Air leakage is not an issue that some insulation manufactures like to bring up. The reason for this is that air leakage can dramatically affect the R-value of certain insulations. The R-value measures a material’s thermal resistance ability but does not account for air leakage. Products can have a stated R-value in an ideal environment, but when an air leakage is created that R-value can be radically reduced. What this means for the consumer in reality is that the product manufactures labeled R-value may not be anywhere near accurate. The American Society of Heating Refrigeration Air Conditioning Engineers or (ASHRAE) did a fiberglass insulation study of the before and after installation comparison between the manufacturers stated R-value and what the consumer really receives. Even with perfectly installed fiberglass the actual effective R-value is substantially lower than what the manufacture stated.