What Building Materials Are Best At Blocking RF Radiation?

Different building materials have different abilities to reduce the strength of cell phone and wi-fi signals coming into your home from outside (besides greater distance from the source).

Cellular and Wi-Fi signals are radio waves (RF), just at a higher frequency than AM and FM. Cellular frequencies are both lower (known as low-band 5G, 4G, LTE) as well as higher (mid-band and millimeter-wave 5G or high-band) than Wi-Fi signals. Wi-Fi is also an RF signal. It too can enter your home from a neighbor’s router or appliances.

The higher frequencies are more easily blocked or reduced than lower frequencies. The 5G technology decade (2018 to 2028) has promised much higher speeds than 4G LTE (2008 to 2018). Much of that increase in speed comes not just from the higher frequencies but from the increased modulation within any given frequency.

The health impact on our body from RF is much attributed to the strength of the RF signal. RF signals are measured in dB, or decibels. We track these decibels through what is called ‘gain’. Gain is measured on a logarithmic scale. For every +3dB that is added, the signal strength doubles. For every –3dB that is taken away, the signal strength is cut in half. Important math to be aware of: We do not divide the dB level by 3 to determine the field strength increase or reduction! For example, reducing the RF field by -9dB means it is half times half times half, that is, 1/8^th the radiation. Another way to compute is -n dB means it is reduced by a factor of 2ⁿ.  So, –32dB means a reduction by 1/1,630 times and -50dB means a reduction of 1/104,056 times!

What Building Materials Block RF Radiation?

Pretty much everything blocks or reduces RF signals to some degree. Even the air can do this although it has a minimal impact. As for building materials, here are 10 kinds of traditional materials used in the building of walls and how much they reduce RF radiation. These numbers are based on frequencies under 2.7 GHz or in cellular terms, low-band frequencies. The higher the frequency, the more that each material will disrupt the signal. I am not proposing that the material that blocks the most RF is best for every building. There are many factors to consider when building a healthy structure.

1. Metal: -32 dB to –50 dB

Materials made of metal have by far the biggest impact on reducing RF radiation. These materials might include aluminum, aluminum foil, lead, brass, copper, steel, or iron. Metal roofs, metal walls, and metal insulation will significantly reduce or completely block most of the RF signal strength.

If a room is completely surrounded by metal, it becomes like a Faraday shield. Faraday shields were named after Michael Faraday, a nineteenth century English scientist who contributed to the study of electromagnetism and electrochemistry. When completely shielding a room from RF it is important to pay close attention to door edges and ensure that there is good electrical contact between adjoining walls. There are window films that contain fine metal mesh that can be used to shield the windows. Using solid materials will generally attenuate RF fields over a broader range of frequencies than mesh will. Even aluminum foil can be used! (If you wrap your phone up in aluminum foil and call your number from another phone, it will go straight to voice mail!

The danger of completely shielding a room is this: The same surface that shields the other side from RF radiation will reflect that radiation. If you bring a cellphone that is turned on and is not turned off or in airplane mode (with all 4 antennas turned off), the signal produced from the cellphone will be at it’s highest level while trying to find a carrier signal and that radiation will reflect and bounce all over the inside of that room! A double issue! You won’t be able to make a call nor text and you will be exposed to extremely high levels of RF radiation.

2. Low-E and Tinted Glass: -24 dB to –40 dB

Low-E glass has become more common in buildings looking to reduce energy costs and lower their carbon footprint. Fortunately, that also causes those windows to significantly block RF frequencies. If your windows are tinted or low-e, they are not only protecting you but are probably saving you money on your energy bills.

3. Concrete: -10 dB to –20 dB

Next after metal for blocking RF radiation is concrete. It is probably the most common building material in the world. Concrete can also help to balance the climate inside a home because it is considered thick wall construction. There are some newer materials such as Autoclaved Aerated Concrete (AAC) that have high levels of hygroscopicity which is a material’s ability to absorb and release moisture from the environment. Not only will AAC have a major impact on preventing mold growth inside a home but it will help reduce RF coming from outside.

4. Brick and Stone: -8 dB to –28 dB

Brick and stone has been used in buildings for centuries. The walls are often built with a plaster or drywall finish which is not only visually pleasing but also serves to further reduce the RF exposure. In Florida where I live, it seems many of the homes are built out of concrete (or cinder block or brick) which is much better for reducing the possibility of mold in a home than lightweight materials such as wood and drywall.

5. Plaster : -8 dB to –16 dB, depending on thickness

Plaster is common in offices and homes. You will never find it on its own. It is generally used as an external and/or internal building material, probably also listed here. Yet it can help to reduce the RF radiation coming through a wall as well as prevent mold growth.

6. Solid Wood : -5 dB to –12 dB, depending on thickness and type

This is one of the oldest and most traditional kind of building material. Solid wood furnishings and hardwood floors, whether it is oak, maple, pine, mahogany, etc., can also help to block RF radiation.

7. Plywood : -4 dB to –6 dB depending on thickness

Plywood is common in interior construction, and, depending on thickness, can also help a little to reduce RF radiation through a wall (unfortunately it is also a great source of food for most types of mold).

8. Clear Glass : -4 dB per pane (~2.5 times reduction in signal strength)

Because building exteriors are often made out of one or more of the materials listed above, this is why sometimes you’re able to make calls when nearer a clear glass window. However, this number can add up fast – double pane glass will reduce by –8 dB or 6.35 times strength reduction.

9. Fiberglass Insulation (-2 dB)

Not too much of a reduction in signal strength in itself (~1.6 times). However, the insulation in your attic or walls is usually layered between 2 materials such as wallboard, etc.

10. Drywall (-2 dB)

Most interior walls are made of drywall. These provide limited protection from RF radiation.

Building Plans Are Already In Place? Other Ways to Shield From RF Radiation.

If your building plans are already in place or the home is already under construction, here is a link for building materials that can be used post construction to shield from RF radiation:

https://safelivingtechnologies.com/building-material-shielding/

Safe Living Technologies also sells many shielding solutions for other types of electromagnetic radiation.

Use code “HIC-5” at checkout to receive a discount.

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