Begin with dates, not the newest ASHRAE edition. The federal Section 179D baseline is selected under the statutory affirmation structure and IRS announcements; the standard adopted by a local building code answers a different compliance question.
Announcement 2024-24 already maps the 2007, 2019, and 2022 editions to service-date windows and preserves a visible rule for property whose construction began before January 1, 2023.
Federal selection
Published does not automatically mean applicable
ASHRAE publishes successive editions, but federal applicability follows the statutory process and effective dates. Modelers should cite the controlling IRS announcement rather than selecting the newest edition by preference.
Record both the conclusion and the facts used to reach it so a later reviewer can reconstruct the choice.
Announcement 2024-24 transition table
Use the service window, then test the pre-2023-start rule.
| Review point | Evidence or measure | Why it matters |
|---|---|---|
| 2015-2026 service | 90.1-2007 | General announced baseline. |
| 2027-2028 service | 90.1-2019 | General announced baseline. |
| 2029 onward | 90.1-2022 | General announced baseline. |
| Construction before 2023 | May use 90.1-2007 | Applies regardless of later service date under the announcement. |
Transition table
Service dates create three announced windows
For property placed in service during 2015-2026, Announcement 2024-24 identifies 90.1-2007. For 2027-2028 it identifies 90.1-2019. After 2028 it identifies 90.1-2022.
Pre-2015 property has separate historical rules and should not be forced into this simplified table.
Grandfather rule
A pre-2023 construction start can preserve 90.1-2007
Property whose construction began before January 1, 2023 may use 90.1-2007 regardless of a later service date under the announcement. Preserve project-level start evidence; do not treat a contract signature alone as conclusive.
For example, otherwise comparable June 2026 starts entering service in December 2028 and January 2029 indicate 90.1-2019 and 90.1-2022 respectively. A December 2022 start may instead use 90.1-2007.
A one-month boundary changes the indicated edition
Two hypothetical June 2026 starts cross the service-date boundary.
June 2026
Both begin construction
Dec. 2028 service
90.1-2019 indicated
Jan. 2029 service
90.1-2022 indicated
Separate review
Cutoff and all other rules
Separate cutoff
The correct baseline does not rescue an excluded late start
Section 179D(i) separately excludes property whose construction begins after June 30, 2026. That enacted cutoff is not a universal placed-in-service deadline.
Recheck current authority before modeling and again before certification. Future affirmations can change prospective baseline selections without changing the historical facts in the file.
Federal baseline versus local code
The same project can require two distinct standards analyses.
| Review point | Evidence or measure | Why it matters |
|---|---|---|
| Permit compliance | Local adopted code | Determined by the relevant jurisdiction and permit facts. |
| Section 179D model | Federal tax baseline | Determined under statute and applicable IRS guidance. |
Prepare the review
Document the reference-standard decision
- Property placed-in-service date
- Property-level construction-start date
- Pre-2023-start evidence
- Announcement version consulted
- Selected ASHRAE edition
- Local code kept separate
- Qualified software and version
- Reviewer conclusion and date
- June 30, 2026 cutoff analysis
- Recheck before certification
Continue the review
Common questions
Practical answers before the review
Does the newest ASHRAE edition always apply?
No. Federal applicability follows the statutory and IRS transition framework.
What changes for service in 2027?
The announced general baseline changes from 90.1-2007 to 90.1-2019, subject to the pre-2023-start rule.
Can a pre-2023 start preserve the 2007 standard?
Announcement 2024-24 says property whose construction began before January 1, 2023 may use 90.1-2007 regardless of service date.