--- title: "Radon and Renovating, Finishing a Basement or Weatherizing" url: https://vermontradon.com/radon-renovation-vermont/ description: "Finishing a basement, adding on or weatherizing? The EPA says test before and after. When to retest, and what to ask if you already have a radon system." last_reviewed: 2026-10-19 source: "U.S. EPA; Vermont Department of Health; CRCPD. Each fact is footnoted to its source below." publisher: "Vermont Radon, an independent guide, not affiliated with the Vermont Department of Health or EPA. Not medical advice." --- # Radon and renovating, finishing a basement or weatherizing Test before you start and again when the work is done. The EPA says major renovations can change the radon level in any home.[^1] ## Finishing a basement - **Test the area first.** The EPA says it is especially important to test before converting an unfinished basement into living space.[^1] - **Fix it during the project if you need to.** If the test shows a problem, radon-resistant techniques can be included inexpensively as part of the renovation.[^1] It is generally less expensive to install a radon reduction system before or during a renovation than afterward.[^2] - **Test again when it’s finished.**[^2] ## Test before you start Order the Health Department Lab’s long-term kit for $25[^3] and leave it in place for 3 to 12 months, ideally including a heating season.[^4] Want day-to-day readings too? A digital monitor records radon continuously while it has power.[^2] Use it alongside the kit, not instead of it: the Conference of Radiation Control Program Directors (CRCPD) says to check its results with an approved test.[^5] [Order the $25 kit](https://vdh.webapps.aidcvt.com/water_supplies/radon) [Shop at Airthings](https://discount.airthings.com?aw_affiliate=eyJjYW1wYWlnbl9pZCI6IjEiLCJ0cmFmZmljX3NvdXJjZSI6InZlcm1vbnRyYWRvbi5jb20iLCJhY2NvdW50X2lkIjoyNDI1N30) (Affiliate link) Use code **vtradon-10OFF** for 10% off at Airthings checkout. If you buy through the Airthings link, Vermont Radon may earn a commission at no extra cost to you. [How we make money](https://vermontradon.com/how-we-make-money/) The Lab kit isn’t an affiliate link. Order by phone: [802-338-4736](tel:+18023384736) or [800-660-9997](tel:+18006609997).[^4] ## Weatherizing, heat pumps and other system changes The Health Department says to test again after significant changes to your home’s structure or mechanical systems.[^4] The EPA notes that radon problems show up in well-sealed and drafty homes alike.[^1] If your project changes how the house is sealed, heated or ventilated, a test before and after tells you whether your level changed. ## If you already have a radon system - **Ask about the warranty.** Before major changes such as finishing a basement, the EPA says to ask your radon contractor whether they could void any warranties.[^6] - **Adding on?** For a new foundation, ask your radon contractor what’s needed to keep radon low throughout the home.[^6] - **Retest afterward** in the lowest lived-in area, to make sure the work didn’t make the system less effective.[^6] [Is my radon system working?](https://vermontradon.com/is-my-radon-system-working/) ## Building new Radon-resistant features cost less to build in than to add later: the Health Department estimates $250 to $750 during construction.[^7] See [Radon-resistant new construction](https://vermontradon.com/radon-resistant-new-construction-vermont/). ## Common questions ### Should I test for radon before finishing my basement? Yes. The EPA says a radon test should be done before starting the project and after it’s finished, and that it’s generally less expensive to install a radon reduction system before or during a renovation than afterward.[^2] ### Should I retest after weatherizing or a new heating system? The Health Department says to test again after significant changes to your home’s structure or mechanical systems.[^4] ### Will finishing my basement void my radon system’s warranty? It might. The EPA says to ask your radon contractor whether major changes, such as converting an unfinished basement into living space, could void any warranties.[^6] ## Next steps - [How to test your home](https://vermontradon.com/how-to-test/) - [Understanding your results](https://vermontradon.com/understanding-results/) - [Fixes for older homes](https://vermontradon.com/radon-older-homes-vermont/) - [Fixing radon: systems and costs](https://vermontradon.com/fixing-radon/) ## Sources [^1]: **U.S. Environmental Protection Agency**. [A Citizen’s Guide to Radon (EPA 402/K-12/002, 2025)](https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf). Checked 2026-10-17. [^2]: **U.S. Environmental Protection Agency**. [Home Buyer’s and Seller’s Guide to Radon (EPA 402/K-24/001, March 2024)](https://www.epa.gov/sites/default/files/2015-05/documents/hmbuygud.pdf). Checked 2026-10-17. [^3]: **Vermont Department of Health Laboratory**. [Radon Test Kits (Health Department Lab webstore)](https://vdh.webapps.aidcvt.com/water_supplies/radon). Checked 2026-10-17. [^4]: **Vermont Department of Health**. [Radon in Your Home](https://www.healthvermont.gov/environment/healthy-homes/radon). Checked 2026-10-17. [^5]: **Conference of Radiation Control Program Directors (CRCPD)**. [Consumer Digital Radon Monitors (CRCPD guidance, reprinted in The Radon Reporter, Q4 2025, p. 39)](https://aarst.org/TheRadonReporter/Radon-Reporter-December-2025/39). Checked 2026-10-17. [^6]: **U.S. Environmental Protection Agency**. [Consumer’s Guide to Radon Reduction: How to Fix Your Home (EPA 402/K-10/005, 2025)](https://www.epa.gov/sites/default/files/2016-12/documents/2016_consumers_guide_to_radon_reduction.pdf). Checked 2026-10-17. [^7]: **Vermont Department of Health**. [Building Radon Resistant (fact sheet, June 2025)](https://www.healthvermont.gov/sites/default/files/document/env-hh-radon-building-radon-resistant.pdf). Checked 2026-10-17.