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The Most Effective Roof Insulation

Because heat rises, the attic and roof are the areas of a house that most need insulation. These areas also need to be sealed effectively to prevent outside air from entering, but also need ventilation to prevent moisture buildup from condensation. Attics usually are vented at the edges on the underneath sides of overhangs, or soffits, to provide air flow while restricting heat loss.

  1. Roof Foamboard

    • Most houses being built today have foamboard insulation installed on roof decking before shingles are applied. This insulation is typically expanded, 1- to 1.5-inch-thick polystyrene (XPS) and is the first line of insulation defense. It has an R value, or heat resistance, of 4 per inch, but must be taped at the seams to make it air-tight.

    Attic Cellulose

    • Attic insulation is the second and most important line of insulation defense. Loose-fill cellulose is the most common type of attic insulation. It is made from old newspaper, shredded and treated with a fire retardant chemical, and is 100 percent recycled material. It is formed in granules which are blown into the attic cavities with an air hose. It covers tight spaces well and has an R value of 3.5 per inch. This is the most cost-effective type of attic insulataion; it has a high R value, is easily installed and is inexpensive.

    Fiberglass and Fiber

    • Other types of loose-fill attic insulation are fiberglass pellets, rock wool made from recycled wool fibers, and cotton or denim granules also made from recycled fiber. All are installed by being blown in with air pressure, and all are good at filling cavities between and around roof joists and edges. Their R values generally are in the range of 3 per inch.

    Blankets

    • Blanket insulation also can be used in attics. Blankets are sheets usually of fiberglass, although rock wool and cotton also might be used. Fiberglass batts are the most common type. Basic fiberglass has an R value of about 3.2, but high-density versions can range up to 4 per inch. Cotton and wool batts have R values of about 3.5 per inch; rock wool with chemicals added has about 3.7.

    Rigid Foam and Minerals

    • Rigid foamboard can be used in attics but is much harder to install, because it lacks the flexibility of blown-in or blanket materials and requires taping at all seams. Other rarely used attic insulation materials are minerals, vermiculite and perlite. These have fairly low R values, 2 to 3, but are fire resistant and can be used around fireplaces and chimneys. They are most often used today to insulate concrete block construction.

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Energy Efficient Homes
  1. Should the Insulation Be on the Top Inside of the Roof?
  2. The Effects of Reflective Attic Insulation On a Roof
  3. Can Foam Insulation Be Applied to the Underside of a Roof?
  4. The Cause of Insufficient Insulation in the Attic
  5. Loose Insulation in the Attic
  6. Foam Insulation to Spray in the Attic
  7. Does Insulation Go Between the Roof Studs in the Attic?
  8. The Most Insulation Recommended in the Ceiling, Walls or Floor
  9. Why Do Homes Have Twice the Amount of Insulation in the Roof Than the Walls?
  10. What Kind of Insulation in the Attic Is the Brown Insulation?
  11. The Most Effective Kind of Attic Insulation
  12. What Is the Proper Way to Insulate an Attic?

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