In order to understand what thermal transmittances I shall impose in a
baseline model for LEED, I have to understand in what climate zone I shall
consider Rome.
In TABLE B-3 "International Climate Zones" of ASHRAE 90.1-2010,
"Roma/Fiumicion" is zone 4, while in the weather file zone 3C is indicated.
The weather file for Fiumicino is available here:

https://energyplus.net/weather-location/europe_wmo_region_6/ITA//ITA_Roma-Fiumicino.162420_IGDG
If you see the .stat file, HDD18?C = 1514, which respects the thermal
criteria for zone 3C (see Table B-4).
Is TABLE B-3 based on other weather data?
Best Regards
Francesco