Do New Construction Homes Have Radon Problems?

There is a persistent assumption that radon is an old-house problem — something that afflicts fieldstone foundations and century-old cellars, not a home built in the last decade. It is one of the most common misconceptions in residential radon, and it gets new homeowners in trouble.

New construction can have elevated radon. In some respects, modern homes are more susceptible than older ones.

Radon Comes From the Ground, Not the House

The core reason the assumption fails: radon is produced by the natural decay of uranium in soil and bedrock. It is a property of the ground your home sits on, not of the home’s age, materials, or condition.

A 2019 build in a Baldwinsville subdivision sits on the same Onondaga County geology as a 1920s home in the city. Both are in EPA Radon Zone 1. The uranium in the soil does not know when the foundation was poured.

What the house determines is how much of that soil gas ends up inside and how much accumulates once it does. And that is where modern construction sometimes works against you.

Why Tight Homes Can Read Higher

Building practice has improved enormously in the last few decades, driven largely by energy efficiency. Modern homes have continuous air barriers, better sealing at penetrations, high-performance windows, and far less unintentional air leakage than older construction.

That is good for heating bills. It is not automatically good for radon.

An old, leaky house dilutes indoor radon constantly through unintentional air exchange. Drafty windows and an uninsulated attic mean outdoor air is continuously mixing in. A tightly sealed modern home does far less of this. Soil gas that enters has fewer paths out and accumulates to higher concentrations.

Modern homes also often have stronger stack effect. Better insulation and greater height differentials mean warm air rising through the building creates more negative pressure at the foundation — which actively draws soil gas in.

Add powerful modern exhaust equipment — a 600 CFM range hood, high-capacity bath fans, a big dryer — and a tight house can be meaningfully depressurized, pulling harder on the soil beneath the slab.

New Foundations Still Have Entry Points

A new basement floor looks solid. It is not sealed against soil gas.

Concrete is porous, and radon moves through it. Beyond that, every new foundation has openings by design or by consequence:

• The perimeter joint where slab meets foundation wall — an intentional expansion gap
• Plumbing and electrical penetrations through the slab
• Sump pits, which are often direct openings to the soil
• Floor drains
• Shrinkage cracks, which develop as concrete cures in the first year or two
• Hollow block wall cavities, which can channel soil gas upward

None of these represent defective work. They are normal features of normal construction, and each is a potential pathway.

What Radon-Resistant New Construction Actually Provides

Some newer homes were built with radon-resistant features, often abbreviated RRNC. If your builder installed these, that is genuinely valuable — but it is important to understand what it does and does not mean.

Typical RRNC includes a gas-permeable gravel layer beneath the slab, a polyethylene vapor barrier over that gravel, sealed joints and penetrations, and a vertical vent pipe running from beneath the slab up through the roof — usually with no fan installed, relying on natural convection.

That last detail is the key one. A passive system reduces radon entry, often substantially. But passive systems are not guaranteed to bring levels below the action level, particularly in a Zone 1 area. Natural convection is weak and varies with weather.

The upside is that a passive system is designed to be upgraded. Adding a fan converts it to an active system, and because the pipe and sub-slab preparation already exist, activation is typically much cheaper than a retrofit from scratch — often at the low end of the typical cost range or below.

So a passive system is a head start, not a solution. It still needs to be tested.

The New Home Blind Spot

There is a practical reason new homes go untested more often than old ones: nobody prompts the buyer.

When someone buys an existing home, a general home inspection usually happens, and radon testing frequently gets offered or requested alongside it. New construction buyers often skip a third-party inspection entirely, reasoning that the home is brand new and under warranty. Builder walkthroughs cover finishes and function, not soil gas.

The result is a lot of newer Central New York homes where nobody has ever measured. Not because anyone decided the risk was acceptable, but because the question never came up.

Local Considerations

Newer subdivisions around Onondaga County — the Radisson area in Baldwinsville, newer development in Cicero and Clay, construction around Manlius and Fayetteville — sit on the same glacial and sedimentary geology as everything else in the county.

Two additional local factors are worth noting. Development frequently involves substantial grading and fill, which can alter how soil gas moves toward a foundation in ways that are not predictable from neighboring lots. And full basements are the norm here rather than slab-on-grade, which means most new homes have a large below-grade surface in contact with soil — and often finished basement living space where people spend real time at the level where radon concentrates.

Two homes on the same new street can also test very differently. Soil composition, fill depth, foundation details, and HVAC configuration all vary lot to lot. Your neighbor’s low reading tells you nothing definitive about your house.

What to Do

If you are buying new construction, arrange radon testing before or shortly after closing. Ask the builder directly whether radon-resistant features were installed, and if so, whether the vent pipe is passive or has a fan. Get it in writing.

If you already live in a newer home and have never tested, test now. If the home has a passive vent pipe and results come back elevated, activation is usually a modest job.

If you are having a home built, ask for radon-resistant construction and consider having the fan installed from the start. The incremental cost during construction is far lower than any retrofit.

Retest after a few years. Shrinkage cracks develop as concrete cures, and a home that tested fine at closing can read differently once it has settled through a few Central New York winters.

New construction in an EPA Zone 1 county is not exempt from radon — it is simply less likely to have been checked.

Serving new and existing homes across Syracuse, Cicero, Liverpool, Baldwinsville, Camillus, Manlius, and DeWitt. Call (315) 234-2853 for certified testing and a free estimate.

New construction is concentrated in Baldwinsville, particularly the Radisson community, and along the Route 11 corridor in Cicero, where subdivisions have expanded steadily.