Shielding & remediation

A continuous metal layer is a near-perfect RF barrier in principle — 40 dB and better — but seams, staples and penetrations mean installed performance is governed entirely by workmanship.

A conductive coating applied to walls and ceilings, quoted at 30–40 dB in the cellular bands; it must be bonded to a grounded conductive strip to also control low-frequency electric fields.

A relay in the consumer unit that de-energises a circuit when no load is drawing current and re-energises it when a switch is thrown, eliminating the bedroom AC electric field overnight.

The only material class that meaningfully attenuates power-frequency magnetic fields, and even then typically by a factor of two to five in a retrofit — which is why distance and source correction are preferred.

Woven or expanded metal used in wall build-ups, vents and window screens; attenuation depends on aperture size relative to wavelength, so a mesh that works at 900 MHz can leak badly at 5 GHz.

Curtains, bed canopies and clothing woven with silver or copper, typically quoted at 30–50 dB across the cellular and Wi-Fi bands — enough to remove 99.9% of incident power density when installed without gaps.

A capacitive filter that shunts high-frequency harmonics on a circuit; effects are circuit-specific, can shift harmonics rather than remove them, and can raise magnetic fields near the filter itself.

A metallised film bonded to glazing, typically quoted at 20–35 dB, and usually the highest-value single intervention because glass is the dominant entry path for outdoor RF.

Screened NYM-style cable or metal conduit with a grounded screen removes the AC electric field at source, and is the correct fix during construction or rewiring.

Replacing radios with cable is the only measure that removes an RF source instead of attenuating it, and it is usually cheaper than shielding the room the source sits in.