Browse to https://www.sierrapacificwindows.com/.
Click 'Windows'.
Under 'By Material' select the material you're considering (e.g., "Aluminum Clad" for Aspen).
Select the type of window (e.g., "Aspen Casement")
Scroll down and expand 'For the Professional'
Select the "NFRC" document type; open the PDF.
Look at the U-factor and SHGC columns under Argon-Filled. You will see that for comparably-constructed windows in the left-hand column (e.g., with the same Warm Edge Spacer), the U-factors are nearly identical while the SHGCs vary a lot.
Note Energy Star Rating Zone column shows the zones for which a particular window qualifies. Eagle is in the Northern (N) zone.
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