EMF Rules of Thumb

EMF Rules of Thumb

Curious about general best practices for minimizing EMF exposure? This post is an excerpt from the Healthy Home Standard, and it includes many great EMF rules of thumb. This is part of a series about the Healthy Home Standard, and there will be another post on additional EMF best practices.

The following EMF rules of thumb are intended to reduce exposure to Magnetic Fields (EMF) and Radio Frequency (RF) Radiation. These low-EMF measures include how to locate the site location, recommended maximum allowable ambient levels of EMF and RF, and best practices for wiring a home to minimize exposure to EMF. As a Building Biologist I find these guidelines helpful for our pre-purchase clients selecting a suitable location, and also for our green building clients desiring to rewire and minimize exposure to EMF/RF.

EMF Rules of Thumb and Best Practices – Part 1 of 2

Building Location & Neighborhood Considerations for EMF:

  • Building more than a ½ mile from electric power transmission lines
  • Building more than 100 feet from Utility Substation
  • Building more than 25 feet from distribution system electrical transformer
  • Building more than 75 feet from overhead or 25 feet from buried electrical distribution lines
  • Building is in a neighborhood without wireless Broadband Internet service
  • Building is not in direct line of sight of any cell phone antenna

EMF/EMR Site Evaluation and Recommended Ambient Levels of EMF/RF:

  • Magnetic fields:  0.2 mG (20 nT) or less
  • Digital communication radiations: 10 µW/m2 or less at 10 ft above site elevation
EMF Rules of Thumb

Magnetic Field Allowable Levels

Utility Services and Magnetic Fields:

  • Cable TV, Phone, Electric power, water service entry points are within 10 feet of each other
  • Water utility pipe into house is plastic or if metal has 3 ft plastic section 10 feet from house
EMF Rules of Thumb

Plastic Pipe on Incoming Water Line to Minimize Stray Current from Neighborhood

  • Electrical meter located more than 10 ft away from bedrooms, family room, HUR
  • Cable TV sheathing, phone cable sheathing bonded to electrical system within 10 feet of entry point

Electrical System Installation for Low EMF and RF (part 1 of 2):

  • Main Electrical Panel (MEP) & sub panel is more than 10 ft away bedrooms, family room, High Use Rooms (HUR)
  • Supply cable from MEP to a sub-panel does not cross beneath or above a bedroom or HUR
  • Electric panel wire lay out minimizes production of magnetic fields
EMF Rules of Thumb

Electrical Panel Wired to Minimize Magnetic Fields – Compliments of Karl Riley’s book, Tracing EMFs in Building Wiring

  • The electric panel design provides a neutral buss running the full length of each circuit  breaker column
  • If metal water pipes are used, the only bond to metallic water piping is at the MEP regardless of the number of sub panels
  • MEP and sub panel are mounted to wood. On concrete surfaces Panel is on ¾” plywood.  No panel mounting screws can penetrate the plywood into concrete.
  • The only bond between neutral & ground buses is in the MEP where the main breaker is located
  • Neutrals from multiple branch circuits meeting in a J-box are kept separate (no ganging of neutrals from different branch circuits)
EMF Rules of Thumb

Common Wiring Error Leading to Elevated Magnetic Fields – Building Biologists Can Find Such Errors in Existing or New Buildings

  • If there are three-way switches, three-way switch circuit hot and neutral are sourced from same location  & three wire travelers are used between switches
  • If there is low voltage lighting, the transformers for 12-volt can lights are not located below bedrooms

Many people are increasingly aware of the health threats from exposure to synthetic radiation. Over the past 100 years we’ve created an entirely new environment… surrounded by silent, odorless, invisible radiation. If you suffer from electrical hypersensitivity, or if you just are being pre-cautious, I hope these EMF rules of thumb and best practices are helpful.

8 Responses to “EMF Rules of Thumb”

  1. David Sasse says :

    I’d recommend an EMF survey of the house or at least the bedroom to measure what frequencies of EMF are high in that area. Shielding strategies differ based on the type and strength of EMF in a given area.

  2. Tony says :

    Hi, We have just installed two new air compressors and air handlers on the other side of the house away from where my wife sleeps it’s approximately 70 feet away. I used a dedicated line and put the thermostats in the garage away from her room. She is feeling sensitive to the new units. I thought that I planned this out perfectly but it’s a problem now for my wife. What can we do to minimize the EMF she is feeling from the compressors and/or the air handlers.

    Thank you,

  3. Anitra says :


    We bought our house about 5 years ago and just now noticed that our next door neighbors, who built a very expensive ‘environmentally conscious’ house and put what looks like the inverter and a large battery pack cabinet for their solar system outside their house about 10 ft from our garage. On top of our garage is our kids’ play room and their bedrooms are on the same side of the house as the play room. Sadly I just noticed this system which would have been in place when we moved in. I am concerned about the batteries and also about the EMF. I will be calling the neighbor to get more info on their system. We live in unincorporated Los Angeles north of Santa Monica and I would have thought that our house would have had to be taken into account with respect to building codes and electrical systems that our neighbors would have installed. I want to get someone out to my house to measure the EMF for sure. Any thoughts?


  4. Mike M says :

    One thing I’ve noticed over the past ~20 years is the use of unfiltered proportional type power controllers employed in heating devices. Old style thermostats used a simple mechanical switch to turn power on or off as activated by, for example, a bimetallic spring. Proportional controllers use an electronic switch that is turning on and off 120 times per second. It turns off when the AC voltage crosses zero then back on at some point after then and 1/120 seconds later depending on the amount of power needed to keep temperature at the set point.

    While the instantaneous turn “ON” event for a mechanical switch might be every few minutes, the electronic switch is doing it at 120 Hz. Harmonics are created (sum of decreasing increment of frequencies 1/3 + 1/5 +1/7 …). Radiative power of course increases by frequency so if the noise is not filtered – the higher harmonics are being broadcast by the heating element. Computer manufacturers were very good to start using things like ferro chokes on computer cables to stop high frequency from being broadcast but manufacturers of cheap heating devices couldn’t care less about the noise created by proportional heating controllers used for electric blankets, space heaters, water bed heaters, etc. I would advise further investigation of such products using proportional controllers to rate their EMF output.

  5. Alex Stadtner says :

    Hi Claudia,

    Thanks for writing with your question about EMF rules of thumb. When it comes to electrical panels most folks are concerned about magnetic fields. The magnetic fields generated from that particular panel are influeced by the following factors:
    1) wiring errors leading to stray current and unbalanced loads – this generally requires an electrician or handyman to troubleshoot
    2) how the panel is wired – are the hots and neutrals kept together as long as possible?
    3) what loads are on the panel. Usually, at night, there are the least loads on the electrical system. Assuming the home is properly wired, lower loads equal lower magnetic fields.

    So I cannot say with any certainty, but assuming no significant wiring errors and low loads at night, 4 feet should be sufficient to mitigate the small impact of magnetic fields coming from the panel. If, however, there are wiring errors or really large loads (pumps, freezers, electric heaters, etc.), then 4 feet might not be enough distance to maintain 0.0-1.0 milliGauss (mG) – the Building Biology goal for sleeping areas.

    You can always hire a healthy building inspector or buy a Gauss meter and measure the impact yourself.

    Be well,
    Alex & Healthy Building Science

  6. Claudia says :

    We are building a house. The electrical panel for the house has been installed in the garage. On the other side of the wall is the master bedroom and our bed is about 4 feet from the wall that the panel is on. Is this too close for safety? We are very concerned and are considering moving the panel but this will be quite expensive. Is there a solution, like using MyMetal sheeting behind the drywall on the bedroom side? Thank you so much for your input.

  7. Alex Stadtner says :

    Hi Leonard,

    Thanks for writing.

    Since hot air is more buoyant and naturally rises, most folks prefer to put radiant heaters in the floor or nearer the floor. Stratification can occur with heaters located high in the room, and you might consider alternative placement or at least fans to help “stir” the heat around. Wouldn’t want a hot head and shoulders and cold feet.

    From an electric heater we would probably focus only on low-frequency magnetic fields (measured in Tesla or milliGauss). Every heater is wired differently, so it’s impossible to say how your system will behave, but I’d suspect mag-fields from a properly wired radiant heater would drop off quickly and be nearly immeasurable at 3 feet away. Because of the large draw (high amperage) of such heaters, the supply cable or electrical cord would also be a point source for magnetic fields. So locating the heaters high on the wall may benefit someone who is sleeping, because the heater would be at least 5 feet away from their head. It would be good if the supply electrical cord was also at least 3 feet from where someone sleeps.

    Good luck – and call a Building Biology Environmental Consultant (BBEC) to test the system once it’s installed to make sure everything worked.


  8. Leonard Wasserman says :

    we are putting elec radiant heaters on an upper wall thru out our house. One of the heaters might go over our bed on an 8′ wall.
    Is this too close to our bed to be safe from emf.
    We could put a longer one on a side wall but this would give us one in the bedroom instead of 2.
    What is our safest bet?


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