Performance Requirements
Energy requirements used to be a box the mechanical engineer checked near the end of design. That is no longer how it works. On the projects I investigate, the energy standards set during the design and documentation phase shape the building envelope, the mechanical systems, and the paper trail everyone relies on years later when something goes wrong. This article explains the standards that govern building energy performance — the IECC, ASHRAE 90.1, and voluntary programs such as LEED and ENERGY STAR — and, from a forensic point of view, where the documentation most often breaks down. I have kept it practical rather than exhaustive; energy codes are detailed, and the goal here is to help you ask better questions during design.
Key takeaways
- The IECC and ASHRAE 90.1 are the two model documents most U.S. energy codes are built on; states adopt and amend them on roughly three-year cycles.
- Most codes offer two ways to comply: a prescriptive path and a performance (energy-modeling) path. The choice belongs in the design phase.
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- LEED and ENERGY STAR are voluntary. They sit above the code minimum and create their own documentation and verification obligations.
- In disputes, the recurring issue is the gap between the energy compliance package and what was actually built and verified.
Why energy standards belong in the design phase
By the time a building is under construction, most of its energy outcome is already decided. Wall and roof assemblies, the ratio of glazing to wall, the type and efficiency of mechanical equipment, and the lighting approach are all locked in on the drawings. Changing them later is expensive and disruptive. There is a second reason this phase matters to me specifically. The compliance documentation generated during design — the energy code path chosen, the calculations, and the permit forms — becomes the reference point if performance is ever questioned. When I am asked to review a building years later, those design-phase records are often the first thing I look for, and their absence is itself a finding.
The energy code landscape: IECC, ASHRAE 90.1, and how they connect
Two model documents sit underneath most energy codes in the United States. The International Energy Conservation Code (IECC), published by the International Code Council, is the model most commonly used for homes. ASHRAE Standard 90.1 — the Energy Standard for Buildings Except Low-Rise Residential Buildings — is the model most commonly used for commercial buildings and for mid- and high-rise multifamily. Both are updated on roughly three-year cycles; the most recent editions are the 2024 IECC and ASHRAE 90.1-2022. A point that causes real confusion: these model documents are not law on their own. A state adopts an edition, usually with amendments for its climate and policy goals, and local jurisdictions may layer on stricter or optional “reach” provisions. The version that governs your project is the one in force in your jurisdiction on the date you pull the permit.
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How national model standards narrow down to the requirements your project is actually permitted to.
What ASHRAE 90.1 actually governs
- Building envelope — insulation levels, assembly U-factors, window U-factor and solar heat gain coefficient (SHGC), and air leakage control.
- Mechanical systems — heating, cooling, and ventilation equipment efficiencies and controls.
- Service water heating — equipment efficiency and distribution.
- Power and lighting — interior and exterior lighting power limits, lighting controls, and certain electrical provisions. The building envelope is where my work concentrates, because envelope requirements and moisture performance are closely linked. An assembly can satisfy an energy target on paper and still cause problems if the details are not buildable or the air and water control layers are not continuous.
Prescriptive vs. performance: two ways to comply
Most energy codes give the design team a choice between two compliance routes, and which one was used is worth knowing before construction starts. The prescriptive path requires meeting each listed requirement directly — minimum R-values, maximum U-factors, equipment efficiencies pulled from tables. It is the simplest to check and the least flexible. The performance path uses a whole-building energy model that compares the proposed design
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against a code baseline, allowing trade-offs across systems. ASHRAE 90.1 sets out a performance method in its Appendix G. It offers more design freedom in exchange for more analysis.
Two accepted routes to the same outcome — the design team selects one, and that choice shapes the documentation.
From a forensic standpoint, the path matters because it tells me what the building was supposed to
demonstrate. A performance-path building carries an energy model and a set of assumptions; if the asbuilt equipment or envelope differs from those assumptions, the modeled result no longer describes the building.
Where Oregon and Washington stand right now
- Oregon. Commercial energy requirements are in the Oregon Energy Efficiency Specialty Code (OEESC). The 2025 OEESC, based on ASHRAE 90.1-2022, took effect January 1, 2025. Residential energy provisions are in Chapter 11 of the Oregon Residential Specialty Code. Oregon also publishes an optional Reach Code for projects targeting higher performance.
- Washington. The Washington State Energy Code (WSEC) has separate commercial and residential provisions. A newer edition has been moving through the adoption process, so the edition in force can vary by project timing. Because adoption dates and amendments change, I treat the specific edition and effective date as facts to verify for each project rather than to assume. In a dispute, the permit date and the code edition tied to it are often the first things that need to be pinned down.
Beyond code: LEED, ENERGY STAR, and voluntary standards
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Code compliance is the mandatory floor. Above it sits a set of voluntary programs that owners choose
- ENERGY STAR, a program of the U.S. EPA and Department of Energy, recognizes better-than-typical energy performance. For commercial buildings it is commonly expressed as a 1-to-100 score; for homes there is a separate certification.
- LEED, administered by the U.S. Green Building Council, is a points-based rating system with levels from Certified to Platinum. It addresses energy but also water, materials, site, and indoor environmental quality, so it is broader than an energy program alone.
Code is the floor every building must meet; voluntary programs reach higher at increasing cost and effort.
These programs are commitments. When an owner pursues one, the project takes on additional
documentation and verification obligations, and those commitments can become contractual. The table below is a quick orientation, not a substitute for each program’s current requirements: Energy code
ENERGY STAR
LEED
Type
Mandatory minimum
Voluntary program
Voluntary rating system
Set by
ICC / ASHRAE, adopted
by states
U.S. EPA & DOE
U.S. Green Building
Council
Scope
Energy use of the
building
Energy performance
Energy plus water, materials, site, indoor quality
Required to occupy?
Yes
No
No
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Energy code
How it is shown
Permit forms, plan
review, inspections
ENERGY STAR
Testing / scoring against program criteria
LEED
Documented credits, third-party review
A measured caution: a certification or score reflects design intent and a verification process. It is not a guarantee that a building will perform exactly as modeled. Actual performance depends on how the building is constructed, commissioned, and operated — which is exactly where forensic questions tend to arise.
Where as-designed and as-built diverge — the forensic core
When I am brought into an energy-related dispute, I am rarely arguing about the standard itself. I am usually tracing the distance between what the documents required and what the building received. That distance accumulates across a predictable sequence of stages.
The energy paper trail. Gaps between these stages are where disputes usually start.
The most common gaps I encounter are not exotic. Equipment or glazing gets substituted without
revisiting the energy basis. Insulation is installed at less than the specified value, or with gaps that defeat its rating. The air barrier is detailed on the drawings but not made continuous in the field. Required testing or commissioning is skipped, or the reports are never collected. Record documents never catch up to the changes made during construction. I want to be careful here: identifying a gap is not the same as assigning fault. Substitutions can be appropriate and well documented; field changes happen on every project. My role is to establish what the records show and where they go silent, and to do that I rely on the documentation generated during the phase this article is about.
Practical steps for the design and documentation phase
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If you are a design professional, owner, or counsel looking at a project in this phase, a few habits make later questions far easier to answer: 1. Confirm the code edition and effective date that apply at permit submission, and keep that confirmation in the project file. 2. Decide the prescriptive or performance path early, and document the basis for the choice. 3. Keep the energy compliance forms and any energy model with the construction set, not in a separate inbox. 4. Track equipment, glazing, and insulation substitutions against the energy basis of design as they occur. 5. Plan for envelope testing and commissioning where required, and collect the reports when they are produced. 6. Maintain record documents that reflect what was actually installed. None of this is glamorous, and none of it is new. It is simply the difference between a project that can answer questions about its own performance and one that cannot.
Frequently asked questions
Is ASHRAE 90.1 the same thing as the energy code? Not exactly. ASHRAE 90.1 is a model standard. It becomes enforceable when a state or jurisdiction adopts it, usually with amendments. The enforceable energy code in your area may reference ASHRAE 90.1, the IECC, or both. Do I have to pursue LEED or ENERGY STAR to meet code? No. Both are voluntary. A building can fully comply with the energy code without participating in either program. Owners pursue them for performance, recognition, or portfolio reasons. What is the difference between the prescriptive and performance compliance paths? The prescriptive path requires meeting each listed requirement directly. The performance path uses a whole-building energy model to compare the design against a code baseline, allowing trade-offs across systems. Most codes accept either route. Which energy code applies to my project? It depends on the jurisdiction and the permit date. States adopt model editions on their own schedules, and local amendments can apply. The reliable approach is to confirm the edition in force where and when the project is permitted. Does a LEED rating or ENERGY STAR score guarantee the building performs as modeled? No. These reflect design intent and a verification process, not a performance guarantee. Actual energy use depends on construction quality, commissioning, and how the building is operated over time.
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