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Where to Place Window Alarm Sensors?

Window alarm sensors are a great tool homeowners can use to protect a property from break ins. Using magnets, the sensors are fitted to windows to alert homeowners or trigger an alarm when the window has been opened.

In this article, we’ll explain where to place window alarm sensors and what the pros and cons of using window alarm sensors are.

Do You Need Window Sensors On All Windows?

The more protection added to a property, the safer it’ll be. Therefore, there’s no limit to how many window sensors can be installed in a house. Some homeowners choose to install window sensors on all windows.

Generally, it’s most beneficial to add window sensors to accessible windows, like those on the ground floor.

The following windows benefit from sensors the most:

  • Downstairs windows
  • Windows at the front of the property
  • Upper-floor windows that can be reached via a tree, balcony, or deck
  • Single-glaze or disrepaired windows

Are Window Alarm Sensors Worth It?

Oftentimes, a window sensor alarm won’t be activated if the window is smashed or damaged without being opened. Plus, if an intruder is aware of the sensor, a magnet can deactivate it temporarily while the window is being opened.

AlfredCam on a glass table
AlfredCam by AlfredCamera.
break-in footage captured by AlfredCamera
Break-in footage captured by AlfredCamera.

Pros of Window Alarm Sensors

  • Scare off intruders that attempt to break in
  • Cover blind spots on security cameras
  • Act as a second line of defense

Cons of Window Alarm Sensors

  • Don’t prevent entry
  • Might not trigger if the window is smashed and not opened
  • Not immediately visible, so intruders may attempt to break in (by damaging windows) before realizing the sensor is installed
  • Can be hacked or disabled quickly (via a magnet or destroying it)
  • Homeowners are unable to tell remotely if the alarm is false or genuine

How Do Window Sensors Work?

Window sensors consist of two pieces, a magnet and a reed switch. These are installed on the window – one on the base and one on the moving part of the window.

When the window is closed, the two parts meet and an electrical circuit is created. If the circuit is broken by opening the window, an alarm is triggered.

Modern window alarm sensors sync to a smartphone app, so users are alerted when the window has been opened.

Here’s a summary of how window sensors work:

  1. Window alarm sensors come in two parts, a magnet and a reed switch.
  2. One part is connected to the moving section of the window.
  3. The other part is connected to the base (stationary) part of the window.
  4. An electrical circuit is created when the two magnets touch.
  5. When the window is opened, the circuit is broken, triggering the alarm.

Where is the Best Place to Put an Alarm Sensor?

Aside from ground floor windows, alarm sensors are best placed in the highest corner of a room facing the doorway. In this position, the sensor will pick up anyone who enters or leaves the room.

Make sure that nothing is obstructing the view when placing alarm sensors high up in a room, like lights or lampshade. 

The best places to put alarm sensors are:

  • In a hallway facing the front door
  • In a lounge facing the entrance
  • In a kitchen pointed towards the back door
  • In a utility room aimed at the side door
  • In the back corner of a garage facing the shutters

How Do Burglars Open Locked Windows?

Burglars use many techniques to break into locked or unlocked windows, including:

  • Smashing the window
  • Wrenching the window open using a crowbar
  • Slipping credit cards under the window to unlock it
  • Unlocking the window with a putty knife
  • Picking the lock

Breaking in via a locked window is harder than entering via an unlocked window, which is why homeowners should always keep windows locked when not in use.


Any home security measure increases the protection of your home and makes it a safer place for you and your family.

Window alarm sensors, especially modern devices that send notifications to the homeowner’s phone, are particularly helpful in alerting to the presence of an intruder.

However, installing security cameras is the best way to protect a property from break-ins. Window alarm sensors are beneficial as an extra security measure, rather than a standalone device.