Township, York County

Radon Mitigation in Windsor Township, PA

Updated September 30, 2026

Windsor Township sits east of Red Lion and surrounds Windsor borough, and it has some of the highest numbers in this set. Its main ZIP code, 17356, has a median of 6.1 pCi/L, and ZIP 17366 on its eastern side has one of the highest medians in the county at 8.8 pCi/L, with 67% of tests at or above the action level. The township has grown a lot since 2000, so plenty of the high tests here are in newer houses.

What the PA DEP test records show for Windsor Township

ZIP codes don't follow township lines, so the 3 ZIP codes below also take in some homes just outside Windsor Township.

• ZIP 17356 (about 60% of Windsor Township's land): median 6.1 pCi/L across 5,341 tests, 19.7% at 20 or higher, top reading 488. Basement median 7.7, first floor 1.4.
• ZIP 17366 (about 15% of Windsor Township's land): median 8.8 pCi/L across 864 tests, 28.2% at 20 or higher, top reading 238. Basement median 9, first floor 5.9.
• ZIP 17402 (about 12% of Windsor Township's land): median 4.6 pCi/L across 10,722 tests, 13.2% at 20 or higher, top reading 260. Basement median 5.4, first floor 2.6.

The spread inside Windsor Township runs from 54.6% of tests high in 17402 to 67.1% in 17366.

The share that matters most is the 20+ column. 16% of tests here came in at 20 pCi/L or more, five times the action level. The single highest reading on record in these ZIP codes is 488 pCi/L. Neighboring houses can differ by a factor of ten, so none of this tells you what your house is. It tells you the odds are high enough that a $15 to $30 test kit is worth buying.

Tests people chose to run, not a random survey. Details on the York County radon levels page.

Basement readings versus first-floor readings

In ZIP 17356, basement tests have a median of 7.7 pCi/L, while tests taken on the first floor have a median of 1.4 pCi/L (668 first-floor tests). The basement number runs 5.5 times the first-floor number, which is the usual pattern: radon comes up from the soil, so it is strongest at the lowest level and gets diluted as it moves up through the house.

This matters for what you test. The PA DEP and EPA guidance is to test the lowest level you use or could use as living space. If the basement is finished, or might be someday, test it there. A finished rec room at 7.7 pCi/L is a different decision from an unfinished storage basement you rarely stand in.

Radon results by decade in ZIP 17356

The share peaked in the 1990s at 70.8% and sits at 53.2% for tests since 2020. A drop that size is mostly about who is testing, not the ground. More recent tests come from home sales and from retests after a system went in, and both pull the share down. The rock under Windsor Township has not changed. 882 tests have been logged in 17356 since 2020, so people here are still testing.

The ground under Windsor Township

Windsor is in the Piedmont Upland, the rolling metamorphic country of southeastern York County. The rock here is schist, phyllite and quartzite rather than the valley's limestone.

USGS found the highest radon in Pennsylvania groundwater in the Piedmont's schists, gneisses and quartzites, and the indoor numbers here line up with that. In ZIP 17366, 28% of tests reached 20 pCi/L or more, five times the action level.

Housing in Windsor Township and what it means for a system

Census Bureau, American Community Survey 2020 to 2024:

31.4% of the homes here were built in 2000 or later, one of the higher shares in the county. New construction is not radon-proof. A tight modern house can hold radon in as well as it holds heat in. Some builders rough in a passive vent pipe during construction, which makes a later active system cheaper, so check for a capped pipe in the basement. More on that in radon in new construction.

78.2% of homes in Windsor Township are single-family detached. A detached house with a basement is the easiest layout to mitigate: one suction point through the slab, a fan outside or in the garage, and a vent above the roof line. It is the standard sub-slab depressurization job covered step by step on our mitigation process page, and it usually lands in the middle of the cost range.

Cost-wise, a newer house with a passive pipe already roughed in can come in under the usual $800 to $1,500, since the installer mostly adds a fan and a gauge. Full ranges on the cost page.

Where we work in Windsor Township

That covers the area around Windsor borough. Routes 24, 74 and 124 cross the township. Public schools here are part of the Red Lion Area School District. Windsor split off from Hellam Township in 1758.

Installers must hold a PA DEP radon mitigation certification (how to check), and permit questions go to the township office at windsortwp.com.

Common questions

Is radon a problem in Windsor Township?

Yes. PA DEP has 16,927 tests on record from the ZIP codes covering Windsor Township, and 57.2% of them came back at or above the EPA's 4.0 pCi/L action level. 16% were at 20 pCi/L or more. The county-wide rate is 52.5%.

What is the average radon level in ZIP 17356?

The median of 5,341 PA DEP tests in ZIP 17356 is 6.1 pCi/L and the mean is 13.8 pCi/L. A mean that far above the median means a long tail of very high readings, topping out at 488 pCi/L.

Nearby

Red Lion 60.9%, York Township 57%, Springettsbury Township 54.1%, Hellam Township 53.7%. Share of PA DEP tests at or above 4.0 pCi/L, against 57.2% here.