Q. Why is Spray Foam Better Than Fiberglass?
A. According to the US Department of Energy, “The most common insulation, fiberglass, does not stop air leakage. In older homes, dirty fiberglass is a telltale sign of air movement (it simply collects dirt like a filter).” If insulation cannot air seal, then it cannot truly insulate. Creating an air-tight structure is the absolute key to achieving the greatest insulation results. Most factory-made insulation suffers a reduction in performance due to its inability to prevent air-movement. Fiberglass has a real-world R-value far below what is stated. In tests conducted at Oak Ridge National Laboratory, commonly installed fiberglass batting was found to have an R-value that was typically 28% less than what the manufacturer claimed. In addition, because of its lack of air barrier qualities, when exposed to a real-world environment with wind, moisture, and cold climate, tests show the effective R-value of fiberglass diminishes by more than 50%. However, foam’s ability to stop air leakage is only a fraction of its benefits, convection suppression is another important characteristic – see question 8. CONCLUSION: Fiberglass insulation is a poor investment; Spray Foam Insulation literally pays for itself and puts money in the bank.
SIDE NOTE: It is interesting to note, applications that demand truly effective insulation use foam – i.e. the space shuttle, freezers, refrigerators, etc. Thanks to foam insulation, new Energy Star refrigerators are capable of running on only 75 watts of electricity! Refrigerators insulated with only 1.5” of foam use 40% less energy than those with 3” of fiberglass.