Read This Before You Insulate Your Attic

For DIY attic insulation, you've basically got two choices: loose fill or batt (the common term for blanket insulation). Both can be added to uninsulated attics or layered over existing material. Once you've decided which type is best for you, examine the material options and prices to home in on the right product. Always check labels for specifics on whatever you buy.

Loose fill
Insulation fibers are packaged in bags and blown in place to the desired depth and density using special machinery you can rent from a home center. You can pour the fill in place and spread it manually, but the process is much more labor-intensive and the results won't be nearly as good.

It works best for:
• Attics with irregular or nonstandard joist spacing
• Attics with lots of obstructions and penetrations to work around
• Attics where there is existing insulation to be topped, since it fills 
gaps and joints well
• Low-clearance attics with limited headroom for maneuvering 
during installation
• DIYers who want to get the job done quickly and are comfortable 
working with power equipment

Material options:
Fiberglass
$$$
R-value per inch: 2.2–2.7
Made of: Recycled glass or sand that's melted and spun into fibers
Bottom line: Lighter in weight than cellulose or mineral wool, but it settles more than those materials, so you've got to put in a thicker layer to get the protection you need.

Cellulose
$$$
R-value per inch: 3.2–3.8
Made of: Fibers from recycled post-consumer paper that are treated for insect and fire resistance
Bottom line: The most common blown-in material used, but it can rot and grow moldy if exposed to moisture.

Mineral wool
$$$
R-value per inch: 3.0–3.3
Made of: Fibers from rock or recycled slag from blast furnaces
Bottom line: Offers natural fire resistance, but costs more than other loose-fill materials.