Cellulose and Fiberglass blown insulation are the most common types of insulation used for attics today. Upgrading the attic is one of the best ways to increase your home’s energy efficiency. These days most attics do not have enough insulation or has insulation that isn’t working as well as it should be.
How does Fiberglass insulation compare with Cellulose insulation materials? Before we begin we would like to state that Insultech promotes and installs both products as great solutions for your attic upgrades.
Fiberglass and Cellulose insulation can be blown into an attic at nearly any R-Value. We recommend that you have at least an R-50. Higher R-Value means greater insulating value. Ice damning is a sure sign that you need an attic upgrade.
Fiberglass loose-fill insulation (blowing wool) may settle slightly (1-3%) resulting in virtually no impact on the thermal performance of the insulation.
In Contrast, cellulose insulation not only settles to a much greater degree (approximately 20%), but also at a higher rate. Installers must account for the settling of cellulose over time by installing additional insulation to compensate. How much will depend on the product.
Fiberglass insulation is made primarily of sand and glass fibers. It is naturally non-combustible and therefore requires no additional fire-retardant chemical treatments.
Cellulose insulation is made primarily of ground-up or shredded newspaper, which is naturally combustible. To protect against fire, cellulose insulation is heavily treated with fire retardant chemicals. Though cellulose is treated with fire retardants, it is not fire fireproof. This means the insulation could still burn if exposed to a heat source.
Fiberglass insulation (as long as it is not saturated) will dry out if exposed to moisture and retain its original R-Value.
Because cellulose is made from shredded newspaper, it will absorb and hold moisture, reducing energy savings. If soaked, cellulose will mat down and the thermal performance can be permanently reduced. Not only does the insulation efficiency suffer, but moisture can affect other building components, such as wood studs, drywall and metal building components. Moisture can also lead to a number of additional indoor air quality problems by promoting mold and mildew growth.
Any type of attic insulation can be installed over any other type fiberglass over cellulose, cellulose over fiberglass, it makes no difference. Each yields an R-factor of approximately R3.5 per inch.
Make sure your roof is free of leaks before upgrading your attic. You must also have sufficient roof vents as well as sufficient vents in the soffit space for best results. The hatch or entrance to the attic should also be upgraded and plumbing stacks sealed to prevent air leaks.