Cellulose Blown-in Insulation
Blown-in insulation is a quick and inexpensive way to insulate your attic, and this method seals air spaces in the attic better than batt insulation. Cellulose blown-in insulation has an R-value of 3.8 per inch of insulation thickness. If you already have Fiberglas insulation installed in your attic, adding cellulose insulation over the Fiberglas will increase the insulating properties. A professional installer uses a blowing machine to lay down the insulation.
Fiberglas Blown-in Insulation
Fiberglas blown-in insulation has an R-value of 2.3 to 2.8 per inch. Because the thickness of blown-in insulation varies, the R-value is less consistent. Fiberglas is a common choice, works well as an insulator and is less expensive than cellulose. There are health concerns with installing Fiberglas, and it is best to have a professional do this type of insulating for you.
Cotton Fiber Batt Insulation
One advantage of batt--also called blanket or roll-in--insulation over blown-in is that you can install it yourself. Batt insulation is removable, so if you have plans to work on your attic in the future, batt insulation would be a good choice. Cotton fiber batt insulation has an R-value of 3.7. It’s safer to work with than Fiberglas, which has fibers that can be a health hazard to your lungs and skin if it not handled with care. Cotton fiber is an excellent insulator and is environmentally friendly, although it can cost twice as much as Fiberglas.
Fiberglas Batt Insulation
Fiberglas batt insulation has a better R-value than the blown-in type--3.1 to 4.2 per inch, depending on the density of the insulation. The lower-density type is more commonly used, but it can lose much of its R-value in colder climates. The high-density batts cost more, but savings in your energy bill can make it worthwhile to invest in this type of insulation. Because of health and environmental concerns, many insulation manufacturers have stopped using formaldehyde as a binder and switched to non-toxic acrylic binders. Although the danger of inhaling fibers is small, wear a dust mask and gloves when installing Fiberglas batt.
The U.S. Department of Energy (DOE) provides a calculator for consumers to determine what the best R-value insulation for your location is and the type of heating you use. When buying the insulation, the DOE advises to check the product label to check the thickness of the insulation so you can properly calculate your recommended R-value. See this website for the calculator and other helpful information: