Start with the complete assembly
A thermal-break profile is only one part of window performance. Compare the frame, glazing, spacer, gaskets, hardware and installation interface as one system.
Ask for comparable conditions
Use the same opening size, glass build-up and test conditions when reviewing U-value, air leakage, water resistance and structural data.
Connect the numbers to the project
Climate, orientation, wind exposure, acoustic targets and maintenance access determine which performance priorities matter most.