Check the Facts of Long-term Thermal Performance and Thermal Drifting
Open-cell and mineral fiber insulations are performing to the manufacturer’s specs (R value) on the shelf in the store under certain density conditions. Materials like fiber insulations are usually tested in an assembly, or only calculated, due to the technical obstacles of conducting hotbox tests. More so, within 2 years of installation, the breakdown of the fiber causes a steep drop in thermal performance, and within 5-7 years the performance can drop to a 1/3 of its original. When accounting for humidity or water penetration, the performance is even lower and actually negative. Example: think of a warm wool sweater keeping you warm. Now what happens if you were spray-misted and now contain 25% water? Not only it will not keep you warm, but will cool you down. Just in the same fashion fiber insulations performance degrades. They hold humidity over time and atmospheric conditions condense humidity to water, dropping the insulation rating, increasingly losing its performance to a negative value. In addition, the trapped water vapor in contact with the OSB creates a habitat for mold, fungus, mildew, and black mold to develop.
EPS, as opposed to open-cell and mineral fiber insulations, keeps constant thermal and mechanical strength performance over time (life expectancy of 425 years) with no thermal drifting, very low perm rate, eliminating the need for weather barrier in exterior wall applications, above grade. As EPS is impermeable, it will not keep water vapor, nor allow it to develop any biological mass such as molds, mildew etc. This super performance has a major positive financial impact when being applied in wet rooms such hotel bathrooms, commercial kitchens, rental units where high dollars and capital reserves are continuously dedicated to the maintenance and repairs instead of going to the bottom line, increasing the ROI.