A mate of mine has tried everything, his Windows are almost constantly steamed up, even the blowers just about keep it at bay, heard its a common problem on this car?
Perhaps he is getting an ingress of moisture into the car? If he is trudging a load of snow etc on his shoes, this won't help.
I'm not familiar with the Civic, but i've heard that in other cars drainage channels can become clogged, hence the moisture not escaping from the cabin.