What I don’t understand is that people insulate their builds up to the point of sealing everything in so it’s airtight with vapor barriers etc . . and then complain that they have condensation issues.
A simple way to demonstrate this problem.
Ever gone camping and at night you’ve zipped up the doors all the way and then in the morning, you find the inner skin is soaking wet?
This is condensation from breathing and the more people you have in the tent the worse it gets.
Now when you go to bed at night leave the door partially (or all the way) open on both sides but zip up the mesh screen and hey presto no more condensation.
I tried this in cold weather earlier this year when I was forced to sleep rough (long story) and at the time I was researching this very issue with regards to my own build.
I was still cold in my tent so zipping up both doors wasn’t really going to solve that issue but I did suffer from very bad condensation problems (I was set up in a derelict house)
So after reading on here, I decided to test out the theory and I can confirm that by leaving the doors open I did not suffer from condensation after that.
I’m guessing the same will be true for a van, my build will have adequate ventilation in the form of windows and fans (but NOT IN THE ROOF) I was going to install a max fan but I do not want to cut holes in my roof which could potentially guarantee water ingress somewhere down the line.
I have found some fairly cheap fans on Amazon and I shall be installing them fore and aft on the side of the van with hoods for further protection from possible water ingress
I know the theory works I have tested it, simply ventilate and move the air throughout the living space with open doors windows and a heater that blows hot air. You need to really look at the kind of heater you decide on as this could possibly add to the problems of moisture in an enclosed space.
Here is the fan I bought off Amazon it’s pretty powerful I’m using one to extract steam over the cooking hob
and two to pull air in from the cab at the front. and one to extract air out the rear.