There are four types of packaging that insulation comes in. They are blankets, batts, rigid boards and loose fill. Blankets come in thicknesses of 1 to 7 inches and from 16 to 64 feet long. They are best used in long runs such as between floor joists in an attic or between rafters in a roof. They also come with and without a vapor barrier. Batts are similar to blankets, but come in 4 or 8 foot lengths for easier handling. The 8 foot lengths easily fit between the studs of a standard wall. Rigid boards are made from plastic foam and offer high insulation values in thicknesses of up to one inch. Rigid boards are often used under vinyl or aluminum siding. They are flammable and should not be covered with wood paneling or left uncovered. Cover rigid boards with wallboard, which resists fire. Finally, loose fill can be spread easily over open, flat areas such as attics, or blown into closed walls and floors through access holes. The biggest problem with loose fill is that it settles in walls over the years, causing gaps in your insulation. Loose fill also requires a separate vapor barrier. A vapor barrier is used to keep water vapor in warm indoor air from passing through the insulation and reaching the cold outside areas of the wall. If the water vapor reaches the colder area, it will condense into water and soak the insulation, causing it to lose its insulating qualities.
The resistance to the movement of heat through insulation is measured on a scale of R-values. The recommended R-value of exterior walls in most of the United States and Canada is R-19. The following are the common types of insulating materials, approximate R-value per inch thickness and some pros and cons of each. First, fiberglass and rock wool both have an R-value of 3.33. They come in blankets, batts and loose fill. They are inexpensive and fire resistant, but can irritate your skin. Cellulose (R-3.70) also comes in blankets, batts and loose fill and is usually used as a blown in application for attics. Made from old newspaper, cellulose is flammable unless chemically treated. Vermiculite (R-2.08) and perlite (R-2.70) are loose fill insulation. They are easy to use but have a low insulating value and readily absorb water. Polystyrene (R-3.45) comes in rigid boards. Being moisture resistant, it is used for insulating below ground. It is very flammable and is dented easily. Finally, Urethane is the best insulating material (R-5.30). It requires professional installation because it is foamed in place. It will give off toxic gasses if caught on fire.
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