienic inside air, is a basic requirement for living in a healthy house.

Ventilation – health aspects

Since the early 1980s there has been much discussion about Sick Building Syndrome (SBS). This refers to allergic disorders, and even illness symptoms, which frequently occur in certain buildings and rooms. This can lead to chronic illness, reducing the person’s ability to work and function in general. This, in turn, results not only in the individual losing his or her quality of life, but it also has a major detrimental impact on the economy and incurs huge costs. Basically, the following potential risks jeopardising people’s health are to be found inside buildings:

  • Toxic pollution caused by harmful chemical substances and dust.

  • Effects of noise, light, odours, dampness and climate.

  • Accumulation of microbes (bacteria, viruses, mould) in terms of infection risks.

  • Exposure to allergens.

These pollutants vary considerably according to the inside climate conditions, the state of ventilation and the design and use of the inside area. When energy-saving measures were introduced in the early 1970s, considerable efforts were made to improve the insulation used in the construction industry. This led to a reduction in the air exchange rate inside buildings. From a health and allergy perspective, the ideal air exchange rate would be 0.5 – 1.0, but in actual fact, air ex change rates in appropriately insulated houses are only between 0.3 and 0.5, which means that the polluted inside air is exchanged far too in-frequently. Based on the reasons given above, an increase in the incidence of complaints affecting the population is inevitable. This is where controlled domestic ventilation can have a particular role to play. Its purpose is to control temperature and dampness, while ensuring that the quality of the inside air is totally hygienic. The relevant technical guidelines and hygiene regulations are stipulated by DIN 1946.

Controlled domestic ventilation


Nowadays we spend around 90% of the time indoors. This undoubtedly places great demands on the climate inside. The inside climate is affected considerably by odours, harmful substances, noise and temperature. In every building there is a certain amount of basic ventilation, even if it is only produced by air coming through windows, doors, pipe ducts and walls. This type of ventilation, in older houses in particular, provides the necessary exchange of air. Ventilation is also provided through opening windows and doors, perhaps also when one or more windows are opened at an angle. Strong wind pressure and a difference in temperature between the interior and the exterior also increase the exchange of air. On the other hand, a weak wind or small temperature difference will reduce the required air exchange rate. This uncontrolled ventilation also accounts for a significant part of the heating costs and causes a considerable proportion of non-renewable energy resources to be wasted. Low-energy house In contrast to this, there is the low-energy house concept. A construction design is used in this type of house that prevents heat from escaping through use of effective thermal insulation. This also means that low-energy houses benefit the environment. But even with this construction design, there is still the problem that the required hourly air exchange rate of 0.5 – 1.0 is not achieved. To achieve the required air exchange rate either the windows would have to be opened, which would run counter to the whole low-energy house concept, or installation of a controlled domestic ventilation system with heat recovery would have to be considered.

Controlled domestic ventilation

Controlled domestic ventilation can be used in both low-energy and older houses. In low-energy houses the controlled ventilation system guarantees the required air exchange rate, even with the doors and windows closed. When older houses are renovated better thermal insulation could be used, along with fitting new windows to enable controlled domestic ventilation to achieve the necessary air exchange rate. These types of older building are often affected by street noise. A ventilation system would therefore be beneficial in these cases too. Controlled domestic ventilation with heat recovery When ventilation based on opening windows and controlled domestic ventilation without heat recovery are used, the energy from the inside air is not used. However the ventilation heat requirement accounts for a considerable part (40 – 50%) of the total heat requirement. In contrast to this, controlled domestic ventilation with heat recovery reuses the energy from the exhaust air. Not only that, the additional heat generated internally from lighting, people and domestic appliances is also utilised through heat recovery. Our FIGHTER exhaust air heat pumps facilitate heat recovery and supply the energy recovered from exhaust air for the domestic hot water and even the heating. Not only does energy recovery ensure a healthy and comfortable form of heating, it also produces considerable savings in terms of heat energy, along with CO2 emissions.

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