Do Motion Sensors Work Through Glass or Windows?

Wondering why an indoors motion sensor facing the outdoors from a window won’t detect anything? Read ahead as we explore why motion sensors don’t work through a window or glass. We’ve also got tips for you to make the motion sensor operate through glasses! 

Will Motion Sensors Work Through Glass?

Motion sensors don’t work through glass or windows. Modern glass is designed to block all infrared radiations through it – the technology powering most motion sensors, today. Since these windows insulate the radiations, the motion sensors don’t detect anything.

You might be wondering:

Why exactly does a window need to block infrared radiations?

Infrared radiation is a type of energy that we typically relate to as ‘heat’. Although it makes sense for your sensor to detect these radiations or heat, would you really like your home to be heated up all the time?

Windows help keep these radiations from the sun, unquestionably the largest source of heat for us, away from your home.

Getting back to the point:

Most motion detection systems today operate on the passive infrared (PIR) technology. This is why most motion sensors don’t work behind window sills or glasses.

Fret not, we’ve still got a few tricks up our sleeves to make this situation a tad bit better for you and your motion sensor. 

How Can I Make Motion Sensors Work Through Glass?

Using non-insulated glasses or a dual technology motion sensor can do the trick. Let’s jump straight into the details of how these methods make your sensor work behind a window:

Non-insulated Glasses

As discussed, 3-pane glasses are insulated to protect you from infrared waves. However, not all glasses are insulated to a degree that they’d be able to block infrared radiations. If you’d like to place your sensor behind a window, replacing the glass facing the sensor might be a sound option.

A small disadvantage of this option would be an unexpected change in energy. PIR sensors can read rapid changes in temperature. And if the window isn’t insulated, even a ray of light on a sunny day might trigger a false alarm. 

For optimal results, it’d be wise to place the motion sensor far away from windows or sources of heat.

Dual Technology Motion Sensor

PIR sensors aren’t the only motion detection systems in the security ecosystem. You’ve got dual-tech motion sensors which combine PIR with microwaves. Since microwaves are able to pass through solid objects, a window might not be an issue for the sensor to trigger.

Microwaves work by sending out pulses of microwaves to objects approaching the sensor. As they reflect back and reach the sensor, an alarm is triggered. However, a microwave sensor without PIR is perhaps the worst option and produces the most false alarms. 

Generally, both these technologies combine to work a dual-tech sensor. These systems require both motion sensors – PIR and microwave – to trigger at the same time. That is, the approaching object should reflect microwaves and also be a source of heat i.e., a human. But, it won’t trigger if only the PIR sensor was triggered via a bursting ray of light. 

To help these sensors run through glasses, you’d have to manually configure the sensor to operate on microwave modes. We’d suggest keeping this installation mode to a minimum to avoid false alarms.

Frequently Asked Questions on Motion Sensors Working Through Glasses

It’s hard to debug motion sensors and we understand. It’s why we’ve created a separate section for some of the frequently asked questions on motion sensors working through glasses. Let’s get to answering them now:

Do motion sensor light bulbs work through glass?

Motion sensor light bulbs won’t work through glass. Just as a motion sensor uses PIR to detect heat and trigger alarms, the light bulbs detect heat to power the bulb. If you’re using insulated glasses, the PIR radiations are blocked and the motion sensor doesn’t work.
It’s wise to place a motion sensor light bulb away from windows. Using a thin glass might help operate the sensor, but will further compromise your security. It’s best to use these bulbs on a porch or an area where they’re away from electrical interference or an active heat source.

Do hue motion sensors work through glass?

Most Hue motion sensors from Phillips don’t work through glass. This is primarily because these sensors operate on PIR radiations only. Insulated glasses can easily block these radiations which might cause your motion sensor to stop raising alarms. 
If you’d still like to place your motion sensor behind a glass, you can use older glasses or a different motion detection system. A pixel-based, microwave, or dual-tech motion sensor might work better in such cases. Similarly, a thin glass might let the IR radiations pass through.
Phillips does release outdoor motion sensors to connect with the Hue security system. If securing the motion sensor was your only concern, simply place the outdoor sensor outside and connect it to the Hue system. Detections go through the outdoor sensor and trigger alarms indoors.

Where is the best place to put a motion sensor?

Motion sensors operate much better if they’re placed in open-ended locations or corners. If the sensor has a good field of view, it’d be able to capture heat signals or changes more easily. Some of the best spots to place a motion sensor include: 
-Living Rooms
It wouldn’t be wise to place a motion sensor close to a heat source or behind insulated materials – a radiator might cause false alarms. However, motion sensors are still prone to false alarms and you might want to see which placement works well for you.

That’s a wrap on our article on motion sensors and their operation through glass. If you had already purchased a sensor and weren’t able to operate it, we hope this article helped. It might be a good idea to replace your sensor with a dual-mode sensor since they’re more likely to work through a glass or windowsill.