Cannot escape home insulation and energy efficient ventillation if you want to ensure healthy environment from the humidity point of view. Bathroom, cooking, laundry, and people as well, all will produce humid air that will form mold on cold surfaces of an uninsulated home if not properly ventillated. Where the proper level of ventillation needs to be quite intensive for the desired effect - causing elevated energy loss or requiring supplemental heat preservation techniques - except if low level of heating (temperature) is maintained, which raises other kind of concerns.