I’ve constructed basic storm windows using 1×1 wood and .220 acrylic sheet.  I’m torn on whether to install them on the exterior or the interior, my 100 year old window casings are the same size on both.

Most of what I’ve read talks of interior storms being air sealed, but I’m certain I’ve seen discussions here (Possibly from Dana) about sealing the exterior.  The windows themselves are reasonably tight and inoperable (caulked shut and weight sashes filled).

I have a few days off to hang them, and I just can’t decide which is the better option!