Ventilation Recommendation

Flo.R1der · February 9, 2026, 8:29pm

When ventilation actually makes sense?
This project provides a set of Home Assistant template blueprints that help you decide when ventilation actually makes sense.

Calculate absolute humidity based on existing sensor values
Estimate the potential humidity improvement
Get clear ventilation recommendation
Reduce indoor humidity effectively
Avoid unnecessary heat loss
For data-driven automations for smart and efficient airing decisions

1. Calculate the Absolute Humidity

This one is the most basic sensor. It simply calculates the absolute humidity based on Temperature (°C) and relative Humidity (%).

Can be used for statistics or as trigger for automation . The Input values are also available as attributes:

Setup

To set up this sensor, you need to do two things:

Import this Blueprint
Add one ore multiple sensors to your configuration.yaml (or template.yaml):

template:
  - use_blueprint:
      path: Flo-R1der/absolute-humidity.yaml
      input:
      temperature: #weather-station-or-forecast-or-room-temperature
      relative_humidity: #weather-station-or-forecast-or-room-humidity
  name: Absolute Humidity #outside-or-room-name
  unique_id: absolute_humidity_ #outside-or-room-name

Obviously you need to fill the correct entity-id for each input sensor. You can set up one sensor for each area you want to track (outside, living room, bedroom, bath, …).

Note: You can see the cocking for lunch and dinner, as well as the ventilation having an effect on both: absolute humidity and temperature. Also the absolute humidity outside is always lower then inside. This sensor makes both values comparable!

2. Calculate the Potential Humidity Improvement

This sensor compares the inside and outside Temperature (°C) and relative Humidity (%) to calculate the theoretical improvement.

Can be used for statistics or as trigger for automation . The Input values are also available as attributes:

This is done in three steps:

Calculates the outside absolute humidity
Calculates the theoretical humidity with the air from outside
Subtracts the calculate humidity from the measured humidity. Result = this sensor value

Setup

To set up this sensor, you need to do two things:

Import this Blueprint
Add one ore multiple sensors to your configuration.yaml (or template.yaml):

template:
  - use_blueprint:
      path: Flo-R1der/potential-humidity-improvement.yaml
      input:
        outside_temperature: #weather-station-or-forecast
        outside_humidity: #weather-station-or-forecast
        inside_temperature: #room-temperature
        inside_humidity: #room-humidity
    name: Potential Humidity Improvement #room-name
    unique_id: potential_humidity_improvement_ #room-name

Obviously you need to fill the correct entity-id for each input sensor. You can set up one sensor for each room you want to track (living room, bedroom, bath, …).

NOTE: When ventilation takes place, the potential improvement drops and rises again afterwards.

3. Ventilation Recommendation

This sensor compares the inside and outside Temperature (°C) and relative Humidity (%) to calculate the theoretical improvement and directly give an advice if ventilation is recommended or not.

Can be used as trigger for automation or as an traffic light system to inform users via UI or any external lights. The Input values are also available as attributes:

Setup

To set up this sensor, you need to do two things:

Import this Blueprint
Add one ore multiple sensors to your configuration.yaml (or template.yaml):

template:
  - use_blueprint:
      path: Flo-R1der/ventilation-recommendation.yaml
      input:
        outside_temperature: #weather-station-or-forecast
        outside_humidity: #weather-station-or-forecast
        inside_temperature: #room-temperature
        inside_humidity: #room-humidity
        minimum_improvement_value: 10 #change-if-required
        threshold_room_humidity: 50 #change-if-required
    name: Ventilation Recommendation #room-name
    unique_id: ventilation_recommendation_ #room-name

Obviously you need to fill the correct entity-id for each input sensor. Adjust the values for minimum_improvement_value and threshold_room_humidity if you like. You can set up one sensor for each room you want to track (living room, bedroom, bath, …).

Tip:
Instead of the fixed numbers in yaml for minimum_improvement_value and threshold_room_humidity, you can also use input_number helpers for more dynamic adjustment of those two input values.
minimum_improvement_value: "{{ states('input_number.min_ventilation_improvement')|int }}"
threshold_room_humidity: "{{ states('input_number.humidity_threshold')|int }}"

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