Last weekend I installed a misting system in my patio garden to help cool down the space during the hot summers in Madrid. The system uses a pressurized water line managed by a Zigbee solenoid valve. The valve is supported and controlled by my Home Assistant setup via Zigbee2MQTT.
Rather than keeping the misting always on (wasting water and risking over-saturation), I wanted a smart automation that:
- Activates misting only when I manually trigger it,
- Adapts to weather conditions like temperature, humidity, and wind,
- Automatically cycles on and off for as long as it’s active,
- Lets me cancel everything with a single press.
The result is a reusable Home Assistant blueprint that anyone can install and tweak for their own use.
Features of the Automation
- On-demand activation: You toggle the valve manually once to start the cycle.
- Fully autonomous operation: Once activated, the system opens the valve, mists for a calculated time, and starts a timer to repeat the cycle.
- Smart weather logic:
- High wind? Skip misting.
- Low humidity and high temperature? Mist longer.
- Mild conditions? Use minimal water.
- Safe manual override: Press the valve switch again to stop everything—no dangling timers.
How the Algorithm Works
The automation adapts two core behaviors dynamically:
1. Valve Open Duration
Base duration = 10 + (temperature - 25) * 2 - (humidity - 50) * 0.1Adjusted for wind:
- Wind > 20 km/h → skip misting (
duration = 0) - Wind 10–20 km/h → half misting time:
max(base * 0.5, 3) - Wind ≤ 10 km/h → full time:
max(base, min_duration_open)
The minimum open time is configurable. I set it to 15 seconds by default.
2. Cycle Interval Duration
Base interval = 120 - (temperature - 25) * 10 + (humidity - 50) * 2Adjusted for wind:
- Wind > 20 km/h →
9999s(effectively halts repetition) - Wind 10–20 km/h →
max(base * 1.5, 60) - Wind ≤ 10 km/h →
max(base, 30)
This gives enough flexibility for dry hot days to cycle more often and cool things down without wasting water.
Try It Yourself
You can import the blueprint into your Home Assistant setup using the link below:
You also can follow this thread in the Home Assistant forum.
Make sure you’ve set up the following:
- A
switchentity controlling your misting valve - Sensors for
temperature,humidity, andwind(e.g., via a weather integration or Zigbee device) - Two
input_booleans (for “active” and “cycle in progress” flags) - A
timerto control cycle repetition
Final Thoughts
This has been a fun and practical automation to build. It helps conserve water while keeping my outdoor space comfortable—even on the hottest days.
Let me know if you adapt or enhance it. Happy misting!