Shielding is the step people reach for first, and it should almost always be the last. Installed incorrectly, it can trap exposure inside a space or even increase it. This guide is a decision sequence, not a product list.
Step 1 — Identify Dominant Sources
Before anything else, establish where the exposure is actually coming from — and what kind of field it actually is. This matters more than it sounds: RF can be shielded with paint, film, or fabric; low-frequency magnetic fields generally can't be (see below).
- External cell tower
- Neighbour's devices
- Internal devices within your own home
- Smart meter
- Wiring faults
Step 2 — Attempt Non-Shielding Interventions First
- Device management (see the Router & Device Management Guide)
- Router relocation
- Sleep-zone optimisation
- Circuit isolation
- Behavioural changes
Most measurable exposure reduction happens at this step, at zero material cost.
Step 3 — Evaluate Whether Shielding Is Actually Needed
Shielding is justified when all of the following are true:
- External RF genuinely dominates the exposure profile
- Internal mitigation (Steps 1–2) has already been attempted and is insufficient
- Sleep-zone exposure remains high despite those changes
- The client is in a vulnerable group, or measured levels are substantially above precautionary thresholds
One important exception: if the dominant exposure is a low-frequency magnetic field — from a wiring fault, a nearby transformer, or shared building risers — shielding materials won't help at all. Magnetic fields pass straight through paint, foil, and fabric; the only real fix is correcting the source, usually via a licensed electrician (see the Low-Frequency Electrical Environments chapter).
Step 4 — Choose Appropriate Materials
- Window film
- Shielding paint
- Shielding fabric
- Conductive mesh
- Metal foils
Different materials attenuate different frequencies to different degrees — a paint that delivers 40–50 dB of attenuation against 2–6 GHz Wi-Fi and cellular signals may do almost nothing against a power-line magnetic field, and specialised materials like mu-metal handle magnetic fields but are impractical for RF (see the Shielding: Materials, Methods & Limitations chapter). Material choice should follow from what was actually measured in Step 1, not a generic recommendation.
Step 5 — Verify Installation
- Pre-testing (baseline measurement before installation)
- Post-testing (confirm the shielding actually reduced exposure where intended)
- Leakage identification (gaps, unshielded penetrations — a single unshielded window can compromise an otherwise well-executed shielded room)
- Grounding verification — an ungrounded shield doesn't just fail to help; it can absorb ambient EMR and re-radiate it back into the room, or become capacitively coupled to the body and actually increase exposure
Skipping Step 5 is the single most common reason shielding installations fail to deliver the expected result.