We just bought a Cape Cod that was built in 2005. The home has a two story atrium with two bedrooms upstairs that would be in what is normally the attic area. Each bedroom has one dormer window. The sloped area of the roof between the dormer areas is storage areas that open into the living area. These storage areas are not conditioned but are easily accessible to the living area through a normal closet door.

Each storage area has insulation in the roof rafters and along any outside wall. The inside of these insulated walls is covered with Tyvek over the insulation.So, if you walk into the storage area, you see a tyvek covered wall over the insulation, just a bare studed wall if its on the interior and carpet on the floor.

I am getting some air infiltration in these areas and would like to tear down the Tyvek 'veneer' on the inside and go back with some sort of insulation board. I thought about drywall but it is too bulky and difficult for me to manuever. Since it is storage area, I am really not concerned with the cosmetics. However, I am a little worried about blocking any moisture between the outside wall and the inside if I cover the inside of the exterior walls with foam board or some other inexpensive insulation board.

Anyone have any ideas on whether or not this would be problematic? IF so, what are some other inexpensive alternatives?