Since after going through my posts you know that there might be several reasons for the mold presence I’m not sure if I can add anything to it. Bathroom fan and a whole house fan are huge sources of warm air so that torn exhaust duct should be repaired, whole house fan louvers or top of the fan insulated for the cold season.
Those are obvious (and the mold) and you can ask for them to be corrected. Anything else, unless it will show on the inspection report is usually difficult to negotiate. If the inspector stated in his report that there are missing some attic vents, attic’s floor insulation, or anything else that might have direct impact on that area and be responsible for mold growth, you can try to negotiate those items with the home owner as well.
In order to determine if an attic is properly ventilated you need to do some calculations, measurements, sometimes “investigate” a little more than the home inspector is permitted do. So, if necessary, ventilation part improvement (if needed) might have to be carried out when the property becomes yours.
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