moreilly - I am having the same problem - condensation - raining from the inside of the building. I am going to try and insulate the inside of the roof/ceiling with some ridgid foam insulation. Other than that or adding heat to the building I think the problem will continue to go on.
Add on - I placed one small sheet of ridgid foam insulation on the underside of the roof yesterday to see what would happen. When the sun came out - no moisture from that area - I think this is going to work.
what is the floor made of? if it's concrete, you can seal it to keep moisture from seeping up through it. if it's just a plywood floor raised above the dirt you may be able to seal it to prevent moisture coming up. if possible you could take up the wood floor and put down a moisture barrier and then put the floor back down.
better insulation all around will help as well, but you need a sealed floor.
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