How to Check Your Home for EMF: A Building Biologist's Guide and Behind The Scenes Home Assessment Video
By Jonathan Farrar, Certified Building Biologist & CRMI, Founder of JF Healthy Homes
Be sure to watch as Jonathan Farrar investigates DefenderShield’s very own COO, Michelle Zofrea’s home during her personal EMF home inspection. See what he uncovers below!
When I walk into a client's home with my meters for the first time, there's almost always a moment of surprise. Sometimes it's mine, like finding a wiring error radiating a magnetic field through a child's bedroom that nobody could have guessed was there. More often, it's the client's. The source they were most worried about, like the cell tower down the road, barely registers, while the phone charging six inches from their pillow is the strongest exposure in the entire house.
That's the value of measuring rather than guessing. As a building biologist, my job is to assess homes the way you'd assess anything else that matters: with instruments, a methodical process, and an honest interpretation of what the numbers mean. But I also know that not everyone can hire a consultant, and I don't believe that should stop anyone from understanding their own home. The good news is that the fundamentals of EMF assessment and reduction are learnable, and many of the most effective changes cost little or nothing.
In this article, I'll walk you through how I test a home, along with following along in a behind-the-scenes video of a real EMF Home Assessment. I'll also go over the hotspots I check on every single assessment, the patterns I see over and over again, and the practical steps I recommend to nearly every client.
First, What Are We Actually Measuring?
"EMF" gets used as a catch-all term, but in building biology we break it into four distinct exposures, each measured with a different instrument and each reduced in a different way:
Radiofrequency (RF) radiation is the wireless signal from Wi-Fi routers, cell phones, smart meters, Bluetooth devices, baby monitors, cordless phones, and nearby cell antennas. This is what most people mean when they say "EMF," and it's the category that has grown the most dramatically in homes over the past fifteen years.
Magnetic fields come from current flowing through wires and appliances: think electrical panels, power lines, transformers, motors, and, importantly, wiring errors inside your walls. Magnetic fields pass through almost everything, including standard shielding materials, which is why the solutions look different.
Electric fields come from voltage on wiring and cords, even when nothing is switched on. These matter most where you spend long, stationary hours, primarily the bed, since your body is inches from energized wiring in the wall behind your headboard all night.
Dirty electricity refers to higher-frequency voltage transients riding along your home's wiring, generated by things like dimmer switches, solar inverters, and many modern electronics.
A quick note on the science, because I believe in being straight with people: regulatory bodies maintain that exposures below current safety limits haven't been proven harmful, while building biology guidelines (developed in Germany and used by consultants like me worldwide) take a precautionary approach, especially for sleeping areas. My philosophy is simple: where exposure can be reduced easily and cheaply, reduce it. You lose nothing by sleeping in a lower-EMF bedroom, and many of my clients tell me they wouldn't go back.
How I Test a Home
EMF Home Assessment Video Notes:
- How a Building Biologist approaches an EMF home assessment
- Smart meter RF and magnetic field measurements
- A live demonstration using DefenderShield® Signature Shielding Material
- Body voltage testing inside and outside the home
- Bedroom and office electrical field mapping
- How individual breakers can affect measurements
- Dirty electricity measurements and common household sources
- RF measurements near a Wi-Fi router
- Practical strategies Jonathan recommends for reducing unnecessary exposure
EMF Home Assessment Overview
Every assessment I do follows the same basic structure, and you can replicate a simplified version of it yourself.
Step One: Interview
Before I take a single reading, I ask where people spend their time. EMF assessment is really an exposure assessment. A high reading in a closet you open twice a year matters far less than a moderate reading at your pillow, your desk chair, or the couch where you spend three hours every evening. Map your home by hours occupied, not by square footage.
Step Two: RF Sweep
I walk the home with an RF meter, checking every room but paying special attention to sleeping areas. I measure with household devices on, then again with them off, which quickly separates what's coming from inside the home (which you control) from what's coming from outside (which you manage differently, often with shielding). For DIY purposes, a mid-range consumer RF meter in the $150 to $400 range is accurate enough to find your hotspots and confirm your fixes are working. A meter with an audio function is worth the small premium; hearing the distinctive pulse of Wi-Fi or a smart meter makes sources much easier to track down.
Step Three: Magnetic Fields
Using a gaussmeter, I check bed locations, desks, and seating areas, then trace any elevated readings to their source. Common culprits are the electrical panel, the smart meter or service entrance, unshielded transformers, and (the big one) wiring errors, which I'll come back to.
Step Four: Electric Fields and Dirty Electricity
These require more specialized measurement (body voltage testing is genuinely tricky to do correctly), so for DIY purposes I usually tell people to focus on RF and magnetic fields first and apply the low-cost electric field reductions I describe below regardless of measurement.
Step Five: Retest After EMF Reduction Changes
This is the step people skip, and it's the most important one. Measurement without follow-up is just data. Make a change, measure again, and confirm the number actually dropped.
The Hotspots I Check in Every Home
After hundreds of assessments, these are the locations I never skip, because they're where the problems almost always are:
The Nightstand
The single most common high exposure I find is a cell phone charging within arm's reach of a sleeping person, often with Wi-Fi, Bluetooth, and cellular all active. Wireless charging pads add their own field. This one spot, eight hours a night, frequently outweighs everything else in the house combined.
The Wi-Fi Router
Not just where it is, but what's near it. I regularly find routers in bedrooms, behind headboards, on desks where someone sits all day, or mounted on the other side of a wall from a crib.
The Bed Wall
I always check what's on the opposite side of the wall behind the headboard. Electrical panels, smart meters, refrigerators, and wall-mounted routers all show up here, and drywall does nothing to stop magnetic fields or meaningfully reduce RF.
Baby Monitors and Nurseries
Many video monitors transmit continuously at close range to an infant. This is one of the first things I check in any home with young children, and one of the easiest to fix with a voice-activated model, added distance, or a wired camera system. Read DefenderShield's blog on reducing EMF in a nursery for more tips and considerations.
The Home Office
Since so many people now spend eight-plus hours at a desk, I check laptop placement (especially laptops used on laps), wireless peripherals, and whether the desk sits near the panel or a bank of electronics.
The Smart Meter and Service Entrance
Utility smart meters transmit in strong, brief pulses. Whether it matters in your home depends entirely on what's on the other side of that wall. A garage, fine; a bed, worth addressing.
Cordless Phone Base Stations
Older DECT bases transmit continuously, 24 hours a day, whether or not a call is happening. I still find them in a surprising number of homes, and they're often one of the strongest RF sources present.
Dimmer Switches, LED Lighting, and Solar Inverters
Common culprits for dirty electricity, along with the switching power supplies in phone chargers and device adapters, which are now in nearly every room. And anything with a motor or transformer near seating and sleeping areas for magnetic fields.
Smart Devices, and Why Most Home RF Is Self-Imposed
When I inventory transmitters in a typical home today, the count usually lands somewhere between twenty and sixty. Fifteen years ago that number would have been two or three. Almost none of that growth came from the utility company or the tower down the road. It arrived in boxes we ordered ourselves.
Here's what I'm finding on assessments now:
Voice Assistants
Echo (Alexa), Nest, and HomePod units maintain a constant Wi-Fi connection and usually Bluetooth alongside it, whether or not anyone is talking to them. They're small and unobtrusive, which is exactly why they end up on kitchen counters, desks, and nightstands. I find them at bedsides constantly, often serving as an alarm clock that a $10 battery clock would handle just as well.
Mesh Wi-Fi Systems
This one deserves special attention, because it's the biggest change I've seen in home RF environments in the last several years. Households that used to have a single router now have three or four access points, all talking to each other continuously, and the nodes get placed precisely where coverage was weakest, which is often a back bedroom. I regularly measure more RF at a pillow in a mesh home than I used to measure in a living room standing next to the router.
Smart Appliances
Refrigerators, ranges, washers, dryers, and dishwashers now ship with Wi-Fi radios enabled by default. Many transmit even when the owner never connected them to anything. These sit in kitchens and laundry rooms that frequently share walls with bedrooms and seating areas.
Children's Audio Players
Toniebox, Yoto, and similar devices are wonderful in concept, and they're also connected devices that spend the night twelve inches from a small child's head. Most have an offline or airplane setting, and most work fine powered off between uses. This is one of the easiest changes a parent can make, and it's one I bring up gently on every assessment with young kids in the house, because nobody buys these with radios in mind.
Everything Else
Video doorbells (Ring and similar), security cameras, smart bulbs (every bulb is its own transmitter, and I've measured homes with two dozen), smart plugs, robot vacuums broadcasting from their dock, smart TVs, streaming sticks, wireless printers, thermostats, wearables, earbuds, and Bluetooth trackers in every drawer.
The honest takeaway from all of this is encouraging rather than alarming. The dominant RF exposure in the overwhelming majority of homes I test is generated inside the home, by equipment the occupants bought, plugged in, and can change their minds about at any time. No permits, no utility negotiation, no landlord approval, no product purchase required. Add the phone and the router to that list and you've accounted for most of what I measure at most locations where people actually spend time.
Distance is the Biggest Issue with Smart Devices
Because so many smart devices are designed to be always on, the question isn't usually whether you keep them, but where they live. Field strength drops off steeply with distance, so a speaker at ten feet is a fundamentally different exposure than the same speaker at two feet, and it does the same job either way.
My general guidance to clients:
Nothing that transmits belongs on a nightstand. Not the phone, not the voice assistant, not the audio player, not the tablet. Sleeping areas are where you're stationary for eight hours in a fixed position, which makes them the highest-value real estate in the house for reduction.
Check the other side of the bedroom wall, too. A mesh node in the hallway does not stop being a mesh node because there's drywall between it and your headboard.
Place connected devices in rooms where people pass through rather than linger. A hub in a utility room or an entryway is doing far less than the same hub on a desk or a bedside table.
Audit for the forgotten devices not serving any purpose. On most assessments I find at least one device transmitting around the clock for a feature the family stopped using a year ago. Unplugging it costs nothing and removes it from the environment permanently.
Then verify. Move the device, measure again, and confirm the number actually came down.
Patterns I See Over and Over
A few trends have held true across nearly every home I've assessed:
Your own devices usually dominate. People call me worried about the cell tower a half mile away, and in most (not all) cases, the exposures at the locations where they actually spend time are coming from equipment inside their own four walls. That's genuinely good news, because those are the sources you control completely and for free.
Distance is astonishingly powerful. Field strength falls off rapidly with distance from the source. Moving a router from your desk, across the room, or a phone from your nightstand to your dresser, routinely cuts the measured exposure by 90 percent or more. Distance is the cheapest shielding there is.
Focus your efforts on the bedroom. You spend a third of your life there, stationary, in one predictable spot. Every meaningful improvement plan I write starts with the bed.
Wiring errors are the hidden issue. In a meaningful share of the homes I test, I find elevated magnetic fields caused by code violations, typically neutrals from different circuits tied together, or current returning on water pipes. These fields don't respond to unplugging anything, they run through occupied rooms, and no consumer product fixes them. If you measure a persistent magnetic field you can't trace to an appliance, hire a licensed electrician (some, increasingly, know how to find these errors). It's a legitimate electrical fault worth correcting for its own sake.
Exposure is cumulative and mostly invisible. No single device seems like much. Twenty of them, layered in a small space around the clock, add up to an environment very different from the one our grandparents slept in.
How to Reduce EMF at Home: What I Actually Recommend
Here is the practical hierarchy I give clients, roughly in order of impact per dollar:
1. Fix the nightstand.
Charge your phone across the room or outside the bedroom, or put it in airplane mode overnight. If you need it for an alarm, airplane mode still works. This is free and it is, in most homes, the single biggest reduction available.
2. Put your router on a timer.
A $10 outlet timer that shuts the router off from bedtime to morning eliminates your largest continuous indoor RF source during the hours you're most stationary. Relocate the router away from bedrooms and desks while you're at it: central to the house, high up, and far from where people sit and sleep.
3. Hardwire what you can.
Ethernet to your work computer, TV, and streaming devices is faster, more secure, and eliminates those transmissions entirely. Then disable Wi-Fi and Bluetooth on the hardwired devices, because a wired device with its radios still on hasn't actually gained you anything. Wired keyboards, mice, and headsets finish the job at the desk.
4. Retire continuous transmitters.
Replace old cordless DECT phones with corded or eco-mode models, and choose voice-activated baby monitors. Move smart speakers and voice assistants out of bedrooms entirely, and switch children's audio players to their offline mode or power them down at night. Then audit the rest of your "smart" devices honestly: keep the ones you genuinely use, turn off the radios in appliances you never connected, and unplug the ones transmitting around the clock for a feature you'd forgotten you had.
5. Move the bed.
If the headboard shares a wall with the electrical panel, smart meter, refrigerator, or router, moving the bed even a few feet, or to the opposite wall, often does more than any product you could buy.
6. Reduce electric fields at the bed for free.
Unplug lamps, chargers, and power strips within about six feet of the bed at night (switching off isn't enough, since cords carry voltage while plugged in). Some clients go further and have an electrician install a demand switch, or simply flip the bedroom circuit breaker at night, which I test on-site to confirm it helps.
7. Address dirty electricity where it's easy.
Dimmer switches are the most common source I find, and replacing them with standard switches in rooms where you spend real hours is a straightforward fix. Poor quality LED bulbs are the second, and swapping a few is cheap enough to be worth trying.
Some people notice they feel different under certain lighting, and that's worth paying attention to even before you measure anything. Past those two changes, this is the category where measurement matters most and guesswork helps least, and it's a large part of why an on-site assessment exists.
8. What you can't fix, shield.
Shielding is real, physics-based, and effective when it's used correctly, and it's the right tool when the source isn't yours to turn off: a nearby cell antenna, a neighbor's router through a shared wall in an apartment, a smart meter the utility won't relocate.
Shielding fabrics, bed canopies, window films, and shielding paint can dramatically reduce RF from external sources, and shielded product cases and laptop pads, like those DefenderShield builds, address the close-range, on-body exposures that distance can't solve, such as a laptop that has to sit on your lap or a phone that has to ride in your pocket.
Two rules I insist on: shield after you've eliminated internal sources (shielding a room that contains an active router can make things worse by reflecting the signal inward), and verify with a meter that the shielding did what you expected.
One honest caveat, because you'll encounter these products the moment you start searching: stickers, pendants, and "harmonizers" that claim to neutralize EMF without blocking or distancing anything do not reduce measurable exposure. If a product works, a meter will show it. That's the standard I hold everything to, including the recommendations in this article.
The Bottom Line
You don't need a consultant to make your home meaningfully lower-EMF.
Start with your phone: put it in airplane mode overnight, and confirm that Bluetooth and Wi-Fi are actually off, because on most phones they stay on unless you switch them off separately. Better still, charge it outside the bedroom entirely. A phone in airplane mode on the nightstand is a real improvement, but a phone across the room or in another room is a better one, and that matters most at night when you're stationary next to it for eight hours. From there: put the router on a timer and move it, hardwire your desk, get the smart speakers and connected toys out of the bedrooms, and clear the plug-in clutter around your bed. Those changes are free or nearly free, and in most homes they address the majority of what I'd find with $5,000 worth of instruments.
Where a professional assessment earns its keep is in the things you can't easily see or fix yourself: wiring errors, dirty electricity, accurate body-voltage testing, external sources that need a properly designed shielding plan, and, maybe most importantly, the confidence of knowing your numbers instead of wondering. If you're in that situation, or you've made the easy changes and want to go further, that's exactly the work I do at JF Healthy Homes. And for the on-body and in-home shielding side, DefenderShield's lab-tested products are the ones I'm comfortable recommending because they hold up to exactly the kind of measurement I've described here.
Measure, change, measure again. That's the whole method, and it's one every homeowner can start using today. But always remember: TEST DON'T GUESS!!!
Jonathan Farrar is a building biologist, certified residential mold inspector and the founder of JF Healthy Homes, providing residential EMF assessments and healthy-home consulting. His battle with mold and Electromagnetic Hypersensitivity Syndrome (EHS) led him to his desire to empower families to identify hidden environmental stressors and build spaces that support true healing.
Learn More about Jonathan: https://www.jfhealthyhomes.com/