What is KNX and how does it work?

A standard, not a brand

KNX isn't a manufacturer: it's an open communication protocol, recognised as an international (ISO/IEC 14543-3) and European (EN 50090) standard. Hundreds of manufacturers make compatible devices, so you can mix brands within one installation.

How it works

All devices connect to a bus: usually a low-voltage twisted-pair cable running through the home. Simple messages travel along it, such as "turn on the living room light" or "the bedroom is at 21 °C".

• Sensors: switches, presence detectors, thermostats, weather stations.
• Actuators: modules in the distribution board that switch and dim lights, move blinds or control heating and cooling.
• System devices: the bus power supply and gateways to the IP network or app.

Distributed intelligence

In KNX there's no single indispensable brain: each device knows what to do. If one element fails, the rest keeps working. And it runs locally, without depending on the internet.

How it's programmed

The installation is configured with ETS, the official tool shared by all manufacturers. The resulting project file documents your installation: with it, any qualified integrator can maintain or extend it.

When it makes sense

• New builds or full renovations, where the bus can be installed.
• Homes meant to last for many years without becoming obsolete.
• Hotels, offices and developments wanting a consistent standard.
• Projects where switch and panel design matters.

What you can control with KNX

• Lighting: switching, dimming, scenes and presence detection.
• Blinds, curtains and awnings: by schedule, sun, wind or as part of a scene.
• Heating and cooling room by room, with thermostats and sensors.
• Technical safety: water leaks, smoke, open windows and alerts.
• Energy: consumption metering, load management and solar.
• Access and audio, through gateways to other systems.

The parts of an installation

• Power supply for the bus, in the electrical panel.
• Sensors: push buttons, presence detectors, thermostats, weather station.
• Actuators: the devices that switch, dim, move blinds or open valves.
• Bus cable: a twisted pair that runs through the property and links every device.
• IP interface: connects the installation to the network for mobile control and visualisation.

Transmission media

The most common is bus cable (KNX TP). There is also KNX RF, by radio, useful in renovations where cable can't be run, and KNX IP, which uses the data network as a backbone in large buildings. They can be combined in one installation.

KNX and security

The standard includes KNX Secure, which encrypts and authenticates communication on both the bus and IP. In new installations it's worth using compatible devices at sensitive points and, in every case, keeping the IP network separate and remote access protected.

What to ask your installer

• Will you hand over the ETS project file when you finish?
• Which device brands will you combine, and why?
• How is it controlled from a phone, and what happens if the internet fails?
• What maintenance does it need, and who does it?
• What is left ready for future expansion?

Common mistakes

• Deciding on automation once the build is closed up: cabling is the hardest thing to add later.
• Not leaving enough space in the electrical panel.
• Ending up without the project file: without it, any future change means reprogramming from scratch.
• Automating everything without thinking about how the home will be used day to day.