Frequently Asked Questions About Insulation

This page primarily addresses the claims that some cellulose manufacturers and installers make. We install both fiberglass and cellulose. When you read the following arguments, we do not have a strong preference related to the use of cellulose over fiberglass. We simply offer you facts to help you decide.

• “Cellulose prevents mold, fiberglass does not”
• “Spray-in-place cellulose and blown-in-batt fiberglass are gap-free, fiberglass batt is not.”
• “Cellulose r-values are more effective than fiberglass R-values”
• “Spray-in-Place Cellulose does not need a vapor barrier”
• “Fiberglass is a possible carcinogen (cancer-causing agent)
• ““Cellulose, not fiberglass, protects from fires.”
• “Blown cellulose outperforms blown fiberglass.”

“Cellulose prevents mold, fiberglass does not”

Cellulose manufacturers (NuWool, Cocoon) now treat their product with a mold fungicide. They highlight cellulose’s mold resistance in their literature. Some say that all of the mold problems are associated with fiberglass.

Instead of simply improving their product so that it inhibits mold, they turn the argument against the fiberglass industry and overstate the case. The cellulose industry suffered a bad reputation with mold growth; so they were forced to improve their product. The truth is any wood fiber (lumber, drywall backing, fiberglass kraft paper and cellulose) soaking in water, in a dark wall cavity, for a long period of time is the perfect breeding ground for dangerous mold growth. Mold prevention does not rest alone in the product. Prevention involves the proper cleanup of a flood emergency and proper building methods. Mold is not a problem normally associated with today’s construction industry. Numerous improvements have been made to prevent moisture from entering the home.

“Spray-in-place cellulose and blown-in-batt fiberglass are gap-free, fiberglass batt is not.”

Spray-in-place and blown-in-batt installers claim that their product is “gap free.” That is, they say that their material fills every gap as opposed to fiberglass batts.

True, fiberglass can be installed with gaps. It is also true that spray-in-place and blown-in-batt products can be installed with gaps. Gaps are possible with any insulating method. If installed improperly, cellulose can shrink and leave gaps. If installed improperly, blown-in-fiberglass installers can miss areas. We have been installing fiberglass since 1975. We are very careful about leaving gaps. We use polyurethane foam around those areas that are most susceptible to gaps and compression (e.g., exterior wall plugs, holes and cracks). See How We Install Fiberglass Batts. The picture at left is often used to show the superiority of spray-in-place cellulose over fiberglass batt. The problem with this picture is two-fold: 1) the fiberglass example is not the way fiberglass is installed. As shown, this would not pass building codes due to the lack of a vapor barrier and improper sealing around the plugs; 2) the cellulose covers pipes preventing them from receiving warmth from the interior of the house.

“Cellulose R-values are more effective than fiberglass R-values”

Cellulose manufacturers heavily support their conclusions based on the University of Colorado Study. These studies conclude that spray-in-place cellulose outperforms fiberglass batts in sealing the house. They further state that measuring insulating efficiency by R-value alone is not appropriate.

What is not said is that the University of Colorado Study was independently reviewed by long-time insulation researcher from Tennessee Techological University. He found that the “facts do not support the conclusion that cellulose insulation limited the air leakage in a building.” When these studies are referenced, the sources are cited but not footnoted. NAIMA interacted with these studies and provided footnotes showing proof that the above studies are far from conclusive.

R-values are important and the remain the standard measuring tool for insulating efficiency. The Department of Energy and the Department for Housing and Urban Development continue to assess insulating performance by R-values. Local building authorities measure insulation by R-value standards. Even cellulose manufacturers continue to measure their product on the basis of R-value.

Insulation effectiveness depends on proper installation, not the product. Both cellulose and fiberglass can be improperly installed. Gaps are eliminated by conscientious, detail-oriented installers, not by a system or product alone. See How We Install Fiberglass Batts.

What is not said is that the University of Colorado Study was independently reviewed by long-time insulation researcher from Tennessee Techological University. He found that the “facts do not support the conclusion that cellulose insulation limited the air leakage in a building.” When these studies are referenced, the sources are cited but not footnoted. NAIMA interacted with these studies and provided footnotes showing proof that the above studies are far from conclusive.

R-values are important and the remain the standard measuring tool for insulating efficiency. The Department of Energy and the Department for Housing and Urban Development continue to assess insulating performance by R-values. Local building authorities measure insulation by R-value standards. Even cellulose manufacturers continue to measure their product on the basis of R-value.

Insulation effectiveness depends on proper installation, not the product. Both cellulose and fiberglass can be improperly installed. Gaps are eliminated by conscientious, detail-oriented installers, not by a system or product alone. See How We Install Fiberglass Batts.

Why is the wall system the main focal point of those who use the spray-in-place cellulose? The main heat loss is through the ceiling. Therefore, it seems that too much is being made of the walls.

Conclusion: Fiberglass and cellulose have nearly the same R-value rating. If one is concerned about increasing the insulation efficiency of one’s home, then the real focus should be on the depth/r-value of insulation in the ceiling, not the walls.

“Spray-in-Place Cellulose does not need a vapor barrier”

Cellulose manufacturers and installers claim that the density of cellulose makes the use of a vapor barrier unnecessary.

Some, not all, building officials allow spray-in-place cellulose installers to eliminate a vapor barrier. Two factors make this practice questionable. First, since framed wall structures are only 3.5 to 5.5 inches thick, water-laden vapor from the warm indoors can meet the cold temperatures. Second, in our northern climate, where indoor/outdoor temperatures often contrast as much as 70º, the force of pressure makes the “cellulose density” claim curious.

“Fiberglass is a possible carcinogen (cancer-causing agent) “

In their 2003 pamphlet, Your_Home_Your_Decision p. 6 Applegate Insulation (cellulose company) lists fiberglass as a possible carcinogen. They cite the National Toxicology Program in footnote 17 as their source.

What the truth is:

• The National Toxicology Program (2005) does not list fiberglass as a possible carcinogen.
• The American Lung Association shows a list of tests by various laboratories and clears fiberglass as carcinogenic.
• The U.S. Department of Health and Human Services provided a technical briefing paper on the health effects from exposure to fiberglass. They also conclude that “studies provide inadequate evidence for the carcinogenicity of fibrous glass in humans.”
• These studies were performed on those in the trades of installing and manufacturing fiberglass. If there is no evidence of fiberglass caused cancer in those exposed to it on a daily basis, one can reasonably conclude that homeowners are not at any risk of fiberglass-caused cancer.

“Cellulose, not fiberglass, protects from fires. “

In their 2003 pamphlet, Your Home Your Decision p. 6 Applegate Insulation claims that cellulose insulation actually helps make homes safer by providing up to 50% better fire resistance than fiberglass. In practical terms, this means that occupants have more time to reach safety in case of fire. Unlike fiberglass, it greatly restricts the amount of oxygen available to support combustion - it won’t pump oxygen to the fire.

What the truth is: Fiberglass is made of densely-packed glass strands (non-flammable), cellulose is made of paper (flammable). Sulfates are added to cellulose, making it fire-retardant. Over time these sulfates will wash away due to condensation. On the other hand, fiberglass is commonly covered with a flammable vapor barrier. Making an argument for or against either product is actually moot. Houses are built with many flammable materials. The drywall has a paper backing which is flammable. The wood framing is flammable. Therefore you should not make a decision on the insulating material when everything else encapsulating it is flammable. Their implication that fiberglass “pumps oxygen to the fire” bypasses the intellect. The North American Insulation Manufacturers Association produced an article which provides another perspective related to the flammability of insulating materials.

“Blown cellulose outperforms blown fiberglass.”

Before the late 1980’s, this statement was true. Blown fiberglass had a rating of 2.2 R’s per inch. Cellulose had a rating of 3.3 R’s (and still does). Fiberglass manufacturers developed a high-density fiberglass which now exceeds cellulose by little over 1 R-value per inch.

	Material		R-value per inch
	Fiberglass Batt		3.71
	High Density Fiberglass Batt		4.3
	Fiberglass loose fill (blown)		4.0
	Cellulose loose fill (blown)		3.2 to 3.8
	Sprayed polyurethane foam		6 to 7.3