Problems Two major problems associated with insulation in the home are poor workmanship during installation and moisture condensation. Failure to properly cut and fit insulation into all areas where you want to reduce heat flow will decrease its effectiveness. You pay for this decreased effectiveness every time you purchase fuel for as long as you own the home. Moisture condensation is a frequent problem, but it can be prevented. All air contains moisture.
Warm air can hold more moisture than cold air.
During winter months, air inside the house is warmer than outside air, and moisture is added continually to air in the home by normal household activities such as washing and cooking, and purposely with humidifiers. If it encounters a cold surface during this migration, it condenses from a vapor to a liquid. When condensation occurs inside an insulated wall, insulation becomes wet, building materials start to decay, and paint peels off the outside of the building. This can be prevented by using a vapor barrier material to stop water vapor from entering the wall or ceiling and condensing on cold surfaces. Vapor barriers are installed over the face of the studs or joists on the side closest to the inside surface.