Have a 70 yr old brick home with no insulation in walls, save Homasote board between brick and sheetrock.  House is in upstate NY.
I discovered significant mildew on inside wall of several closets, so I suspect lack of air flow and condensation have done their job.
Other than gutting sheetrock to insulate, upgrade electrical, etc., what suggestions would you offer?
If gutting’s the best choice, what recommendations do you have concerning doing this one room at a time to avoid disturbing the entire house and keeping costs low?   I plan to do this as DIY project.  
Thanks.