Woman opening a window in a bright living room

Ventilation control in the smart home: energy efficiency, health and value retention

Q: What should I pay particular attention to when planning a ventilation control system?

Key factors are demand-based sensing (humidity, temperature, CO₂), suitable controllers with scenarios, and smooth integration into your home. A good system ventilates only as long as needed, protects against moisture and mould, and remains easy to use.

Q: Who can help me plan and install a ventilation control system?

Qualified professionals in electrical installation, building automation or HVAC assess your needs, design a suitable concept and install the devices. In new builds, plan the system from the start; in existing homes, wireless retrofit solutions are often ideal.

Q: What should I consider when selecting suitable devices?

Sensors should detect humidity, temperature and ideally CO₂. Controllers need flexible scenarios and compatibility with heating and ventilation. Ventilation units must reliably act on measured values. Consider smart-home integration and expandability for the future.

Q: Which rooms benefit most from a ventilation control system?

Bathrooms and kitchens (high humidity peaks), bedrooms (night-time CO₂), living and working rooms (comfort), and basements (protection against condensation).

Q: Can I change or extend my ventilation system later on?

Yes. Many systems are modular. Start small—e.g., a humidity sensor in the bathroom—and add rooms, sensors or a central controller later. Wireless solutions enable expansions without major construction work.

Q: Can I implement my ventilation control with KNX, and what should I consider?

Yes. Sensors deliver humidity, temperature and CO₂ values via the KNX bus. The controller combines them with heating, cooling and shading for coordinated scenarios such as night cooling in summer or reducing heat loss in winter. Plan scenarios upfront, ensure component compatibility, and keep operation simple with clear status feedback.

Why ventilation control is becoming increasingly important

Modern homes are now so well insulated that hardly any fresh air enters naturally. While this saves heating energy, it also creates a problem: humidity and stale air remain trapped indoors. The consequences range from fogged-up windows to mould growth, which can damage both your health and your home.

A smart ventilation control system ensures that fresh air is supplied according to demand and predefined rules – automatically, without wasting energy and without you having to remember to open or close the windows. This helps you maintain comfort, healthy air and the long-term value of your property.

In this article, you’ll find out why proper ventilation matters, what risks can arise without control, and how smart home technology can support you in achieving intelligent, energy-efficient ventilation.

Ventilating correctly in winter

Why proper ventilation is so important

Especially during the heating season, manual ventilation can be quite a challenge. Keeping windows permanently tilted cools down the walls and wastes heating energy, while shock ventilation (briefly opening windows wide) is effective but often forgotten in everyday life. The result: insufficient air exchange, poor air quality and rising heating costs. An automatic ventilation control system takes care of this reliably – according to demand and without unnecessary heat loss.

For example, a family of four releases several litres of moisture into the indoor air every day – through breathing, showering, cooking or drying laundry. If this moisture isn’t removed, it condenses on cold surfaces, leading to damp patches and eventually mould.

A smart ventilation system responds before critical values are reached. It automatically removes excess humidity and ensures a constant flow of fresh, dry air – improving health, comfort and the protection of your home.

Learn more about the connection between air quality and wellbeing in our Smart Home Guide article 'Room air quality: measurement and control'.

Modern bathroom with open window (AI generated)

Practical implementation

Automatic ventilation with smart technology

An automatic ventilation control system doesn’t simply replace manual window opening – it takes things a step further. It ensures that air exchange happens as needed and energy-efficiently, without you having to think about it. For this to work reliably, three components need to interact seamlessly:

Sensors that measure humidity, temperature or CO2 levels.
Controllers with stored rules and scenarios that determine how the ventilation behaves in specific situations.
Motorised ventilation units or window controls that supply fresh air or extract stale air.

It’s only the interaction of these elements that makes a ventilation control system truly smart. This way, ventilation takes place automatically – before moisture can build up and create a risk of mould.

A practical example: after showering, humidity levels in the bathroom can quickly rise above 70%. Sensors detect this value and send it to the controller. The system then automatically activates the ventilation unit until the humidity returns to a healthy level. Afterwards, it switches off again, so no energy is wasted.
The result: fresh air, reduced risk of mould and a noticeably more pleasant indoor climate – all without any manual effort. In the next step, the question arises: Which technology can best support you in implementing this at home?

This is where the specialised solutions from Elsner Elektronik come in – providing comfortable and reliable control for a healthy, energy-efficient home.

Radio Ventilation Module

RF-VM

RF-VMis a motorised ventilation unit that connects wirelessly to a building control system, such as the WS1 or WS1000. Together with the building control system, it automatically regulates ventilation according to stored programmes or automatic scenarios.

RF-VM is particularly suitable for conservatories, glass façades or other glass structures. In these areas, sunlight and plants can quickly lead to high temperatures and humidity, which may cause condensation on the glass. In combination with the controller, RF-VM ensures the necessary air exchange without manual ventilation, keeping the indoor climate pleasant and protecting the building structure.

Thanks to its radio-based technology, the device is flexible for use in both new builds and modernisation projects. The RF-VM is now available again in a new, updated version.

To RF-VM

RF-VM motorised ventilation unit with radio control

Building control systems for the smart home

WS1 and WS1000

With the WS1 and WS1000 building control systems, ventilation, heating, cooling, shading and lighting can be connected to work together. This means your home operates as a coordinated system – for example, it cools down automatically at night or provides fresh air in winter without unnecessary heat loss.

The control units manage the coordination between systems, ensuring that they don’t work against each other – for instance, preventing windows from opening while the heating is running. With time programmes (e.g. regular ventilation at set times) and lock logics (e.g. heating automatically switches off during ventilation), the processes can be further optimised.

For you, this means less energy loss, more comfort and a noticeably healthier indoor climate.

To the building control systems

WS1 (top) and WS1000 (bottom) building control systems by Elsner Elektronik

Ventilation control devices available in our Online Shop

{ node.setAttribute('aria-selected', node.classList.contains('active')); });" >

Window control for natural ventilation

Arexa 230 V

The Arexa 230 V window control system automatically opens and closes your windows, guided by temperature, wind and rain sensors. The system consists of an outdoor weather station and an indoor control unit. The weather station measures the current conditions and transmits them wirelessly to the control unit. There, the data are analysed and the appropriate command is issued according to your settings: when it gets too warm, the window opens; in case of rain or strong wind, it closes again.

To allow the windows to move automatically, a motorised window drive is connected to the weather station. The Arexa control unit then determines when the window should open or close.

This creates natural air exchange without any manual action required. The opening width of the windows can be set individually – for example, half-open in summer or just a small gap in winter. Because the weather station and control unit communicate via radio, no additional wiring is needed. This makes Arexa ideal for retrofitting projects or for use in conservatories, glass façades and roof windows.

The result: fresh air, a pleasant indoor climate and reliable weather protection – all fully automatic.

To Arexa 230 V

Arexa radio window control with weather station and control unit for automatic window ventilation

CO2, humidity, dew point

Sensors for air quality and humidity

Sensors are the key data source of any smart ventilation system. They measure the most important indoor parameters such as temperature, humidity and CO₂ concentration, and send the data to the controller. There, thresholds and rules are stored: once these values are reached or exceeded, the ventilation starts automatically; when the readings return to the target range, it switches off again.

Cala KNX IL CO2 measures the CO₂ level in the indoor air (including temperature) and provides the key reference value for demand-based ventilation – ensuring fresh air whenever CO2 levels rise.
Cala KNX AQS/TH measures relative humidity and temperature, allowing the controller to start ventilation before excess moisture builds up.
Dew point sensors complement these readings by monitoring surface temperature in relation to humidity. They send a signal as soon as the dew point is reached – before condensation can form on windows or external walls.

This creates a reliable basis for ventilation control: the system activates at exactly the right time and runs only as long as needed – protecting both your health and the building structure.

To the sensors

Cala KNX IL CO2: Indicator Light Green/Yellow/Red and/or CO2 indicator light

Info

Ideal humidity levels at home

The right level of humidity is crucial for both health and the condition of your home. If it’s too high for a long time, the risk of mould increases. If it’s too low, your mucous membranes dry out, and the indoor climate feels uncomfortable.

The ideal range in living spaces is usually between 40 and 60 percent relative humidity – short-term fluctuations, for example after showering or cooking, are completely normal. Recommended values also depend on the room:

Bedroom: slightly drier, around 40–50%, for a restful sleep.
Living and working rooms: 40–60%, for comfort and concentration.
Kitchen: 50–60%, as cooking produces a lot of moisture.
Bathroom: temporarily 50–70%, but should be reduced quickly afterwards to prevent mould.
Children’s room: 40–55%, similar to the bedroom.
Cellar: 45–55%; in summer, ventilate only when the outside air is cool, otherwise condensation may form.

An automatic ventilation control system helps to keep these values stable – regardless of time of day or user behaviour.

For more details on how to prevent condensation, read our techincal article ‘Dew Point Monitoring and Ventilation Control’.

Conclusion

Why ventilation control is essential today

At first glance, ventilation might seem like a simple routine – open the window, let in some air, done. But modern construction methods show that this is no longer enough. Airtight building envelopes keep warmth inside, but they also prevent natural air exchange. This makes ventilation today a key interface between building physics, energy efficiency and health.

The key insight: proper ventilation is no longer a spontaneous everyday action – it’s a task that only technology can manage reliably. Sensors measure air quality and humidity, controllers apply stored rules, and motorised ventilation units carry them out automatically. The result is a system that prevents condensation and mould, reduces energy losses, and maintains a healthy indoor climate at all times.

For homeowners, this means that automatic ventilation control isn’t a luxury – it’s part of modern living quality. It protects your health, increases comfort and helps preserve the long-term value of your home.

FAQs

Frequently asked questions about ventilation control

What should I pay particular attention to when planning a ventilation control system?
A good ventilation system depends on several key factors working together:

Demand-based control: Make sure the sensors can measure humidity, temperature and CO₂. Only then will the system ventilate reliably instead of “on guesswork”.
Integration into everyday life: Check whether the control system suits your home. In new builds, wired systems can be planned in; for existing buildings, wireless solutions are often the better choice.
Energy efficiency: A good system ventilates only as long as necessary, avoiding unnecessary heat loss.
Protection against damage: The control system should respond to rising humidity early to prevent condensation and mould.
Comfort: Automatic ventilation should make life easier – not require constant adjustments.

This ensures your ventilation control not only provides fresh air but also saves energy and protects your home in the long term.

Who can help me plan and install a ventilation control system?
Installing an automatic ventilation system is a task for qualified professionals in the fields of electrical installation, building automation or HVAC technology. They can assess your building’s requirements, create a suitable concept and install the devices correctly.

For new builds, it’s worth including the ventilation control system in the planning from the start. In existing buildings, installers and system integrators are the right people to contact for retrofit solutions.

What should I consider when selecting suitable devices?
Make sure that the devices can measure and control according to demand:

Sensors should detect humidity, temperature and ideally CO2.
Controllers should support automation scenarios and be compatible with your existing heating and ventilation systems.
Ventilation units must be able to implement the measured values reliably.

Also think about future-proofing: systems that can be integrated into a smart home environment are generally more flexible and durable. However, standalone systems can also be an effective, simple retrofit solution – for example, when automating roof windows.

Which rooms benefit most from a ventilation control system?
Automatic ventilation is particularly useful in humid rooms such as bathrooms and kitchens, where humidity levels vary greatly. Bedrooms also benefit, as CO2 levels rise during the night. In living and working rooms, ventilation control improves comfort, and in basements it helps protect the building structure from condensation.

Can I change or extend my ventilation system later on?
Yes. Many systems are designed to be modular and expandable. This means you can start with a simple setup – for instance, just a humidity sensor in the bathroom – and later add more rooms, sensors or a central controller.

Wireless systems in particular make it easy to expand the setup without major construction work. The key is to ensure device compatibility and integration into your existing smart home system.

Can I implement my ventilation control with KNX, and what should I consider?
Yes, a ventilation control system can be integrated into a KNX smart home. Sensors measure humidity, temperature and CO2, transmitting the data via the KNX bus. The control system can then combine this information with other functions such as heating, cooling or shading. This enables coordinated scenarios, such as automatic night cooling in summer or reducing heat loss in winter.

Key points for planning:

Define the desired scenarios in advance (e.g. humidity control in the bathroom, CO₂ management in the bedroom) so the devices can be used effectively.
Check compatibility with existing components – especially if mixing KNX and non-KNX systems – to avoid isolated setups. KNX-certified devices can usually be combined without issues.
Esure the system remains easy to use with clear status displays, so daily operation stays convenient. Building automation should support people, not complicate their lives.

This way, ventilation control becomes not just a single feature, but a fully integrated part of your smart home system.

Further Smart Home Guide Articles

You might also be interested in:

Schematic drawing of dew point monitoring

Dew Point Monitoring and Ventilation Control

Smart dew point monitoring provides reliable protection against condensation and mold growth.