Summer
Before the glass
A solid curtain, fully down, stops most of the sun that would have entered the room. A blind inside is already too late.
External roller shutters
The shutters on German and French houses sit outside the pane. On a British extension they cut summer gain, cover cold glass after dark, and make a rear bifold less of an invitation. Internal blinds are a different product.
Summer
A solid curtain, fully down, stops most of the sun that would have entered the room. A blind inside is already too late.
Winter
The same curtain is an air gap in front of a cold pane. Up in the morning if you want the low sun.
One window
A 2026 band for an ordinary fitted opening, before a wide bifold, scaffold or a security specification.
South-facing bifolds and lanterns are why these turned up on British houses.
Solar motors stay on the outside of the wall. They still need a sky.
A locked curtain over the glass while you are out or asleep.