Search "Iowa new construction radon law 2026" and you'll find a handful of real estate blogs stating, with total confidence, that as of July 1 every new single-family and two-family home built in the state now includes a passive radon mitigation system. That's the headline version. It's also not what actually happened.
House File 2297, the bill behind that claim, was signed by Governor Reynolds on May 19, 2026, and its effective date is indeed July 1, 2026. But read past the press release and the legislative text says something narrower: the law directs the State Building Code Commissioner to add a passive radon mitigation requirement to the state building code at some future point, and that requirement will only apply to construction that starts after the Commissioner formally adopts it. On June 25, 2026, the Iowa Department of Inspections, Appeals, and Licensing confirmed exactly that reading: HF 2297 doesn't create an enforceable requirement on its own. It's an instruction to write one later. That guidance didn't include a date for when the Commissioner would actually amend the code, so the honest answer for a buyer today is to ask rather than assume: confirm with your builder or the city whether that code amendment has since been adopted, rather than treating the mandate everyone's citing as automatically binding on a Johnston lot right now.
If you're touring quick move-in homes in a community like Crosshaven this fall, or comparing a new build to something in an established Johnston neighborhood, that distinction changes what you should actually ask a builder, and it's separate from a second, very specific problem that shows up in Johnston's older housing stock. Both are worth understanding before you write an offer.
What HF 2297 Actually Requires, and What It Doesn't
Strip away the paraphrasing and the bill does one thing: it tells the Commissioner to fold a passive radon mitigation method, drawn from Appendix AF of the 2021 International Residential Code, into the state building code. It does not specify a deadline for that adoption. It does not apply retroactively. And it explicitly limits itself to construction that "commences after the adoption of the requirement," language straight from the bill text. Until the Commissioner acts, there's no statewide code line a builder is violating by skipping a passive system.
That's a meaningfully different claim than "every new Iowa home now has radon protection built in." One is a law that exists on paper. The other is a construction detail you'd need to confirm on a specific house.
A quick timeline makes the gap easier to see:
| Date | What happened |
|---|---|
| May 19, 2026 | Governor Reynolds signs HF 2297 into law |
| July 1, 2026 | The law's effective date, but only as an instruction to the Commissioner |
| June 25, 2026 | DIAL issues guidance clarifying the mandate isn't self-executing |
| No date announced as of DIAL's June guidance | Commissioner's formal code amendment, which is when the requirement actually starts applying to new permits |
Most builders already install passive radon features as standard practice, since retrofitting a mitigation system after drywall is far more expensive than building it in from the slab. That's a real reason the gap between "law signed" and "code amended" matters less than it sounds. But "most builders do it anyway" is a different guarantee than "the law requires it," and if you're relying on the second claim in a purchase decision, you're relying on something that isn't currently true.
Why Polk County Complicates the Story Further
Here's where Johnston specifically gets interesting. Before HF 2297 existed, Iowa already had a short list of jurisdictions that required radon-resistant new construction under the older 2017 IRC Appendix F standard. That list includes the counties of Bremer, Johnson, Linn, and Polk, plus the cities of Altoona, Bondurant, Carroll, Iowa City, North Liberty, Norwalk, and Pella.
Johnston sits inside Polk County. That means the county-level requirement may already have applied to new single-family construction in Johnston for years, independent of anything happening in the state legislature this session. The City of Johnston adopted its own current set of building codes, including the 2024 International Residential Code, effective February 1, 2026, with local amendments layered on top. Whether the county's radon standard flows through to city-issued permits, or whether it depends on how Johnston's own adopted code handles Appendix F, isn't something a buyer can safely assume either way from a blog post.
The practical move is simple: ask the builder directly whether the home already includes radon-resistant construction features, and ask for it in writing rather than taking "the new law covers that" as an answer. Given that Iowa's own health data puts every one of its 99 counties in the EPA's highest radon risk zone, with 71.6% of tested Iowa homes exceeding the action level of 4.0 picocuries per liter, this isn't a box-checking exercise. It's a health and negotiating detail that belongs in the file before closing, not something to sort out after the inspection report lands.
If a test does come back elevated, a standard mitigation system in this market typically runs $900 to $1,800 and takes about a day to install. That's worth knowing whether you're a buyer weighing a concession request or a seller deciding whether to test before listing.
The Older Half of Johnston Has Its Own Version of This Problem
New construction isn't the only place where "the code requires it" and "the house actually has it" can drift apart. Johnston's established neighborhoods, the ones built through the 1990s and early 2000s in areas like Barnsley and Heather Bow rather than newer conservation-style communities, carry a different and better-documented issue: basement bedrooms finished with windows that were never built to meet Iowa's egress standard.
Iowa Administrative Code 481-301.8 requires at least one emergency escape and rescue opening in every basement and in every basement sleeping room. Under the version of the International Residential Code Iowa has adopted, that opening needs a minimum net clear area of 5.7 square feet, a minimum clear height of 24 inches, a minimum clear width of 20 inches, and a sill no more than 44 inches above the finished floor. A basement finished with a small hopper window, common in that era of Johnston construction, almost never clears those numbers.
The consequence isn't cosmetic. A basement bedroom without a compliant egress window cannot legally be marketed or appraised as a bedroom at resale, and local remodeling crews working in Johnston have flagged this as one of the most common and costly issues they find once a homeowner decides to sell. Ceiling heights in that same generation of Johnston basements often sit right at the 7-foot minimum required for habitable space too, which means a finish job that looks complete can still fail on two separate code points at once. Full basement finishing projects in Johnston typically run $35,000 to $90,000, and egress corrections, along with moisture control and bathrooms, are consistently the biggest cost drivers in that budget.
If you own one of these homes and you're not sure whether that lower-level bedroom would hold up under appraisal, that's a conversation worth having before you list, not after an offer falls through the day an appraiser walks the basement.
What This Means If You're Acting This Fall
For buyers touring new construction:
- Ask the builder in writing whether the home includes radon-resistant construction features, and don't accept "the new state law covers that" as a full answer since the mandate isn't code-enforceable yet
- Request a radon test during your inspection period regardless of what the builder says is already built in
- Confirm the home's permit date, since Polk County's older radon-resistant construction standard may already apply independent of anything happening at the state level right now
For buyers or sellers dealing with resale, especially anything built in the 1990s or early 2000s:
- If a basement bedroom is part of the listing's bedroom count, verify the window meets the 5.7 square foot, 24-inch height, 20-inch width standard before you rely on that room count in your offer or your asking price
- Sellers are required under Iowa Code sections 543B.9 and 543B.18 to disclose any known radon test results, and both parties must acknowledge receiving the state's radon fact sheet as part of the disclosure paperwork
- A high radon reading found during inspection typically gives a buyer grounds to renegotiate or walk away without losing earnest money, so schedule that test early in the contingency period rather than near the deadline
A Few Quick Answers
Does this mean new Johnston construction has no radon protection at all? No. Most builders already install passive systems as routine practice, and Polk County's older radon-resistant construction standard may already apply here. It means the specific state law making headlines right now isn't the thing guaranteeing it.
Is the egress window issue something inspectors always catch? It's flagged often enough that local remodeling crews describe it as one of the more common findings in Johnston resale transactions, but a general home inspection is visual, not a code review. If the room's listed as a bedroom, it's worth measuring the window yourself or asking directly before you rely on that count.
What should I actually ask for in writing? From a builder: written confirmation of any radon-resistant construction features included in the home. From a seller: the disclosure form covering known radon test results, plus straight answers about whether any basement bedroom was ever permitted and inspected for egress.
Buying new or selling something built decades ago in Johnston both come down to the same habit: verify the specific thing on the specific property rather than relying on what a headline or a listing description implies. If you're weighing a new build in Johnston against something established, or you're getting ready to list a home with a finished basement, London Orosco and the team at Slavin & Partners can walk the details with you before you're standing in front of an inspection report trying to figure out what it means. You can also start with a free home valuation or read more about what's happening in Johnston right now.
