What is your climate? How many occupants and sqft. of space? Comparing inside/outside dew points and number occupants will provide info on natural fresh infiltration. You should have a fresh air intake to change the air a minimum of 4-5 hours typically.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"