Ah, I see where our misunderstandings are. Exterior blinds are pretty rare in the US, despite being flush with exterior shutter adornments. So in the US, any talk of blinds is going to be about interior things, which was my assumption. I have heard functioning exterior blinds/shutters are more common in parts of Europe. Meanwhile, the US does also use "curtain" and "blinds" to mean separate things: blinds are the adjustable slats (or accordion cellular styles) while curtains are the more decorative textiles usually pushed to the sides. So it still sounds like we were talking about the same thing, using curtains to cover the gaps in the blinds, while talking about entirely different blinds.

How do you operate the exterior blinds? Are there controls going through the wall or do you reach out the window?

Also of note, American homes tend to have pretty bad wall insulation. Wood frames, plywood+siding outside, sheet rock inside, and probably slouching thin insulation. A wall can exchange as much heat as a curtainless window