Updated: 08.11.2026
In brief: Replacing double glazing with triple or laminated safety glass makes the sash about half as heavy again. For bottom-hung and fanlight windows, the existing actuator is usually still sufficient. With roof windows and dome lights it often gets tight – calculate beforehand.
How much heavier does the sash get?
Glass weighs about 2.5 kg per m² and mm of glass thickness. Double glazing 4-16-4 weighs around 20 kg/m², triple glazing 4-14-4-14-4 around 30 kg/m². More under Glazing build-up and laminated safety glass.
Is the actuator still sufficient?
- Bottom-hung and fanlight windows in the facade: The actuator carries only a small part of the weight. A 250 N actuator is usually still sufficient, see Bottom-hung window with triple glazing.
- Roof windows and rooflights: The actuator lifts about half the sash weight. Here, recalculate with the Window actuator calculator and 50 % Reserve .
- Wide wings: From about 1.5 m width, plan two actuators.
What else to check
- Hardware and hinges: approved for the new weight? The window manufacturer will clarify this.
- safety stay: still suitable for the higher weight?
- Stroke unchanged? If the sash height changes, check the stroke length.
If the old actuator is too weak, see the guide Repair or replace?. We are happy to check your case using photos via the Project enquiry.
Frequently asked questions
Do I need a stronger actuator after replacing the glass?
Rarely for bottom-hung and fanlight windows, more often for roof windows and dome lights. What matters is sash weight, installation position and reserve.
How can I tell that the actuator is too weak?
The actuator runs more slowly, stops before the end position or switches off, especially in wind or cold.
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
