EMF Electric Fields – Design Consulting

by / Friday, 24 October 2014 / Published in Green Building Consulting
Visualize Electric Fields

EMF Electric Fields

EMF design consulting for human-generated electrosmog should involve Radio Frequency (RF) radiation, dirty electricity (high-voltage transients), low-frequency magnetic fields, and low-frequency electric fields. These four elements can be wrapped under the umbrella term, “electromagnetic radiation,” or “EMR.” This blog focuses on basic practices to minimize low-frequency EMF electric fields during design and construction. This summary of electric field design guidelines is part 2 in a 4-part series.

AC EMF only exists in the “extremely low frequency” (ELF) and “low-frequency” (LF) portion of the ElectroMagnetic Spectrum. In this lower-frequency bandwidth we can distinguish between electric fields and magnetic fields.

ElectroMagnetic Spectrum EMF Electric Fields

ElectroMagnetic Spectrum EMF Electric Fields

Most EMF consultants in the US have been trained and certified through the International Institute of Building Biology & Ecology (IBE). They offer an entry-level 5-day seminar that is over the heads of most folks without any electrical engineering or electrical installation experience. They also offer more advanced trainings and focus on minimizing exposure around sleeping areas. Some of the following diagrams come from IBE. There are a few EMF experts in the US that have not gone through the Building Biology trainings.

Measuring EMF Electric Fields

Measuring EMF Electric Fields

Electric Fields – How to measure, and how much is too much?

When performing EMF surveys many “EMF consultants” only evaluate low-frequency magnetic fields.  When folks call and say they “have an EMF meter” and are measuring “high emf,” they generally have a Gauss meter and are measuring magnetic field field strength or magnetic flux. Most Building Biologists focus on Alternating Current (AC) electromagnetic fields, and in addition to magnetic fields we evaluate low-frequency electric fields. Building Biologists place low-frequency electric and magnetic fields under the umbrella term “electromagnetic fields,” or “EMF.”  In higher-frequency radiation the electric and magnetic fields cannot be measured separately, but in low-frequency radiation we can distinguish between electric and magnetic fields. They behave differently and are measured in different units.

Electric fields can easily be detected using a voltage detector. These nifty and affordable gadgets can tell you if you have a live wire, and more sensitive voltage detectors can also alert you to ambient electric fields if the field strength is high enough. EMF electric fields can also be directly measured and data logged with an ambient electric field meter, like the NFA1000, or measured indirectly with a specially calibrated multimeter via “Body Voltage Testing.” Body voltage testing originated in Germany and remains a suitable way to measure relative impacts of surrounding electric fields. Healthy Building Science uses both methods for EMF testing.

Electric Field Allowable Limits

Electric Field Allowable Limits

Ambient electric fields are measured in Volts per meter (V/m). Body voltage (indirect electric field) readings are in millivolts (mV). Building Biologists would prefer electric fields below 0.3 V/m or 10 mV in sleeping areas, but most accept anything up to 1.5 V/m or 100 mV as an acceptable target for sleeping areas. It is not uncommon to find initial readings well above these conservative targets. But don’t panic. Our industry groups will save us! Perhaps not surprisingly, the Building Biology targets for sleeping areas are WAY below the American Council of Governmental Industrial Hygienists (ACGIH) recommended exposure limits.

Building Biology Limits for Electric Fields

Building Biology Recommended Precautionary Limits for Electric Fields

What are Low-Frequency Electric Fields?

Electric fields are present whenever voltage is present. Voltage is “electrical potential,” and is independent of current flow (amperage).  EMF electric fields are present even if a device is not on. Electric fields emendate from any “live” electrical cord or energized wire. If one could visualize electric fields they would look more like lightening bolts, hair, or spaghetti – emanating from a live source – and,  for lack of a better term, “finding the path of least resistance to ground.” Because of this natural “attraction to ground,” it makes shielding electric fields relatively easy.

If you were to stand barefoot under a power line you would become like lightening rod for electric fields. Some artists have visually illustrated EMF electric fields by jamming tube lights into the earth beneath power lines. They will light up!

Visualize Electric Fields

Visualize Electric Fields

Electric fields are very unlike magnetic fields, which are only present when there is amperage (current flow). And magnetic fields are shaped more like donuts which get predictably less intense further from the source. Shielding magnetic fields is much more challenging.

Common Point Sources for EMF Electric Fields

  • lamp or clock radio cords
  • extension cords
  • in-wall wiring and outlets (plugs)
  • overhead light fixtures
  • computers and other electronics
  • power lines

Electric Field Design Consulting

When starting from scratch there are many easy opportunities to minimize electric field exposure. This is a sample of items we generally include in healthy wiring guidelines:

  • distance and wiring layout
  • MC Cable (metal clad wiring) around sleeping and high-use areas
  • demand Switch or “Kill” Switch
EMF Mitigation - Electric Fields

EMF Mitigation – Electric Fields

Electric Field Shielding – EMF Mitigation

Minimizing electric field exposure in existing buildings is much easier than mitigating magnetic fields. Most commercial buildings are wired using metal clad wiring so electric fields are shielded and relatively low. However, here’s a sampling of relatively easy ways to minimize electric field exposure in existing homes:

  • distance from live wires and appliances (unplug bedside light, extension cord, etc.). As long as a device is plugged in it has voltage (electric fields) to the switch.
  • shield between known sources (usually wiring) and high-use areas. There are special fabrics, meshes, and paints for the job. Electric field shielding must be grounded.
  • shield electric cords for appliances and extension cords.
  • install and automatic or remote control demand switches to turn off circuits around high-use areas.

For more information about electric field consulting please visit our other EMF blogs, check out our EMF testing page, or give us a ring.

8 Responses to “EMF Electric Fields – Design Consulting”

  1. Alex Stadtner says :

    That language is a bit confusing.
    Upon further consideration, the most common scenario for finding electric fields (voltage) downstream from the switch is when the switch or plug has been mis-wired so the hot and neutral are reversed. When this happens the voltage is allowed to go all the way through the fixture even when the switch is OFF.

    Clear as mud?

    If there are other wiring errors, such as a neutral-to-neutral or neutral-to-ground wiring error, than all bets are off and voltage may be present anywhere in the system – including but not limited to plumbing pipes, gas lines, phone/data cable, metallic studs, rebar, etc.

  2. J says :

    In the comment 5) above, you say that there should be no electric fields, etc. present between the switch and the light fixture when the switch is “OFF” unless it is an “N-N Interior New Current fault”. Could you please explain that further? We have high electric fields in some rooms, particularly near the ceiling (we have overhead lights) when our switch is “OFF”, like 2300mV on a top bunk. We have been turning the breaker off at night and only then does it decrease to 300mv (when the plugs and lights are off in that room). It is puzzling to our building biologist and our electrician.

  3. […] Inverter frequently asked questions. EMF Electric Fields – Design Consulting Best Practices. […]

  4. Mark Blossom says :

    Thank you David and Cameron for your very helpful comments raise additional questions.

    It is true that water vapor passing through a wall, into an interior space could condense on an impervious layer on the interior of the wall. It has been recommended to have a ventilated air space behind cabinets or a wall mirror. And I have taken pains to make my walls vapor permeable. So that eliminates solid metal flashing.

    What about using aluminum or steel window screen? Would standard insect mesh be adequate, or would a finer mesh be better? Extra fine window screen is available.

    How am I to confirm/mitigate that no Interior or Exterior N-G wiring faults are in the wiring? Would any Interior faults exist if standard wiring practices are followed? We are on the end of a rural power line, nearest neighbor is 1/4 mile away,

    Thanks again, I TRULY appreciate your help!

  5. Cameron says :

    Hi there Mark,

    Glad to hear that you are taking such care in the building of the house.

    Please let me elucidate a couple things here:
    1) Twisting the NM/Romex will only decrease the magnetic fields slightly. The reason that BX wiring produces less magnetic fields than NM/Romex is that the hot and neutral are closer than in NM/Romex wiring. NM/Romex wiring, even when twisted, have the conductors in parallel at roughly 3/16th” apart with the ground line between. In BX wiring the hot and neutral lines are roughly 1/16th” apart and the ground line is beside them, not between. Therefore, the magnetic cancellation is better for BX than NM/Romex by virtue of the proximity of the wires and secondarily by the twisting. Though, Twisting the NM/Romex will likely decrease the Dirty Electricity induced on the lines by RF radiation as the twists negate RF radiation induced ‘static’ on the line (This is the main reason CAT6 cables have their wires twisted in pairs.).
    2) NM/Romex is a good and cost-effective option when you are using energy efficient appliances and lights so the associated electrical current (creating the magnetic fields) is low. I wouldn’t be concerned with switching to BX if you’ve already put so much work into the NM/Romex type. When using energy-efficient lighting: use LEDs with low color temperature (Soft White, 2700K) would be the best option as the high color temperature versions creates alot of blue light which confuses the Circadian Rhythms of the body.
    3) Metal outlet covers and switch plates are preferred, especially in close proximity to the beds of the home.
    4) The metal flashing in strips over the NM/Romex wiring areas should work well. There are a couple things that must be taken into account, however. a) The metal flashing would need to be grounded to be able to shunt the electric fields to earth. b) You must confirm/mitigate that no N-G wiring faults (Interior Net Current) are present in the wiring as the metal flashing would create another current return path and would exacerbate the magnetic fields. c) You must confirm/mitigate Exterior Net Current sources, as the metal flashing can exacerbate the magnetic fields from this issue as well.
    5) There is no electric fields, magnetic fields or RF radiation present between the switch and light fixture when the switch is off (barring a N-N Interior Net Current fault, which you should already be checking for). So, no reason to use a DPST switch to cut off the neutral.
    6) I would suggest a 6″ (inch) wide metal flashing (centered on the wire, extending 3″ (inches) to each side of the wire). You might be able to do less, but 6″ should insure the electric fields are well-captured to be shunted to earth ground.
    7) Any metal is fine, Aluminum foil is good. Electric fields are easily conducted away so a very light gauge aluminum foil would work fine. No need to use heavy gauge material.
    8) You can connect the metal flashing to ground in multiple places, no problem, as long as: a) You confirm/mitigate so that no N-G wiring faults (Interior Net Current) are present in the house wiring. b) You confirm/mitigate Exterior Net Current sources.

    I will state that using metal foil is a bit risky as humidity can condense on it if it is on the cooler side of the exterior building envelope, and this condensation can create a mold condition over time. Please make 1) sure to have the metal foil or metal mesh on the interior drywall side of the exterior wall [this works in CA, but is problematic in other areas of the country], 2) the walls are properly insulated, 3) that interior sources of humidity (kitchen and bathrooms) are properly ventilated and used.

    Hope this helps!

    Cameron Freres
    Environmental Inspector, EMF Consultant

  6. David Sasse says :

    Shielding for magnetic fields is very difficult and often at best moderately effective. Twisting the wires will have an effect and should reduce MF. The flashing and other items may not shield MF. Electric fields can be shielded effectively with grounded metal. Metal clad wiring is best for this, but grounded mesh and Y-shield paint are also effective.
    David Sasse,
    Senior Environmental Inspector, CMI, CIE
    Council-Certified Microbial Investigator
    Council-Certified Indoor Environmentalist
    Board-awarded by the American Council for Accredited Certification
    Healthy Building Science
    Environmental Assessments & Green Building Consulting

  7. Mark Blossom says :

    I am building a two story house, and have completed the wiring on the
    upper level, using twisted Romex (approx. 6 turns per foot ). There
    are no separated neutrals. The breaker box is in the entry way, about 12′ from occupied areas.

    The cables are run horizontally through notches on the edges of the
    studs, then along studs to outlet boxes and switch boxes and into
    the attic for ceiling lights. All boxes are metal and will be

    Would metal outlet and switch plates be helpful?

    My idea is to apply metal flashing to the studs, over all of the
    cables, to provide shielding. The shielding would cover the cables on
    both sides of interior walls, and only on the inside of the exterior
    walls. The walls are still open, sheet rock would be applied over the

    It would be difficult to do this for the ceiling light fixtures,since
    the ceiling sheet rock is in place, but not impossible,since the attic insulation is not yet in.

    Is there any radiation from lighting circuits, between the switch
    and the light fixture when the switch is off? Would it be beneficial to cut both conductors
    with a DPST switch?

    Would sheet metal flashing applied to the surface of the studs be
    effective to shield the cables?

    How far should the sheet metal shielding extend beyond the wiring?

    Would there be a difference between galvanized steel or aluminum,
    and would the thickness gauge make a difference? Is aluminum foil
    useful for shielding?

    Should the shielding be connected to ground wires inside the metal boxes,
    or independently to the breaker box or to earth, and with what gauge wire?

    If this is effective shielding, it may be useful for retrofitting.

  8. […] Current (AC) electromagnetic fields, and in addition to magnetic fields we like to evaluate low-frequency electric fields, “dirty electricity,” and radio frequency radiation. This blog focuses […]

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