Adding insulation to an unfinished attic is one of the most effective ways to save money on your energy bills. Before you call a contractor, however, it's important to understand the options and costs involved. It can cost anywhere from $1,700 to $2,100 or between $1.50 and $3.50 per foot to insulate an attic depending on what insulation material you choose. Blown-in insulation is the least expensive option and ideal for older attics. Spray foam, while the most expensive, is best for noise reduction and new construction. Expect to pay an attic insulation installer about $70 per hour. In some cases, you may also need the expertise of an electrician to safely insulate around junction boxes or cables; expect to pay an additional $85 per hour for this service.

Depending on the difficulty of your job, the size of your attic and the type of insulation material you choose, the final cost for professional placement will likely fall between $1.50 and $3.50 per foot. Here's a quick overview on your options for attic insulation, including the average cost of each material:

On This Page:

1. Batt Insulation
2. Loose Fill Insulation
3. Spray Foam Insulation
4. Alternative Insulation Materials
5. Attic Insulation Considerations

Batt ("Blanket" or "Rolled") Insulation

Batt insulation consists of long rolls of insulation fibers, which are held together with a paper or reflective foil backing. The insulation fibers may be comprised of fiberglass, cellulose, mineral wool or even recycled blue jeans. While rolled batting works well for expansive spaces, it does not fill tight, awkward spaces well -- regardless of material. A professional installer will need to tailor bits of insulation to fit around framing and electrical junction boxes, where it's easy to leave voids.

• Best for: Attics with standard spacing of joists, new construction free of obstructions or existing insulation
• R-value (resistance to heat flow) per inch:
• Fiberglass: 2.9 - 4.3
• Cellulose: 3.7 - 3.8
• Mineral wool: 3.0 - 3.3
• Cotton: 3.7 - 3.8
• Average cost: $2,091

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Loose Fill ("Blown-In") Insulation

Loose fill insulation is sold in large bags containing tiny chunks of cellulose, fiberglass or mineral wool fiber, which a professional installer will use a blowing machine to install. As opposed to batt insulation, loose fill is excellent for completely filling small, empty areas and gaps. You can purchase a bag that lightly covers up to 40 square feet for less than $12. R-values vary based on the type of material and the thickness of the installation.

• Best for: Attics with irregular framing or obstructions between joists, older attics that already contain some insulation
• R-Value per inch:
• Fiberglass: 2.2 - 2.7
• Cellulose: 3.2 - 3.8
• Mineral Wool: 3.0 - 3.3
• Average cost: $1,796

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Spray Foam

Spray foam insulation is the most expensive insulation, and it is available in open cell and closed cell options. Open cell is the less expensive option; however, it does not provide any vapor barrier. Closed cell, on the other hand, is more dense, and it provides an excellent barrier against air and water. Spray foam insulation sticks to whatever surface you spray it to; so, your installer can apply insulation to the ceiling in addition to the rest of your attic for added protection. Spray foam products are most easily installed in newly constructed homes.

• Best for: Insulating against noise, new construction, outdoor applications (closed cell)
• R-Value per inch: 5 - 6
• Average cost: $2,208

To determine the best insulation for your attic, contact a professional.

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Alternative Materials

Structural insulated panels: These are layered pieces of rigid foam insulation attached to oriented strand board (OSB) or plywood. These can be fabricated for any kind of home design, are extremely strong, energy efficient and inexpensive. If you build a home attic and insulate it with structural panels like these, you'll spend less time, money and professional expertise on the installation than you would with other types of insulation.

Reflective insulation: This is a shiny layer of aluminum foil that may added to rigid foam, plastic film or polyethylene bubble insulation. This type of insulation is designed to prevent radiant heat from getting into the action. It faces an enclosed air space and can be more effective than other types of insulation if the space is less than ⅜ inches wide. You should only install reflective insulation if you have a small, confined attic area. The amount of insulation you'll need will depend on your local climate and the way in which your home is constructed. Your local insulating professional will have a good idea of which type works best in your area. No matter where you live, energy efficiency is always a wise home investment.

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Attic Insulation Considerations

Adding insulation cuts down on energy required to keep the temperature regulated in your home. Having it in the attic also helps repress air leaks and the outside temperature. You should especially have attic insulation installed in such cases, including:

• Small attic: You need to insulate the attic even if you can't easily access it, because it's a huge risk for air leaks and potential heat loss.
• Air sealing: You need to make sure that ductwork is properly sealed to prevent moisture build up in the attic. If you have a fan, pull down stairs or other fixtures in the attic, they also need to be sealed.
• Proper ventilation: Your attic needs to have good ventilation to prevent problems. This also means that anything ventilating into it -- like the bathroom vent, for example -- is redirected out. You don't want moisture to build up in the attic from poor ventilation.
• Mold: If you do have mold in the attic, you'll need to have it treated and removed by a professional before you add insulation.
• Additional storage: If you want more storage space in your attic, you can add shelving or other configurations.

To get an exact price, get an insulation professional out.

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