Remember that light travels in straight line. So if it doesn't have an opportunity to 'reflect' off glossy or semi glossy surfaces, a 'light trap' works very effectively to keep light from entering a space.

So I would shield the glass area to mask out most of the light during the day, but also use a secondary shield over the window opening on the inside wall as a 'trap' to catch any light that would sneak in past the mask. over the glass.
Same principle (two layers, one inside the room and one outside the room, separated by the space of the door frame) would allow me to enter and exit the room yet sufficiently block the light to use my enlarger for color printing.