In cold climates, water vapor from the heated air inside your home travels through unsealed holes and cracks and condenses on cooler surfaces such as exterior walls, the roof overhang and within insulation. This condensation can cause a great deal of damage including wood rot and paint bubbling, can destroy insulation and damage the roof itself. A professionally installed vapor barrier between the interior heated surfaces and the insulation can help to minimize this problem.
There exists some confusion between moisture barriers and vapor barriers, but the main difference lies in where the barrier is placed. Moisture barriers are properly installed on the exterior of a frame wall, directly on top of the sheathing, and under the siding. Moisture barriers help prevent water from entering the wall cavity. Whereas vapor barriers are installed on the inside of a frame wall between the studs and the drywall. Vapor barriers help prevent water vapor from the interior of the house filtering through the wall and condensing on the warm side of the insulation.
Vapor barriers are also installed under basement slabs to prevent water and ground gasses (such as radon) from making their way through the concrete. A vapor barrier can decrease air and moisture infiltration into your rooms and make your home more energy efficient, and there are cases where this may be appropriate. The energy efficiency experts at EcoEnergy Retrofitters can inspect your current insulation and recommend the appropriate means of adding a vapor barrier to reduce energy costs in your home.