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What's 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.
The problem with R-value : A machine in a laboratory gives a relative number that can be used to compare products, but your house is not a laboratory and a laboratory R-value does not tell everything you need to know about the effectiveness of those products. Insulation is subjected to a wide range of temperature conditions in your house. Insulation can be affected by air movement, and it is also degraded by the convection forces that develop within the insulation material. Convective Loops
A convective loop, whether inside a wall cavity or in another part of the building structure, occurs when air rises along a warm surface and falls along a cold surface, creating a circular movement of warm and cold air. A convective loop transfers heat through the building assembly, requiring more energy to replace the lost heat in heating seasons and the lost cool air in cooling seasons.
Air Leakage's role in heat loss and insulation effectiveness Research shows that air leakage into and out of the building envelope is a primary factor in moisture accumulation and heat loss, however, building code officials, building inspectors, many builders, and the codes themselves, focus their attention on the R-values of materials to increase the energy efficiency of homes and focus their efforts on vapor retarders to prevent moisture accumulation in ceilings and walls. Air tightness is many times considered a secondary factor for keeping the heat in or out. Because air infiltration can account for between 25% to 45% of the total heat loss in a typical home, the R-value of an insulation material alone is not a true measure of its effectiveness. Insulation materials, through improper installation, will have more leaks, reducing the "Effective R-Value." Cellulose Insulation, when properly installed, greatly reduces air leakage, providing a superior R-value in "real world" environments, like your home. Cellulose Insulations's higher "Effective R-value" results in energy savings of up to 40% compared to conventional insulation.
What the research shows!!! 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:
The NRDC has concluded the following:
• 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
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 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." Keep in mind that both structures had the same "measured R-value."  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. Bottom line: when the temperature in the attic is 20 degrees, the fiberglass insulation in the attic will lose 40% of its R-value. The researchers at ORNL recommended that: "attics with fiberglass insulation be covered with as little as 3 inches of cellulose to stop the loss of R-value in the fiberglass!" ColoradoHomeEnergyPros uses Blown Cellulose and expanding foam insulation! In our Home Performance with Energy Star experience we had concluded all the same conclusions as the above studies, before we read the studies. |
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