From what I've been reading condensation and damp develops as a result of water leaking into your car via things like leaving wet shoes in car, leaks in the ventilation system, sunroof etc.
I couldn't see any such things in my car. However my condensation and damp problem developed after leaving it idle in the cold for 2-3 months. Mechanic said you don't need to have a leak or leave wet items in and leaving car idle for few months would have caused it.
If you dont have wet items in car, leaks etc allowing moisture to be in/go into the car, why should leaving it idle for a few months cause the condensation and damp to develop in carpet and seats?
I do remember one day last summer leaving a window open and a lot of rain going into the car, however this dried up and didnt cause any smells or problems. Its only months later due to leaving it idle as mentioned did I notice this problem. Might this rain from that day be the cause of my problem or is it still normal for a car left idle for a few months to develop condensation and damp?