Radio Science

Shielding by a house from the electric field of a power line


  • Ronold W. P. King


The claim that “a typical house shields about 90% of electric fields from outside” is examined when the house is located near a high-voltage 50- to 60-Hz transmission line. Calculated electric fields near such a line are used. In order to provide an accurate analysis, the usual house shape is approximated first by a hemisphere, then by a cylinder, and finally by a box-like shape on the conducting earth. It is shown that when actual materials and wall thicknesses are used, the electric field in the house is 99–100% of the incident field, so that there is no shielding. The electric field scattered into the house by an iron plumbing vent that extends from the ground to above the roof is found to be significant near the pipe. Scattered fields from plumbing and heating pipes and electric wiring are significant only within a meter or less. It is concluded that the superposition of incident and scattered fields from pipes and wires in the walls yields widely varying fields at different points but that the average exposure of persons living inside the house is not greatly reduced below exposure to the unmodified field of the power line.