Apologies if this is a dumb question. Recently due to the summer heat I've been turning on the ventilation in my house as we do not have AC. I would like to know why the entire house starts smelling like the basement when it is turned on. Isn't the whole point of ventilation to bring fresh from outside to inside the house and not the circulation of the same old air?
What part of the country is your home located in? Ocupants add moisture to the air in their home. House air is outside that is passing through depending on the stack effect, wind velocity, and mechanical ventilation,(clothes drier, bath fans, kitchen hood, and mechanical ventilation.
Outside winter air is dry and summer air is wet. The measure is grains of moisture per lb. of air or dew point. When the moisture when the %RH rises above 60%RH, mold, bacteria, and dust mites grow. They smell like a basement.
You need fresh air ventilation more in the summer than the winter because natural ventilation declines.
You need a good dehumidifier to maintain <50%RH during the times of the year when outside is damp.
Check out the whole systems like Ultra-Aire/Santa Fe to maintain 50%RH throughout and have fresh air whenever the home is occupied.
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"