The R-value of insulation is a measure of its thermal resistance, which is the ability of the insulation to prevent heat transfer. A higher R-value indicates that the insulation is more effective at preventing heat loss or gain. For example, an insulation material with an R-value of R-10 is more resistant to heat transfer than one with an R-value of R-5. When selecting pipe insulation, it’s essential to choose a material with an R-value that meets the required specifications for the specific application.