Radon on Cape Cod: Barnstable County Testing and Costs

EPA's 1993 Map of Radon Zones rates Barnstable County, Cape Cod, Zone 2: a predicted county average indoor screening level of 2 to 4 pCi/L, the range where EPA says to consider fixing. In EPA's file, 10 of Massachusetts' 14 counties are Zone 2 and 3 are Zone 1.

The Census Bureau relationship file maps 47 ZIP areas to the county, all in Zone 2. The Massachusetts Department of Public Health says buildings with high radon are found in every county in the Commonwealth and recommends testing all homes (MDPH).

HomeGuide's Feb 2026 survey prices a standard sub-slab system at $1,200 to $2,000 installed; Cape homes on private wells may also need water treatment.

Licensing and permits

No state radon license: MDPH says the Commonwealth does not certify radon professionals but recommends using one certified by the National Radon Proficiency Program or the National Radon Safety Board. MDPH publishes a monthly list of nationally certified mitigators.

Contractor registration: residential contractors working on owner-occupied one-to-four-unit homes must register as Home Improvement Contractors under M.G.L. c. 142A, and work estimated at $1,000 or more needs a written contract (Massachusetts Office of Consumer Affairs).

Town permits: each of the Cape's 15 towns runs its own building department; an electrical permit may apply to the fan. HomeGuide puts radon permits at $25 to $150 where required.

Wells: MDPH advises testing private well water for radon as well as air.

Local conditions

Cape Cod is built of glacial sediment: sandy outwash plains on the south side and the Sandwich and Buzzards Bay moraines along the north and west, left by retreating ice. Coarse sand and gravel are highly permeable, so soil gas moves easily under slabs and through basement floors.

Housing ranges from antique capes with fieldstone or brick cellars in the old village centers to seasonal cottages on piers or crawlspaces near the shore and newer year-round homes with poured basements along US 6 and Route 28.

Many Cape homes draw from private wells in towns without full municipal water, which is why MDPH pairs its air-testing advice with a well-water test.

Salt air and storms are part of the design brief on the Outer Cape and along Nantucket Sound. Exterior fans and pipe brackets take a beating near the water, so ask what housing the fan sits in and how the vent is anchored before a nor'easter season.

Year-round population on the Cape has grown as seasonal cottages were winterized. A cottage built for summer use on piers or a shallow crawlspace, later closed in and heated, can trap soil gas it never held before; that conversion is a good moment to test.

What drives local prices

Basement homes: one suction point in permeable outwash sand is often enough, $1,200 to $2,000 based on HomeGuide's published survey.
Crawlspace cottages: submembrane depressurization was $1,000 to $2,500 in EPA's 2010 guide (2010 dollars).
Well-water radon: HomeGuide lists $1,200 to $1,800 for a carbon filter or $4,000 to $5,000 for aeration.
Permit $25 to $150 and professional retest $125 to $400 (HomeGuide).
Seasonal homes: scheduling off-season work can be easier on the Cape, from Bourne and Sandwich out to Provincetown (our observation, not a published figure).

Common jobs

Sub-slab systems in year-round homes with poured basements.
Crawlspace membrane systems in shore cottages.
Air plus well-water radon testing for sales.
Sealing fieldstone cellars in antique capes.

From test to fixed, and where we cover

Step 1: test the air and any private well. Step 2: at 4 pCi/L or more in air, get two bids from nationally certified mitigators who hold a Massachusetts HIC registration.

Step 3: compare them with the calculator. Step 4: retest after installation.

We cover all 15 towns, including Barnstable and Hyannis, Falmouth, Yarmouth, Dennis, Sandwich, Bourne, Mashpee, Brewster, Harwich, Chatham and Orleans.

Communities: Hyannis, Falmouth, Yarmouth, Dennis, Sandwich, Bourne, Mashpee, Brewster, Harwich, Chatham, Orleans

Before you sign

Take time to compare written bids; EPA treats radon as a long-term exposure (EPA Citizen's Guide). For jobs of $1,000 or more, Massachusetts requires a written contract.

Questions about Barnstable County

Is radon a problem on Cape Cod?

EPA rates Barnstable County Zone 2, and MDPH says high-radon buildings are found in every Massachusetts county. Test to know.

Does Massachusetts certify radon mitigators?

No. MDPH recommends NRPP or NRSB certification; contractors also need HIC registration under M.G.L. c. 142A.

Should I test my well for radon?

MDPH advises testing private well water as well as air.

What does mitigation cost on the Cape?

HomeGuide's national range for a sub-slab system is $1,200 to $2,000; crawlspace cottages and wells change the price.

Sources

Nearby counties

Radon in Norfolk County, MA

Rules and fees change; confirm with the state radon office. Price your own system with the radon mitigation cost calculator, read the radon mitigation cost guide, or check any ZIP with the radon levels by ZIP tool.