The R-value and U-value are two related but distinct concepts in HVAC. R-value measures a material’s resistance to heat flow, while U-value measures its ability to transfer heat. A higher R-value indicates better insulation, whereas a lower U-value indicates better insulation. In other words, R-value is a measure of how well a material resists heat flow, whereas U-value is a measure of how easily heat can flow through a material.