HUD radon requirements: testing, mitigation and new construction

For FHA multifamily mortgage insurance under the MAP Guide, HUD requires a radon report, testing to ANSI/AARST protocol, mitigation at or above 4.0 pCi/L, and radon-resistant construction for all new construction (MAP Guide §9.6.3).

Since 2024 a separate HUD-wide notice, CPD-23-103, also requires radon to be considered in every environmental review under 24 CFR Parts 50 and 58.

Scope limit: CPD-23-103 “does not apply to the purchase of single family homes with an FHA-backed mortgage” (CPD-23-103).

• Testing follows ANSI-AARST MAMF-2017: 100% of ground-floor units and 10% of upper-floor units in all buildings (MAP Guide §9.6.3.2.D).
• Alternative: mitigate all ground-level units instead of a full testing assessment (§9.6.3.2.D).
• Threshold: 4.0 pCi/L (§9.6.3.2.D). What the numbers mean at that 4.0 pCi/L threshold, set beside the EPA, WHO, and Health Canada figures, is explained in a separate reference.
• Section 223(f): testing no earlier than 1 year before application, or go straight to mitigation (§9.6.3.3).
• Occupants are notified per MAMF (§9.6.3.2.E).

Edition note: AARST has since folded MAMF and MALB into MA-MFLB-2023, and EPA lists a 2023-12-01 compliance date. The March 2021 MAP Guide text still names MAMF-2017. An earlier HUD Office of Multifamily Production memostates that “HUD requires reliance on the most recent standard or guidance document in force.”

For a single home, see short-term versus long-term radon tests.

• Testing and mitigation are done by or under a Radon Professional certified by AARST-NRPP or NRSB, plus a state license where the state requires one (MAP Guide §9.6.3.2.B).
• The radon report is signed and certified by that Radon Professional (§9.6.3.2.B).

MAP Guide §9.6.3.2.F names:

• Existing multifamily: RMS-MF 2018.
• New multifamily: CC-1000-2018, or the named sections of ASHRAE 189.1-2017.
• One-and-two-family structures: CCAH-2020.

EPA notes that SGM-MFLB-2023 consolidates RMS-MF and RMS-LB. See ANSI/AARST SGM-MFLB-2023.

• The radon mitigation system has to be shown in the architectural plans.
• “HUD relies on the Project Architect to design and incorporate any required radon mitigation system”; HUD encourages the architect to seek a radon professional's advice.
• Post-construction testing happens before the final completion inspection. If results come in above the threshold, the system is activated or retrofitted.
• Phased projects: the CC-1000 Pressure Field Extension results per building stand in for the radon report on intermediate phases (MAP Guide footnote 40).

Sources: MAP Guide §9.6.3.2.A.2 and §9.6.3.5; HUD memo §B.

From MAP Guide §9.6.3.2.G–K:

• New construction and substantial rehab: mitigation and follow-up testing are done before final endorsement.
• 223(f): mitigation repairs are completed within 12 months after Closing.
• The certificate of completion is uploaded to HEROS.
• The OM&M plan is held as a Firm Commitment condition for the life of the mortgage.
• Existing systems are evaluated.
• The lender provides the cost estimate, including ongoing O&M.

• Radon must be considered in the contamination analysis (CPD-23-103).
• The notice “does not impose radon testing requirements” but recommends testing.
• The EPA Map of Radon Zones may not be used for the site-specific analysis.
• At or above 4 pCi/L, the Environmental Review Record needs a mitigation plan: the level, the occupant risk, a system description, a maintenance plan, a timeframe, and post-installation testing.
• Issued 2024-01-11, effective 90 days later for most recipients (HUD Exchange: 2024-04-11).
• The tribal effective date has been extended; see HUD Exchange for the current date.

• The radon zone and system description on the architectural plans (HUD memo §B).
• The CC-1000 elements of the system.
• Pressure Field Extension results for phased work (MAP Guide footnote 40).
• The OM&M plan (MAP Guide §9.6.3.2.G–K).

Related: multifamily radon-control design, SGM-MFLB-2023 and ANSI/AARST CC-1000.