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Building with ICFs — will it lower the EMFs?

Kami Kline | Posted in General Questions on

HI,, I am building in SD with ICF construction for the basement and main floor. One poster suggested a metal roof to create a faraday cage. I am looking to keep the EMF’s low and would like all the input I can get. I didn’t realize I could use the rebar in the walls to my advantage. I am not sure about pricing on a metal roof. If I didn’t use a metal roof, do you have any other options?

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  1. GBA Editor
    Martin Holladay | | #1

    I find the evidence linking EMF exposure to human health problems to be unconvincing.

    That said, here is some advice you can find on the web. Like a lot of advice you get on the web, it's worth roughly what you pay for it.
    "Guidelines to reduce EMF exposure in a home:

    "Electric meters and subpanels are powerful EMF emitters. Place these on walls of spaces where occupants spend the least time. Both sides of the wall should be in low usage regions as EMF’s are not blocked by walls. An example of a suitable location would be an outside garage wall.

    "Keep heater/air conditioner blowers away from high usage areas of the house.

    "Use romex wire exclusively.

    "First floor fluorescent ceiling fixtures should not be located under second floor areas of high use at floor level such as a children’s playrooms.

    "Grounding by rods into the earth near the meter eliminates EMF’s emanating from water pipes due to electrical grounding

    "Locate the overhead secondary service wire or the underground secondary service trench in a little-used area of the yard.

    "Locate the wiring in the walls, floor, and ceiling away from high use areas of the home. If practical, run wires under the roof and drop them down through the walls to reach switches, outlets, etc.

    "Due to the number of appliances in a kitchen, it is an area of high EMF’s. However, it is an area of short-term exposure in most cases. Locate kitchen appliances on a wall away from high use areas that may adjoin the kitchen such as bedrooms or living rooms."

    More advice from a different website:

    "Reduce Electric Field Exposure

    "Best to use flexible steel MC (metal clad) or rigid (EMT) cable for all circuits to avoid AC electric field exposure

    "At least create an electrically clean sleeping environment by using MC cable for each circuit within 10-15 feet around, above, and below each bed and day use area (desk, easy chair)

    "Run remaining Romex circuits well away from bedrooms and daytime sitting areas

    "Always wire smoke detectors with MC cable."

  2. Kami Kline | | #2

    good advice Martin. I have a lot of this written down, but I hadn't read about the MC or EMT cable. EMF's are real to me. I can feel it and it makes me weak so I want to make sure I have my basis covered. Just curious what others have come up with.

  3. Expert Member
    Dana Dorsett | | #3

    To be a Faraday cage all conductive elements need to be electrically connected- how are you intending to connect the metal roof to the rebar?

    Powerline frequency EMFs are everywhere in a house that is wired for AC power, whether Romex or other. Twisting the conductive pairs will result in far lower powerline frequency EMF emissions from the current in the wiring and using a twisted cable rather than Romex would be a far better bet. Romex won't save much at all on EMF over other standard wiring, but I s'pose it's better than knob & tube.

    But the grounding structure and neutral connections (even from stray capacitance in plug loads) can defeat even foil-shielded twisted pairs.

    Magnetic ballasted fluorescent fixtures do not meet present-day efficiency standards, but produced fairly high line-frequency (and harmonics thereof) EMF. Electronically ballasted fluorescents (self-ballasted CFLs and LEDs too) produce a lot of higher frequency (10s of kilohertz to maybe 20 megahertz) emissions.

    Cathode ray tube displays (older non flat-screen TVs & computer monitors) had huge low frequency EMF issues. The power supplies in flat screen TVs produce a lot of higher frequency (100kHz-20MHz) emissions.

    All AC electric motors produce large low frequency EMFs.

    To lower EMF risk by very much you'd have to use only DC power, at a fixed voltage, and no plug loads that have internal power supplies that change that voltage, and nothing that has an electric motor (not even DC motors), and stay at least 1/4 mile from the nearest grid transformer or powerline. The notion that you can achieve any useful shielding with the building enclosure has no basis. Radio frequency shielded chamber buildings that are full Faraday cages that are lined with carbon loaded foam EMF absorbers used for emissions & immunity testing still have measurable line frequency EMF inside the buildings. Skin depth on very low frequency EMFs are large- effective shielding against line frequency requires extremely conductive metals (gold works, silver does too, but aluminum might be more affordable) that are thicker than 24 gauge roofing, or use of exotic alloys with extremely low magnetic reluctance (known in the trade as "mu-metal"). But as soon as you penetrate the Faraday cage with an electrical conductor (aka "antenna") all bets are off, be it wiring (powered or otherwise) or metal plumbing, etc.

    I've spent a significant part of my career as an electrical engineer chasing interference and emissions issues at high power and low, high frequency and low. (I even have a low frequency magnetic EMF meter in the desk drawer where I'm currently sitting, not that I use it often- otherwise it would be buried in the rest of clutter on top of my desk! :-) ) Most of the CRAP out there from websites warning about the risks and recommending remediation methods are just that, crap- utter nonsense with very little basis in physic beyond a 5th grade understanding of electricity & magnetism, and how to deal with it. (Take it from someone who has actually measured it, and designed electrical & electronic equipment as well enclosure designs with hard specified emissions limits on emissions across a very broad range of power & frequency.)

    I suppose if you live by candle light in an iron-mine cave you'd have pretty limited exposure to line frequency EMF, but if you want to live in the 21s century you'll have to live with some exposure. But the only well documented health risks are occupational exposures at very EXTREME levels (installing transformers in live power substations, are we?) many orders of magnitude higher than you would see an any residence. And even those people have many other factors in their lives of comparable or higher risk to health & life.

  4. David Meiland | | #4

    Kami, is this an issue where you live now, or in other people's homes? I'm curious about this. We have a friend who had a home built with minimizing EMF as one of the guiding principles. As I recall, she had trouble even finding a contractor or electrician who could grasp it.

    Dana, is there a useful EMF meter for residential inspection? I get asked about this periodically. The tool catalogs have many varieties. Any recommendations?

  5. Kami Kline | | #5

    Thank you Dana, I am just wanting to cover all basis. My home is ok as far as I know. I have tested with a tri-field meter. I just do basics. I don't have tv's plugged in my bedroom. No electronics plug in by my bed on both sides of the wall.
    So this is what really bothered me and I don't know if it was emf's. This summer when the air conditioner ran, I couldn't stand the feeling. It might have been the emf's or the vibrations. The wiring for the air conditioner went through the length of my LR and bedroom. So it would run for about 3 hours and really bother me so much so that if I wasn't planning on moving, I could move the darn thing to the other side of the house so the wiring doesn't run through the LR and Bedroom.
    I can't go to stores and last for long with the overhead fluorescent lights. They make me weak. I don't have any in my house and don't intend to.
    I basically want to make sure the wiring is done so to minimize EMF's.

  6. Jin Kazama | | #6

    Wow you seem to be affeced much by this ... :(

    I would gladly take the opportunity to build a house in a remote location , off the grid !!!!!!!!!!!!!!!!!!
    Solar power with DC electricity shouldn't bother you too much.

    Dana Dorsett: if he'd use DC to AC inverter type of thing, would it emit only when in use ?

    I believe it is possible with some attention to details to connect all rebars from the house, to each other by using regular steel wire ties .. i'm pretty sure that more than 90% of my house walls rebars are all connected together.

    You could use some sort of grounding cable connector to connect it to the metal roof if required,
    but i would have a serious dicussion with someone that has alot of knowledge about galvanic corrosion and such ... as the roof will see alot of water and friction, could also have some kind of electrical "soup" with the ICF wall rebars.

    I see metal roofs that look to be at least 100 years old around here so i'd take a sheet roof
    anytime before any disposable shingles anyway ..
    Just get informed before connecting it to the rebars so it actually lasts.

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