Steel Door Inc.

Why Have Thermal Performance Ratings Changed?

SDI member manufacturers’ published U-values have changed as a result of an update to the testing method of SDI 113 (Standard Practice for Determining the Steady State Thermal Transmittance of Steel Door and Frame Assemblies). Previously, only the central portion of a door panel was tested. This does not reflect operable conditions as it does not include the entire door, frame or hardware, which affects the transfer of heat. The updated method now tests the entire operable assembly and employs the use of ASTM E1423-06 as the basic test standard.

It may appear that SDI’s hollow metal door and frame manufacturers’ products have higher thermal conductivity than they did previously. But that is not true—the products perform the same as they did before. The difference is that the U-value now accurately reflects operable conditions. This improved data helps design professionals estimate the energy efficiency of the building. Always verify the doors and frames you specify provide U-values tested with the improved testing method.