Our windows are single glazed, and since the house was built in the early 90s, the glass thickness is 0.5 mm less than the current standard. We had to replace a pane a few years ago, and the installer had to widen the channels in the frames cause they were slightly too small.

We do have roller shutters and curtains which help with the cold slightly.

For the window seals, if you’re planning on replacing them eventually, run silicone or sicaflex along the edges. Doesn’t look flash, but helps a lot.