Are new homes exempt from radon problems?

No. Radon originates from the soil beneath a home rather than the building materials, so new homes in Indianapolis can still test above the EPA action level despite their age. Some new homes, being more tightly sealed, can even trap radon more effectively once it enters.

What is passive radon-resistant new construction?

It refers to a set of features, including sub-slab gravel, a vapor barrier, and a vent pipe routed to the roof, built into a home during construction to allow natural or later mechanical venting of soil gas. It reduces radon potential but does not guarantee levels below 4.0 pCi/L on its own.

My new home has a radon vent pipe. Do I still need to test?

Yes. EPA guidance recommends testing every home regardless of construction features, since passive systems vary in effectiveness and can only be confirmed adequate through an actual radon measurement.

How is a passive system converted to an active one?

An inline fan is installed along the existing vent pipe route, typically in the attic or an exterior location, converting passive airflow into active, fan-powered sub-slab depressurization. This is usually simpler than a full new installation since the piping is already roughed in.

When should I test radon in a newly built home?

Testing as soon as practical after move-in is a reasonable approach, and many buyers choose to test during the closing process for new construction. Testing under closed-house conditions, often easiest during cooler months, provides the most representative short-term result.

Radon in New Homes: Why New Construction Isn't Automatically Safe

Radon in New Homes

New construction homes in Indianapolis are not automatically free of radon risk, since the gas originates from soil rather than building materials or age. While many new homes are built with passive radon-resistant features, these systems require testing to confirm effectiveness and sometimes need activation with a fan to meet the EPA action level of 4.0 pCi/L.

Why New Construction Can Still Have High Radon

Radon comes from the soil beneath a home, not from the building materials or its age, so a brand-new house sitting on the same Marion County or Central Indiana soil as an older neighboring home faces the same underlying geologic radon potential. In some cases, tighter, more energy-efficient new construction can actually trap radon more effectively once it enters, since reduced natural air leakage means less dilution from outdoor air exchange.

Passive Radon-Resistant Construction Explained

Many new homes in Indianapolis are built with passive radon-resistant new construction (RRNC) features, which typically include a layer of gravel beneath the slab, a vapor barrier, a vertical vent pipe routed from beneath the slab through the roof, and sealed foundation penetrations. These features are designed to allow for easy future activation of an active system if needed, but on their own they rely on passive stack-effect airflow rather than a fan.

Passive systems can meaningfully reduce radon levels compared to a home with no radon-resistant features at all, but they do not guarantee levels will fall below the EPA action level. Because passive systems rely on natural pressure differences rather than mechanical suction, their performance varies more than an active, fan-powered sub-slab depressurization system.

Crawl space with sealed vapor barrier membrane and a sub-membrane depressurization pipe penetration

Converting a Passive System to Active

If testing shows a new home with passive radon-resistant features still has elevated radon, the existing vent pipe can typically be converted to an active system by installing an inline fan along the pipe route, usually in an attic, garage, or exterior location. This conversion is often simpler and less invasive than installing a mitigation system from scratch in a home with no existing rough-in, since the piping and roof penetration are already in place.

Locate the existing passive vent pipe rough-in
Install an inline fan at an appropriate point along the pipe run
Confirm proper electrical connection and fan orientation
Test with a manometer to verify system vacuum
Conduct a post-installation radon test to confirm results

Testing Timing for New Homes

New homeowners in Indianapolis should test as soon as reasonably possible after moving in, and ideally as part of the closing process for new construction, though this varies by builder and buyer preference. Waiting until closed-house conditions are practical, such as during cooler months when windows are naturally kept closed, can also provide a more representative reading.

It is worth noting that even homes built with passive radon-resistant features are not exempt from testing recommendations; EPA guidance to test every home applies regardless of construction date or the presence of passive systems, since actual performance can only be confirmed through measurement.

Continuous radon monitor on a tripod recording readings in a home lower level under closed-house conditions

What to Ask Your Builder

Homeowners purchasing new construction in Indianapolis can ask the builder directly whether passive radon-resistant features were included and request documentation of what was installed, such as the presence and routing of a vent pipe and sub-slab gravel layer. This information helps a testing or mitigation contractor understand the existing infrastructure and plan more efficiently if activation becomes necessary.