Insulation is primarily used to prevent or reduce transfer of heat or sound. The standard unit of measure commonly used in North America for a products insulating value is “R-value”. “R” stands for resistance to heat flow and is a measure of how effective the installed insulation will be. The higher the R-value, the greater the insulating power. Metric measurements are also commonly used and are referred to as the RSI value.
In order for light density fibreglass insulation to perform at its labelled R-value the product must be allowed to recover from its packaging to its optimum thickness. For example; 3.5” (R-12) residential batt insulation will only perform at an R-12 if it is allowed to fill the 3.5” cavity produced in 2x4 wall construction. If the product does not recover to 3.5” thickness due to poor packaging or improper installation, the insulation will only perform to a portion of the R-value.
The same can be said about any light density fibreglass covered with black polyethylene. An R-12 base insulation will only perform at R-12 if it is allowed to recover completely. Many products on the market are packaged too tightly which crushes the insulation past the point of full recovery.
Most light density fibreglass insulations are manufactured for 1 time packaging. What this means is these products are compressed down to +/- 1/10th their original size for shipping from the manufacturing plant. Residential batt insulation would be one of these products (we’ve all seen how much a bundle of batt insulation expands once it’s been cut open). If these insulation products are compressed again during secondary production the fibreglass manufacturer may not guarantee that the product will recover to its intended thickness (or full R-value) as the product was not designed to be compressed twice.
The North American Insulation Manufacturers Association (NAIMA) has developed a standard for insulation that will go through secondary compression. This standard is NAIMA 202-96 (Rev. 2000). Nu-West only uses NAIMA 202-96 (Rev. 2000) insulation that has dual compression built into the fibreglass matrix. Our insulation is also compliant with the Canadian Standard CAN/ULC-S702-97. Our product is designed to be compressed twice. It is compressed once by the manufacturer then once by our production department. This ensures that our customers in the field are receiving the highest possible R-value from the base insulation.
Products that are designed to be installed as a wrap are usually done so at a recommended 25% compression. This will mean that the insulation, after installation, should be 2 5/8” thick and will perform at R-9. The only possible method to increase from this R-9 is to either use a higher R-value base insulation or to install the wrap at less than 25% compression.