Ventilation in Home Assistant: smart control of heat recovery and room ventilators

Mechanical ventilation does not have to run in one mode around the clock.

If Home Assistant can access temperature, humidity, occupancy, indoor air quality and the state of other systems, it can adapt ventilation to the actual conditions in the home.

With decentralised single-room heat recovery units, several devices can also be controlled independently and treated as one ventilation system.

The main goal is not simply to raise or lower fan speed. Good control should consider what is happening across the entire home.

The available control depends on the device and its integration. Home Assistant may be able to:

• turn the unit on and off;
• change fan speed;
• select an operating mode;
• change airflow direction;
• read temperature, humidity and other parameters exposed by the device.

Not every feature is available on every heat recovery unit. Always check the entities and actions actually exposed by the integration.

Humidity can rise quickly after a shower, cooking or drying laundry. Home Assistant can temporarily boost ventilation and return to a quieter level after conditions improve.

A single fixed threshold should not drive the entire strategy. Comparison with another room, the rate of increase, the duration of high humidity and outdoor conditions can all provide useful context.

Relative humidity alone does not always show whether airing a room will actually help dry it. Warm and cold air with the same relative humidity can contain different amounts of water vapour.

When suitable data is available, compare both temperature and humidity indoors and outdoors. With a large temperature difference, absolute humidity or dew point may give a more accurate picture.

In summer, when it is warmer indoors than outside, increased airflow may help limit overheating if the equipment and conditions allow it.

In winter, the same decision can increase heating demand. Home Assistant can therefore consider indoor and outdoor temperature, time of day and heating state before increasing ventilation.

Ventilation and heating affect one another. If the system knows that a boiler, heat pump or another heat source is currently heating the home, it can treat intensive airing differently than when heating is inactive.

In a home with a thermal buffer, its temperature can provide extra context. A useful heat reserve may permit a short boost, while a low reserve may favour limiting unnecessary heat loss.

This is an example of interaction between systems, not a universal algorithm. More context is available in Home Assistant heating and energy costs.

A practical scenario is a timed ventilation boost lasting several minutes. The system can also consider whether heating is currently running.

In some installations it may be reasonable to reduce heating briefly during intensive airing and then resume normal operation. A boiler or heat pump must never be switched off by bypassing its own control logic, requirements or safety functions.

Reliable CO2 sensors can indicate the real need for air exchange. As the concentration rises, Home Assistant can increase ventilation and return to a lower rate after conditions improve.

Other indoor air quality data can be used in the same way when the sensors are reliable and correctly integrated. One universal CO2 threshold does not fit every room or pattern of use.

Ventilation can operate differently when nobody is home. Home Assistant may reduce airflow in an empty building and restore the normal mode when people return.

This should not mean switching ventilation off completely without checking the requirements of the building and equipment. Moisture, building materials and any required minimum airflow still matter.

At night, lower noise, reduced fan speed and stable bedroom conditions may take priority.

If CO2 or humidity rises, the system can boost ventilation temporarily and later return to a quieter mode. Home Assistant can combine time, occupancy and air quality instead of maintaining one fixed speed all night.

When the devices and integration support it, each unit can be controlled independently while several ventilators form one logical system.

All units may boost together, while selected rooms receive different settings according to temperature, humidity or occupancy.

A real control interface is shown on the Home Assistant projects page. This guide develops the logic beyond that short project description.

Some single-room heat recovery ventilators can change airflow direction or switch between supply and extract modes. If the specific equipment supports this, the function can be useful in summer.

Units on the cooler side of the building could supply air while units on the warmer side extract it, creating controlled cross-flow. This only makes sense when outdoor temperature and the other conditions genuinely support cooling.

Sun-facing rooms may heat up faster than shaded rooms. Humidity, CO2 and occupancy patterns can differ as well.

With suitable sensors, Home Assistant can control ventilation by zone and respond to differences between rooms.

The automation should not change speed or mode after every small sensor fluctuation. In practice it may need:

• hysteresis;
• a condition confirmation time;
• a minimum run time;
• a minimum interval between mode changes;
• a limit on the number of changes.

Exact values depend on the unit, room and comfort goals. The principles are explained further in Home Assistant automations.

When ventilation, heating and cooling operate independently, they can work against one another. One device may add heat while another removes it at a high rate.

Home Assistant can combine information from several systems to reduce such conflicts. Consumption and energy flow data can also be related to the methods described in Energy in Home Assistant.

A good ventilation strategy can consider several inputs at once:

• humidity;
• indoor and outdoor temperature;
• CO2;
• occupancy and time of day;
• heating or cooling operation;
• the temperature of a buffer tank or another thermal store;
• the current ventilation mode;
• differences between rooms.

The right decision comes from the context of the whole home, so there is no single ready-made algorithm for every installation.

First establish:

• whether the ventilation unit can be integrated with Home Assistant;
• which controls and sensors it exposes;
• whether multiple units can be controlled independently;
• whether continuous minimum ventilation is required;
• how ventilation relates to heating and cooling;
• which rooms have the greatest humidity, temperature or CO2 problem.

Only then should the automation and manual control rules be designed.

Home Assistant should only control ventilation within the limits intended by the manufacturer. Minimum airflow, frost protection, balanced supply and extract, unit synchronisation and other safeguards must not be bypassed.

Automation should also handle unavailable sensors and lost communication safely. The appropriate fallback mode depends on the installation.

If you have a central heat recovery system or several single-room units, I can assess the available control based on temperature, humidity, CO2, occupancy and heating operation.

I can also design Home Assistant logic for multiple ventilators, night mode, timed airing and summer scenarios.

This guide was verified on 13 August 2026 using the current Home Assistant documentation:

• Home Assistant
  Fan entities and available actions
• Home Assistant
  Automations
• Home Assistant
  Sensors, including relative and absolute humidity
• Home Assistant
  Statistics and humidity trend analysis
• Home Assistant
  Ventilation integration example with CO2 and humidity sensors