What is the Best Attic Insulation?

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The attic is one of the worst areas for heat loss in a home, and proper insulation is key to keeping the overall cost of heating and cooling down to a minimum. Insulation minimizes heat loss by providing a barrier to keep the heat in during the winter. During the summer, proper insulation can keep hot air from entering the home. Properly installed attic insulation can reduce the energy cost of a home by as much as 30 to 40 percent.

There are four basic types of insulation used in the attic, and each has its own set of pros and cons. Choosing the best type of insulation for an attic depends on cost, energy efficiency and the local climate of the area.

The strength of insulation is measured by its R-value. The R-value is the measurement of thermal resistance in a material. A general rule is: the higher the R-value, the more effective the insulation.

Loose-Fill Insulation

This is a popular form of insulation for unfinished attics because of its low-cost and ease of installation. Loose-fill insulation is made of lose fibers or fiber pellets that are blown into the attic using special equipment. This is good for attic floors because it simply sits on the floor, and doesn't require any packing. Loose-fill insulation has an R-value of about 3 to 4 per inch.

Loose-fill is made of either cellulose, which is chemically treated strips of recycled newspaper, fiberglass or rock wool. It saves on energy costs by providing a loose barrier to keep the heat inside the home. Its major flaw is that there is the potential for several areas of open space.

Batt or Blanket Insulation

Batt or blanket insulation are strips of fiberglass or rock wool that fit snugly in ceilings, within walls and below floors. Attic walls and floors that are straight, and of a uniform width, are ideal for this type of insulation.

The blankets are rolled out to a specific length and fit into the area between the studs. The key to insulating an attic using batt or blanket insulation is proper installation. The insulation must fit tightly between the studs and not allow for any open spaces on the sides, at the top or at the bottom.

This type of insulation is perfect for the do-it-yourselfer and is available at most home improvement stores. It requires no special equipment to install, just a precision hand to get the right measurements. The primary problem for this type of material is that it is prone to becoming home to rodents over time. It has an R-value of about 3 per inch.

Rigid Board Insulation

Rigid board insulation is not generally used in attics unless the roof is either flat or cathedral-shaped. The rigid boards are made of a fiberglass or polyurethane foam, and like blanket insulation, is placed snugly between the joists and studs. What makes this a poor choice for attics is its lack of flexibility. Blanket insulation can bend to fit any awkward spaces or bends in the roof, but rigid board insulation doesn't bend. Another downside is due to fire codes, the material must be covered with a layer of gypsum board after installation for interior insulation such as an attic.

Since it is a rigid foam, the material is easy to cut and shape, but the cuts must be precise, otherwise it creates spacing, which allows heat to escape. This material doesn't allow for any air to pass through it and is one of the best insulations on the market when installed properly. Rigid board insulation has an R-value between 4to 8 per inch.

Spray Foam Insulation

Anyone with an attic with odd bends, little nooks and crannies, and other hallmarks of an older home will find spray foam the perfect choice. A sprayer shoots a liquid foam made of a polymer and a foaming agent into the walls. The foam expands to fill every inch of space and then hardens, creating an airtight seal.

Spray foam typically requires professional installation and special equipment. Attic areas that have chimneys or duct work with exposed spaces can benefit from spray foam insulation. This type of insulation has an R-value of about 6 per inch.

Bottom Line

There are few places in the home worse for heat loss than the attic, and insulating can help save a significant heating and cooling expense. Determine the R-value you need by examining climate, heating and cooling methods and the extreme temperatures of the region in order to choose the insulation that is best suited for your home.

Last Updated: July 22, 2011
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About Brock Cooper Brock Cooper is a freelance writer for IdealHomeGarden.com. 

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