On a home inspection the other day I popped my head into the attic space of a vintage 1950 home. At first glance the attic felt unusually warm and moist. From the outside the gable vents appeared to be large enough and should have kept this attic effectively ventilated however the current renter had some other ideas. He told me that he had been in construction for years and was currently unemployed.
This vintage home had a minimum amount of insulation and the gable vents were covered with plastic!! All of the warm moist air coming up out of the home was being trapped in this unheated, unvented, ideal mold growing limbo. The roof sheathing was covered with a soft and fuzzy patina, very artistic but not very pleasing for home maintenance and air quality.
The moral of the story is those openings in your attic and there for a reason and very important. They are not there to make you suffer when it is time to pay the heating bill. Insulation should be used on HEATED surfaces. Your attic is not a heated space. The floor of the attic is next to a heated space and this is the only surface that should be insulated. The rest of the attic should have enough vents to keep the attic as close to the exterior temperature as possible. This will vent excess moisture, cool the roof system and provide a good environment for maintenance of the structure of the roof.
Home inspections in Salem, Oregon. Mold, Inspector, Keizer