I probably will replace with something similar, but not before giving the inside a seriously good sealing first.
I agree it can be bad to sleep in for some, but because it is much warmer with the insulation we pretty much always sleep with something open, which keeps ventilation up and condensation down!
At home I always sleep with a window open, no matter the temperature. It's one of the reasons I hate staying in hotels (in The Before Times). I would rather have fresh air and sleep under an extra blanket than be all cooped up