Cellulose Insulation
Cellulose insulation, which has been an important part of the retrofit market for many years, is rapidly growing as a new construction material. Builders throughout the United States are increasingly offering cellulose as their standard insulation material, or as an upgrade. The Resource Conservation Research Home constructed in the NAHB National Research Home Park is insulated with modern spray-applied and
pneumatically
installed loose-fill cellulose insulation. Loose-fill cellulose insulation was
installed in the home's attic area and side walls are insulated with cellulose
wall-spray applied materials.
Recycling
Cellulose insulation
is a recycled product made from recovered newsprint, one of the largest single
components of the residential waste stream. Insulating a typical 1,500 square
foot ranch-style home with cellulose insulation productively recycles as much
newsprint as an individual will consume in 40 years. (ref.1)
If America's new homes
were insulated with cellulose, over 3.2 million tons of waste newsprint could
be removed from the refuse stream every year and put to productive use
conserving vi tal energy resources. This projection is based on 1.5 million new
homes with an average area of 1,500 square feet, insulated to R-30 in the
attics and R-13 in the side walls. (ref. 2) If more stringent insulation
standards, such as those of the Model Energy Code, were followed even more
recyclable material would be removed
from the waste stream.
Energy Conservation
Just as significant as
its recycling advantage is the superiority of cellulose as an insulating
material. Most independent insulation authorities agree that cellulose is the
best fiber thermal insulation, and an impressive body of scientific research
supports this belief.
Studies at Oak Ridge
National Laboratory have proven that cellulose is not subject to the convective
effects that degrade the actual R-value of other loose-fill fiber insulation
materials at low attic temperatures. Using the Large Scale Climate Simulator at
Oak Ridge, scientists have found that the effective R-value of tested
mineral fiber
insulation dropped from approximately R-18 at +45 degrees F to R-11.1 (and in
one test run to R-9.2) at -18 degrees F. Over a similar temperature range
nominal R-19 cellulose showed a slight R-value gain of about 10 percent.(ref.
3)
Cellulose has long
been regarded as superior to other fiber insulation materials in sealing the
building envelope against air infiltration. This characteristic was
"conventional wisdom" until researchers at the University of Colorado
at Denver put the concept to the test in the winter of 1989-90. Two structures
identical in every respect, except for the insulation system used, were built.
One building was
insulated with R-19 of wet-spray cellulose in the walls and R-30 of loose-fill
cellulose over the ceiling. (This is essentially the same insulation system to
be used in the NAHB Resource Conservation Research Home.) The second building
was insulated with R-19 unfaced mineral fiber batts in the walls and R-30
kraft-faced batts over the ceiling.
Blower door tests
demonstrated that the cellulose insulation system tightened the building 36 to
38 percent more than the mineral fiber material. After recording the actual
energy performance of the buildings over a period of many weeks the researchers
stated:
The research suggests
that the performance of cellulose versus fiberglass is as much as 38 percent
better. Cellulose achieves a tighter building cavity, allowing less heat loss
due to air infiltration and its overall performance appears to be about 26
percent better in tempered climates. It may be concluded that this benefit
would become more significant in more severe climates. (ref. 4)
Additional Energy Efficiency
Factors
Cellulose
not only insulates better than mineral fiber materials, it has two other
important energy efficiency advantages. The first of these advantages is less
"embodied energy." It takes much less energy to make cellulose. Mineral fiber
insulation is produced in furnaces that gulp natural gas and release greenhouse
gases
into the atmosphere. These
furnaces burn day and night, month after month, regardless of how much insulation is needed. Cellulose is
produced in electrically-driven mills. They consume relatively little energy
when they are operating, and they consume no energy once the production day
ends.
On a strictly theoretical basis it
can be calculated that "R" for "R" mineral fiber insulation
takes 15 to 20 times more energy to make than cellulose insulation. Data
reported to the Canadian Standards Association suggest mineral fiber
production actually requires 59 times more energy than cellulose production,
on a
pound for pound basis. (ref. 5)
Adjusting for weight differences, mineral fiber materials take 25 to 30 times
more energy to make than cellulose of equivalent R-value.
Adding to this "embodied
energy" advantage of cellulose is the fact that cellulose is produced from
locally available material. Other than the fire retardants, which represent
about 20 percent of cellulose insulation by weight, it is not necessary to transport
feedstocks long distances to cellulose insulation plants.
Another collateral energy
efficiency advantage of cellulose is its potential to reduce energy
expenditures for waste transportation. Many cities and states, especially in
the Northeast, are running out of landfill space. There are serious proposals
to transport waste from New England and the Middle Atlantic region as far west
as Kansas. If substantial amounts of newsprint were removed from this transport
stream and recycled locally as cellulose insulation the amount of waste moved
to distant landfills could be substantially reduced, with corresponding savings
in the amount of energy required to transport the waste.
Safety
Because it is an organic material
cellulose is treated with fire retardants. It is the only common residential
and light commercial construction material that always receives such treatment.
This makes cellulose insulation one of the safest construction materials on the
market. Studies of actual fires and demonstration burns have proven that the
dense fiber structure of cellulose and the fire retardants slow the spread of
fire through a building, giving occupants more time to escape and fire fighters
more time to save the structure. (ref. 6) A comprehensive research
program sponsored by the cellulose, fiber glass, and rock wool industries,
among others, at the National Research Council Canada Fire Laboratory found
that fiber glass in a wall slightly decreases the fire resistance of the wall,
while cellulose increases the fire resistance of a wall 23% to 55%.
Studies
by researchers associated with Oak Ridge National Laboratory have proven that
the fire retardants in cellulose do not deteriorate, evaporate, sublime, leech
out, or otherwise disappear over time. After studying the permanency of
borate-based fire retardant formulas scientists reported that it would take 300
years for there to be significant change in the chemical content of cellulose
insulation. (ref. 7) A more recent study of ammonium sulfate by the same
researchers revealed that this fire retardant was even more stable than the borates. This
finding was confirmed by tests of aged cellulose insulation taken from homes in
Florida. The tests indicated cellulose treated with ammonium sulfate becomes
more fire resistant over time. (ref. 8) This may be due to continuing
absorption of the fire retardant by the fibers.
Cellulose has historically been
regarded as a relatively low technology product. That view is gradually
changing as cellulose products and installation technology become more
sophisticated.
Light density cellulose is one
example of this growing sophistication. Ten years ago 2.6 pounds per cubic foot
was a typical settled density for cellulose. Introduction of mills
incorporating new technologies during the past few years, and refinement of
older production equipment, have reduced the typical settled density of
cellulose to the 1.8 to 2.0 pcf range. Cellulose products with settled
densities of 1.5 or 1.6 pcf are offered by several producers.
Traditionally "open
blow" installation of any insulation has been a dusty process, and
cellulose has been regarded as especially dusty. Now low-dust cellulose for
blown installation is available. This material produces virtually no visible
dust during pneumatic installation, resulting in a much cleaner job and more
pleasant working conditions for installers.
Cellulose wall cavity spray is one
of the fastest-growing insulation products in new construction. This material
is much more effective in preventing air infiltration than insulation batts, as
the Colorado study demonstrated, and it is not subject to settling. Several
producers offer similar products for "open blow" installation in
attics. These materials use adhesive and a small amount of water to limit settling.
The products
are now known as “stabilized
cellulose.”
The entire matter of settling has
been the subject of misconception. Far from being a liability, the settling
characteristics of cellulose are one of its greatest strengths. It's because
the fine cellulose fibers settle after they are installed that the material is
so effective in preventing air infiltration. Other fiber insulation with
lighter fibers and a more open structure does not settle into cracks and gaps
in the structure as cellulose does. Predictable settling is a favorable
cellulose characteristic.
Sellers of other types of
insulation occasionally attempt to mislead consumers by stating that the
R-Value of a cellulose insulation system will decrease as the material settles.
It will, but under federal law and in accordance with the accepted industry
standard, cellulose insulation R-values and coverage data are always stated at
settled density. Far from being "cheated" out of R-Value as the
insulation settles, home owners with cellulose systems actually benefit from an
R-Value bonus until the material reaches settled density. There is considerable
doubt if most cellulose systems ever reach nominal settled density in the real
world of housing.
There has been considerable
competitive debate about the moisture performance of cellulose insulation as
compared with other common insulation products. Cellulose is a hygroscopic
material that stores moisture; other fiber insulations are non-hygroscopic and
their producers promote this as a benefit. Recent studies, one of which was
reported at the 1999 Bugs, Rot, and Mold Conference, indicate that the presence
of cellulose insulation in a wall reduces the moisture content of the siding,
sheathing, and interior finish materials at all times of the year. These
studies were based on the performance of cellulose without a vapor retarder,
supporting the cellulose insulation industry position that vapor retarders are
not necessary with cellulose insulation.
The Cellulose Insulation
Manufacturers Association
The Cellulose Insulation
Manufacturers Association (CIMA) was established in June 1992 when the members
of the Cellulose Industry Standards Enforcement Program (CISEP) adopted new
bylaws ending standards enforcement activities and restructuring the organization
as a trade association. Standards enforcement by an industry organization was
believed to be unnecessary since several independent
organizations, including
Underwriters Laboratories and the NAHB Research Center, had cellulose
insulation labeling programs based on CISEP regulations.
Footnotes
1. Based on data from the National
Solid Wastes Management Association.
2. Calculation by Koffer and
Associates
3. Wilkes, K., Proceedings of the
International Symposium on Roofing Technology, 1991 Childs, P.; and Wilkes, K.,
Report to CISEP on CRADA 90-0029, August 1991
4. Boonyartikarn, S. and Spiezle, S.,
University of Colorado 1990
5. Letters to Canadian Standards
Association from G. van der Zanden, Roxul; and B. Wiley, Therm-O-Comfort, Ltd.
6. "The Big Burn" Insulators
Guide, September 1978
7. Chiou, N., and Yarbrough, D.,
"Permanency of Boric Acid Used as a Fire Retardant in Cellulosic
Insulation", Energy and Buildings, 14 (1990)
8. Study by United States Testing
Company for Suncoast Insulation 1991
For
More Information
The Cellulose Insulation
Manufacturers Association (CIMA)
The Cellulose
Insulation Manufacturers Association (CIMA) represents the technical,
scientific and professional interests of nearly forty (40) producers of
Cellulose insulation materials in the United States. CIMA is dedicated to
fostering greater energy efficiency through the use of thermally effective and
environmentally sound insulation products in the Nation's buildings.
136 South Keowee
Street
Dayton, Ohio 45402 USA
Phone: (937) 222-2462
Fax: (937) 222-5794
E-mail: cima@dayton.net
Web Site: http://cellulose.org/
The material in this
fact sheet came from the Cellulose Insulation Manufacturers Association web
site and is being used with their permission: