Is the Mold Indicator correct?

Configuration
1

I am trying to monitor for the mold risk in a room.

The readings are currently:

Indoor Temp: 20c
Indoor Critical: 10.9c
Outdoor Temp: 7.4c
Humidity: 74%

(temp_indoor - temp_outdoor) / (temp_criticalpoint - temp_outdoor)
(20 - 7.4) / (10.9 - 7.4) = 3.6 calibration

Code I am using:

sensor:
  - platform: mold_indicator
    name: "Mould"
    indoor_temp_sensor: sensor.esphome_web_a581fb_temperature
    indoor_humidity_sensor: sensor.esphome_web_a581fb_humidity
    outdoor_temp_sensor: sensor.outside_temperature
    calibration_factor: 3.6

I have had this running for a day or so and it has just been stuck on 100% and hasn’t updated. How often should it poll this sensor to update the dashboard?

I have checked the logs:

2023-11-17 12:05:06.752 DEBUG (MainThread) [homeassistant.components.mold_indicator.sensor] Update state for sensor.lilly_mould
2023-11-17 12:05:06.753 DEBUG (MainThread) [homeassistant.components.mold_indicator.sensor] Dewpoint: 14.643631 °C
2023-11-17 12:05:06.753 DEBUG (MainThread) [homeassistant.components.mold_indicator.sensor] Estimated Critical Temperature: 10.733333 °C
2023-11-17 12:05:06.753 DEBUG (MainThread) [homeassistant.components.mold_indicator.sensor] Mold indicator humidity: 100
2

Never used that before (wasn’t even aware it existed), but 74% humidity is awfully high and it won’t take a very low outside temperature for that to start condensing on/inside an exterior wall.

3

74% humidity is where mould starts to grow, but it is very local as brookesben11 mention.
Your room temperature might be 20 degrees celsius, but if your window is poor isolated then it will be way colder there and once the air temperature drops, then the airs ability to carry water drops too. That means the humidity will rise too and you will have the conditions in that local area, butmaybe nowhere else in the room.
Best solution is to really conservative with the numbers and then also vent and heat.
Drawing cold air in from the outside and heat it is the best way to prevent mould.
Cole air can’t hold much water,but when you hear it it can hold more, which it has to get from the rest of the room.
You can keep venting and heating untill inside and outside humidity is the same, so an outdoor humidity sensor would be a good help.

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