Attic Insulation Tutorial

R-value

• An important gauge of whether your insulation can give you the amount of heat retention you need lies in its "resistance to heat flow" rating. This measurement of insulating strength, called the R-value, depends on the type of insulating material used, its thickness and density, according to the U.S. Department of Energy. For example, most fiberglass insulation has an R-value of about 2.9 to 3.8 per inch. How much R-value you need to efficiently insulate an attic depends on your local climate.

Fiberglass Batting

• One of the most widely used types of insulation, fiberglass batting comes in blanket form, with a vapor barrier, such as paper or polyethylene, attached to the bottom. Fiberglass batts come in standardized widths so they will fit in the spaces between joists or studs. Place fiberglass batts between the attic joists snugly, but do not compact them, which decreases the insulation's R-value. Avoid letting any batts touch the roof's sheathing. For a higher R-value when insulating an unfinished attic, apply a second layer of batting on top of and perpendicular to the first layer.

Blown-in or Loose Fill

• Blown-in or loose-fill insulation consists of loose fibers of cellulose, fiberglass or rock wool. An operator blows this type of insulation into the appropriate space with a machine. Blown-in or loose-fill materials often make good choices for finished attics since installing fiberglass batting might involve removing drywall or floorboards. Because of the machinery involved, professionals typically install blown-in insulation. You can rent a machine to install it yourself, but you will need at least one other person to help you.

Mixing

• You can mix two different types of insulation in your attic. For example, you can place a layer of fiberglass batts between the floor joists and add a layer of loose-fill insulation on top. You can also lay the batting on top of the loose-fill material. Generally, however, when you combine two different types of insulation, place the material with the higher R-value on the bottom to avoid allowing the material with the lower R-value to weaken the combined layers.