Aqara Presence Sensor FP2 — Does It Detect Through Glass?

Aqara Products
, , ,
1

Hi everyone :wave:

I’m testing the Aqara Presence Sensor FP2 and was wondering about its detection capabilities.

  • Can it detect motion/presence through glass (for example, if the sensor is placed behind a window or glass door)?
  • Does the detection accuracy drop compared to open space?
  • Has anyone tried different setups (e.g., glass thickness, tinted glass)?

It would be great to hear your experiences before I decide on a permanent installation. Thanks in advance! :pray:

4 Likes
2

In my experience, the sensor works very well with plexiglass shower enclosures, meaning it detects people even through the plexiglass.

However, it doesn’t like pure glass or mirrors. Placing an FP2 directly opposite a mirror or a window can trigger error messages. At least, that’s my experience.

In this case, the sensor wasn’t placed directly behind a pane of glass, but in a corner of the room with the window directly opposite. Angling the sensor significantly reduced the error messages.

1 Like
3

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” :red_car::house:

Check this out: Topics to remember – Bookmark and keep coming back!

2 Likes
4

Spot on and the triple layer is for sure a no go as then distance between the 3 layers varies to also cancel out sound waves so all for of waves would be heavily reduced.

1 Like