Something many people do not understand about insulation and basements, as well as concrete slab foundations is that moisture can creep in. Moisture breeds mold and mildew. It also makes your home more difficult to heat and cool. Some insulation materials can absorb moisture. When insulation absorbs and holds moisture, it can lose as much as half of its insulating efficiency. The purpose of a vapor retardant between the air inside your home and the insulation is to prevent humid air (warmer air) from seeping into your insulation and becoming trapped there. The principal here is quite simple, and you can often see it on your windows. When warm air meets cool air, it creates condensation, which is moisture. A vapor retardant outside concrete or insulation prevents the creation of condensation where the warm air and cool air meet. You can choose to install insulation with a vapor barrier already attached, or you can simply purchase sheets of vapor barrier and apply it inside your home. Placing vapor barrier beneath a concrete slab foundation or outside the foundation or basement walls will prevent the seepage of moisture from the ground.

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