What Is 179D for Architecture & Engineering Firms?
Section 179D is a federal tax deduction for energy-efficient commercial buildings. Most firms know it as a building owner's incentive. What most A&E firms don't know: since 2022, you can claim it yourself — even if you never owned the building.
This works through the Designer Allocation Mechanism (IRC §179D(d)(4)), introduced by the Inflation Reduction Act. When you design energy systems for a tax-exempt building — a government agency, public school, nonprofit hospital, or housing authority — the building owner cannot use the 179D deduction (they pay no income tax). So the law allows them to allocate that deduction directly to you, the designer.
The government building your firm designed qualifies for a large tax deduction — but the government doesn't pay taxes. So Congress made that deduction transferable to your firm.
This is not a new incentive that requires new projects. Projects completed in 2022, 2023, 2024, and 2025 are all eligible. Retroactive claims going back to 2022 are still possible. If your firm has designed energy-efficient systems for government or non-profit clients in the last three years and hasn't claimed 179D, there's money on the table right now.
Who Qualifies as a Designer?
The 179D designer allocation is available to:
- Architects who designed the building envelope (insulation, windows, exterior wall assemblies)
- Mechanical/HVAC engineers who designed qualifying HVAC and hot water systems
- Electrical engineers who designed the interior lighting systems
- Energy modelers and commissioning agents who prepared the energy certification for the building
- Design-build firms that handled design and construction of qualifying systems
The IRS requires that the designer created the technical specifications for the energy-efficient property — not just installed it. An architect or engineer who prepared construction documents meets this standard. A general contractor who subcontracted the design typically does not.
Multiple designers can receive allocations for the same building — an architect claims for the envelope, a mechanical engineer for HVAC, an electrical engineer for lighting. Each firm claims only the system(s) it designed.
What Buildings Qualify?
The Designer Allocation Mechanism applies when the building owner is a tax-exempt entity. The most common categories:
- Federal government buildings (GSA, military, VA, federal agencies)
- State and local government buildings (courthouses, transit facilities, state offices)
- Public K–12 schools and public universities
- Nonprofit hospitals and healthcare facilities (501(c)(3) organizations)
- Affordable housing authorities and public housing developments
- Tribal government buildings
- Other 501(c)(3) nonprofits
Private commercial clients — office buildings, retail, hotels — cannot allocate the 179D deduction to their designers. The building owner must be tax-exempt.
The building must achieve at least 25% energy reduction versus the applicable ASHRAE 90.1 baseline year. This threshold applies per qualifying system (HVAC, lighting, or envelope) for partial deductions, or across all systems for the full deduction.
How Much Can Your Firm Claim?
Deduction rates depend on the project year, prevailing wage compliance, and how many energy systems qualify. Rates are applied per square foot of the total building floor area — not just the renovated space.
| Project Year | Max Rate (Full Building) | Prevailing Wage Required? | Per-System Partial Rate |
|---|---|---|---|
| 2023, 2024, 2025 | $5.65/sqft | Yes (for max rate) | ~$1.88/sqft per system |
| 2022 (retroactive) | $1.88/sqft | Not required | ~$0.63/sqft per system |
| 2021 and prior | $1.88/sqft (legacy rate) | Not required | ~$0.63/sqft per system |
What does this mean in dollar terms?
For a 200,000 sq ft public school your firm designed the HVAC system for (2024 project, prevailing wage met, HVAC only):
- Partial deduction rate (one system): ~$1.88/sqft
- 200,000 × $1.88 = $376,000 deduction
- At a 35% effective tax rate: ~$131,600 in tax savings for your firm
For a full building with all three systems qualifying at $5.65/sqft: 200,000 × $5.65 = $1.13 million deduction.
Enter your building square footage, systems designed, and project year to get a fast estimate. Try the 179D Calculator →
Step-by-Step Claim Process for A&E Firms
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1
Identify Qualifying Projects
Audit your project list for 2022–2025. Flag any projects where the client was a government agency, public school, nonprofit hospital, or other tax-exempt entity. Pull square footage and identify which systems you designed (HVAC, lighting, envelope).
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2
Engage a Qualified Energy Modeler
179D certification requires a qualified energy modeler to run energy simulations comparing your building's performance against the ASHRAE 90.1 baseline. This produces the required certification statement. Your firm cannot self-certify — the certifier must be independent and licensed.
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3
Obtain Allocation Letter from the Building Owner
The tax-exempt building owner must provide a signed allocation letter specifying: (a) the building and project, (b) the systems being allocated, (c) the deduction amount, and (d) your firm as the recipient designer. Without this letter, you cannot claim the deduction.
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4
Assemble Required Documentation
Required documents include: the energy certification from the qualified modeler, the allocation letter from the building owner, construction drawings/specifications showing your firm's design scope, and prevailing wage certification (for 2023+ projects claiming the full rate).
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5
Claim on Your Firm's Tax Return
The deduction is claimed on Form 3115 (change in accounting method) or directly on your firm's income tax return using the deduction amount from the allocation. Work with a CPA experienced in 179D — the deduction is straightforward once documentation is assembled, but the filing mechanics require tax expertise.
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6
Retroactive Claims: File an Amended Return
For 2022 projects (and earlier years still within the statute of limitations), you can file an amended return (Form 1040-X for individuals, 1120-X for corporations) to capture deductions you missed. Consult a tax professional on filing deadlines for your specific situation.
Critical Deadlines
179D Timeline for A&E Firms
The 3-year statute of limitations for amended returns means 2022 tax year returns (filed in spring 2023) approach their window in spring 2026. If your firm has 2022 qualifying projects, this is urgent. Contact a 179D-experienced CPA this week.
Common Questions from A&E Firms
We designed the HVAC but not the lighting or envelope — can we still claim?
Yes. Partial deductions are available for single-system improvements. If you designed only the HVAC system and it achieves the required energy reduction, you claim approximately one-third of the full-building rate. You do not need to design all three systems to qualify.
The building owner says they've never heard of this. What do I do?
The Designer Allocation Mechanism was new in 2022. Many government and nonprofit procurement teams are unaware they can provide allocation letters. Point your contact to IRS Notice 2023-29 (or the updated guidance) and IRC §179D(d)(4). Alternatively, a 179D specialist firm can help you approach the building owner with the proper documentation template.
Can we claim 179D on multiple projects in the same tax year?
Yes. Each qualifying project generates its own deduction based on that building's square footage and systems designed. There is no annual cap on 179D deductions for designers — you can aggregate deductions from multiple government/nonprofit projects in the same tax year.
Does prevailing wage apply to our design fees or to the construction labor?
Prevailing wage requirements apply to the construction laborers and mechanics who installed the energy systems — not to your design fees. If the contractor who built the systems paid prevailing wages, the full $5.65/sqft rate is available. If they did not, the deduction drops to approximately $1.13/sqft for 2023+ projects.