Replacing a chiller, rooftop unit, air handler or makeup air unit at an Illinois public school does not mean bringing the whole building up to the 2024 energy code. But it isn't a free pass either. Here is the line — with the sections cited.
This page is a contractor's plain-language summary, not legal or design advice. Code applicability is determined by the registered design professional of record and the authority having jurisdiction — for most Illinois public schools, the Regional Superintendent of Schools (ROE). Every citation below links to the primary source so your design team and the ROE can verify it. Editions and effective dates current as of July 2026.
Most of the confusion on Illinois school HVAC projects comes from mixing up four separate things: the school construction code, the state energy code, the stretch code, and the design professional's own project standards. They are not the same document and they are not triggered by the same events.
Before anyone argues about energy recovery, settle jurisdiction. Three different regimes cover Illinois school buildings, and they carry different amendments, different reviewers, and different enforcement.
The school board files an Application for a Building Permit with the Regional Superintendent. The ROE is the authority having jurisdiction. Part 180 incorporates the ICC codes directly, and states that "no later amendments to or editions of these standards are incorporated."
Practical consequence: the ROE path points at the ICC's 2024 IECC as published — not automatically at the Capital Development Board's Illinois-amended edition. Which document the design team used should be stated on the drawings.
Districts governed by Article 34 of the School Code are subject only to the Part 180 sprinkler provisions (§ 180.250) and "in all other respects shall comply with local building codes."
Practical consequence: a CPS project runs on Chicago's own energy and mechanical provisions, which carry their own amendments. Do not analyze a CPS job with the ROE playbook.
The Capital Development Board administers the statewide Illinois Energy Conservation Code (71 Ill. Adm. Code Part 600) under the Energy Efficient Building Act. Its Subpart C is written around privately funded commercial facilities, and its stretch code reaches state-funded buildings and municipalities that adopt it.
Practical consequence: if CDB is authorizing or funding any part of the work, read the grant and appropriation documents before pricing — the stretch code changes the answer.
Health/Life Safety Code for Public Schools. Adopts the 2024 ICC family for design contracts executed on or after 1/1/2025. Amended at 49 Ill. Reg. 1774, effective January 30, 2025.
Illinois Energy Conservation Code & Illinois Stretch Energy Code, administered by the Capital Development Board under 20 ILCS 3125 (Energy Efficient Building Act).
Chapter 5 of the IECC (existing buildings) and Chapter 7 of the IEBC (Level 1 alterations) are the two sections that keep a chiller swap from becoming a whole-building retrofit.
School district competitive bidding. Relevant because Part 180's "minor repairs" definition is keyed to whether the work is subject to this bidding threshold — currently $35,000.
They are separate actions by separate agencies with separate trigger dates. Getting them straight resolves most preconstruction arguments before they start.
The trigger is the date the design contract was executed, not the bid date and not the permit date. On or after 1/1/2025 → 2024 IBC, IECC, IEBC, IFC (excl. Ch. 4), IFGC, IMC, IPMC. A project bid in 2026 under a 2024 design contract may legitimately still be on the prior edition — the drawings must say which.
Adopted by the Capital Development Board on May 13, 2025. Trigger here is the permit application date — applications on or after 11/30/2025 use the 2024 edition. This is the CDB-administered program under 71 IAC 600, which overlaps but is not identical to Part 180's direct adoption of the ICC text.
CDB describes the 2026 stretch code as under development; proposal and draft materials have been published. The currently effective commercial stretch code is the 2023 edition (effective January 1, 2025). A draft is not an adopted code, and it does not retroactively govern an awarded contract.
Two doors, and only two:
This classification drives everything downstream. Part 180 defines "like activity" broadly — reconstruction, substantial alteration, repair, remodeling, renovation, change in use — and excludes only qualifying minor repairs. Mechanical system replacement is expressly carved out of the minor-repair exclusion.
Classification is the ROE's call on the specific submittal. This table reflects how these scopes are ordinarily treated under 23 Ill. Adm. Code 180.30 and the 2024 IEBC; it is not a substitute for a written determination.
2024 IEBC § 708.1: Level 1 alterations "do not require the entire building or structure to comply with the energy requirements of the International Energy Conservation Code" — the altered portions conform to the energy code as it relates to new construction only.
2024 IEBC § 701.2 also sets the floor in the other direction: a building "shall not be altered such that the building becomes less safe than its existing condition."
2024 IECC § C501.2 routes existing-building work to § C502 (additions), § C503 (alterations), § C504 (repairs) or § C505 (change of occupancy) — instead of applying every new-building requirement to the whole facility. The work performed complies; untouched portions generally do not have to be rebuilt. The alteration also may not make the building less compliant than it was.
Normally in scope: current full-load and part-load chiller efficiency; load-based sizing; chiller and pump isolation; variable-flow / variable-speed provisions; chilled water temperature reset; pump pressure reset; multiple-chiller plant control; insulation on newly installed piping; controls integration; TAB; functional performance testing of the affected plant.
Normally not triggered by the chiller alone: outdoor-air energy recovery, on-site solar or off-site renewable procurement, whole-building envelope work, replacement of every air handler, electrification of heating, EV infrastructure.
Typical functional test list: chiller enable/disable, pump proving, isolation valves, lead/lag staging, CHW reset, differential pressure reset, low-temperature safeties, flow switches, BAS alarms and point verification.
More exposed than a chiller, because the unit directly controls fans, outside air, relief/exhaust, economizer, heating, cooling, ventilation and zone control.
Normally in scope: equipment efficiency per § C403.3; load calculations and sizing; fan power limits and variable-speed control; economizer compliance (and economizer fault detection where applicable); demand control ventilation; outdoor-air measurement/control; off-hour and optimum start controls; simultaneous heat/cool limits; duct insulation and sealing; acceptance testing under § C503.3 and § C408.2; TAB and owner documentation.
Easy to miss: 2024 IECC § C503.3.6 — on roofs with insulation entirely above deck, replaced or added roof-mounted mechanical equipment must be set on curbs that allow for future addition of insulation. That is a real, priceable curb detail that did not exist in prior editions.
The highest-risk category, because § C403.7.4 energy recovery keys on exactly the variables a MAU maximizes: supply airflow, percent outdoor air, climate zone and operating hours.
What we and the engineer document together, before pricing: MAU supply CFM; OA percentage; which exhaust systems serve the same spaces; exhaust locations and schedules; whether exhaust is contaminated; whether the systems run concurrently; whether recovery can physically be routed; and the specific table and exception being relied on.
A true 100% OA unit with no usable matching exhaust stream may have a defensible applicability argument. "It's a makeup air unit" is not, by itself, an exception.
This is where six-figure change orders come from. Handle it deliberately.
For spaces other than nontransient dwelling units, § C403.7.4.2 requires an energy recovery system where the design supply airflow of a fan system exceeds the values in Tables C403.7.4.2(1) and (2). Those tables key on climate zone and percentage of outdoor air (bands running from roughly 10% up past 80%), and return a minimum design supply fan airflow in CFM.
Where required, the system must generally provide an enthalpy recovery ratio of not less than 50% at design conditions. Where an economizer is required, the recovery system must allow economizer operation via bypass or controls.
You cannot determine the threshold from CFM alone. Illinois counties fall in IECC climate zones 4A and 5A, and the zone changes the table value. The county's zone must be identified.
The 2024 IECC carries a list of exceptions for § C403.7.4.2 covering, among other circumstances: systems where energy recovery is prohibited by the IMC; exhaust containing toxic, flammable, corrosive or contaminated material; laboratory fume hood systems; certain Type 1 kitchen exhaust arrangements; spaces heated below a threshold temperature; systems with limited annual operating hours; and cases where there is no usable matching exhaust or relief stream.
The exception must be identified by section number and documented in the design calculations. If the drawings don't cite it, the reviewer is entitled to assume it wasn't analyzed.
It is commonly asserted that ASHRAE 90.1-2022 exempts direct-replacement equipment from energy recovery. That overstates it. Standard 90.1-2022 § 6.1.4 governs HVAC alterations and § 6.1.4.1 addresses new equipment installed as a direct replacement of existing equipment; § 6.5.6 contains the energy recovery requirements. ASHRAE itself has since published Addendum da to 90.1-2022 specifically because the Section 6.1 alteration language "was unclear regarding alterations other than direct replacements."
The defensible position: a true direct replacement is entitled to the alteration provisions rather than being treated as an entirely new building system — but the designer still has to perform and document the § 6.1.4 and § 6.5.6 applicability analysis. Less satisfying than "no ERV required." Considerably more useful when the reviewer is holding the permit.
2024 IECC § C401.2 lets a commercial building comply via § C401.2.1 (IECC prescriptive or simulated performance), § C401.2.2 (ASHRAE 90.1), or in Illinois § C401.2.3 (a Passive building option added by Illinois amendment, § C410). Additions, alterations, repairs and changes of occupancy complying with Chapter 5 are excepted from the base-chapter application.
Illinois' own energy code training program states it directly: projects must choose one compliance path, and designers are not permitted to "cherry-pick" a customized path by combining provisions of ASHRAE 90.1-2022 and the 2024 IECC. Using 90.1 for HVAC and the IECC for lighting is not permitted.
In practice that means you cannot take the easier IECC economizer rule and then switch to ASHRAE for energy recovery, controls or commissioning. Either standard must be used in its entirety, with the applicable Illinois amendments.
Note also that the ASHRAE path is not a total escape hatch: the IECC lists sections that still apply in Table C401.2.2 when the 90.1 path is selected.
For commercial work, the 2024 Illinois Energy Conservation Code amendments to the 2024 IECC are narrower than people assume. They touch scope and adoption (§ C101), compliance documentation (§ C104.1.1), a new electrification-infrastructure documentation requirement (§ C105.2.2), appeals (§ C109), definitions (§ C202), the compliance-path structure (§ C401.2), air barrier construction (§ C402.6.1.2), horticultural lighting (§ C405.4), and a new Passive building compliance option (§ C410).
They do not rewrite § C403.7.4 energy recovery, § C405.15 renewables, § C408 commissioning, or § C503 alterations. Those come through as published. The heavier additions people associate with Illinois — EV charging, electrical storage, substantial-improvement EUI targets — live in the stretch code amendments, which only apply through the two doors described above.
These get used interchangeably in preconstruction meetings and they are four distinct scopes with four distinct deliverables. One firm may perform more than one if properly qualified and accepted — but the paperwork stays separate.
Mechanical and service water heating systems must be commissioned, with documentation provided to the owner and made available to the code official. Elements: commissioning plan (C408.2.1), systems adjusting and balancing (C408.2.2), functional performance testing (C408.2.3), preliminary commissioning report (C408.2.4), and final commissioning documentation (C408.2.5).
The exception requires both: under 10,000 sq ft of gross conditioned floor area and combined heating, cooling and SWH capacity under 960,000 Btu/h. Most schools fail both halves comfortably.
Where an alteration requires compliance with § C403, the mechanical systems serving the alteration must comply with §§ C408.2.2, C408.2.3 and C408.2.5 — adjusting and balancing, functional performance testing, and final commissioning documentation.
Scope note: this reaches the altered system and new equipment. It is not a mandate to commission every unrelated HVAC system in the building.
The regional superintendent may not issue a certificate of occupancy until Called Inspection Records for the IBC, IECC, IFC, IFGC and IMC show a qualified inspector's signed authorization to proceed after each phase.
Energy and mechanical reviewers/inspectors must hold the applicable ICC certification (e.g. Commercial Energy Conservation Code Plans Examiner) plus 4,000 hours of relevant experience, or qualify as a licensed design professional under 180.110/180.120.
TAB measures, adjusts and balances air and water systems and issues the report. It feeds the commissioning functional testing; it does not replace it, and the balancer is not the commissioning authority by default.
Separately, Part 180 § 180.200(d)(4) requires an evaluation report from an approved inspection agency where the work involves a closed, prefabricated mechanical system such as a packaged HVAC unit. That is an equipment listing/evaluation item — not field commissioning.
Not automatically by the base IECC. § C408.2 permits commissioning documentation to be completed or certified by the registered design professional or an approved agency. An independent commissioning provider may still be required by the owner's project requirements, CDB standards, grant conditions, the project specifications, a certification system such as LEED, the ROE's interpretation, or a conflict-of-interest clause in the spec. So "third-party commissioning is required" may be entirely correct on your project — just not because every Illinois school replacement universally requires it. Ask which document imposes it.
The 2024 IECC added a significant on-site renewable electricity requirement: a DC nameplate rating of not less than 0.75 W per square foot, applied to the gross conditioned floor area but capped at the combined area of the three largest floors. It reaches buildings in climate zones 0 through 7 — which includes all of Illinois.
Read the exemptions carefully before celebrating: buildings under 5,000 sq ft and shaded buildings are exempted from the on-site requirement, but exempted buildings must then satisfy the off-site renewable procurement requirements of § C405.15.2 — PPAs, community renewables, RECs, green tariffs, or a renewable energy investment fund.
Does a chiller or AHU replacement trigger it? Ordinarily no. Chapter 5 treats additions and alterations differently: § C502.3.8 expressly applies the renewable energy requirements to an addition, while § C503 does not impose § C405.15 merely because equipment was replaced. A mechanical-only replacement is not a direct solar trigger.
Alterations that qualify as substantial improvements must earn additional efficiency credits under §§ C406.2 and/or C406.3, in the number required by Table C406.1.1(1). Exceptions apply.
The 2024 IECC defines substantial improvement using a building-level valuation test: repair, reconstruction, rehabilitation, alteration, addition or other improvement whose cost equals or exceeds 50% of the market value replacement cost of the structure before the improvement is started.
That test is not: 50% of the chiller cost, 50% of the mechanical system cost, 50% of the HVAC scope, a tonnage threshold, or a public bidding threshold. A $500,000 chiller project at a $40 million school is very unlikely to qualify. A comprehensive $12 million renovation of a $20 million building might.
Note the related trap in the other direction: § C502.3.7 requires additions to earn 50% of the C406 credits for their occupancy and climate zone. If any part of your "replacement" is actually an addition, the credit math changes.
The 2024 IECC ships with optional appendices and resources for solar-ready construction, EV charging, electric-ready construction, demand-responsive controls, electrical storage, all-electric buildings and zero-energy pathways. Appearing in the code book does not make them mandatory — they generally apply only when specifically adopted by the governing jurisdiction or pulled in through another requirement such as the stretch code, a CDB funding condition, or the owner's criteria. A chiller replacement does not inherently require converting boilers to heat pumps, installing EV chargers, adding batteries, creating solar-ready roof zones, or electrifying the school.
On every significant Illinois school HVAC replacement, Roberts sits down with our engineering and architectural partners and works these determinations out together, early. Nobody hands anybody a demand list. When these are settled up front, the district gets a real number and a real schedule — instead of an undefined code obligation that surfaces after the permit is in review.
Roberts puts its qualification language right on the proposal so the district, the design team and the ROE are all reading the same scope. It is not a shield and it does not defeat a valid code requirement. It simply makes the assumptions visible, so that if the analysis lands somewhere else, everyone finds out during design instead of during construction.
Energy Code and Existing-Building Qualification. Pricing is based on the project being classified as an alteration and direct replacement of the existing HVAC equipment serving the same areas, with no material increase in system airflow, outdoor air quantity, capacity, occupancy, operating hours or areas served. Pricing includes compliance requirements specifically applicable to the replacement equipment and directly affected systems. Unless expressly shown in the Contract Documents, pricing excludes new energy recovery systems, renewable energy generation, off-site renewable energy procurement, building electrification, whole-building energy efficiency credits, unrelated HVAC system upgrades, envelope improvements, and independent third-party commissioning. Any such requirements imposed by the ROE, CDB, code official or design professional after bid shall constitute a change in scope and contract price.
Before the permit set goes in, our team and the engineer of record walk through IECC §§ C503.3, C403.7.4, C408.2, C405.15 and C503.6 together — and, where the ASHRAE path is selected, 90.1-2022 §§ 6.1.4 and 6.5.6 — and confirm the reading with the ROE.
That shared determination is the boundary between a legitimate replacement project and an accidental campus decarbonization program. Getting it right is a design-and-construction decision, made jointly, in the district's interest.
A true like-function replacement should generally be treated as an alteration limited to the new equipment and the systems serving the alteration. A redesign, an addition, a substantial increase in capacity or outdoor air, or a substantial improvement can trigger much broader energy requirements.
Both statements are correct. Which one applies to your building is a documentation question, and it should be answered before bid — not after the permit is held up.
No. 2024 IECC § C501.2 routes existing-building work to the existing-building provisions, and 2024 IEBC § 708.1 states that Level 1 alterations do not require the entire building to comply with the energy code. The work performed complies; the untouched portions generally do not have to be rebuilt. The alteration also cannot leave the building less compliant than it was.
Almost certainly yes. Part 180 § 180.30 defines "like activity" broadly and its "minor repairs" definition expressly excludes the "addition to, alteration of, replacement, or relocation of… mechanical or other required building system." Section 180.200 prohibits construction or like activity from beginning until the board obtains a permit, with plans and specifications prepared under the supervision of an Illinois architect or engineer, and requires that any reference to the incorporated codes identify the specific edition, section and subsection.
Under Part 180, the trigger is the date the design contract was executed, not the bid or permit date. On or after January 1, 2025 → 2024 ICC family. Under the CDB program (71 IAC 600), the trigger is the permit application date, with the 2024 Illinois Energy Conservation Code effective November 30, 2025. If the two point different directions on your project, that is exactly the kind of thing the drawings should resolve explicitly.
Not automatically — but expect scrutiny, and do not assume the answer. § C403.7.4.2 keys on climate zone, percent outdoor air and design supply airflow through Tables C403.7.4.2(1) and (2), with a 50% enthalpy recovery ratio where required. The exceptions are real (IMC prohibition, contaminated or toxic exhaust, laboratory fume hoods, certain kitchen exhaust, low-temperature spaces, limited operating hours, no usable matching exhaust stream) but each must be identified by section and documented. A 100% OA unit with no available exhaust stream may have a strong argument; it still needs to be written down.
Ordinarily no. § C405.15 renewable energy is applied to additions by § C502.3.8; § C503 does not impose it merely because equipment was replaced. Renewables can become relevant if the project includes a qualifying addition, is effectively new construction, qualifies as a substantial improvement where renewables are selected as a C406 credit measure, falls under a stricter stretch-code path, or is required by CDB funding conditions or the owner's criteria.
Not by the base IECC. § C408.2 allows commissioning documentation to be completed or certified by the registered design professional or an approved agency. Independence may be required by the owner's project requirements, CDB standards, grant conditions, the specification, a certification program, or the ROE's interpretation. If a project team says third-party Cx is required, the right follow-up is "under which document?"
Only if CDB authorized or funded the project, or a municipality that has adopted the commercial stretch code is your AHJ. The currently effective commercial stretch code is the 2023 edition (effective January 1, 2025); the 2026 edition is still in development as of July 2026. Receiving general State education funding does not by itself make a project a CDB project — review the grant and appropriation documents.
It is a building-level valuation test: improvement cost equal to or greater than 50% of the market value replacement cost of the structure before the work starts. It is not 50% of the mechanical scope and not a tonnage or bidding threshold. If it applies, § C503.6 requires the alteration to earn additional efficiency credits from §§ C406.2 and/or C406.3 per Table C406.1.1(1), with exceptions.
Partly. Districts governed by Article 34 of the School Code are subject only to the Part 180 sprinkler provisions and comply with local building codes in all other respects. Chicago maintains its own amendments to the commercial energy and mechanical provisions, including energy recovery. A CPS project must be analyzed under Chicago's code, not the ROE framework described here.
No. Illinois' energy code guidance is explicit that projects must choose one compliance path and may not cherry-pick by combining ASHRAE 90.1-2022 and the 2024 IECC — using 90.1 for HVAC and the IECC for lighting is specifically called out as not permitted. Either standard must be used in its entirety with the applicable Illinois amendments. Note that even on the ASHRAE path, IECC Table C401.2.2 identifies requirements that still apply.
Every statement above traces to one of these. Where a source is a code text behind a publisher's paywall, the section number is given so your design professional can pull it.
Definitions (180.30), applicability and adopted code editions (180.60), reviewer/inspector qualifications (180.110, 180.120), permit application (180.200), inspections (180.220). Amended at 49 Ill. Reg. 1774, effective January 30, 2025.
ISBE rule text (PDF) · JCAR
CDB rules implementing the Energy Efficient Building Act (20 ILCS 3125), including Subpart C (commercial), the stretch code, and the Illinois amendments to the 2024 IECC.
JCAR full text
2024 Illinois Energy Conservation Code adopted May 13, 2025; effective November 30, 2025. Illinois-specific amendments to the 2024 IECC published 10/30/25.
cdb.illinois.gov
2023 Illinois Stretch Energy Code effective January 1, 2025; applicability to State-funded facilities and municipalities that adopt it. 2026 edition under development.
Stretch code · 2026 proposals
State energy code training resource. Source for the ROE-as-AHJ statement for public schools, the no-cherry-picking rule between ASHRAE 90.1-2022 and IECC 2024, and the 11/30/2025 permit-application trigger.
FAQ · ILECC overview
§§ C401.2, C403.3, C403.7.4, C403.7.8, C405.15, C406.1.1, C408.2, C501.2, C502.3.7, C502.3.8, C503.3, C503.3.3, C503.3.5, C503.3.6, C503.6, and the C202 definition of substantial improvement.
ICC Chapter 4 [CE] · C403.7.4 · C405.15
§ 701.1 scope, § 701.2 conformance, § 708.1 energy conservation ("Level 1 alterations… do not require the entire building or structure to comply with the energy requirements of the International Energy Conservation Code").
ICC IEBC Chapter 7
Industry summary of the 2024 commercial changes, including the C408.2 exception thresholds (10,000 sq ft / 960,000 Btu/h), C503.3.3 duct testing, C503.3.5 sizing/controls, C503.3.6 roof curbs, C503.6 substantial improvement credits, and C405.15 on-site/off-site renewables.
PDF
§ 6.1.4 alterations, § 6.1.4.1 direct replacement, § 6.5.6 exhaust air to outdoor air energy recovery. Addendum da was issued to clarify Section 6.1 because the alteration text "was unclear regarding alterations other than direct replacements."
Addendum da (PDF)
Competitive bidding threshold, raised from $25,000 to $35,000 effective January 1, 2024. Referenced by the Part 180 "minor repairs" definition.
ILGA full text
Roberts Environmental Control Corp. has been building and servicing Illinois institutional mechanical systems for decades. We self-perform the mechanical work and carry the design under one contract — working shoulder to shoulder with our engineering and architectural partners to land on the course of action that genuinely serves the district, not just the one that is easiest to permit. And we schedule around the summer window that school projects actually live in.
708-429-7700 · Sales@RobertsHVAC.com