My son is in the last stages of finishing the interior of his new house. My question is twofold. The metal ribbed roof was not placed over an insulation roof blanket ( our builder told him it really wasn't necessary!), but we are afraid that he is gong to have condensation problems. He only has ventilation at the channels of the bottom of the ribs of the roof and at the end of his ridge cap. He has placed a plastic vapor barrier between the drywall and the blown in insulation. He is going to install a power ventilator in the roof to circulate air. We were told by the insulation contractor that he should have glue on insulation placed on the underside of the roof, but we are afraid that will cause the small amount of air coming from the bottom of the roof ribs to be blocked. I have seen advice on the web suggesting placing foam board insulation between the roof rafters. Would this be a better alternative? Also we have found a vapor barrier primer from Benjamin Moore paints that look like they might be a good additional step. Does anyone know if this can be painted on as a primer before the ceiling texturing is done, will it effect the texturing in a negative way?