Is there a glass fence behind the big balcony to seal the window?

Of course. After it must be removed, close the balcony with integral windows.

The original protective railing can play a certain role in safety protection, but if the window is directly added to the protective railing, the overall strength of the window will not go up, and windy weather will easily cause safety hazards. The original protective railings were single-layer tempered glass or laminated glass, which did not play a good role in heat insulation. Single-layer tempered glass or laminated glass has average sound insulation performance and will not play any role in the later stage.

It is not feasible to install directly on the upper part of glass protective railing, no matter from the aspects of safety, heat preservation and sound insulation.