HomeMy WebLinkAboutMemo - Mail Packet - 10/21/2025 - Memorandum from Selina Lujan de Albers and Emily Olivo re Council Inquiry Follow-Up- Regarding Active Radon Mitigation in New Residential ConstructionEnvironmental Services Department
222 Laporte Ave.
PO Box 580, Fort Collins, CO 80522
Cc: Tyler Marr, Deputy City Manager
MEMORANDUM
Date: October 15, 2025
To: Mayor and City Councilmembers
Through: Kelly DiMartino, City Manager
Jacob Castillo, Chief Sustainability Officer, Sustainability Services
From: Selina Lujan de Albers, Manager, Environmental Sustainability
Emily Olivo, Lead Specialist, Environmental Sustainability
Subject: Council Inquiry Follow-Up- Requiring Active Radon Mitigation in New
Residential Construction
The purpose of this memo is to follow up on Council inquiry regarding the rationale behind not
requiring active radon mitigation systems in new residential construction.
BOTTOMLINE
Through the adoption of several building codes since 2005, the City requires all newly
constructed homes to have a certain level of radon mitigation. At a minimum, all new residential
buildings must be constructed with passive radon mitigation systems, and builders are required
to perform radon testing of that system and install an active system if results meet or exceed the
level specified in code. If Council wishes to require active systems in all new residential
construction that result in radon levels below what is specified in code, this can be considered
as part of the next update to City building codes.
CONTEXT
Through policies and programs focused on radon testing and mitigation, the City of Fort Collins
has prioritized reducing the risk of radon throughout the community for several decades. Key
local policies include:
• Radon Disclosure Requirement: Since 1997, City code has required that every
property seller provides radon information to the purchaser prior to the execution of any
contract for the property.
o Note: Due to more comprehensive state-level disclosure requirements as of
2023, this code is currently being considered for repeal (Ordinance No. 161) and
will go to Council for 2nd reading on October 21, 2025.
• Radon-Resistant New Construction (RRNC): Advancing beyond radon disclosure, as
of January 1, 2005, Council amended the building code, consistent with Appendix F of
the International Residential Code (IRC), to require passive radon mitigation systems in
single-family homes and duplexes.
o Note: While state law and local ordinances mandate the disclosure of radon
information at the point of the sale of a residential property, mitigation is not
required unless negotiated as a part of the sale.
Docusign Envelope ID: BC51B0A1-35FC-432A-B135-A2A0C276B4C7
In 2006, the City conducted a study demonstrating the efficacy of passive radon mitigation.
Using the Environmental Protection Agency’s protocol for “cap-on/cap-off” radon studies, the
City tested 65 new Fort Collins homes that were built in accordance with RRNC requirements.
Results of the study determined that RRNC (passive mitigation systems) reduces radon by an
average of 49%. In the 2021 code and carried into the 2024 code, the City of Fort Collins took
RRNC requirements a step further through the adoption of Appendix BE Radon Control
Methods of the IRC. Per section BE104.1 Testing, testing shall be further specified by the
following items regarding active mitigation:
1. Testing shall be performed after the dwelling passes its air tightness test.
…
9. Written radon test results shall be provided by the test lab or testing party. The final
written test report with results less than 4 picocuries per liter (pCi/L) shall be provided to
the code official or a fan installed as per #10.
10. Where the radon test result is 4 pCi/L or greater, the fan for the radon vent pipe shall be
installed as specified in Sections BE103.9 and BE103.12.
11. Where the radon test result is 4 pCi/L or greater, the system shall be modified and
retested until the test result is less than 4 pCi/L.
• Item #11 is a part of Appendix BE that was not adopted in the building code.
The current measures within code are intended to help ensure newly constructed homes
receive the right level of mitigation at the point of construction.
If further action is desired, there is an opportunity to amend code to require active mitigation as
a part of the upcoming building code adoption, which will go to Council for 1st reading on
December 2, 2025. A consideration, however, of requiring active mitigation is that if a builder
were to activate a system at the onset, the exclusion of item #11 under section BE104.1 from
the code removes the following testing requirements:
1. Prior testing to determine whether mitigation is needed and/or to right-size the system
based on tested radon levels.
2. Testing post installation ensuring that the activation of the system lowered radon levels
to < 4 pCi/L.
If Council were to pursue the requirement of active mitigation, it is recommended to include the
adoption of item #11 under section BE104.1. An additional consideration is that state law would
still require radon information and testing and mitigation disclosures at the time of sale; and City
radon education efforts would still recommend that community members regularly test their
home every 2 years.
Note that the decision by Council regarding Ordinance No. 161, repealing the code for radon
disclosure of radon information in real estate transactions, would not affect current or future
mitigation requirements.
Docusign Envelope ID: BC51B0A1-35FC-432A-B135-A2A0C276B4C7