Condensation

Not breathing helps also.

you probably had the trailer completely sealed up with the furnace on.
big mistake!
the same thing could happen in a regular RV if no air movement is present.

you need air movement and PUG's/solar blankets.
you need to allow for air to move and put the blankets on top of the tent ends.
you should have a vent cracked along with opening a tent window a little bit.

for most, this will cure the condensation issue.

'Tis the season. There will be an instant replay for those who are getting out for the first time in the cool, damp spring weather. Either the space blankets from Cabela's or similar or the Pop Up Gizmos will go a long way toward fixing this. Note I didn't say WILL fix it. We also bought a product used in boating applications called HyperVent. Sworn to remedy the problem. Not quite, but what it did do was elevate the mattress about 1" above the deck so that it didn't get damp. Some folks swear that if you slightly open a window, problem solved. DH wouldn't even think of opening a window when it's cold outside and he's trying to get it warm inside, so no big news to report there. We did use the fan only on the furnace and it helped, but an oscillating fan sitting on the table will likely accomplish the same thing. Some folks have never had a single problem. Others swear that they're about to drown. My strictly unscientific study has shown that what works for one won't work for another. Trial and error. One thing you can do to help considerably is to make sure you don't do things like boiling water or heating where you have steam in the evenings - be sure to run your stove venthood for a good long time. We never had moisture dripping from the top, but in spite of all, we did check under the mattress & HyperVent every morning and just wipe it with a towel if needed. If it was more moist than usual, we'd stick a couple of tall cans or similar to hold up the mattress until you were sure it's dry. One 99% guarantee is that if the pillow slips against the end of the canvas area, the moisture will wick and the pillow will get damp. All this is just part of the charm of hybrid camping and you'll figure out what works for you and what doesn't, but moisture is a stinker and you'll just have to work on it. The greater difference in the inside and outside temps is one of the culprits. Meanwhile, just enjoy!

This my friend is an extremely common complaint on this forum. I see the archives only go back a few days for some reason, so I can't copy and paste what I just wrote, but here is the jest of it.

In my case solar blankets bought at Cabelas for about $10 each solved the problem entirely. The sheets fit perfectly over the roof of my bunkends and were easy to attach with strong paper clips! There are eylets so you can also tie a small rope. Shiny side up on hot days to keep heat out, dark side up on cool nights. If budget is not a concern you can mail order popupgizmos which are custom-sized solar blankets equiped with bungy cords.

Condensation is greatly reduced that way, and the bunkbed is much darker which is useful in early morning. It's helpul to keep one or two window corners open in the bunkend to evacuate the moist air we breath out through the night.

For cold nights, Reflectix sheets cut to the size of windows and slipped from the inside between the window pane and the bug screen work very well to keep the space warm. Also, with the Roo you get the added benefit of heated mattresses.