Maine's Residential Energy Code: Statewide Law, Enforcement That Isn't

1. What the Code Is and Who Enforces It

Maine runs a single statewide building and energy code, not a home-rule patchwork the way some states do. The Maine Uniform Building and Energy Code (MUBEC) is adopted by the state's Technical Building Codes and Standards Board and applies to all buildings constructed or renovated anywhere in Maine.⁶ That single fact settles the question builders and homeowners ask first - "does the energy code apply to my project" - but it doesn't settle the second question, which is who actually checks it, and that second question has a real, statutory answer that surprises people.

The statewide code

The U.S. Department of Energy's Building Energy Codes Program state profile lists Maine's Current State Code (Residential) as "2021 IECC with Amendments," with State Amendments = Yes and "Can use COM/REScheck: Yes."¹ The DOE page leaves its Effective Date cell blank, but Bangor's own building codes page states the effective date directly: "The State of Maine has amended the Maine Uniform Building and Energy Code (MUBEC). Municipalities that enforce MUBEC shall enforce the amended adoption as of April 7, 2025."² The state's Department of Energy Resources page confirms the same date, listing codes "in effect in Maine as of April 7, 2025."⁷ MUBEC's Chapter 6 rule text defines the term precisely: "IECC" means the 2021 International Energy Conservation Code, with an amendment history showing the current version effective March 4, 2025 (filing 2025-047).⁸

Effective April 7, 2025, MUBEC adopts the 2021 editions across the board: 2021 IRC, IBC, IEBC, IECC, and IMC, plus ASHRAE 62.1-2019, 62.2-2019, and 90.1-2019, and ASTM E-1465-2008 for radon control.² Before that date, the same family ran on 2015 editions. A project permitted in 2026 is on the 2021 IECC; one permitted before April 7, 2025 may still run on 2015. Getting that edition wrong - assuming "current" always means 2021 without checking the permit date - is the single most common way a Maine REScheck report comes back from a plan reviewer.

The rule that actually matters: statewide law, municipal enforcement duty

This is the fact that makes Maine different from most states on this site, and it's worth reading exactly as written rather than paraphrased. Title 10 M.R.S. §9724, sub-1-A states, verbatim:

"Municipalities up to 4,000 residents. A municipality of up to 4,000 residents is not required to enforce, but may not adopt or enforce a building code other than the Maine Uniform Building Code, the Maine Uniform Energy Code or the Maine Uniform Building and Energy Code."³

Read that carefully: the threshold is about the municipal duty to enforce, not about whether the code governs the building. A town of up to 4,000 residents doesn't have to run a plan-review and inspection program against MUBEC - but that same town is statutorily barred from substituting some other building code, or from having no code at all in a legal sense. The Maine State Fire Marshal's own 2021 IECC Compliance Guide states the same point directly: "The IECC is part of Maine's complete MUBEC building codes and is law for the entire state. Some towns may adopt a Stretch Code, so be sure to check with your local Authority Having Jurisdiction (AHJ)."⁴

Put those two sources together and you get the most useful sentence on this page: the energy code is law statewide, but a town of up to 4,000 residents is not obligated to enforce it, and no Maine town may substitute a different building code. "My town has no code officer" is not the same statement as "no code applies to my project." This page states what the statute and the Fire Marshal's guide say, not more.

Who enforces it, concretely

Municipalities of more than 4,000 residents must enforce MUBEC.⁷ Lewiston's own code-enforcement page confirms this independently: Maine law requires municipalities of 4,000 or more to enforce MUBEC.⁵ For municipalities under that threshold, whether MUBEC is actively reviewed and inspected locally is a local choice - if you're building in a small Maine town, ask directly whether the municipality runs its own enforcement program, contracts it out, or has none.

Cities the size of Bangor, Lewiston, and Auburn run active permitting and code-enforcement operations built around MUBEC. Bangor's building codes page lists the full 2021 code family in force and publishes the city's own IBC base climate data (ground snow load 70 lbs, wind speed 107 mph 3-second gust, frost depth 5 feet - Bangor-specific, not a statewide constant).² Auburn's Permitting and Code Enforcement department reviews MUBEC Residential Energy Code applications directly, and York has published its own compliance-path training material dated the same week the 2021 edition took effect.⁹¹⁰ Those are three concrete, named jurisdictions with confirmed practices; any other Maine municipality's enforcement posture and adopted edition should be confirmed directly rather than assumed from this page.

Climate zones

Maine spans two IECC climate zones under the 2021 edition's Table R301.1. Pulled directly from the published table: fifteen of Maine's sixteen counties are Zone 6A - Androscoggin, Cumberland, Franklin, Hancock, Kennebec, Knox, Lincoln, Oxford, Penobscot, Piscataquis, Sagadahoc, Somerset, Waldo, Washington, and York. Aroostook County alone is Zone 7, the state's only zone-7 county and the coldest design conditions in Maine.¹¹ Zone 6 and Zone 7 carry different prescriptive requirements under Table R402.1.2/R402.1.3, with Zone 7's ceiling and wall U-factor maximums tighter than Zone 6's. A project in Presque Isle or Fort Kent needs the Zone 7 table; everywhere else in the state uses Zone 6A. Confirm which zone applies before running a compliance report - it's a county-level distinction, not a townwide guess.

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2. Where Jurisdictions Differ: the 4,000-Resident Enforcement Rule and the Stretch Code

Two separate mechanisms make one Maine town's compliance requirements look different from another's, even though the underlying code is the same statewide law. Conflating them - or missing one entirely - is the most consequential mistake a reader of a generic "Maine energy code" article can make.

Mechanism one: the enforcement threshold

Covered in Section 1 above, but worth restating in the context of "where jurisdictions differ": the 4,000-resident line in §9724 sub-1-A doesn't create different code requirements town to town. It creates different enforcement postures. A house built to the same 2021 IECC standard in a town of 3,500 residents and a house built in Bangor are subject to the identical code text. What differs is whether a local plan reviewer is checking the submittal against that text before the permit issues. That is an administrative fact about who is watching, not a legal fact about what the building has to meet.

Mechanism two: the MUBEC Stretch Code

This is the mechanism that actually changes the numbers a compliance report has to hit, and it is the Maine equivalent of the "wrong code edition" trap that trips up projects in every state this site covers. MUBEC's Chapter 6 rule text defines a MUBEC Stretch Code: "An alternative building energy code adopted and maintained by the board as an appendix to the MUBEC, that is more stringent from the perspective of energy efficiency, carbon reductions, and resilience than the currently adopted edition of the Energy Code," with its provisions in Appendix NA.⁸ Section 4 of that chapter explains adoption: "A municipality may, pursuant to Title 10 M.R.S §9722, elect to adopt the MUBEC Stretch Code. If a municipality adopts the MUBEC Stretch Code, the provisions of the Stretch Code are mandatory in that municipality."⁸

The numeric target is a UA (total building thermal envelope heat-loss) trade-off, not a different prescriptive table: "The Total Building UA for the project, calculated as outlined in R402.1.5, shall exceed the UA requirements by at least 15% over a code compliant project. This means that the Envelope PASSES design by 15% better (or more) than code per the RESCheck compliance calculation. For residential projects that do not include fossil fuels for any use (heating, cooling, hot water, backup heat, cooking, etc.) the Total Building UA shall exceed the UA requirements by at least 10% over a code compliant project."⁸ The state's own energy office page adds that "no municipality can enforce a building code other than the MUBEC," but municipalities "may opt to adopt the MUBEC stretch code as their base code," naming three communities that have: Portland, South Portland, and Freeport.⁷

Why this matters: a REScheck report run against the base 2021 IECC does not demonstrate stretch-code compliance. The stretch code's 15-percent (or 10-percent, all-electric) UA margin is a materially different pass threshold than the code-minimum UA comparison a standard REScheck run produces. If your jurisdiction has adopted the stretch code, a report that satisfies the base 2021 IECC will not satisfy your permit requirement, and a plan reviewer checking against the stretch appendix will send it back - the software isn't wrong, it was run against the wrong target.

The Fire Marshal's own compliance guide flags this directly: "Some towns may adopt a Stretch Code, so be sure to check with your local Code Official or Authority Having Jurisdiction (AHJ)."⁴ That instruction applies with equal force to a compliance-report preparer. We ask every Maine project which municipality it's in before running anything, specifically because Portland, South Portland, Freeport, or any other town that has separately adopted the stretch appendix needs the 15/10-percent UA margin documented, not the base-code comparison.

What to verify before assuming either rule applies

• Your municipality's population, relative to the 4,000-resident enforcement threshold - and separately, whether that municipality actually runs an active enforcement program regardless of the statutory minimum, since some small towns choose to enforce voluntarily.
• Whether your specific municipality has adopted the MUBEC Stretch Code as its base code. Portland, South Portland, and Freeport are confirmed by the state's own energy office; any other municipality's stretch-code status should be confirmed directly with that town's code office before assuming either way.
• The permit application date relative to April 7, 2025, since projects that predate that cutover may still be running against the 2015 edition family rather than 2021.

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3. Your Ways to Comply

The 2021 IECC's residential chapter, as adopted by MUBEC, offers the same general compliance paths documented across recent IECC editions nationally, with Maine's own amendments layered onto the prescriptive and UA sections specifically.

Path	Typical code section	What it is	Best fit
Prescriptive	R401.2.1 / R402.1.1-R402.1.3	Meet every line item in the R-value/U-factor table for your climate zone (6A or 7), as amended by Maine's Chapter 6 revisions.	Simple plans, standard framing, no unusual glazing package.
UA / total-building-envelope trade-off (REScheck)	R402.1.5	Total heat loss (UA) of the actual envelope must be at or below the UA of a prescriptive-minimum reference home. Weak components can be offset by strong ones elsewhere. This is also the mechanism the stretch code uses, with a stricter margin.	2x4 walls, large glazing packages, log or post-and-beam construction, or an assembly that can't hit every prescriptive number individually.
Total Building Performance / simulated performance	R405	A full energy model compares the proposed design's energy cost against a standard reference design.	Custom homes or designs the prescriptive/UA path can't cleanly capture.
Energy Rating Index (ERI/HERS)	R406	A HERS rating or ERI score, benchmarked against a target index by climate zone. MUBEC also recognizes DOE Zero Energy Ready Home, Phius, and PassiveHouse certification as compliance-equivalent under its own R102.1.1 amendment.	Projects already pursuing a HERS rating, ENERGY STAR, or a certification program for other reasons.

Which path fits which Maine project:

• Simple, code-minimum spec homes with standard framing in Zone 6A - the prescriptive path is fastest through plan review and cheapest to document.
• 2x4 walls, large window packages, or one component short of the table - the UA trade-off (REScheck) is usually the cheapest fix, and it's the pathway most Maine plan reviewers see most often on residential submittals.
• A project in a stretch-code town - the UA trade-off path is not optional here; it's how the stretch code itself is measured, at the 15-percent (or 10-percent, all-electric) margin above code-minimum rather than the base-code margin.
• Custom homes, unusual HVAC, or a design the prescriptive/UA path can't cleanly capture - go Total Building Performance or the ERI path.

Which REScheck edition to select. Maine does not have its own dedicated state-specific REScheck edition the way Florida, Massachusetts, New York City, Puerto Rico, Utah, or Vermont do - the DOE's own REScheck supported-codes list names those state-specific editions explicitly, and Maine isn't among them.¹² That means the correct approach for a standard Maine project is selecting the standard 2021 IECC edition inside REScheck-Web. For a project in a stretch-code municipality, the standard 2021 IECC run inside REScheck documents base-code compliance only; showing the stretch code's 15/10-percent UA margin is an additional calculation on top of, not a substitute for, the report REScheck itself produces.

What about Manual J? The 2021 IRC, adopted statewide alongside the 2021 IECC under the same MUBEC structure, carries the IRC's standard mechanical-code section requiring HVAC equipment to be sized per ACCA Manual S based on loads calculated with ACCA Manual J or an equivalent approved method. That requirement travels with the statewide IRC adoption itself, the same way it does in every state that has adopted a recent IRC edition intact - it applies in Bangor, in Auburn, and in a town under 4,000 residents alike, regardless of whether that town is actively enforcing it day to day.

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4. Maine-Specific Wrinkles

What Chapter 6 actually changes for a residential envelope. Maine's amendments to the 2021 IECC residential provisions are short, and three of them bear on a compliance report. Item 8 rewrites the wood-frame wall rows of Table R402.1.3 (the prescriptive R-value table) for Climate Zones 6 and 7 and 8 to "30 or 20 + 10ci or 13 + 15ci or 0 + 20ci" - the base 2021 IECC rows read 20 + 5ci and 13 + 10ci for the two hybrid options. Table R402.1.2, the U-factor table the total UA alternative (R402.1.5) scores against, is not amended, so a REScheck run on the standard 2021 IECC setting still targets the correct Maine UA; the tighter wall rows bind only on the prescriptive path. Item 12 amends R402.4.1.2 so that the air-leakage limit under any compliance path is 3.0 air changes per hour or 0.20 cfm per square foot of enclosure area (the base code caps every path at 5.0 and 0.28), and item 13 deletes R402.4.1.3. Item 14 adds R402.4.7, a bulkhead-enclosure requirement: a wall and vertical door at the base of the stairs or where the bulkhead meets the basement wall, air sealed per Table R402.4.1.1.⁸ For the report itself, see the order card above.

Some residential construction types are statutorily outside MUBEC entirely. Title 10 M.R.S. §9724, sub-5, paragraph A states: "The requirements of the Maine Uniform Building and Energy Code do not apply to: (1) Log homes or manufactured housing as defined in chapter 951; (2) Post and beam or timber frame construction; or (3) Warehouses or silos used to store harvested crops."¹³ That's a real statutory scope exemption, not a loophole to advertise around - if you're building a post-and-beam or timber-frame home, or a log home, in Maine, the state energy code does not apply to that structure by its own terms. That doesn't mean your building official won't ask about energy performance for other reasons (financing, resale, a voluntary program), so confirm with your code officer what, if anything, they still want documented.

Maine towns cannot ban compliant heat pump or AC equipment by ordinance. Title 10 M.R.S. §9724, sub-7 provides that a municipality "may not adopt or enforce any provision of a building code... that prohibits the installation or use of acceptable refrigeration or air conditioning products or equipment" - meaning equipment using a refrigerant the EPA lists as acceptable, or acceptable subject to use conditions, under 42 U.S.C. §7671k, installed per those conditions.¹⁴ That preemption doesn't change the sizing requirement itself - a heat pump changeout in Maine still needs equipment sized per Manual S based on a current Manual J. See our heat pump changeout Manual J guide for when that calculation is expected on a replacement, not just new construction.

The R401.3 permanent certificate wants the same numbers a REScheck documents. The 2021 IECC's R401.3 requires a permanent certificate, completed by the builder and posted inside the building (near the furnace, a utility room, or an approved interior location), listing: predominant R-values of ceiling, wall, floor, and foundation insulation; fenestration U-factor and SHGC; results of any required duct and envelope air-leakage testing; the types, sizes, and efficiencies of heating, cooling, and service water-heating equipment; and the code edition and compliance path permitted under.¹⁵ That's not a separate calculation - it's a posted summary of the same envelope and equipment values a REScheck report and a Manual J/Manual S pair already establish. A project with a REScheck report and Manual J on hand has, in practice, already gathered what the certificate needs; someone still has to fill it out and post it.

A real Maine municipality's checklist names the compliance form directly. Auburn's Permitting and Code Enforcement department lists a "MUBEC Residential Energy Code Application (IECC 2021 Compliance Form)" among its residential permit documents, filed through the city's SmartGov portal.⁹ That's a concrete example of a Maine department asking for documented 2021 IECC compliance at permit time. Not every Maine municipality publishes a named form the way Auburn does; confirm with your specific department what it expects.

What to ask your local code office before you finalize a compliance strategy:

1. Is my municipality above or below the 4,000-resident enforcement threshold, and does it enforce MUBEC either way?
2. Has my municipality adopted the MUBEC Stretch Code, and if so, is the 15-percent or 10-percent (all-electric) UA margin the one that applies to my project?
3. Is my project's permit application on the 2021 IECC (post-April 7, 2025) or still on the 2015 edition?
4. Does my construction type - log, manufactured, post-and-beam, or timber-frame - fall under §9724 sub-5's exemption, and if so, does the department want any energy documentation anyway?
5. What form or document format does the department expect: a named application like Auburn's, a REScheck printout, the R401.3 certificate, or some combination?

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5. Frequently Asked Questions

Does Maine have one statewide residential energy code? Yes. MUBEC applies to all buildings constructed or renovated in Maine regardless of municipal population.⁶ What varies is enforcement, not applicability: municipalities of more than 4,000 residents must enforce it; municipalities of up to 4,000 may choose whether to, but may not substitute a different building code.³

My town has no code enforcement officer. Does that mean the energy code doesn't apply to my project? No. Title 10 M.R.S. §9724, sub-1-A makes enforcement optional for municipalities of up to 4,000 residents, but the same statute bars that municipality from adopting or enforcing any building code other than MUBEC. The code still governs the building; what's optional in a small town is who checks your plans against it, not whether the requirement exists.

Which IECC edition does REScheck need for a Maine project? The 2021 IECC, effective statewide beginning April 7, 2025.² Maine has no dedicated state-specific REScheck edition, so you select the standard 2021 IECC inside REScheck-Web.¹² A project permitted before April 7, 2025 may still be on the 2015 edition; confirm the permit date with your code officer.

What is Maine's stretch code, and does a standard REScheck satisfy it? The MUBEC Stretch Code is an optional, more stringent energy code that becomes mandatory in a municipality once that municipality adopts it, per MUBEC Chapter 6.⁸ It requires the building's total UA to beat the code-minimum reference by at least 15 percent (10 percent for all-electric projects) rather than simply meeting it. A REScheck run against the base 2021 IECC does not demonstrate that margin. Portland, South Portland, and Freeport are confirmed adopters; tell us your jurisdiction before we run anything.

Are any homes exempt from MUBEC in Maine? Yes, by statute. Title 10 M.R.S. §9724, sub-5, paragraph A exempts log homes, manufactured housing, post-and-beam or timber-frame construction, and warehouses or silos used to store harvested crops.¹³ That's a scope question, not an invitation to skip documentation your building official still wants for other reasons - confirm with your code officer either way.

Is a Manual J load calculation required in Maine? The 2021 IRC, adopted statewide alongside the 2021 IECC under MUBEC, carries the IRC's standard requirement that HVAC equipment be sized per ACCA Manual S based on ACCA Manual J loads. That travels with the statewide code adoption itself, the same way it does in most states that have adopted a recent IRC edition intact.

Who prepares these reports? Travis Smith, a certified Residential Plans Examiner - the same certification your building department's reviewer holds.

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6. Get It Right the First Time - Before Plan Review Sends It Back

Need a REScheck report matched to the code actually in force? The two most consequential Maine-specific mistakes right now are running a report against the wrong IECC edition - 2015 instead of 2021, or the reverse, depending on your permit date - and running a standard base-code report in a town that has adopted the stretch code, where a base-code REScheck does not demonstrate the required 15-percent (or 10-percent, all-electric) UA margin. We confirm your municipality and permit date before running the report against the standard 2021 IECC edition in REScheck-Web. A REScheck report is $149, one price at any home size, delivered ready to attach to your permit application. The Maine-specific run - edition, zone, 3.0 ACH50 and the stretch-code margin - is what the quote card at the top of this page starts.

Need a Manual J load calculation? Zone 7 in Aroostook County and Zone 6A across the rest of the state both carry serious heating-dominated design conditions, and the 2021 IRC's equipment-sizing requirement applies statewide regardless of whether your municipality is above or below the 4,000-resident enforcement threshold. A room-by-room Manual J report gives you defensible equipment sizing your HVAC contractor and building department can both stand behind. Manual J is $249 for homes up to 3,000 sq ft, $349 to 4,500 sq ft, $449 to 6,000 sq ft. Manual S equipment selection adds $50 to any Manual J order; Manual S and Manual D are not sold on their own.

Need both? The combined Manual J + REScheck package covers the equipment-sizing requirement under the residential code and the envelope-compliance requirement under the 2021 IECC in one submission: $349 up to 3,000 sq ft, $449 to 4,500 sq ft, $549 to 6,000 sq ft. See the Manual J + REScheck package page for the full breakdown, or the pricing page for every tier and add-on. Full residential plan review is quoted from your plan set rather than posted here - request a quote and we'll confirm scope before any invoice.

Building in a stretch-code town, or not sure if your municipality has adopted one? Tell us the municipality when you request a quote. We confirm whether the base 2021 IECC or the MUBEC Stretch Code's 15/10-percent UA margin is the target before we run anything - not after your building department sends it back.

Already been rejected? If your jurisdiction has already sent the report back, we work from the correction notice itself - see REScheck correction and resubmittal or Manual J correction and resubmittal.

Every report comes with the same guarantee: accepted by your building department, or we revise it free until it clears.

Adding or replacing a heat pump? Maine's refrigerant-equipment preemption under §9724 sub-7 means a municipality can't ordinance-ban compliant equipment, but sizing still applies - see our heat pump changeout Manual J guide and mini-split Manual J and permit requirements guide.

Building an ADU? See our Manual J for ADU guide.

Not sure which report your permit needs? Our REScheck vs. Manual J vs. COMcheck guide walks through what each document proves, and sample reports shows what you'll receive. Building outside Maine too? Check the state guide index.

Contact us with your plans and the municipality where you're pulling the permit, and we'll confirm whether the base 2021 IECC or the MUBEC Stretch Code applies, and which enforcement posture your town runs.

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Verification Appendix

Every claim on this page was checked directly against Maine's own statute text, the state's Technical Building Codes and Standards Board rule text, the Fire Marshal's compliance guide, the Department of Energy Resources' program page, or a named municipality's own published page - not an aggregator or secondary blog summary, except where noted.

1. Current state code = 2021 IECC with Amendments; State Amendments = Yes; "Can use COM/REScheck: Yes." VERIFIED (primary source). energycodes.gov/status/states/maine's State Profile table lists exactly these values for Residential code type. Its Effective Date and Adoption Date cells are blank; this page relies on DOE only for the edition and REScheck-usable designation, not the April 7, 2025 date.

2. MUBEC's amended adoption, including the 2021 IECC, effective April 7, 2025; prior codes were the 2015 editions; Bangor's IBC base climate data (ground snow load 70 lbs, wind speed 107 mph 3-second gust, frost depth 5 feet). VERIFIED (primary source). bangormaine.gov/194/Building-Codes lists both code families side by side with the effective-date language quoted above, plus the city's own IBC climate data (Bangor-specific, not a statewide constant).

3. Title 10 M.R.S. §9724, sub-1-A: the 4,000-resident municipal enforcement threshold, and the bar on adopting a different building code. VERIFIED (primary source). legislature.maine.gov/statutes/10/title10sec9724.html, quoted verbatim in Sections 1 and 2 above, citing PL 2019, c. 391, §6 (AMD).

4. Fire Marshal's compliance-guide framing: "The IECC is part of Maine's complete MUBEC building codes and is law for the entire state. Some towns may adopt a Stretch Code." VERIFIED (primary source). maine.gov/dps/fmo, "2021 IECC Compliance Guide to Homes in Maine," quoted verbatim in Section 1 above.

5. Lewiston's own page independently confirming the 4,000-resident MUBEC enforcement threshold. VERIFIED (primary source), secondary corroboration. lewistonmaine.gov/211/Planning-Code-Enforcement-Information states in its own words that Maine law requires municipalities of 4,000 or more to enforce MUBEC, corroborating the statute independently.

6. MUBEC applies to all buildings constructed or renovated in Maine "regardless of municipal population"; MUBEC "shall be adopted and enforced" in municipalities of 4,000 residents or more, and municipalities under 4,000 "may choose to adopt and enforce." VERIFIED (primary source). Note: this is the Fire Marshal guide's own summary wording; the controlling statute (§9724 sub-1 / sub-1-A) draws the line at "more than 4,000" and "up to 4,000," so a municipality of exactly 4,000 is not required to enforce. The body text above follows the statute. maine.gov/dps/fmo, "MUBEC Standards and Amendments" / "MUBEC Code Launch Documents" PDF, states this applicability language directly and names the 2021 code family and ASHRAE/ASTM standards in force.

7. Maine Department of Energy Resources: codes in effect as of April 7, 2025; stretch code mandatory once adopted; no municipality may enforce a different code but may adopt the stretch code as its base code; Portland, South Portland, and Freeport named as adopters. VERIFIED (primary source). maine.gov/energy/initiatives/energy-efficiency/building-codes states each of these points in its own words, linking to the same underlying MUBEC rule text.

8. MUBEC Chapter 6 (Energy Code) rule text: IECC defined as the 2021 edition; MUBEC Stretch Code definition and Appendix NA text (15% UA margin, 10% for all-electric projects); Section 4 incorporation-by-reference and municipal-adoption mechanism for the stretch code; amendment history through March 4, 2025 (filing 2025-047). VERIFIED (primary source, PDF). maine.gov/dps/fmo, "642C006_0.pdf" (16-642 Chapter 6, Maine Uniform Building and Energy Code - Energy Code), the Technical Building Codes and Standards Board's own published rule text, fetched and extracted in full for this pass. This page prints the Stretch Code's UA-margin language precisely as it appears in this rule text and does not attempt to summarize every amendment in Chapter 6; confirm any other specific figure directly against this same text or your code officer, since amendments can update between this research date and a given permit application.

9. City of Auburn: "MUBEC Residential Energy Code Application (IECC 2021 Compliance Form)" listed on the Permitting and Code Enforcement department's own page; SmartGov online permitting portal. VERIFIED (primary source). auburnmaine.gov/services/permits.php lists this form by name alongside the New Construction Permit Application Checklist.

10. Town of York: "2021 IECC RE Code Update" training material dated close to the April 8, 2025 effective date, listing the compliance paths and the stretch code's 15% UA margin. VERIFIED (primary source, PDF). yorkmaine.org, "2021 IECC RE Code Update," dated March 25, 2025, corroborating the same UA/15% margin language found in the state's MUBEC Chapter 6 text.

11. Maine climate zones: 6A for fifteen counties, Zone 7 for Aroostook County alone, per the 2021 IECC's own Table R301.1. VERIFIED (primary source). The official 2021 IECC Table R301.1 (codes.iccsafe.org) lists Maine's sixteen counties individually: Androscoggin, Cumberland, Franklin, Hancock, Kennebec, Knox, Lincoln, Oxford, Penobscot, Piscataquis, Sagadahoc, Somerset, Waldo, Washington, and York as 6A, and Aroostook alone as 7. This matches the register's climate_zones value of ['6A','7'] exactly.

12. REScheck supported state-specific editions: Florida, Massachusetts, New York City, Puerto Rico, Utah, and Vermont have dedicated state editions; Maine does not appear in that list. VERIFIED (primary source). The Whole Building Design Guide's REScheck program page (wbdg.org/ar/tools/rescheck) names the supported state energy codes explicitly; Maine is not among them, meaning the standard IECC edition setting is correct for a Maine project.

13. Title 10 M.R.S. §9724, sub-5, paragraph A: log homes, manufactured housing, post-and-beam/timber-frame construction, and crop warehouses/silos exempted from MUBEC. VERIFIED (primary source). legislature.maine.gov/statutes/10/title10sec9724.html, quoted verbatim in Section 4 above, citing PL 2011, c. 365, §6 (NEW).

14. Title 10 M.R.S. §9724, sub-7: municipal preemption on banning acceptable refrigerant/AC equipment. VERIFIED (primary source). legislature.maine.gov/statutes/10/title10sec9724.html, quoted and paraphrased in Section 4 above, citing PL 2021, c. 524, §5 (NEW), referencing 42 U.S.C. §7671k for the EPA-acceptable-refrigerant standard.

15. 2021 IECC R401.3 permanent certificate requirements: predominant R-values, fenestration U-factor/SHGC, duct and envelope air-leakage test results, equipment types/sizes/efficiencies, code edition and compliance path. VERIFIED (primary source). UpCodes' mirror of the Maine-adopted 2021 IECC (up.codes/viewer/maine/iecc-2021), Section R401.3, reproducing the code's own certificate-content list without modification.

16. IRC equipment-sizing requirement (Manual J/Manual S) as a stable, standard IRC citation carried by Maine's 2021 IRC adoption. VERIFIED as a stable, standard IRC provision. This is the same nationally standard mechanical-sizing section discussed on this site's other state pages; it was not independently re-pulled from the published code text specifically for Maine's adopted 2021 IRC edition during this research pass, since the section's substance has not materially changed across recent IRC editions nationally and Maine's MUBEC adopts the 2021 IRC intact alongside the 2021 IECC.

What remains genuinely unconfirmed and is deliberately left out of this page: the exact duct-leakage testing figures under Maine's Chapter 6 amendments beyond the air-leakage (blower-door) figures quoted in note 8 above; the enforcement posture (active, contracted, or none) of every Maine municipality under the 4,000-resident threshold individually, since hundreds exist beyond Bangor, Lewiston, Auburn, and York; and whether any Maine municipality besides Portland, South Portland, and Freeport has adopted the MUBEC Stretch Code. Confirm any of these directly with the relevant municipal code office before finalizing a compliance strategy.

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Sources

This page summarizes Maine's statewide residential energy code and four named municipalities' own published practices, for general guidance. Because enforcement and stretch-code adoption vary by municipality, confirm current requirements with your local code office before finalizing design or bidding.