It would help if you set this up as a new topic since it is different from the above question, but I will try to give you some leads. My guess would be that your best bet would be to stop the humidity coming up through the soil in your crawlspace. You did not say what was on the floor, but it would help quite a bit to know this. If the floor is plain dirt, then lay down a sheet of 6 mil plastic and some gravel to hold it down. Then insulate the cold air duct. This will save you money as the cold will not be lost in the crawl space as well as stopping the condensation from forming. Even cold water pipes running through the space will cause condensation so insulate them also if you have them. There are many similar and pertainent questions below, so check them also.