Which Radon Rules Apply to Your Multifamily Loan: HUD, Fannie Mae, Freddie Mac, or Your Lender

1. Why your financing decides the radon rules

Owners and acquisition teams often ask a reasonable question that does not have a single answer: what does the government require for radon on a multifamily building? The reason there is no clean answer is that radon requirements for apartments do not come from one place. They come from whoever is putting capital behind the loan. Change the financing and you can change the rule.

In practice there are four sources to keep straight. HUD and FHA-insured loans run on their own track. Loans sold to Fannie Mae or Freddie Mac follow each enterprise's current multifamily guide. Individual lenders can layer their own credit-policy requirements on top of any of those. And state and local law plus the judgment of the environmental professional shape what testing actually looks like on a given deal. The same physical building can sit under different requirements depending on the loan attached to it.

2. HUD and FHA-insured loans: a separate track

HUD insures and finances a large share of the country's apartment stock through its multifamily mortgage programs, and those programs carry their own radon requirements through the environmental review process. The important point for this article is that HUD is institutionally separate from Fannie Mae and Freddie Mac. HUD's requirements were not part of the 2025 FHFA action and remain in force on their own terms.

So if your deal is HUD or FHA-insured, you are following HUD's framework, not the enterprise guides, and you should not assume that anything that changed for Fannie Mae or Freddie Mac changed for you. We cover HUD's requirements in detail in our companion guide on HUD radon requirements for multifamily properties. As always, confirm the exact scope that applies to your loan with your lender.

3. Fannie Mae and Freddie Mac: each sets its own

Fannie Mae and Freddie Mac are the two large enterprises overseen by the Federal Housing Finance Agency (FHFA). Each one maintains its own multifamily radon requirements through its current guide, and those requirements are not identical to each other or to HUD. If your loan is headed to one of these enterprises, the enterprise's current guide is what governs your testing scope.

We deliberately do not quote a specific testing percentage or a unit count here. Each enterprise sets and updates its own requirements, and the controlling number for your loan is whatever its current guide says on the day your deal is underwritten. Treat any fixed figure you find in an older article or checklist as a starting point to verify, not as a settled fact. The reliable source is your lender, working from the current enterprise guide.

4. The March 2025 FHFA action and what it changed

In 2022, the FHFA had issued a directive that standardized radon testing requirements across Fannie Mae and Freddie Mac, pushing the two enterprises toward a uniform approach. On March 26, 2025, the FHFA rescinded that 2022 uniform directive. The effect was not to eliminate radon requirements for enterprise loans. It was to step back from a single mandated standard and return more discretion to each enterprise's own guide.

After the rescission, the practical reality for an enterprise loan is that the environmental professional's judgment, combined with state and local law and the enterprise's current guide, carries more weight in deciding what testing is required. For a full breakdown of the change, see our companion guide on the 2025 Fannie Mae and Freddie Mac radon changes.

5. Your lender can add requirements on top

Program rules are a floor, not a ceiling. An individual lender can apply its own credit-policy requirements on top of whatever the program calls for. A bank making a balance-sheet loan that never touches an agency or enterprise can still require radon testing as part of its environmental due diligence. A lender originating an enterprise loan can choose to be more conservative than the enterprise guide. The point is that even after you identify the program, the lender's own policy can add to it.

This often shows up through the Phase I environmental site assessment. If a Phase I flags radon as a recognized environmental concern, that can trigger testing independent of any program mandate. For an acquisition team, the safe assumption is that the lender's requirements may be broader than the program minimum, and the only way to know is to ask the lender directly.

6. Where state and local law and the environmental professional fit in

With a single uniform federal directive no longer in place for the enterprises, two other inputs matter more. The first is state and local law. Some states regulate radon testing or mitigation directly, and where they do, those rules apply on top of whatever the financing requires. Georgia does not have a state radon testing mandate, but a property elsewhere in a lender's portfolio might sit in a state that does.

The second is the environmental professional who prepares the assessment. Their judgment about radon risk, informed by EPA radon zones, building type, and site conditions, helps shape what testing is recommended for a given property. The common thread across all of these inputs is the 4.0 pCi/L action level: where testing finds radon at or above that level, mitigation and a confirming retest are the expected response, regardless of which framework sent you to test in the first place.

7. How to find the controlling rule for your deal

Cutting through the layers is simpler than it looks once you ask the questions in the right order. Start with the loan, not the building.

The answers point to a single controlling requirement: the most demanding rule among the ones that apply. Get those answers in writing during due diligence, before you order testing, so the scope you pay for matches what the lender will accept at closing. Confirming scope early is the single highest-leverage thing an acquisition team can do on radon.

8. What this means in metro Atlanta

Georgia does not have a state radon testing law, which leads some owners to assume radon is not a local concern. The data says otherwise. On the EPA Map of Radon Zones, four metro Atlanta counties, Fulton, Cobb, DeKalb, and Gwinnett, are Zone 1, the highest category, meaning a predicted average at or above 4.0 pCi/L. Several surrounding north Georgia counties also carry elevated designations driven by the region's granite and uranium-bearing bedrock.

For an Atlanta-area multifamily deal, the takeaway is to pair the right requirement with the local reality. Once you know which framework governs the loan, build the testing into your due-diligence timeline, because in higher-radon parts of metro Atlanta elevated results are common enough that a late requirement can stall a closing. Our overview of multifamily radon testing walks through what the work involves.

9. Frequently asked questions