Window walls are built one floor at a time and are supported by the slabs above and below them. In other words, window walls are built within the slab edge.
Curtain walls are structurally independent and don’t require support on every floor. They tend to span multiple stories and are built outside the slab edge.
Both systems are built to be an all-in-one cladding system that acts as the building’s envelope barrier. They also both provide some insulation and can transfer their load to the building structure.
However, curtain walls are more expensive than window walls and tend to be more complicated to install. In addition, curtain walls aren’t typically operable, whereas window walls can be.
There’s also the issue of fire-stopping and noise pollution. With window walls, you don’t have to worry about either issue.