Demand-controlled ventilation for bathroom and bedroom

The problem

The ventilation unit sets its airflow from the air it extracts from the bathroom and the kitchen. The bedroom falls outside that. On the automatic setting, bedroom CO₂ rose to 1660 ppm at night. The target for a bedroom is below 800 ppm.

Bedroom CO₂ over one night on the automatic setting. The dashed line is the 800 ppm target, the green band the level at full power.

The solution

Home Assistant adjusts the unit based on two measurements:

• Bedroom: between 21:00 and 08:30 the ventilation switches to full power as soon as CO₂ goes above 800 ppm. It goes back to the automatic setting once CO₂ drops below 650 ppm, or in the morning when the sleep mat sees you have got up.
• Bathroom: after a shower the ventilation switches to full power until humidity is back to its normal level.

When neither room asks, the unit stays on its automatic setting.

The ventilation in Home Assistant: current setting, the temperature of the four airflows and the settings to pick yourself.

Left, the CO₂ meter in the bedroom. Right, the humidity sensor in the bathroom.

Result

• Bedroom CO₂: around 780 ppm instead of 1660 ppm.
• Bathroom: usually back to its normal humidity within 20 to 45 minutes.
• Full power only when it’s needed.

Built with Home Assistant and the standard Duco and Withings integrations.