Wall insulation - Fiberglass batts can be applied if walls are opened to the interior. Care must be taken to not compress or leave voids in the insulation in order to maintain thermal performance. Penetrations (such as wires, electrical boxes, pipes) must be carefully sealed with caulking or spray foam to prevent air leakage.
As with a glass of ice water, condensation occurs when warm, moist air touches a cold surface. When this happens in your home, it can cause mold, mildew, and damage to building materials and reduce the effectiveness of the insulation.
A vapor retarder slows the movement of air and water vapor through building materials; in fact, a good vapor retarder will allow very little moisture to pass through. Some vapor retarders also serve as air barriers. A good vapor retarder and good air-sealing can improve the energy-related performance and durability of your home.
Most homes built before 1970 do not have a separate vapor retarder component; however, the predominance of oil-based paints in those homes usually provides an adequate vapor control function.
Whenever you install insulation, always include a vapor retarder. If you’re adding insulation to an area that already has a vapor retarder, you do not need to add another one. Vapor retarders include: