Look up the maximum U-factor and SHGC a commercial curtain wall or storefront glazing system must meet under the IECC for a specific climate zone.

Steps

1. Confirm the governing table is IECC Chapter 4 [CE] Commercial Energy Efficiency, Section C402.4 ('Fenestration'), specifically Table C402.4 for maximum U-factor and SHGC by climate zone and fixed/operable fenestration category
2. Note that as of the 2021 IECC, the SHGC compliance table changed from an orientation-based approach (separate values for north/south/east/west-facing glazing) to a fixed-vs-operable fenestration category basis, with overall stringency increased in several climate zones versus prior editions — confirm any specific numeric U-factor or SHGC delta only against the licensed code table itself, not a secondary summary
3. Access the actual numeric table values through a licensed codes.iccsafe.org Premium subscription or the jurisdiction's adopted print/PDF code copy — the free public-access view of Digital Codes does not expose full table contents for this section
4. Confirm which code edition and any state/local amendments (many states amend IECC commercial fenestration tables) apply to the specific project jurisdiction before using ICC's base-code numbers
5. Verify the selected glazing system's tested U-factor/SHGC via its NFRC label/Certified Products Directory listing against the applicable Table C402.4 maximums for the project's climate zone