Full heating comfort – low generation of noise

Kermi heat pumps operate exceedingly quietly. With their exceptionally effective sound and vibration absorption they generate scarcely more noise emission than a ticking alarm clock. As a result, these heating systems can in most cases be conveniently installed in industrial areas and outdoors without addtional construction measures. Operation as quiet as a whisper and night reduction mode ensure that the systems installed outdoors and indoors will not disturb the neighbours.


  • Particularly efficient noise insulation
  • Noise and vibration optimised design
  • No additional noise reducing measures requried
  • Night reduction mode available for even quieter operation of models installed outdoors
Kermi x-change heat pump extra quiet and Kermi x-buffer storage
Kermi x-change heat pump sound level infographic

The optimum outdoor installation

At an increasing distance from the sound source, sound scatters onto a larger surface and decreases at certain points as a result. However, sound reflections on obstacles like walls, for example, usually amplify the sound. Therefore, surrounding sound-reflecting surfaces have to be taken into account as regards sound propagation in each instance. Naturally, the particular material properties play a role as well, which, however, are not taken into account here.

This is what you should take into account:

  • The distance to the neighbouring property should be adequately large.
  • The air flow must not be impeded at any point.
  • The installation site should be sufficiently far enough removed from bedrooms and quiet rooms.
  • The air/water heat pump should be installed sheltered from the wind.
  • It is necessary to keep a minimum distance of 3 m from the exhaust opening to footpaths. At lesser distances ice formation may also result here at temperatures in plus degrees.
  • The exhaust opening must not be aligned to the building or directly to walls, terraces, and pathways toward another obstacle.
  • The distance to the property line should be at least 5 m. Please take the applicable limit values in the appendix “Sound Theory” into account.
  • Do not install the heat pump in recesses, interior courtyards, or the like. There is a risk here or an air short circuit.
  • The heat pump's installation area must not be surrounded by sound-reflecting surfaces (e.g. interior courtyard): the greater the sound-reflecting surfaces, the greater the generation of noise.
  • Keep minimum distances to exterior lightning protection systems according to DIN EN 62305, VDE 0185-305.
Kermi x-change dynamic AW E air/water heat pump with outdoor installation

Limit values for sound immissions for heat pumps installed outdoors

The technical instructions on noise serve to protect the community and the neighbourhood against harmful environmental effects due to noise. The technical instructions on noise are incorporated in the Federal Immission Control Act. The sound pressure level is determined in building areas centred 0.5 m in front of the open window of the room in the greatest need of protection. In building areas without rooms in need of protection or in unconstructed areas the sound pressure level is determined at the side most heavily affected, where the construction of a room in need of protection would be permitted in accordance with the building permit.

6:00 to 22:00
during the day
22:00 to 6:00
during the night
Industrial area 70 dB(A) 70 dB(A)
Commercial area 65 dB(A) 50 dB(A)
Central, village, mixed areas 60 dB(A) 45 dB(A)
Housing and small residential estate areas 55 dB(A) 40 dB(A)
Purely residential areas 50 dB(A) 35 dB(A)
Spa areas for hospitals and nursing facilities 45 dB(A) 35 dB(A)
Source: excerpt from the technical instructions on noise

Acoustic power level

The acoustic power level is a sound source specific, distance and direction independent factor that can only be determined by way of calculation. Devices can be compared against one another sonically on the basis of the acoustic power level. (source BWP sound handbook)

Sound pressure level

Sound pressure is understood in acoustics as the metrologically recordable level that is generated by a sound source at a particular distance. The sound pressure level measured is always subject to the distance to the sound source. (source BWP sound handbook)

The optimum indoor installation

The installation of an air heat pump inside the building is another option, involving the quietest installation option. Sound in the house usually spreads across floors and walls. It is necessary to take into account here that when connecting air ducts or pipeline connections a disruption of structure-borne noise is made sure of by the use of a flexible line connection. Potential narrowing flow channels in the air ducts and on the weather protection grate need to be prevented so that annoying flow noises at the air inlets and outlets do not result.

This is what you should take into account:

  • Solid walls in the installation room.
  • A heavy, tightly closing door.
  • The wall and ceiling ought possibly to be lined with a sound absorber.
  • Do not install a heat pump above rooms “in need of protection”.
  • Prevent thermal short circuit.
  • Prevention of narrowing flow channels on the weather protection grate.
Kermi x-change heat pump indoor installation

Prevention of structure-borne noise

  • Fit heat pump line connection by means of flexible pressure hoses included in the scope of delivery on the heating pipes.
  • Make wall breakthroughs for heating pipe lines possibly using ancillary protective conduit and elastic insulation.
  • Insulate wall breakthroughs for air duct lines (outlet and inlet side) deadening structure-borne noise.
  • Provide circumferential screed cut-out in floating screed with impact sound insulation at the installation site.


Our x-change dynamic AW I units installed indoors are already equipped with a triple vibration-free compressor. The EPP ventilation ducts can be installed directly without the added installation of a canvas duct connector over the EPP air adapter on the EPP housing.

Limit values for sound immissions for heat pumps installed indoors

When installing heat pumps in buildings, so-called “rooms in need of protection” (according to DIN 4109) need to be taken into account.

Rooms in need of protection

Immission values

Living space and bedroom during the day 35 dB(A)
Workrooms / office during the night 25 dB(A)
Classrooms / seminar rooms during the night 25 dB(A)
Children's rooms during the night 25 dB(A)

Noise calculator

The noise calculator enables the evaluation of noise immissions from air/water pumps with a heat output of a maximum of 35 kW according to the technical instructions on noise in daily operation at times of high sensitivity and during the night.

Kermi is a member of the

Kermi is a member of the Bundesverband Wärmepumpen e.V.