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Radon Mitigation

Background

Radon is a colorless, odorless radioactive gas that seeps up from the earth. When inhaled, it gives off radioactive particles that can damage the cells that line the lung.

Long term exposure to radon can lead to lung cancer. In fact, more than 21,000 lung cancer deaths in the US each year are caused by radon, making it a serious health concern for Minnesotans.

In Minnesota, two in five homes have radon levels that pose a significant health risk, and nearly 80% of Minnesota counties are rated high radon zones. Some factors that further contribute to Minnesota's high radon levels include:

  • Minnesota's geology produces an ongoing supply of radon.

  • Minnesota's climate affects how our homes are built and operate

 

Requirements

All multifamily projects receiving funding from Minnesota Housing shall meet the following requirements.

New Construction
All Multifamily type buildings without underground parking shall provide a Passive sub-slab depressurization system. For the purpose of system design, the subfloor preparation, vent pipe, electric outlet and other requirements under the Minnesota State Building Code for Single Family new construction shall apply to New Multifamily Construction with the following amendments:
  • Provide at least one 4” diameter (in lieu of 3”) vertical vent pipe per 3,000 square feet of building foot print; or, at least one 4” diameter vertical vent pipe per dwelling unit (at townhomes). An exterior Radon mitigation system is not allowed.

  • All ground-connected floors of the building shall be tested when the project is complete (prior to initial occupancy).  If testing finds Radon levels to be 4 pC/l or greater, the Passive system  shall be converted to an Active system by:

  • Adding a fan which remains in full operation continuously and is approved by manufacturer for Radon use.

  • In apartment buildings with common area, the continuously operating fan shall be tied to a common area power source.

  • In townhome (without common space) buildings, the continuously operating fan for each unit shall be tied to the power source (meter) of the dwelling unit it serves.

  • Testing protocols shall be as per the American National Standards Institute – American Association of Radon Scientist and Technologist (ANSI-AARST) Standard: “Protocol for Conducting Radon and Radon Decay Product Measurements in Multifamily Buildings”  (ANSI/AARST MAMF 2012).

Substantial Rehab
All Multifamily Substantial Rehab projects shall provide, at a minimum, a Passive sub-slab depressurization system which meets the requirements defined under the Minnesota State Building Code for Single Family new construction with the following amendments:

  • Prescriptive or Performance approaches

    • A Prescriptive approach shall include:

      • At least one 4” diameter (in lieu of 3”) vertical vent pipe per 3,000 square feet of building foot print; or,

      • At least one 4” diameter vertical vent pipe per dwelling unit (at townhomes).

      • At each vertical pipe location, the pipe shall extend 1” below the concrete slab into a suction pit (void area), that is a minimum 3’ in diameter and 1’ deep.

      • Or, a Performance approach which involves a custom analysis and design by a Radon Contractor/ Mitigation Service Provider.

  • Testing protocols shall be as per the ANSI-AARST “Protocols for Radon Measurement in Homes Standard” MAH 9/2005.

  • All ground-connected floors of the building(s) shall be tested when the project is complete (prior to initial occupancy). If testing finds radon levels to be 4 pC/l or greater, the Passive system shall be converted to an Active system as noted in New construction above (1bi, 1bii, and 1biii).

 

Moderate Rehab
Radon testing and/or Radon control are not required by Minnesota Housing.

  • Exceptions:

    • Radon testing shall be provided if required by a loan insurer or as part of a federally required environmental review or assessment.

    • Projects receiving HUD Multifamily Accelerated Process (MAP) funding shall provide a Radon Report/ Test per HUD Office of Multifamily Development Radon Policy (Notice H 2013-03).

  • If voluntarily testing is conducted or if testing is required for any other reason, it shall follow the testing protocol and Radon control noted above for Substantial Rehab (2a, 2b, & 2c).

  • If testing finds Radon levels to be 4 pC/l or greater,   a Passive or Active Radon mitigation system shall be installed with following procedures:

    • Consult with a Radon contractor or mitigation service provider to identify and design a Radon control system; and/ or

    • Consult with the Minnesota Department of Health, Indoor Environments & Radiation Section, Indoor Air Unit (see Radon Technical Assistance in the “Resources and Links” below).

  • Underground Garages Serving Multifamily Projects.

    • Radon testing is not required for any buildings with underground garage designed and vented to meet applicable Minnesota codes and regulations. Underground garages vented as such do not require any other source of Radon control.

  • Exterior Radon Mitigation Systems

Regardless of construction type (New, Substantial Rehab, or Moderate Rehab), exterior Radon Mitigation Systems are not allowed.

 

Resources