KNX on indoor air: measure first, then control
The KNX Association makes its case for demand-controlled ventilation, and we explain why a CO₂ sensor belongs in the majlis before a screen does.
Ventilation on demand, not on a schedule
On 26 September 2026 the KNX Association made the case for measuring CO₂, humidity, temperature and occupancy, and for letting the building ventilate on demand rather than on a schedule. That means more fresh air as CO₂ rises, with the air handling, automated windows and the heating and cooling all coordinated on one bus. The note gives no thresholds, because "target values and ventilation requirements depend on the building type, occupancy, local requirements". Its principle is "measure first, then control", backed by certified products from more than 500 manufacturers. Source.
Why the majlis needs it most
In a UAE villa, the room that needs this is the majlis. Picture twenty people behind closed doors with the air conditioning working hard; by the second hour everyone is tired without knowing why, and that is CO₂. A KNX presence sensor with a CO₂ element, set in the majlis ceiling and tied to the fresh-air damper or the energy-recovery ventilator (ERV), fixes a problem most owners have never named. It costs less than the second room screen people usually ask for, and it does more.
A sensor needs ventilation that can listen
We specify combined presence and air-quality sensors in the majlis and the family living room, and plain presence sensors in the corridors, stairs and WCs, where they belong. None of it helps unless the air handling can listen, which is a question for the MEP design, so we ask it early: is the fresh-air unit controllable, and by what? If the answer is "it has a switch", we say so on the design rather than draw a sensor that talks to nobody.