Which county, which office
Windsor is both a Larimer County and a Weld County town, as a 2020 local radio piece explains. So two addresses in the same town can have different county programs. Severance is in Weld County, so Weld's kit program is the one to ask about. Its building work goes through the town's own permit office. In Windsor, check your property record or tax bill to see which county your address is in.
A working way to sort it out, which is this site's reading of how these offices describe their programs and worth confirming when you call:
- Building work inside town limits goes to the town's building department, whichever county you're in.
- County health programs, such as test kits, follow the county of the home's address. Weld residents use Weld's kit program, not Larimer's.
- State and federal rules are the same in both counties: EPA's guidance and the SB23-206 disclosure law.
Who to call
| Office | Phone | Address and email |
|---|---|---|
| Windsor permit technician | 970-674-2436 | 200 N. 11th St., 80550 |
| Severance permit clerk | 970-686-1218 | 3 S. Timber Ridge Pkwy., 80550 |
| Weld County (health and building main line) | (970) 400-4000 | 1150 O St., Greeley 80631 |
| Larimer County main line | (970) 498-7000 | 200 W. Oak St., Fort Collins 80521 |
| CDPHE (state, general line) | 303-692-2000 | 4300 Cherry Creek Dr. South, Denver 80246 |
Test kits by county
Weld County addresses. Weld County offers free short-term kits to its residents, "one per household, while supplies last." Its kits run 3 to 7 days. Call to confirm availability.
Larimer County addresses. The county has offered free kits with prepaid postage, most recently in January 2026, "while supplies last." Call (970) 498-7000 to ask what's available now. See the county page for pick-up points it has used.
Either county. Larimer County's page says state kits are free for a limited time, while CDPHE's testing page calls them discounted, so check before you order. CDPHE also says kits are "available at home improvement stores from about $10 to $50."
The testing guide covers how to run a test so the result means something.
What's known about radon here
No Windsor or Severance average turned up in the sources reviewed for this site, and this page won't invent one. The nearest published figures are county-wide or statewide. Larimer County's health page lists an area average of 7.8 pCi/L with no year or sample. A Weld County publication from January 29, 2026 says about half of Colorado homes are above 4 pCi/L. A 2014 CDPHE release says "all 64 Colorado counties are categorized as Zone 1 for radon."
None of that predicts a house. Colorado's notes on its own test records say "These data do not give us measures of actual radon levels," and that levels can vary widely between neighboring homes. EPA says "All homes should be tested, regardless of zone designation."
Permits in each town
No local page reviewed for this site says whether adding a radon system to an existing home needs a permit. Permit rules vary, so ask the building department before work begins. Here's what the general pages say:
- Windsor. The town's building permit page has no general list of work needing a permit.
- Severance. The town's "What Needs a Permit" sheet lists electrical changes among the work needing one. It doesn't mention radon.
- Unincorporated Weld County. The county's building page describes an application for all projects, plus a published list of structures needing no permit. It doesn't mention radon.
- Unincorporated Larimer County. See the county page.
What the system involves
The same method applies on both sides of the county line. EPA's Consumer's Guide calls sub-slab suction "the most common and usually the most reliable radon reduction method." Crawlspace homes use submembrane suction, and newer homes may already have a passive pipe. These guides cover each:
New construction in these towns
A national list current as of September 20, 2021 doesn't show Windsor, Severance or Weld County as having adopted the radon appendix. That list is old, and not being on it doesn't mean a town doesn't require one. For a new home here, look for a pipe, ask the builder whether any system is passive or active, and test. A Colorado state report describes buyers of homes "marketed to them as having a radon mitigation system installed," so ask the question directly.
Your electric bill
This site's fan math uses Fort Collins Utilities rates, which won't apply here. Your utility's rate decides the number. As a rough outside check, Minnesota's health department works a 20 watt fan at 11¢ per kWh to "about $19.27 per year." Multiply your fan's watts by 8.76 to get kWh per year, then by your rate.
What commonly goes wrong
- Calling the wrong county. Check your address first, especially for kits.
- Assuming a neighbor across the line has the same rules. Town and county building departments each have their own.
- Treating county averages as your reading. Test.
- Waiting until a sale. The disclosure law applies in both counties.
Cost
No local contractor prices were collected for this site. Colorado's agency figures are $1,000 to $2,000 and about $1,300 to $3,000 from CDPHE (both undated), and about $1,200 on average, $800 to $2,500 from a state report dated October 15, 2026. See the cost guide. The state's low-income assistance program applies statewide, but the income limit quoted there comes from Larimer's page. Weld's limit wasn't found, so ask CDPHE.
Hiring in either county
The questions are the same on both sides of the county line. The hiring guide lists them, along with what a contract should say.
Questions homeowners ask
I'm in Windsor. Which county's free kit do I use?
The one for the county of your address. If you're not sure, your property record will tell you, or call either county.
Who handles permits in Windsor?
Start with the town's permit technician at 970-674-2436, and ask whether a radon system needs one.
Who handles permits in Severance?
The town's permit clerk at 970-686-1218.
How this site helps
LarimerRadon.com is a referral service: a request here goes to one independent local contractor, who quotes and does any work directly with you. Tell them your town and county when you get in touch.
Sources
- Town of Windsor, Building Permit. Town of Severance, What Needs a Permit. Both read November 2026.
- Weld County, radon page (© 2026), Building Permit Applications, Radon: A Hidden Risk on air.weld.gov (Jan 29, 2026).
- Larimer County, health page (Nov 1, 2026), Jan 7, 2026 release.
- KMAX radio piece on Windsor (2020).
- CDPHE, testing page and FAQ (© 2026, undated); county zone release (Mar 31, 2014); state radon dataset notes (undated).
- EPA, Consumer's Guide, Colorado zone sheet.
- Colorado Department of Regulatory Agencies, radon report (Oct 15, 2026). AARST, code adoption data (Sept 20, 2021). Minnesota Department of Health, energy costs (Sept 13, 2023).