Updated: 08.11.2026
In brief: Yes, in most cases. A bottom-hung window measuring 1.2 × 1.0 m with triple glazing weighs around 40 kg, but at 300 mm stroke needs only about 63 N, around 80 N with 30 % reserve. A VS-KA with 250 N therefore has more than enough force. Limits are set rather by the sash width (two actuators from 1.5 m) and the tilt hardware.
Why does a bottom-hung window need so little force?
On a bottom-hung window the hinges are at the bottom. The sash tilts inwards only a little, and the hardware carries most of the weight. The actuator at the top edge only has to push the sash out of the vertical. The usual approximation is F = 0.54 × m × g × stroke / sash height – the smaller the stroke relative to the sash height, the less force.
Worked examples with triple glazing 4-14-4-14-4
| sash | Weight | Stroke | Force | with 30 % reserve |
|---|---|---|---|---|
| 1,2 × 1,0 m | approx. 40 kg | 300 mm | ca. 63 N | approx. 80 N |
| 1,2 × 1,0 m | approx. 40 kg | 150 mm | ca. 31 N | ca. 40 N |
| 1,4 × 1,4 m | ca. 65 kg | 200 mm | ca. 49 N | approx. 65 N |
Weight estimated with 30 kg/m² glass plus 10 % frame, see Glazing build-up. For heavy aluminium or timber frames, better use the real weight.
What really matters
- Tilt hardware and stay: Many tilt-and-turn windows only tilt 100 to 180 mm. The actuator’s stroke must not be larger, otherwise it pushes against the safety stay.
- Wing width: From about 1.5 m we recommend two actuators with Synchronous control oder den Doppelkettenantrieb VS-DKA 800.
- Seals: New windows with three sealing levels close tightly. The reserve covers this.
- Locking: A chain actuator does not open a locked tilt-and-turn fitting. Locking actuators such as the VS-VA 600 are available for this.
Which actuator fits?
For visible mounting, the VS-KA with 250 N in 24 V or 230 V, for concealed installation in the profile of the VS-CKA 300. If the window is to be operated via app or building management system, the smart VS-KA-i.
Frequently asked questions
Do I need a stronger actuator for triple glazing than for double glazing?
With bottom-hung windows usually not. The weight rises by about half, but the required force stays well below 250 N. Roof windows are different: there the actuator carries about half the sash weight.
How far should the bottom-hung window open?
100 to 200 mm is often enough for ventilation. More stroke brings more air, but also more force required and more wind exposure.
See also in the glossary: Tilt-and-turn window · Lever arm
Tools: Calculate force and stroke with the Window actuator calculator, find the right model in a few questions with the actuator finder.
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
Questions? 040 50694631 · info@ventsystems.de
