Insulation Comparison and FAQ
provided by NAIMA
What are the major uses of fiber glass insulation?
Fiber glass serves a number of useful purposes, but the most important application of wool-type fiber glass is as insulation used primarily to control temperature and sound in homes, commercial buildings and industrial operations. Wool-type fibers are also used to manufacture a variety of sound-control products and insulation for air ducts, pipes, roofs, walls, floors, automobiles, mobile homes, aircraft, refrigerators, domestic cooking appliances, as well as other appliances and equipment.
What are the benefits of fiber glass insulation?
Fiber glass insulation is a cost-effective, energy-saving product that saves money for individuals and businesses through lower utility bills while increasing the comfort levels for all building occupants.* In addition, adequate levels of fiber glass pipe insulation for industrial processes have helped make industry more efficient and more profitable by cutting energy losses and decreasing production costs. By avoiding the added energy generation necessary to heat and cool buildings, fiber glass insulation continues to be a benefit to the environment by helping to reduce pollution emissions.
Fiber glass insulation products play a significant energy-savings role by reducing energy use in homes, office buildings, businesses and manufacturing plants. In 1996, a study was conducted jointly by the Alliance to Save Energy and Energy Conservation Management, Inc. regarding the energy and environmental benefits of insulation. The report, entitled "Green and Competitive," found that insulation currently in place in residential buildings throughout the United States saves 10.41 quadrillion Btu's each year. That is enough energy to generate 36% of America's annual electric consumption or the equivalent of a 255-day supply of gasoline for the entire United States.
While the energy savings from fiber glass insulation are significant, so are the environmental benefits. By making buildings more energy efficient, fiber glass insulation helps reduce the amount of fossil fuel combustion needed to heat and cool homes, businesses, and factories. That, in turn, decreases the amount of carbon dioxide emitted into the atmosphere.
Because carbon dioxide is one of the principal "greenhouse gases" contributing to global warming, insulation plays a significant role in protecting the environment. For example, according to the "Green and Competitive" report, insulation currently in place in residential buildings reduces the amount of carbon dioxide emissions into the atmosphere by 1.35 trillion pounds each year. Almost 300 million acres of trees would have to be planted to remove this much carbon dioxide naturally from the atmosphere.
* Savings vary. Higher R-value means greater insulating value.
Thermal Performance - Installed R-value
When insulating a home, it is important to get the R-value specified by the local energy code or the Department of Energy recommendations. It's also important that the product provide long-lasting thermal performance. For more information on insulation recommendations for a specific area, contact the local building department or the local gas or electric utility for their recommendation.
While R-value "per inch" is promoted by some manufacturers, the overall R-value installed is what counts. Fiber glass insulation products come in R-values ranging from R-11 to R-38 for fiber glass batts and rolls. Fiber glass insulation can be blown in an attic to nearly any R-value. More R-value alternatives provide greater flexibility in meeting code energy requirements in your area.
In order to ensure the expected energy savings, it is important that the insulation does not deteriorate, or settle, over time. Fiber glass batts and rolls do not settle. Fiber glass loose-fill insulations 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. If cellulose insulation is being considered, make sure the installer understands that most cellulose insulations settle in attic loose-fill applications - that's a significant loss of insulating effectiveness. In fact, the Insulation Contractors Association of America recommends that an additional 25% of thickness be added for cellulose insulation to compensate for this extreme loss of R-value.
Fiber glass and cellulose perform very differently in terms of fire safety. Fiber glass insulation is naturally non-combustible because it is made from sand and recycled glass. The insulation requires no additional fire-retardant chemical treatments.
Most facings attached to fiber glass insulation are combustible and should never be left exposed. Other special flame-resistant facings may be left exposed where desired, such as on a basement or crawl space wall.
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 proof. This means the insulation could still burn if exposed to a heat source. Also some tests have shown that fire retardant chemicals can lose their effectiveness over time.
Tests conducted by the California Bureau of Home Furnishings and Thermal Insulation demonstrated that most cellulose samples failed the standard fire safety test only six months after installation. Smoldering and re-ignition problems present additional concerns with cellulose insulation should a fire start.
Insulation will lose its insulating efficiency or R-value when wet. Fiber glass insulation is not absorbent and, if exposed to moisture, will not wick up or hold water. It will dry out 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.
Some cellulose insulations are actually applied with water added by what is called a wet-spray method. Wet-spray applications do not achieve their R-value until dry. A study conducted by the NAHB Research Center in 1997, found that cellulose insulation had installed moisture content greater than 40%. According to the study, under summer conditions, the walls dried rapidly to below 30% in the first day, but under fall and spring conditions, the walls dried much slower and were still above 30% when the dry wall was installed.
Waiting until the cellulose is dry to cover up is difficult with today's building construction schedules. If wet-spray applications are covered up too soon, moisture problems will occur. Not only does the insulation efficiency suffer, but moisture can affect other building components, such as wood studs, drywall and metal building components which can suffer corrosion from moisture and salts. Moisture can also lead to a number of additional indoor air quality problems by promoting mold and mildew growth.
Thermal insulation, whether fiber glass or cellulose, when installed in side walls has very little to do with air infiltration. The U.S. Department of Energy estimates that up to 40% of a home's heat loss can be from air infiltration. But only 14% of the total loss from air infiltration occurs through side wall cavities, and most of that is around electrical outlets, a problem easily solved with inexpensive, easy-to-install electrical insulated outlet gaskets.
Air infiltration generally occurs in the areas of a home that are not insulated, such as around windows, doors, fireplaces, HVAC ductwork and perimeter joints. It can, and should, be controlled with the use of housewrap, proper caulking, and sealing of band joists, sill plates, header plates, and insulation around doors, windows, electrical outlets and other openings.
Recently there have been claims that some insulation products are better because they reduce air infiltration. Numerous research studies have been conducted to investigate this issue, among them studies by the National Association of Home Builders Research Center, researchers at Penn State University, and by a St. Louis utility. The research consistently demonstrated that if a wall cavity has been properly constructed, using drywall, sheathing and caulking, very little air will flow through the wall cavity regardless of the type of insulation.
As the environmental consciousness of Americans has been heightened, the building industry has responded. This kind of rethinking has led to a strong push to use building materials with lower environmental impact.
Fiber glass insulation manufacturers have responded to this call for conservation by using increasing amounts of recycled materials in their products. As an industry, fiber glass insulation manufacturers recycle more material by weight (glass cullet - up to 40%) than any other type of insulation used in the building and construction sector.
The environmental benefits of fiber glass insulation, however, go far beyond its recycled content when analyzed from a life-cycle perspective. A life-cycle analysis is an appraisal of the environmental impacts connected with a product through an examination of the product's environmental traits during many stages including pre-manufacturing; manufacturing; distribution/packaging; use, reuse, maintenance; and waste management. In reviewing each of these stages, a life-cycle evaluation of fiber glass clearly shows its environmentally beneficial attributes. As an example, consider fiber glass versus cellulose insulation.
Cellulose manufacturers claim environmental benefits, even though they may be removing newsprint from an existing recycling loop. More trees must be cut and more energy used to make new newsprint and cardboard to make up for what has been used for cellulose insulation. And when it comes to insulating the same size home, pound for pound, it takes up to three times more cellulose than fiber glass to achieve the same insulating efficiency. Both insulations use the same amount of virgin material but the virgin material in fiber glass is sand - which is classified by the U.S. Environmental Protection Agency as a "rapidly renewable resource."
NAIMA has developed a brochure outlining the various life-cycle characteristics that specifiers should consider in determining the most relevant attributes of an environmentally preferable insulation product: "Using Recycled Material Is Just the First Step...(N016)" Also see Insulation and the Environment.
For additional information:
There are two types of fiber glass insulation: fiber glass loose-fill (blown in) insulation, and fiber glass blanket insulation. Fiber glass loose-fill insulation comes in bags. Fiber glass blanket insulation comes in batts and rolls in various densities, widths and lengths to fit particular home insulation applications.
What is the function of the 'facing' on insulation?
The facing material is generally a vapor retarder and is usually applied toward the "warm-in-winter" portion of the home to help resist the movement of moisture vapor to cold surfaces where it can condense. This means that in the ceilings the vapor retarder faces down; in the walls, it faces the inside; and in the floors over unheated spaces, it faces up. In hot, humid climates, a vapor retarder may not be needed. Check local building practices or building codes in your area.
Yes. Fiber glass may cause itchiness and temporary skin irritation in many people handling the products. With respect to more serious effects, fiber glass insulation is one of the most thoroughly tested building materials in use today. Nearly 70 years of extensive research and comprehensive reviews by independent research organizations have concluded that there is no convincing evidence that exposure to fiber glass is associated with respiratory disease or cancer in people. Other insulation materials do not enjoy the same long history of testing as fiber glass insulation.
Cellulose, for example, remains a largely untested commodity. Even though it is composed of approximately 20% chemicals by weight, the cellulose industry has performed little, if any, health and safety testing on its products. Questions about the health and safety aspects of cellulose insulation persist in the building industry. The limited scientific testing conducted on cellulose to date provides no assurance as to the safety of the material, particularly given its high exposure levels. For example, documented worker exposures to respirable cellulose fibers have been measured at 50 to 200 times higher than fiber glass. Clearly, more research is needed. For a complete review of the health and safety information on fiber glass, click on NAIMA's Commitment to Safety or visit the Literature Library Health and Safety Publications section.
Fiber glass insulation products have a positive impact on the indoor environment by controlling heat loss or gain; by reducing condensation which can lead to air pollutants; and by providing sound control. In 1990, the World Health Organization Working Group on Indoor Air Quality reviewed all previous scientific studies and concluded: "Current airborne man-made mineral fiber concentrations in indoor environments are considered to represent an insignificant risk." More than 20 other studies conducted at noted universities and laboratories, examining concentrations of fiber glass and other synthetic vitreous fibers (SVFs) - in residential and commercial buildings, consistently found that SVFs from insulation products in residential and commercial buildings do not significantly contribute to indoor air pollution, and would not be expected to adversely impact the health and/or well being of occupants of such buildings.1
Fiber glass is one of the most thoroughly tested building products in the world with health and safety research on fiber glass spanning nearly 70 years. This research has been designed to investigate the possible human health effects of fiber glass and other SVFs.
In October 2001, an international expert review by the International Agency for Research on Cancer (IARC) re-evaluated the 1988 IARC assessment of glass fibers and removed glass, rock and slag wool fibers from its list of substances “possibly carcinogenic to humans.” All fiber glass and rock and slag wools that are commonly used for thermal and acoustical insulation are now considered not classifiable as to carcinogenicity to humans (Group 3). IARC noted specifically: “Epidemilogic studies published during the 15 years since the previous IARC Monographs review of these fibers in 1988 provide no evidence of increased risks of lung cancer or mesothelioma (cancer of the lining of the body cavities) from occupational