hang on, the units must be sealed to an extent, otherwise each time you switch on your lights you light up the engine bay which leads to less light out front.
so where does the moisture escape to when you switch them on? it doesnt/cant.
we have the same prob with our 16vs in that the fogs mist up and never clear. i took mine out and put them on the radiator for a week, siliconed around the seam and there fine. (then i used the holes for cold air feeds but there we go)