we remodeled a trailer home recently, removed the aluminum siding, put up osb in place of the siding, then used the Lowes brand of house wrap. we installed new vinyl siding over that without using any of the thin fan board insulation that some people use.. on the inside, we are replacing drywall in areas where we took out or modified for new windows. we have waited for a week or so before placing the drywall and we noticed moisture between the insulation and the osb, question is, has this occurred mainly because the drywall was left off for several days while it is cold outside and warm on the inside of the house? we are hoping that the fact we didn't use that thin fan board insulation behind the vinyl is the reason for this problem. can anyone relate to this or know if I have a problem that will continue even with the drywall installed?
You need vapour barrier (the plastic you put up before drywall) and air barrier.
To count as an air barrier you stop air flow by using sheathing tape on:
Some people think that you only need a vapour barrier or that the vapour barrier is also an air barrier. This is not true. You can make it an air barrier by sealing the joints and seams with tape and mastic, but otherwise it is only to stop Vapour Diffusion and not Air Flow.
Long story short: you had condensation because you did not have a proper vapour barrier, air barrier, or both. Since you seem to have a VB built in to your insulation, all you need to do is tape the seams and seal the edges at the top and bottom plate to make an air barrier.
You did the right thing by sheathing the house in OSB and using a good house wrap. That is not the problem. It is more structurally sound and will hold your vinyl siding well for decades assuming it was installed correctly.
First you should rule out any other potential sources of moisture. Is this in a basement? Is there water leaking in through the foundation? Was the siding installed correctly?
A bit of condensation on the outside wall to the insulation can be perfectly normal. Make sure that you placed insulation with the vapor barrier (plastic or paper side) facing the outside wall. This will protect the insulation from soaking up moisture and potentially creating a mold problem. The moisture on the OSB cannot be helped, but is normal when you have an extremely cold outside and a warm inside.
The fact that you haven't placed the drywall yet has little to do with this. 1/2" gypsum board has a very small R value so it doesn't afford you very much more in heat loss to cause a condensation problem.