“There is a good chance that your contractor will identify several ideal areas for a half bath. When presented with options, try to choose a section that is close to the exterior walls.
The reason for this is ventilation. Ventilation exhausts should always be located on the exterior of the house (you’d be surprised how many people make this mistake). It would be less expensive to install a ventilation system that is already near the exterior wall.”
https://dalbuilders.net/chicago-bathroom-remodeling-tips-remember-adding-half-bath/
