Thanks for the suggestions. I think the slight dampness on the carpet above the gas pedal, on the bottom of the engine fire wall is likely the start of the blocked vents you mention.

However, the floorboards in front of the seats are bone dry. The moisture that worries me the most is coming from behind the seats, the carpets in that area are moist, which means its likely from another source. I can only think of something from the roof, but the head liner is dry, no idea where the water is coming from.