1970s build?

Windows are terrible at efficiency. Yes, even modern ones with three panes and filled with argon. A building with minimal windows is generally going to have better thermal efficiency than one with lots of them, and that started to be really important during the 1970s oil crisis. The result was a bunch of schools like this that look like prisons.

If you get some local mural artists to paint the concrete in bright, whimsical images, it fixes a lot.