EMF in new construction

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ActionDave

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Staff member
Our company is going to wire a custom home for a EMF sensitive client.
I've searched the forum and the web, but have found very little on actual construction techniques.

I already know about the Faraday Cage. Does anybody have any other helpful info pertaining to new construction?
 

__dan

Senior Member
EM sensitivity

EM sensitivity

I'll throw a few ideas at you. I take it at face value when someone says they are bothered by something or have experience. I believe it is true.

I would be interested and talk specifically to the individual affected. Ask what specifically is associated with discomfort or other phenomena. Are triggers solar flares, cosmic radiation, radio transmitters, specific electronic devices, wifi, cell phones, cell towers, HV transmission lines.

If they are aware, they are probably already using some techniques and countermeasures. Ask the customer what they know works and what they know to avoid.

When insulating, you can order / specify aluminum foil faced fiberglass batts, for the ceiling you can specify a rigid foam board layer, polyisocyanurate with foil both sides. Specify rebar in the footing and bond to it. Hardwire all network, CATV, and phones, no wifi, no radio transmitters.

There may be something else other them EM that also triggers a sensitivity reaction, materials, chemicals.
 

__dan

Senior Member
Windows

Windows

Windows. The standard Andersen 400 low E glass has a relatively new self cleaning feature using a TiO2 titanium dioxide coating. TiO2 is activated by UV solar radiation and breaks down dirt, mold, bug residue into basic components, mostly CO2 and H2O. I'm thinking the standard Andersen low E glass is pretty good at mitigating EM transmission into the house. I checked the website and they still list the self cleaning feature but pulled the TiO2 information. Something else to look at. Andersen has some higher end metal screens also, invisible stainless steel.

http://www.andersenwindows.com/servlet/Satellite/AW/AWProduct/awProductDetail/AWProduct/1139265007773/1102951372825?tab=1-2&tabname=Options & Accessories&tableftnav=Glass Options
 

dbuckley

Senior Member
I'd suggest first step is all metallic construction. Metallic panelboard(s), metallic conduit everywhere, all metal boxes, metallic fronted switches and receipticals. Everything enclosed by metallic so farady cage around the entire wiring system.

Also run a ground wires everywhere, and ideally (but I fear not code compliantly) seperate the grounds at the receptical so the ground pin of the receptical uses the ground wire, and there is no continuity between the ground pin and the metallic conduit and box. Otherwise you've got ground leakage flowing through the conduit and you've just destroyed the value of the farady shield, may as well use romex...
 

hardworkingstiff

Senior Member
I'd suggest first step is all metallic construction. Metallic panelboard(s), metallic conduit everywhere, all metal boxes, metallic fronted switches and receipticals. Everything enclosed by metallic so farady cage around the entire wiring system.
That was my 1st thought too.
Also run a ground wires everywhere, and ideally (but I fear not code compliantly) seperate the grounds at the receptical so the ground pin of the receptical uses the ground wire, and there is no continuity between the ground pin and the metallic conduit and box. Otherwise you've got ground leakage flowing through the conduit and you've just destroyed the value of the farady shield, may as well use romex...
If you used isolated ground receptacles, wouldn't that be code compliant (to keep the ground on the receptacle separate from the conduit system)? I don't now what you would be able to do about switches though.
 

Dennis Alwon

Moderator
Staff member
My house is done with NM cable and I have used a gaussmeter and have gotten no readings. There should be no reason that nm cable properly installed will cause emf's. EMF's are produced everywhere there is an electrical current. The amount that is noticeable at the floor level is important. You will get readings if you hold the meter right up to a bulb or refrigerator motor.

I am no expert by any stretch of the imagination............:)
 

winnie

Senior Member
My first question is: are you helping to design a home that mitigates _external_ emfs, or are you trying to provide electrical service that doesn't cause emfs?

IMHO the biggest part of this job will be the combination of educating the customer and learning from them. Educating them as to what are the different issues may need to be dealt with, and learning from them as to what they are actually sensitive to. Before you do any construction in their home, you will first need to find out what they are sensitive to, design to meet those needs, and then test your designs to see that they satisfy the customer. Since I think that this will be a bigger job than the actual installation, I think that you should bid your job to cover these experimentation costs.

The term 'EMF' has become a catch-phrase that covers a vast array of different (though fundamentally related) issues.

Saying that one is sensitive to 'EMF' is like saying one is sensitive to 'air pressure'. One might be prone to ear-ache due to sudden pressure changes, and not be able to fly in airplanes. One might have joint pain associated with the weather and smaller, slower pressure changes. Or one might simply _hate_ the music (air pressure waves) that the neighbor plays at all hours.

When you have separated charges (voltage), you get an electric field. You can have large electric fields with no current flow at all. When charges move, you have current flow and you get a magnetic field. You can have large magnetic fields with very little electric field. Add in the fact that we use AC power, and you get both alternating electric and magnetic fields. On top of this, a changing electric field can create a magnetic field, and vis-versa (this is how you get electromagnetic waves).

If you look up Karl Riley, you will find a wealth of information. In his experience, people who are sensitive to 'EMFs' in the home are predominantly sensitive to _magnetic_ fields.

A faraday cage shields electric fields only. It will block any locally generated electric fields, and will block electromagnetic waves of high enough frequency, but it cannot block locally generated magnetic fields. A faraday cage is useful if you are trying to eliminate externally produced electromagnetic waves, but won't help for local magnetic field sources. Using metallic wiring methods will help with electric fields generated by the wires, but won't help with magnetic fields.

Magnetic fields in the home are mostly solved simply by following code. This is because magnetic fields are caused by unbalanced current flows in the circuit conductors. As long as you have equal and opposite currents flowing in close proximity, the magnetic fields cancel out, and you get zero net outside of the cable. Bootleg neutrals, improper switch loops, multiple neutral-ground bonds, etc. will cause unbalanced currents and large magnetic fields. Proper wiring with NM cable will have minimal magnetic field; improper wiring with MC cable will produce lots of magnetic field.

A big exception to 'follow code and you will not have magnetic field problems' is associated with grounding the neutral. The neutral-ground bond system can create parallel paths and unbalanced current flows. You will want to carefully design the grounding electrode system and the neutral-ground bonding to prevent this. For example, houses that share a transformer and have common underground water piping will often have a large portion of their neutral current flowing on the water pipe. You may need to use non-metallic underground pipe to prevent this sort of parallel path.

-Jon
 

brian john

Senior Member
There is an engineering firm in our area that specializes in this, not cheap the cost of the design and shielding easily exceeds the cost of the EC's work.

If you design this base on ideas you pickup and she later feels the effects of what she considers your poor design are you prepared for the liability when her lawyer ask you "What is your experience in designing and installing EMF safe homes?"
 

Ragin Cajun

Senior Member
There is an engineering firm in our area that specializes in this, not cheap the cost of the design and shielding easily exceeds the cost of the EC's work.

If you design this base on ideas you pickup and she later feels the effects of what she considers your poor design are you prepared for the liability when her lawyer ask you "What is your experience in designing and installing EMF safe homes?"

Excellent point. Some projects simply are not worth the risk/liability. This sounds like one project where no mater what you do or how well - you lose!
 

brian john

Senior Member
Excellent point. Some projects simply are not worth the risk/liability. This sounds like one project where no mater what you do or how well - you lose!
The few cases I have been involved with all involve women, typically high strung, neurotic and very emotional about the issue at hand. I did not question their needs or motives I just did my job. In the EMF cases involving health concerns, I passed them on to the EMF specialists.
 

ActionDave

Moderator
Staff member
I did not question their needs or motives I just did my job. In the EMF cases involving health concerns, I passed them on to the EMF specialists.
That is what is going to happen in this case. There is an architect, double e, and a general contractor involved before we even start.

We are staying away from any design. But I am both interested from a physics/electrical theory standpoint and want the project to be a success.
 

__dan

Senior Member
tin foil

tin foil

Tin foil will shield for everything that is an "electric field" and for much low energy particle radiation, alpha and beta, the charged helium nucleus, stray electrons, low energy solar radiation, and cell towers. For very high energy EM above the high ultraviolet, xrays and gamma are very penetrating, you could be talking about lead plus concrete, if you have a source you need to shield from. Xrays, gamma, and neutron radiation are ionizing, very different animal from non ionizing EM.

Magnetic fields are penetrating, permeability. Similarly, first you need a source, high current carrying equipment, before you have a shielding problem. Field strength drops rapidly with distance, unless you are in the magnetic field path, then intensity does not drop with distance. Tin foil will have some induced eddy current shielding for stray magnetic field. It provides a path other than through the air and through the customer, the eddy current makes a counter emf. Iron is preferred by magnetic fields for path, magnetic field density is ~ 1000 x air in iron. Magnetic fields will penetrate but they will be countered in conductive materials by induced counter emf and in the presence of iron will take the path of least impedance, through the iron. Magnetic flux is trying to close the loop from north to south pole.

In a residence, I would expect no source of strong magnetic fields like from high current power distribution. Similarly very high energy cosmic radiation, ionizing radiation, nuclear radiation do happen but are low probability of occurance. An EMF survey is a likely start but could be likely inconclusive, you could find nothing to shield from, does not mean shielding is ineffective.

Liability should be a piece of cake on this one. Offer mitigating recommendations and exclude health performance guarantees, exclude "full satisfaction" guarantees, exclude "personal satisfaction" guarantees. Offer simply to warranty the work as customary in the industry and have the customer preapprove the work plan. Foil faced insulation is standard commercial grade material, nonstock but easily available, and inexpensive as an adder. I have the foil faced foam board in my ceilings and it's very difficult to tune in FM and TV signals from inside the house.. The antenna is inside the attic above the foil and gets everything.

No shielding will cover everything, the sources will be inside the house, appliances and devices. These will have to be eliminated or mitigated also.

Ask the power company for a single dedicated transformer for the service if available. As already noted if the service transformer and the water line are shared, there will be multiple neutral to GEC connections and shared neutral current on the water line and ground paths. If that is the case install an isolating dielectric fitting on the incoming water line and bond on the customer side. Consider not connecting to the utility water line as a GEC, if it is acting as, arranged as, a shared neutral conductor. Use a rebar in the footing GEC and ground rods. RGS for the service and EMT for anything over 25 amps is a good bet. Most important thing is to find and eliminate any unbalanced current flows. All circuits must balance exactly in current to result in zero net external magnetic field.
 
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brian john

Senior Member
T
Liability should be a piece of cake on this one. Offer mitigating recommendations and exclude health performance guarantees, exclude "full satisfaction" guarantees, exclude "personal satisfaction" guarantees.
Have you dealt with any of the folks that have fears like this either real or imagined regarding any health issues? Your suggestion while a good idea would never fly with them.
 

__dan

Senior Member
yes

yes

I met a woman who was really knocked back by solar flare radiation, she knew when the sun was active and had a hard time going outside. She could see auras and energy fields in color. I was very interested in this gift. I recall asking her about a tin foil umbrella, she said nothing worked, she could not turn it off. Long time ago.

Solar flare radiation is bullish for the stock market.

I met a woman who knew the energy fields of rocks. She said she could look at a person and know what rock was right for you. I assumed she meant colored rocks, crystals. Her sister could see auras.

I did wiring in the home of a woman with chemical sensitivity. Everything in the basement was wrapped in poly - plastic and duct tape.

I met a man who could communicate with animals, they would talk to him, tell him things.

All very especially nice people, people I enjoyed meeting. At no time did I ever consider this to be neurosis. I believe people have a wide range of very rare gifts.

The "perform to the personal satisfaction of" clause is simply bad contract language that is very commonly found in many contracts. It should always be crossed out and initialed. It's negotiable, never sign for that, especially with a neurotic customer. Similarly, he is selling wiring, not a health cure for an existing condition. Negotiate in good faith, do good work, and don't get screwed by the contract language, although many times the screwing is what the customer is looking for. I like to run the other way quickly when someone's idiocy or imagination is going to harm me.
 
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