Mid December we noticed frost and wet areas below our insulated northeast and northwest basement wall. We have insulation on the top 4 feet of the wall per code. It has a plastic backing with a r-13 value. I also have a daylight basement with that wall framed with 3 windows and blown in insulation with a vapor barrier on the inside. The rim joists have batt insulation in them. I pulled back the insulation and had 18 feet of frost on the wall along with wet and moldy rim joists. The builder came and cleaned the mold and wanted to put in batt insulation again and hang the original insulation on the walls. We have not let them do that because we don't know why its doing it. My humidity level is 35-45% in the basement with a temp of 60-65 degrees. It was recommended we put foam board in the rim joists and hang on the walls with a good seal but not sure if this is the answer. Help would be appreciated.
