Updated: 08.11.2026
On hot days, walls, ceilings and furniture in an office store a lot of heat. Letting cool outside air flow through the rooms at night removes this heat again. Doing it by hand rarely works because nobody opens the windows at night. Electric window drives do it automatically.
In brief: With night cooling, window drives open in the evening when it is cooler outside than inside, and close in the morning or when it rains or gets windy. It works best with windows on two sides or at the top and bottom.
How night ventilation works
- In the evening the windows open as soon as the outside air is cooler than the room air.
- At night cool air flows through the rooms and absorbs heat from walls and ceilings.
- In the morning, before work starts, the windows close again.
- In rain or strong wind, a sensor closes the windows immediately.
What you need
| Component | Task |
|---|---|
| Window drive (chain or spindle) | Opens and closes bottom-hung or fanlight windows |
| steering | Supplies the drives and groups them |
| Rain or wind and rain sensor | Closes in bad weather |
| Timer or building automation | Sets the ventilation times |
Read more about controlling several windows in the guide Ventilation control for window actuators.
Safety and burglary protection
High fanlights and windows on upper floors are particularly suitable for night ventilation. A tilt gap of a few centimetres is often enough. For ground-floor windows, clarify burglary protection and insurance beforehand.
Frequently asked questions
How much cooler will the office get?
It depends on the building, ventilation area and night temperature. We cannot promise a fixed figure. What you notice most is that the room starts the morning at a lower temperature.
Can I retrofit existing windows?
Yes, bottom-hung and fanlight windows can usually be retrofitted with a chain drive. See the guide Retrofitting electric window openers.
Technically reviewed by Dietmar Heiken, Sales, Vent Systems HDI GmbH, Hamburg – around 20 years of industry experience. Questions? Phone +49 40 50694631 or info@ventsystems.de
Last updated: 08.11.2026
