Comprehensive Radon Testing in Franconia: Fairfax County Zone 1 Guide

You cannot see or smell radon, but it can affect your health and your home sale. If you are buying or selling in Franconia, understanding radon is a smart way to reduce risk, protect value, and keep your timeline on track. In this guide, you will learn how radon works, when and how to test, what mitigation looks like, and how to handle documentation during a real estate transaction. Let’s dive in.

What radon is and why it matters

Radon is a colorless, odorless radioactive gas that forms naturally from uranium in soil and rock. It can enter a home through tiny openings in the foundation and build up indoors.

The health risk is real. The U.S. Environmental Protection Agency reports that radon is linked to about 21,000 lung cancer deaths per year in the United States. Risk increases with higher levels and longer exposure, and it is higher for people who smoke. You measure radon in picoCuries per liter (pCi/L). The EPA’s action level is 4.0 pCi/L. Levels below 4.0 pCi/L still carry some risk, and many professionals aim for lower targets when possible. You can learn more in the EPA’s overview on radon and health at the EPA radon hub.

Franconia radon context

Homes in Northern Virginia, including Fairfax County, often appear on national maps as areas with potential for elevated indoor radon. Every home is different due to soil, weather, and construction, so the only way to know your home’s level is to test. For statewide guidance and current best practices, check the Virginia Department of Health Radon Program, and for geology-based context see the USGS overview of radon and geology.

How and when to test

Test types you can trust

• Short-term tests: 48 hours to 7 days. Options include charcoal canisters, electret detectors, or continuous radon monitors (CRMs) that log hourly readings. CRMs are preferred in real estate for accuracy and defensibility.
• Long-term tests: 90 days to 1 year. Alpha-track detectors or long-term electronic monitors estimate your annual average exposure.
• DIY vs. professional: Both exist, but many agents and lenders prefer tests from NRPP or NRSB certified professionals using approved devices. Find credentialing information at the National Radon Proficiency Program and the National Radon Safety Board.

If you are a seller

• Pre-listing test: To avoid surprises, run a professional short-term test before you go live. If time allows, a 90-day long-term test offers a stronger annual picture.
• If under 4.0 pCi/L: Include the report in your disclosure packet.
• If at or above 4.0 pCi/L: Mitigate before listing or disclose and be ready to negotiate credits or repairs.

If you are a buyer

• During the inspection period: Add a radon test contingency. Require a professional CRM short-term test or, if timing allows, a long-term test.
• If the seller has older or short-term-only results: Consider your own professional test. If you close without current results, start a long-term test right after move-in.

Seasonal factors

Radon varies during the year and can be higher in colder months when homes are closed up. You can test any season. Short-term tests under closed-house conditions provide a fair comparison for transactions.

Contract language tips

To keep testing clear and enforceable, specify in your offer or addendum:

• The device type, ideally a continuous radon monitor
• The testing period and closed-house protocol
• Who pays, who places the device, and who controls access
• How results will trigger next steps or remedies

For a transaction-focused overview, the EPA’s buyer and seller guide is a useful reference: EPA Home Buyer, Seller, and Radon Guide.

Interpreting results and acting fast

• Below 4.0 pCi/L: Keep your test report. Retest after major renovations or changes in HVAC or foundation.
• At or above 4.0 pCi/L: Plan mitigation with a qualified contractor and confirm performance with a post-mitigation test.
• Closed-house protocol matters: Before and during short-term tests, keep windows and exterior doors closed except for normal entry and exit, maintain normal HVAC settings unless told otherwise, and avoid high-suction appliances. Record test start and end times and indoor conditions.

Radon mitigation basics

How the standard system works

The most common and effective method for basements and slab-on-grade homes is sub-slab depressurization (SSD), also called active soil depressurization (ASD). A contractor creates a suction point through the slab or in a sealed sump, routes PVC piping to the exterior up to the roofline, and installs an inline fan that draws soil gas from below the foundation and exhausts it outside. Sealing major cracks is a helpful companion step but is rarely enough on its own.

Properly installed systems often reduce indoor radon by 50 to 99 percent, typically bringing levels under 4.0 pCi/L and often into the 1 to 2 pCi/L range.

Cost, timing, and what to expect

• Typical cost: The EPA estimates home mitigation systems usually range from about $800 to $2,500, depending on size, foundation type, and complexity. Large or complex homes, or those needing multiple suction points, can cost more.
• Installation timeline: Usually one day for a typical single-family home.
• Post-installation testing: Always verify performance with a short-term CRM test, then consider a long-term test for a stronger average.

For practical health summaries and homeowner guidance, see the American Lung Association’s radon resources.

Choosing the right mitigator

Select mitigators certified by NRPP or NRSB, and ask for:

• A written estimate and a simple system diagram
• Example installation photos
• A clear performance target below 4.0 pCi/L and a plan for rework if needed
• Post-mitigation testing by an independent qualified tester, or by the installer if acceptable to both parties

Check any local permit needs with Fairfax County’s building and land development offices. Start with the county’s Land Development Services to confirm current requirements.

Real estate checklists and documentation

Seller checklist

• Test before listing with a professional CRM short-term test or a 90-day long-term test if time allows.
• If below 4.0 pCi/L: Include the full test report in your disclosure materials.
• If at or above 4.0 pCi/L: Hire a qualified mitigator, complete mitigation, and include the post-mitigation test report, system diagram, and warranty in your listing packet. If you choose not to mitigate, disclose results and be ready to discuss credits or repairs.

Buyer checklist

• Add a radon test contingency that names the device type, timing, and who pays.
• Require a professional CRM short-term test during the inspection window, or a long-term test if feasible.
• If elevated: Address remediation in writing. Typical options include seller-installed mitigation with a post-mitigation test, a credit, a price adjustment, or accepting the risk.
• If you close without recent testing or mitigation: Start a long-term test in the first 90 days after move-in.

What to keep on file

• Original test reports with dates, device type, and certification details
• Mitigation invoice, system diagram, installation photos, and warranty
• Post-mitigation test report and any follow-up tests
• Copies of permits if required by Fairfax County

Attach these records to your disclosure packet and pass them to the buyer at closing.

Quality control for reliable results

• Use certified measurement professionals for real estate testing. Look up credentials at NRPP or NRSB.
• Follow closed-house protocols for short-term tests: close windows and exterior doors for at least 12 hours before and during the test, keep HVAC at normal settings unless instructed, and limit high-suction appliance use.
• For verification after mitigation, start with a short-term CRM test, then follow with a long-term test for your annual average.
• Confirm any Virginia seller disclosure rules with your agent and refer to the Virginia Department of Health radon guidance. If you need legal language for a contract, consult a local real estate attorney.

Maintain and monitor your system

• Fan life: Many radon fans run continuously and last about 5 to 10 years. Check the system’s pressure gauge or indicator regularly.
• Retesting: Retest after major renovations, HVAC changes, or if you notice changes in the pressure gauge. A long-term test is a strong way to confirm your annual average.
• Home types: SSD is standard for basements and slabs. Crawlspaces may use sub-membrane depressurization or controlled ventilation.

Get help from a local advisor

A thoughtful radon plan can keep your deal clean and your home safe. If you want to pre-test before listing, craft clear contingency language, or decide between seller repairs and credits, you deserve an advisor who treats radon like the risk-management item it is. Connect with Riggs & Co to structure testing, timelines, and negotiation terms that protect your goals. Request a Strategy Consultation.

FAQs

What is radon and why should Franconia homeowners care?

• Radon is a colorless, odorless radioactive gas that can enter through foundation openings and is linked to thousands of lung cancer deaths each year; testing is the only way to know your home’s level.

What is a safe radon level for a home purchase in Fairfax County?

• The EPA recommends action at or above 4.0 pCi/L; many professionals aim lower when feasible, but decisions in a purchase should at least address anything at or above 4.0 pCi/L.

How long does a radon test take during a home inspection?

• A professional short-term test with a continuous radon monitor typically runs 48 hours under closed-house conditions and produces an hour-by-hour report.

How much does radon mitigation usually cost in Northern Virginia?

• The EPA estimates most systems run about $800 to $2,500, with complex homes or multiple suction points costing more.

How effective are radon mitigation systems in reducing levels?

• Properly installed sub-slab depressurization systems commonly reduce indoor radon by 50 to 99 percent, often reaching the 1 to 2 pCi/L range.

Do I need permits or special documentation for mitigation in Fairfax County?

• Permit needs can vary; confirm with Fairfax County’s building and land development offices and keep all test reports, mitigation invoices, system diagrams, and warranties with your real estate disclosures.