We put tinfoil on our windows to stop cellphone signals – and it didn’t work

Concern over the effects of electromagnetic fields is not new, and those fearful of the potential negative consequences of extended exposure have long used aluminium foil to try and mitigate the effects.

Using tinfoil hats is one method people have used to attempt to block radio waves and their electromagnetic radiation from reaching the brain.

The proliferation of cellular networks has raised similar concerns, with the International Agency for Research on Cancer (IARC), a specialised agency in the World Health Organisation, recently classifying radio frequency radiation as a possible human carcinogen.

It explained that the classification means that a causal association between radio frequency radiation and cancer is considered credible, but chance, bias or confounding can’t be ruled out with reasonable confidence.

Earlier this year, researchers from the Ramazzini Institute in Italy showed that rats exposed to cellular radiation developed brain and heart tumours.

However, despite exposing rats to a high dose of radiation for extended periods, the increase in occurrence of tumours was not statistically significant.

Researchers explained that findings such as these do indicate that further research into a possible link between cellphone signals and cancer is needed.

From tinfoil hats to tinfoil windows

Aside from potential cancer concerns, some people have reported that cellular signals have impacted their health in other ways — from headaches to mood swings.

At the end of 2016, residents of the Durban neighbourhood Glenmore said that they were suffering from short tempers, aggressive pets, and sleepless nights because of a new cellphone tower in the area.

Residents said they were “hoodwinked” into believing that the mast was put up for CCTV cameras, only to find that no cameras had been installed and MTN logos were on the tower instead.

One resident covered his bedroom windows in tinfoil, and reported that this improved the disrupted sleeping patterns he had been experiencing as a result of the tower.

Curiously, the city council said at the time that the tower was not active yet. The ill effects residents said they were feeling could therefore not be as a result of radio frequency radiation from the new tower.

This was not the first time residents of a neighbourhood complained about negative effects on their health, despite the fact that the tower they were complaining about was switched off.

To see if there is any merit to trying to block wireless signals by covering your windows in tinfoil, I repeated the experiment in my own home.


Before covering my room’s window with aluminium foil, I measured the strength of the signal my phone was receiving.

The phone was connected to the Telkom mobile network, which is well-suited for a test like this, as Telkom has not been assigned any low-frequency spectrum to use in its mobile network.

Lower radio frequency spectrum lets cellular network providers cover a larger area with a single tower, and offer greater indoor penetration.

While Vodacom, MTN, and Cell C have spectrum assignments in the 900MHz band, the lowest frequency spectrum Telkom has to work with is around double that frequency — in the 1,800MHz band.

For the duration of this test, my phone remained connected to Telkom’s LTE and LTE-Advanced network, which runs on the operator’s 1,800MHz and 2,300MHz spectrum assignments.

Signal strength was measured using the MyBroadband Speed Test app. It reports the strength of the signal as seen by the Android operating system, in dBm.

Measurements were taken with the door open, closed, and with foil on the window.

  • Door open: –110dBm to –106dBm
  • Door closed: –110dBm to –106dBm
  • Foil on window: –110dBm to –106dBm

There was no perceptible difference in signal strength after the window was covered in foil.

This is to be expected. Even if foil reflected or absorbed the radio frequency signals used by cellular networks, such signals do not seek openings to reach your phone.

It is unlikely that covering your windows in foil will have any significant effect on the strength of the signal in your home, as it can simply penetrate the walls that surround those windows.

To truly block out the signals from a cellphone tower, you would have to construct a Faraday shield or cage of some kind but, as we previously discovered, that is easier said than done.

Window covered in tinfoil

Foil over window

Now read: Tinfoil really does boost your Wi-Fi

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We put tinfoil on our windows to stop cellphone signals – and it didn’t work