Attic Insulation

Fiberglass

Cellulose

Properly installed fiber glass batts and rolls do not settle. Fiberglass loose-fill insulation will experience negligible settling (less than 2%) over time. When manufacturers’ installation procedures are employed, fiberglass insulation maintains its thermal performance for the life of the building.

Cellulose manufacturers agree that their products settle over time. Most set the settling rate at about 20%. Therefore, always consult the “minimum settled thickness” and the “initial installed thickness” listed on the cellulose manufacturer’s coverage chart, which is required by the FTC, to ensure future settling is accounted for.

Fiberglass insulation is made from sand and other inorganic materials which are melted and then spun into glass fibers. Fiberglass is naturally noncombustible and remains so for the life of the product. It requires no additional fire-retardant chemical treatments. Unfaced fiberglass insulation is recognized by building code groups as an acceptable fire stop in residential wood frame walls.

Cellulose insulation is made of ground-up or shredded newspaper which is naturally combustible. In fact, cellulose insulation is regulated as a recognized fire hazard by the Consumer Product Safety Commission (CPSC). To protect against fire hazards, cellulose insulation is heavily treated with fireretardant chemicals prior to installation. These fire-retardant chemicals can leach out of the cellulose insulation over time. Tests conducted by the California Bureau of Home Furnishings and Thermal Insulation have demonstrated that some cellulose samples failed the standard fire safety test only six months after installation. Additionally, smoldering combustion and re-ignition problems are concerns with cellulose insulation should a fire start. Even properly treated cellulose insulations will burn at about 450°F, the surface temperature of a 75 watt light bulb.

Between 1992 and 2008, the fiberglass insulation industry recycled over 18 billion pounds of pre- and post-consumer glass containers, eliminating the need for millions of cubic feet of landfill space. Many fiberglass insulation manufacturers have plants that use up to 40% or more recycled materials in their products. The current industry average is 30% recycled content. Manufacturers are currently exploring ways in which their use of recycled materials can be increased without compromising the performance of their insulation products.

Cellulose insulation is generally made up of about 80% recycled newspaper and 20% fire-retardant chemicals. Three times more cellulose material by weight than fiber glass is needed to insulate a typical home. An average 1,200 square foot attic insulated to R-38 with cellulose insulation would introduce 300 pounds of fire-retardant chemicals into the home.

Insulation made of fiberglass is not absorbent. Under normal conditions, all insulation is exposed to humidity in the air. Fiberglass will not wick up and hold water, thus it resists permanent loss of R-value. Because it is inorganic, it is naturally fire resistant. If fiberglass insulation becomes saturated as the result of flooding or other catastrophic events, the manufacturer of the product should be consulted to determine whether the product should be replaced.

Cellulose insulation is made of shredded newspaper with an added fire retardant. Two relevant properties of shredded newspaper are as follows: (1) without special treatment it will burn; and (2) it naturally absorbs moisture from the air. This can result in the cellulose insulation losing its added fire retardancy as it ages. Cellulose insulation that is saturated because of a flood or other catastrophic event can lose its fire retardants, and even if it can be dried, it should not be reused without consulting the product’s manufacturer.

Fiberglass is inorganic; mold cannot grow in or on it.

Cellulose is organic; cellulose itself is a food source for mold.

Fiberglass insulation is not corrosive and contains no chemicals that can corrode pipes and wires.

Certain chemicals routinely applied as a fire retardant to most cellulose insulation (particularly the sulfates) can cause the corrosion of pipes, wires, and fasteners under some conditions.

Being inorganic, fiberglass is bug proof. It will not attract bugs as food source.

Being organic, cellulose has to be treated with insecticides which will wear off.

Fiberglass insulation is the most thoroughly tested insulation material in use today. The great amount of medical scientific evidence compiled over more than 70 years by industry, government, and independent research organizations supports the conclusion that fiberglass insulation is safe to use when manufacturers’ recommended work practices are followed.

Questions about the health and safety aspects of cellulose insulation persist in the building industry because very little medical scientific testing of the products has been conducted. Repeated requests by union and contractor groups that such testing be undertaken have been ignored. Full toxicological testing of dust from cellulose building insulation and indeed dust from pure cellulose fibers as well is needed. Given the high levels of exposure to fibers and dust measured during cellulose installation, only after long-term experiments are available will the safety of cellulose insulation be known.