Besides degradation of the insulation due to having the vapor barrier on the cold side (in winter), resulting in condensation of interior moisture diffusing through the insulation to the cold surfaces, I have to wonder if long-term accumulation of moisture has damaged the bottoms of the floor joists. Wetness held there by that plastic vapor barrier won't dry to the exterior easily.
As part of your later renovation efforts, and assuming you have a crawl space under the living space, you might think about enclosing that crawl space, eliminating any air leaks into it, insulating its walls, and having a sturdy vapor barrier over the ground. A lot of good information on all this can be found on greenbuildingadvisor.com.
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