Rockwool Comfortbatt R15

R-Value measures thermal resistance — how strongly a batt slows heat flow; the higher the number, the better it insulates. The number itself is the measured rating, and it sits on a scale: our stone wool batts come in R-11, R-13 and R-15, so R-15 slows the most heat flow, R-13 sits in the middle and R-11 the least. A higher number means less heat passes through the same wall depth — heat flow falls in proportion to the inverse of the rating, so an R-15 batt lets roughly a quarter less heat through than an R-11 batt. For Comfortbatt R15, the 'R-15' rating describes the batt's thermal performance installed in a standard 2×4 wall cavity — the highest of the three, so it slows the most heat flow without needing a deeper wall. The rating is a thermal measure only, never a sound rating; that same dense stone-wool structure is also what delivers the acoustic absorption, so one batt gives you both thermal and sound benefits.