What is the R-value?
R-Value is a measurement of how well an object (insulation, window, drywall, etc) resists the flow of heat or cold through it. R-value is determined by a laboratory test in which an insulation material is sandwiched between a cool and a warm surface.The ability of the material to resist temperature changes results in an R-value for that material.

Are all insulations the same if they have the same R-Value?
Different insulations are made from fundamentally different materials. Tests at Oak Ridge and Brookhaven National Laboratories and the University of Illinois reveal that insulations with the same laboratory R-values do not perform equally in real homes. Researchers found that the effective R-value of blown fiberglass plunges during cold weather, while the effective R-value of cellulose actually increases. The researchers also discovered that summer temperatures offer no relief for fiberglass, since it's effective R-value withers then, too.
The study found Utility bills were 32% lower in the cellulose insulated building.
~ Leominster Housing Authority

The Oak Ridge National Laboratory Test
Researchers at Oak Ridge National Laboratory (ORNL) tested insulation under "real world" conditions in a full-scale attic simulator. The temperature of this simulator can be varied to reflect different temperature conditions, just like the temperatures your house experiences. Their research found that fiberglass products declined as much as 40% in R-value as the temperature difference between conditioned (inside) air and ambient (outside) air increased.

The Colorado Study
The University of Colorado School of Architecture tested the "real world" performance of cellulose and fiberglass insulation. They built two structures and insulated one with fiberglass using R-19 in the walls and R-30 in the ceiling (attic). The other structure had the same measured R-values, but was insulated with cellulose insulation. The cellulose insulated building was seven degrees warmer than the fiberglass structure after a nine hour heat loss test. But more importantly, after three weeks of monitoring the cellulose insulated building used 26.4% less energy than the fiberglass structure. The researchers concluded that "cellulose insulated buildings perform 38% better than fiberglass insulated structures."

Cellulose vs. Fiberglass
The following is a summary of an extensive Natural Resources Defense Council (NRDC) report. The NRDC is a non-profit environmental membership organization with over 300,000 members and contributors nationwide.

  • Cellulose insulation manufactured from recycled paper is the least polluting and most energy efficient insulation.
  • Cellulose has the highest post-consumer recycled content. The fiberglass industry averages 35% recycled glass, while the cellulose industry averages a minimum of 75% recycled content.
  • It takes more than 10 times as much energy to produce fiberglass insulation as cellulose insulation.
  • Due to air circulation and natural convection, the R-value of blown-in fiberglass insulation decreases by as much as 50% as the temperature drops from 45 degrees F to 18 degrees F.
  • Cellulose has better resistance to air flow and prevents the upward movement of air caused by temperature differences (the R-value of cellulose actually improves during cold weather).
  • Substantial and well-documented public health threats are associated with fiberglass.
  • No adverse health effects from cellulose insulation have been identified. Cellulose is non-toxic. Biologically, cellulose is innocuous.
    ~ Dr. Arthur Furst, Toxicologist