1. Recycling
2. Energy Conservation
3. Additional Energy Efficiency Factor
4. Safety
5. History

1. Recycling
Cellulose insulation meets the research objectives of the Resource Conservation Home from several standpoints. Cellulose building thermal 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 vital 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.

2. 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)

3. 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.

4. 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)

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.

5. History
Cellulose insulation has been produced and installed in new and existing homes for more than 40 years. During the Energy Crisis period of the mid-1970s heavy demand for insulation induced many new producers to enter the cellulose industry. The population of the industry grew from about 50 companies to as many as 750 companies within a few years. Unfortunately, many of these new producers lacked the technical competence — and sometimes possibly the desire — to make high-quality products that conformed to government and industry standards.

Now the number of active cellulose producers has returned to the pre-Energy Crisis level of about 60 companies. Overall quality standards have also improved. Today cellulose is covered by the most comprehensive and rigorous government and industry standards of any insulation. The vast majority of producers document compliance with these standards through a regular testing program.