Condensation in cab

[71 C20 CS]

My cab is getting really wet inside on the roof and windshield. The door seals are new and I checked they’re sealing properly and there’s no leaks, carpet is dry everywhere, but somehow moisture is getting in, there is so much condensation on the roof, it gets really wet, I have to towel it off.

Anyone have any experience with this? I was told by a mechanic to put dynamat on the roof and it will stop, but that sounds odd to me.