The Microwave Factor: EMF Rules of Thumb

Tuesday, May 14, 2013

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 rules of thumb for EMF 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

Utility Substation – 100 Foot EMF Rule of Thumb. 20 milliGauss shown on meter.

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

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

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

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)

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.

If you think that “green building” rating systems in the US should consider EMFs, please join us and sign thisPetition!