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Freeze sensor recipe

A cold space where pipes run, a crawlspace, a garage, an attic or a cabinet on an outside wall, falling toward freezing.

A cold space where pipes run, a crawlspace, a garage, an attic or a cabinet on an outside wall, falling toward freezing. Beside the pipes in the space the furnace does not heat, away from a vent or a draft that would read colder than the pipe. In Home Assistant it shows up as a sensor, device class temperature. When the space stays below 40 F for 15 minutes, tell you to open the cabinets and let a faucet drip. Water freezes at 32 F. The recipe alerts at 40 F so there is time to act, and only after the space has stayed there for 15 minutes so one draft does not wake anyone. Both numbers are the cluster's own choice, shared with Leak and Freeze.

What it catches

A cold space where pipes run, a crawlspace, a garage, an attic or a cabinet on an outside wall, falling toward freezing.

Where it goes

Beside the pipes in the space the furnace does not heat, away from a vent or a draft that would read colder than the pipe.

How it shows up in Home Assistant

As a sensor, device class temperature. Battery sensors usually talk over a low-power mesh radio (Zigbee, Z-Wave or Thread) to a hub or a USB stick on the Home Assistant machine.

Why the recipe looks like this

Water freezes at 32 F. The recipe alerts at 40 F so there is time to act, and only after the space has stayed there for 15 minutes so one draft does not wake anyone. Both numbers are the cluster's own choice, shared with Leak and Freeze.

Write it for your sensor

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SensorRadioAutomationYou

Freeze sensor. When the space stays below 40 F for 15 minutes, tell you to open the cabinets and let a faucet drip.

F
minutes

automations.yaml

Download
- alias: "Freeze: below 40 F"
  mode: single
  triggers:
    - trigger: numeric_state
      entity_id: sensor.crawlspace_temperature
      below: 40
      for:
        minutes: 15
  actions:
    - action: notify.mobile_app_your_phone
      data:
        title: "Freeze risk"
        message: "{{ trigger.to_state.name }} is at {{ trigger.to_state.state }} degrees. Open the cabinet doors and let a faucet drip."

Rename the entities to your own, then paste. Syntax: Home Assistant: Automation triggers.

Sources

  1. Home Assistant: Sensor (device classes temperature, humidity, power, battery) Home Assistant
  2. Home Assistant: Numeric state trigger Home Assistant
  3. American Red Cross: Preventing and thawing frozen pipes American Red Cross
  4. Illinois Extension: Water pipes (disaster preparedness) University of Illinois Extension

Drafted with a language model on October 26, 2026 from the sources listed above. Every recipe on the page is written by the site's own code and parsed by a test. The editor samples pages after they publish; nothing here is advice from a licensed electrician or plumber.

Found an error? See Corrections.

Freeze sensor recipe | Sensor House