Understanding Thermal Ratings in Hollow Metal Doors: R-Value & U Value 07/15/2025|Admin|Codes, Resources When thermal performance shows up in door specifications, you’ll often see references to R-value and U-value. But what do they really mean? And how do they apply to hollow metal doors? Let’s break it down in plain language. Why Thermal Ratings Matter in Hollow Metal Doors … Continue reading Understanding Thermal Ratings in Hollow Metal Doors