What IECC Energy Code Is Your State On? Does Your State Actually Require Your New Home to Be Blower Door Tested?

US Residential Energy Code Adoption

Which IECC edition is each state on for new homes? (Updated April 2026)

2024 IECC

2021 IECC

2018 IECC

2015 IECC

2012 IECC

≤2009 IECC

2006 IECC

Own code (CA)

No statewide code

Blower Door Testing on New Homes

The 2012 IECC was the first edition to require mandatory blower door testing with no visual inspection alternative. States on 2012+ should require it — but many have amended the requirement or don't enforce it consistently.

IECC Edition	Model Code Requirement	ACH50 Limit	Real-World Enforcement
2024 IECC	Mandatory blower door test	≤2.0–2.5	IL, RI, NV, ND enforcing.
2021 IECC	Mandatory blower door test	≤3.0	Northeast states generally enforce. LA amended to 7 ACH50 for CZ 2.
2018 IECC	Mandatory blower door test	≤3.0	FL enforces (5 ACH50 w/ amendments). ID raised to 5 ACH50. IN allows visual inspection instead.
2015 IECC	Mandatory blower door test	≤3.0	Mixed. GA requires DET verifier testing. TX, AL — varies by jurisdiction.
2012 IECC	Mandatory blower door test	≤3.0	MN enforces. Also requires balanced mechanical ventilation.
2009 IECC	Testing OR visual inspection	7 ACH50 if tested	Visual inspection is the norm. SC, AR, WV — testing rare.
≤2006 or none	No blower door requirement	N/A	Build however you want.

Duct Leakage Testing (Duct Blaster) on New Homes

The 2009 IECC was the first edition to require duct leakage testing. Until the 2021 IECC, ducts entirely inside the thermal envelope were exempt — a massive loophole. The 2021 code closed it: all ducts must be tested regardless of location, though ducts inside the envelope get a more lenient limit.

IECC Edition	Duct Test Required?	Limit (CFM25 per 100 sq ft)	Key Details
2024 IECC	All ducts	≤4 (outside envelope) ≤8 (inside)	Continues 2021 approach. Tighter in some climate zones. Buried duct credit requires ≤1.5.
2021 IECC	All ducts	≤4 post-construction ≤8 (inside envelope)	Big change: No more exemption for ducts inside envelope. All systems tested.
2018 IECC	Outside envelope only	≤4 post-construction	Ducts entirely inside thermal envelope: EXEMPT from testing.
2015 IECC	Outside envelope only	≤4 post-construction	Same as 2018. Ducts inside envelope exempt.
2012 IECC	Outside envelope only	≤4 post-construction	Tightened from 2009 limits. Ducts inside envelope exempt.
2009 IECC	Outside envelope only	≤12 post-construction	First edition to require duct testing. Much looser limits. AR made testing optional.
≤2006 or none	Not required	N/A	No duct leakage testing requirement.

The enforcement gap — what "adopted" really means

Even states on the 2018 or 2021 IECC have often amended away the teeth. Indiana lets you do a visual inspection instead of a blower door test. Louisiana loosened to 7 ACH50 — which is like saying "your house can leak, just not catastrophically." Idaho went to 5 ACH50 and allows sampling instead of testing every home. West Virginia adopted the 2009 IECC in 2013; the 2009 code remains what's actually on the ground despite paper updates. And then there's the rural enforcement problem: Ohio technically requires 3 ACH50, but outside Columbus, Cleveland, and Cincinnati, good luck finding an inspector who owns a blower door.

The bottom line: "adopted" ≠ "enforced." The code on the books and the code in the field can be very different things.

Political headwinds — codes are moving backward in some places

Oklahoma at 2006 IECC is genuinely shocking — no blower door requirement, minimal insulation standards, no duct testing. South Carolina on 2009 isn't much better, and future updates require legislation.

Several states are actively trying to freeze or roll back energy codes:

• Missouri HB 2384 (2026) would prevent local jurisdictions from adopting codes exceeding the 2009 IECC.

• Washington HB 2141 (2026) would freeze state energy code updates for a decade.

• Nebraska LB 1134 would halt adoption of codes more stringent than the state code until 2031.

• North Carolina HB 488 (2023) effectively froze residential energy code updates.

• Vermont EO 06-25 reinstated older 2018-based codes as an alternative, citing cost concerns.

Home rule states — the wild west

AZ, KS, MO, MS, SD, AK, WY have no mandatory statewide residential energy code. Large cities often adopt recent IECC editions on their own — Phoenix is on the 2024 IECC — but drive 30 minutes outside city limits and you're in unregulated territory.

Amendments matter more than the edition number

Most states adopt the IECC with amendments that can significantly weaken requirements. Indiana adopted the 2018 IRC but amended air leakage to 5 ACH50 and allows visual inspection. Louisiana adopted 2021 IECC but loosened to 7 ACH50 in CZ 2. New Hampshire adopted 2021 IECC but NAHB notes requirements haven't substantially changed from 2018 levels. When someone says "we're on the 2021 code," ask which parts they kept and which they cut.

The duct testing loophole that lasted 12 years

From 2009 through 2018, if all your ductwork was inside the thermal envelope, no duct blaster test was required. The 2021 IECC closed this loophole. All ducts get tested now — ducts inside the envelope just get a more lenient 8 CFM25/100 sq ft limit vs. 4 CFM25 for ducts outside.

California

Uses its own Title 24, Part 6 energy code (2025 edition effective Jan 2026), generally at least as stringent as the 2021 IECC. Requires blower door and duct testing. 2025 edition added heat pump prescriptive path.

What homeowners should actually do

Call your local building department and ask two questions: (1) "Do you require a blower door test on new residential construction? What's the ACH50 limit?" (2) "Do you require a duct leakage test? What's the CFM25 limit?" Those two answers tell you more than any map.

Sources

DOE Building Energy Codes Program (energycodes.gov); BCAP State Code Status; ACEEE State Policy Database; NAHB State Adoption Status (Nov 2024); NEEP Building Energy Codes Roundup (Dec 2025); Regional Energy Efficiency Organizations (REEOs): NEEP, SEEA, MEEA, SWEEP, SPEER, NEEA; state building code agency websites. Community corrections verified against primary sources: Daniel Baur-McGuire (Iowa), Eric George (Kentucky), Noah Lawrence (New York), Linda Toth (Virginia), Timothy Kisner (Texas). Tiebreaker: where BCAP and ACEEE conflict, more recently updated source wins. Data compiled April 2026. Always verify with your local building department.

□ Methodology — Per-State Sources (50 states + DC) ▼

Tiebreaker rule: Where BCAP and ACEEE conflict, the more recently updated source wins. Community corrections verified against primary state agency sources. REEOs (Regional Energy Efficiency Organizations) — NEEP, SEEA, MEEA, SWEEP, SPEER, NEEA — are the authoritative regional trackers.
Scope: Mandatory statewide residential energy codes only. Home-rule states with no statewide mandate shown as "No statewide code" even if major cities have adopted codes. ~60% of states amend the model code, often weakening key provisions.
Note: DOE BECP publishes a separate "Code Efficiency Category" that models actual energy savings including amendments — a state claiming 2021 IECC may rate lower after weakening amendments. See DOE methodology and download the raw data (Excel).

State	Code	Source(s)	REEO

Map: CSHVAC — natethehousewhisperer.com · Updated April 2026 · State boundaries: US Census Bureau (us-atlas)

Does Your State Actually Require Your New Home to Be Tested?

You might be surprised by the answer.

I spent some time mapping which residential energy code every state is on right now after my friend Glenn T Remington asked about what energy codes each state was on. 

Then I posted it on social media and got corrected within the hour — four states wrong, several more out of date. So I spent a bit more time verifying every state against five different databases, discovered the databases disagree with each other, and learned more about energy codes than 15 years in HVAC ever taught me. What started as both curiosity and a question from my friend Glenn T Remington on LinkedIn took me down a rabbit hole I wasn’t expecting.
The result is an interactive map you can hover over to see your state’s status, including whether blower door testing and duct leakage testing are required on new homes.
The short answer for most of you: maybe on paper, probably not in practice.

The IECC — the code your new home was (probably) built to

Almost every state bases its residential energy code on the International Energy Conservation Code, or IECC. It gets updated every three years — 2006, 2009, 2012, 2015, 2018, 2021, 2024. Each edition gets a little tighter on insulation, air sealing, and duct leakage.
Here’s the problem: states adopt these codes on wildly different timelines. Right now in 2026, the spread looks like this:

• Rhode Island, New York, Illinois, Nevada, and North Dakota are on the 2024 IECC — the newest and tightest.
• Most of the Northeast, plus states like Michigan, Nebraska, Wisconsin, and Utah are on the 2021 IECC.
• A chunk of the Midwest and South is still on the 2015 or 2018 IECC.
• Oklahoma is on the 2006 IECC. That’s twenty years old. No blower door test. No duct testing. Minimal insulation standards.
• Seven states have no mandatory statewide residential energy code at all.

My own state of West Virginia? We’re on the 2009 IECC. The legislature passed a bill in 2022 to update to the 2015 code, but it never effectively went through. And honestly, even the 2009 code barely gets enforced outside the larger cities. Sometimes being 30 years behind has its charm — handshakes still mean something here. Sometimes it doesn’t.

Why blower door and duct leakage testing matter

Here’s what I really want you to understand: the code edition matters less than whether your state actually requires testing — because testing is how you know the house was well built.

The 2012 IECC was the first edition to require a mandatory blower door test on every new home — no visual inspection alternative. That was a big deal. It meant someone had to show up with equipment and prove the house didn’t leak like a sieve.

But here’s what happened: states adopted the 2012+ codes and then amended out the teeth. Indiana adopted the 2018 code but lets builders do a visual inspection instead of an actual test. Louisiana adopted the 2021 code but loosened the air leakage limit to 7 ACH50 — which is like saying your house can leak, just not catastrophically. Idaho raised the threshold to 5 ACH50 and allows sampling instead of testing every home.

Duct leakage testing has the same problem, with an added twist. From 2009 through 2018, if all your ductwork was inside the thermal envelope — meaning inside conditioned space — no duct blaster test was required. The 2021 IECC finally closed that loophole. But plenty of states haven’t gotten to 2021 yet, and even on the states that have, enforcement varies by jurisdiction.

The sources don’t agree with each other

This was the part I didn’t expect.
I cross-referenced BCAP, ACEEE, NAHB, NEEP, and DOE’s Building Energy Codes Program. They disagree on a surprising number of states. BCAP’s entry for Iowa showed Indiana’s data — a straight copy-paste error. BCAP listed Kentucky at 2015 IECC, but that’s the building code version; the energy provisions actually reference the 2009 IECC. Eric George, who builds houses in Kentucky, knew this instantly.
William Parlapiano, who tracked this stuff painstakingly for Knauf before he retired, told me roughly 60% of states amend their adopted codes — very few adopt as-is. He pointed me to the Regional Energy Efficiency Organizations (REEOs) as the most reliable source. The six REEOs — NEEP, SEEA, MEEA, SWEEP, SPEER, and NEEA — cover 46 states and are genuinely on the ground watching code adoption happen in real time. They were the best source I found.
The lesson: no single database has it right for all 50 states. You have to cross-reference, and even then you might be wrong. Which is why the crowd-sourced corrections turned out to be the most reliable data of all.

The gap between “adopted” and “enforced”

This is the part that should make you uncomfortable if you’re building or buying a new home. “Adopted” and “enforced” are not the same thing. Ohio technically requires 3 ACH50 on new homes, but outside the major cities, good luck finding an inspector who owns a blower door.
And it’s getting worse in some places. Missouri has a bill that would prevent local jurisdictions from adopting anything more stringent than the 2009 IECC. Washington has a bill to freeze code updates for a decade. North Carolina froze its residential code in 2023.

This isn’t just inertia. It’s organized pushback — some of it genuine concern about housing costs, some of it builder lobbying against any standard that requires testing and verification.

What you should actually do

Forget the map for a minute. Here’s the most useful thing I can tell you:
Call your local building department and ask two questions. First: “Do you require a blower door test on new residential construction, and what’s the ACH50 limit?” Second: “Do you require a duct leakage test, and what’s the CFM25 limit?”
Those two answers tell you more about the quality of new construction in your area than any color-coded map ever will. And if they can’t answer clearly? That tells you something too.

The map DOE already built

​After all this work, I discovered the Department of Energy already has something better than what I was trying to build. Their Building Energy Codes Program doesn’t just track which edition each state adopted — they model the actual energy use of each state’s code, including all the amendments, and compute what the code is functionally equivalent to. A state that claims the 2021 IECC but gutted it with weakening amendments shows up at its true performance level, not its label.

You can explore it yourself on DOE’s interactive dashboard, or download the raw state-level data from energycodes.gov. This is ultimately what I was trying to understand — not just what’s on the books, but what’s actually in effect.
The interactive mapI’ve published a full interactive map with state-by-state details, blower door requirements, duct testing requirements, per-state sources, and all the footnotes and caveats. Check it out and see where your state stands.
Because the HVAC system in your new home is only as good as the code that’s actually enforced — and the contractor who actually follows it.

Corrections & contributors

This map started rough and got better because people spoke up:

• Daniel Baur-McGuire — Iowa correction (2012 IECC, not 2018)
• Eric George — Kentucky correction (2009 IECC for residential, not 2015)
• Noah Lawrence — New York update (2024 IECC via 2025 ECCCNYS)
• Linda Toth — Virginia correction (2021 IECC)
• Timothy Kisner — Texas detail (the IRC/IECC/ERI compliance path breakdown)
• William Parlapiano — The REEOs recommendation and the reality check on amendments that became the thesis of this whole piece
• Ken Zemach — The enforcement comment that started everything: “If inspectors actually held builders accountable to the energy code from years ago, most houses would be way better already.”

If you see something wrong, tell me. I’ll verify it and update. This is a living document.

​
Nate Adams is a building scientist and author of Common Sense HVAC, a homeowner’s guide to getting a quality HVAC installation. He lives near the New River Gorge in West Virginia.