(a) For new Federal buildings for which design for construction began on or after January 3, 2007, but before August 10, 2012, each Federal agency shall determine energy consumption levels for both the IECC Baseline Building 2004 and proposed building by using the Simulated Performance Alternative found in section 404 of the IECC 2004 (incorporated by reference, see § 435.3).

(b) For new Federal buildings for which design for construction began on or after August 10, 2012, but before January 10, 2018, each Federal agency shall determine energy consumption levels for both the IECC Baseline Building 2009 and proposed building by using the Simulated Performance Alternative found in section 405 of the IECC 2009 (incorporated by reference, see § 435.3).

(c) For new Federal buildings for which design for construction began on or after January 10, 2018 but before April 5, 2023 each Federal agency shall determine energy consumption levels for both the IECC Baseline Building 2015 and proposed building by using the Simulated Performance Alternative found in section R405 of the IECC 2015 (incorporated by reference, see § 435.3).

(d) For new Federal buildings for which design for construction began on or after April 5, 2023 each Federal agency shall determine energy consumption levels for both the IECC Baseline Building 2021 and proposed building by using the Simulated Performance Alternative found in section R405 of the IECC 2021 (incorporated by reference, see § 435.3).