I am completely new to this site so go easy on me, I was looking for advice on alternative living, power etc, and then I see you lot talking about vans and condensation. this is a topic I am familiar with having lived in a soaking wet caravan and am working on my second van conversion.
Avoid foam mattresses, we had these in the caravan, and you could ring them out in the morning!!! for the base of our bed we used the slatted bed bases from Ikea and futon mattresses, these weren’t cheap but well worth it. Our last van had a small workshop wood stove, I work with wood so fuel is cheap, and if you run out you can always find wood to burn by the road. Never use gas for heating, terrible condensation and it’s not good for you. Don’t try to make your van air tight, JessenB is spot on, and finally curtains are good at stopping your bus heating up too much, you can line your ceiling with just about anything, we have a section in the middle which is just fibre glass and my wife has made a curtain for that too, amazing difference (I think bright colours work best hope that is of some help to someone.