Yes, mmWave presence sensors like the Aqara FP2 can technically detect through glass, since radar waves are not blocked by transparent materials in the same way as infrared.
BUT — it depends heavily on the type of glass:
- Standard window glass: Usually works fine. Radar waves pass through with only minimal loss, so presence detection generally still works.
- Double- or triple-glazed windows: These can reduce signal strength, especially if they have metallic coatings (like low-emissivity/low-E layers used for insulation or mirrors). That can block or reflect the radar signal — and then detection may become unreliable or even fail entirely.
- Also, radar sensors sometimes pick up reflections, which could cause unexpected results or false positives.
So while the answer is technically “yes”, the real-world performance will vary.
Best advice: Test it in your environment before relying on it for critical automations.
Always remember: “If your car is smarter than your home… you’re driving into the future while living in the past” 
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