The §179D Deduction requires energy modeling whereby the building is compared to the same building constructed to the minimum requirements of a specified ASHRAE 90.1 Reference Standard. In Announcement 2023-1, the IRS affirmed ASHRAE 90.1-2019 as the new Reference Standard. The new standard will be applicable for any projects placed in service after 2026. The IRS also clarified that ASHRAE 90.1-2007 will remain the Reference Standard for any projects placed in service before the newer standard goes into effect. In addition, taxpayers who began construction before 2023 may utilize Reference Standard 90.1-2007 regardless of when the building is placed in service....