There has been so much said about insulation, it is difficult to choose which is best from the wide variety of different types of insulation on the market. After everything is said and done you should only use insulation with a vapor barrier. The best insulation in this category is fiber batt insulation. If the insulation does not have a vapor barrier it will not be an effective insulator.

When installing, the insulation vapor barrier it should always go to the warm side of the house or the inside.

Obviously the warm side changes from summer to winter as well as from day to night. If it is 10 F below zero outside, the inside of an occupied house is certainly the warmest side. During the summer months when the sun is shining brightly, the warm side is the outside.

When we talk about the R-values of insulation and vapor barriers we are concerned primarily with the conservation of heating energy. If we insulate against heat lost during winter, the same insulation will prevent heat gain during periods of air conditioning.

One would think that it would be wise to put a vapor barrier on both sides of the insulation so the insulation and vapor barrier will be affective during the winter and the summer.

Vapor barriers will stop most of the moisture but not all. If there were two vapor barriers small amounts of moisture will move into the fiber insulation between the two vapor barriers and become trapped. The vapor will accumulate as the temperature swings back and forth and become a huge problem. The moisture will get trapped between the vapor barriers and saturate the fiberglass insulation to the point that is an ineffective insulator.

Fiber insulation needs ventilation on one side therefore the vapor barrier should go on the side where it will do the most good and that is toward the inside of the house. Only use insulation with a vapor barrier if you want the best insulator for your home.

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