does anyone know a source for rain guards, I would like to leave my windows open to decrease interior fogging.
Aircon not working? Or do you have a leak causing dampness in the car?
A/C works great, I am not sure of the cause. I have tried many options found on this site but it still persists.
The demist flap prevent fogging. Unfortunately mine was broken and I removed it. After many years of perfectly clear windscreen in all weathers, I now have fogging summer and winter. 
I have the same issue, when the car sits I get a coating inside of the windows.
So running the A/c doesn’t clear the fogging? An old remedy for fogging was to wipe the inside of the screen with dish washing liquid.
It’s not moisture It’s more of a chemical.type coating.
Most likely coolant escaping from your heater core. Does your coolant level drop over time as the car is driven?
Not currently, I put barrs stop leak in awhile back and it seemed to help.