External venetian blinds on a house façade

Triple glazing in summer: too hot or not?

Triple glazing does not make a home hotter in summer. It slows heat transfer in both directions. What heats a room is direct sunshine coming through the glass. The real answer is external shading, such as a roller shutter or external venetian blinds, combined with airing the house well at night.

By Marcio Barros · Updated 31 October 2026 · 4 min read

Where does the heat come from in summer?

In summer, heat gets in mainly as solar radiation passing through the glass. Once inside, it warms the walls and the furniture. The number of panes makes little difference to this. Triple glazing actually slows down the outdoor heat that travels through the glass by conduction.

How to keep a room with triple glazing cool

External shading: roller shutters or external venetian blinds. Stopping the sun before it reaches the glass works far better than an indoor curtain.
Close by day, air at night: close the shading on the sunny façades and open the windows wide when the outside air is cooler.
Think about orientation: south and west façades get the most sun. That is where motorised shading is most useful.

And in winter?

This is where triple glazing makes the difference: less heat loss, no cold feeling next to the window and less condensation. This highly insulating glazing is also what is required for Klimabonus for windows, the Luxembourg renovation grant.

To find out more, see our triple glazing page.