Young family is looking for a property

Iris Graustein (Germany) has been looking for months a residential building in the suburban area. Finally, the broker reports with a financially appropriate offer. After inspecting the property Iris is in doubt. Because at a distance of ten meters leads a power line with two conductors to garden and house over. The utility company tells the family that it is a 20 kilovolt line. Contradictory information about magnetic fields near power lines can be found on the Internet. Even the called building biologist can not provide remote diagnosis. On the one hand, a much lower current flow is to be expected with the 20 kV line than with a large 380 kV line; On the other hand, the cables are very close to the house. The building biologist advises a long-term measurement over 24 hours to obtain certainty about the magnitude of the magnetic field in the apartment.

The measurement shows significant fluctuations

The result curve (see picture left) shows significant fluctuations during the measurement period. At midday and early evening, the magnetic field strength reaches the maximum value. From 11:00 pm until 5:00 am the level drops and reaches its lowest point at three o’clock. The trace shows that there is no significant current decrease at night. The real estate buyer should not always assume this classic case. If a large industrial company is located nearby, the power consumption at night could be particularly high. A similar scenario would arise with the energy turnaround when many households charge their electric vehicle with cheap nighttime electricity.

The standard of building biology measurement technology as a guideline

Building biologists assess the alternating magnetic fields from the power line according to the building biology standard (SBM-2015). The strict guideline values are explicitly valid for sleeping places. If necessary, further reference values can be consulted. The World Health Organization (WHO) has a precautionary value of 0.3 microtesla (μT). The TCO standard applies to the office workplace. It provides for the screen a guideline of 0.2 microtesla at a distance of 30 centimeters. When using the SBM-2015 for sleeping places, 0.02 to 0.1 microtesla are considered weak and 0.1 to 0.5 microtesla are very noticeable.

In fact, no shielding of magnetic fields next to the power line

The German Federal Office for Radiation Protection (BfS) writes on its website: “As with any type of radiation also applies to electric and magnetic fields: Basically, the field strengths decrease with the distance from the field sources. Electric fields are well shielded by common building materials and by the soil. Electric fields of overhead lines are therefore relevant only outdoors and only in the vicinity of overhead lines. Magnetic fields, on the other hand, are hardly attenuated and can penetrate buildings. Unlike electric fields, they can only be shielded with great effort.”
The German Federal Office for Radiation Protection warns against dubious shielding material in the field of magnetic field radiation: “So-called shielding mats against electrosmog are only very limited effectiveness. The products are usually mats made of a conductive textile, which can be grounded, for example, by means of a cable via the protective conductor of a socket or via a heating pipe. Low frequency magnetic fields can not be significantly shielded by such materials.

Iris Graustein: In doubt for the health

The results of the long-term measurement lie in the border area of the SBM-2015 between weak and strong conspicuousness. Therefore, the decision for the real estate buyer is not easy. At night, the magnetic field strength drops steadily to the lowest point to 0.1 microtesla. As mentioned above, future nighttime power usage through charging of electric vehicles could lead to higher values. If in doubt, Iris Graustein decides on health and looks for another property – away from power lines and transformer stations.

Link recommendation

Standard of building biology testing methods (SBM 2015)