I have problems with condensation, dew when I camp above tree line in European mountains. The problem is that my down sleeping bag gets wet from the outside. Even when I use single wall tent the fabric is wet and some of it goes to my sleeping bag.
I think the issue is when camping, bivouacking in the open. If I do that below tree line under cover of trees I don't have that issue. The problem are always exposed spots with no tree cover. Ventilation is good. I don't know is that issue solvable, because dew is present almost every morning even if the days are hot, grass is wet. I don't have time to dry down sleeping bag every day and sleeping on the top of the mountain is just so great.
How would you solve the problem? Double wall tent is just too heavy.