Fiberglass vs Cellulose
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Insulating your home will reduce your energy bill and improve your home’s comfort and energy efficiency. Fiberglass and blown cellulose are the most commonly used insulation fibers, but it's important to know which is the best option for your home.
Fiberglass insulation is sold as batts or loose fill. Batts are narrow blankets that come in rolls. Batts are installed in walls, floors, and attics. They often have a paper or foil face that helps slow moisture movement but this facing makes installing batts correctly more difficult. Unfaced batts fill cavities better and are easier to cut. If you install fiberglass batts in your wall cavities, cut them accurately to size. Fit fiberglass batts carefully around electrical boxes and wires. A sloppy fit can negate some of the insulating value of fiberglass blankets.
Fiberglass loose fill is installed in attics and wall cavities. It is a good material in moist, humid climates since it absorbs very little water. It's also a good material for retrofitting the wall cavities in metal-skinned mobile homes. Its low density puts less pressure on the ceiling or underbelly, reducing the potential for damage to the structure. Fiberglass loose fill is usually installed by professional insulators. It's easy to over-fluff loose-fill fiberglass in an attic installation, reducing the blown fiberglass insulation’s density and encouraging air convection within the insulation. Be sure your insulator installs blown fiberglass at the manufacturer's recommended density.
Cellulose insulation is purchased as a loose-fill material, and is always installed with an insulation blower. It's made from recycled paper that is treated with a flame retardant and pest deterrent. You can purchase it at lumber yards and home stores. You can rent a blower and install it yourself in your attic. Densely packed cellulose creates a better air seal than fiberglass because its small fibers pack into corners, crevices, and small air leaks. Because of this, cellulose is frequently used in the walls of older homes. Cellulose is also cheaper than fiberglass.
You shouldn't install cellulose insulation if you live in a very humid climate since it absorbs moisture easily. This will tend to wash out the fire retardant, decreasing its fire resistance and possibly corroding metal siding, wiring, or roofing.
If you have questions about which insulation is right for you, consult a professional insulator and enjoy a more comfortable home in all seasons. Both The Homeowners Handbook to Energy Efficiency and Residential Energy contain more information on insulation types and installation.
