Friday, November 13, 2015

Shielding of Electric Fields in a Residential Bedroom

E-fieldElectric fields are created by the voltage present in the electrical system, either the building wiring or power cords. A current flow is not necessary to create an electric field. This means a device does not have to be turned on to create an electric field. Electric fields can usually be easily eliminated or shielded. Electric field measurements complex as the investigator’s body affects and diverts the electric field which in turn influences the measurement results. Electric fields are measured in Volt per meter (V/m). The most common source for electric fields in residential buildings is the internal wiring system due to the use of unshielded, plastic sheeted Romex cables and unshielded power cords.

The electric (E) field emissions in this residential bedroom are originating from the electrical wiring system inside the wall cavity. The electrical conduit is running horizontally about 20 inches above the floor level connecting the electrical outlets in the room. An additional E-field source is the ungrounded/unshielded power cord for the reading light. Therefore, we need a two pronged approach. First, eliminating the E-field emissions from the walls, and secondly rewiring the light with a power cord with a shielded and grounded power cord.

The benchmark or target goal of this E field mitigation is E-field level of below or equal to 0.3V/m. The Building Biology Evaluation Guidelines for Sleeping Areas SBM-2015 and the Austrian Medical Association (ÖÄK) use the following criteria for bedrooms.

Baubiology Guideline

The first step is to unplug the reading light and to conduct E-field measurements at the bed site. The photo on the left shows the bedroom with the bed in place and the headboard wall. E-field measurements are conducted area at nine (9) different points at the top surface of the bed. The color graphic show the electric field levels detected in Volt/meter (V/m) at each location. The top represent the headboard area of the bed and the bottom the foot area.

Electric Fields Before

    Bedroom before shielding


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