How to Prevent Radon in New Construction
When you’re building a new home, every detail matters. You may be thinking about how your kitchen should function, what flooring feels best underfoot, or even where to place outlets for maximum convenience. While those choices shape your daily comfort, there’s another decision that quietly impacts your family’s long-term health and safety: radon protection.
Radon is an invisible gas that can seep into homes from the soil. It’s the second leading cause of lung cancer in the U.S. Considering this, planning for radon-resistant features during new construction is one of the smartest and most cost-effective choices you can make.
Starting from the blueprints, here’s what Tennessee homeowners, builders, and developers need to know about reducing radon risks through radon-resistant construction.
Why Radon Protection Matters in New Homes (And Old)
Radon is an odorless, invisible gas that forms naturally in the ground — and it doesn’t care if your home is new or old. Whether your home was built in 2025 or 1885, it’s still prone to radon exposure. The risk is especially high in the Southeast, particularly in Middle Tennessee, where soil conditions make radon more likely to accumulate. Because it comes from natural uranium in the soil, radon gas can seep indoors through cracks, joints, and foundation openings.
Once a house is complete, installing radon mitigation can be messy and expensive. By contrast, adding radon-resistant features during construction costs far less and ensures a safe, healthy living environment from day one.
Tennessee Radon Requirements for New Construction
You may wonder if you are obligated to have a radon system installed in your home in Tennessee. The short answer is: It depends!
Tennessee does not have a statewide law requiring radon-resistant construction in every new home. However, the Tennessee Department of Environment and Conservation strongly recommends it, and many local jurisdictions — particularly in Middle- and East Tennessee’s high-radon counties — require at least a passive radon system on new builds.
Radon System 101: Passive vs. Active Systems
Before we get too deep, let’s break down the two key radon systems involved in radon mitigation: passive radon systems and active radon systems.
What Exactly Is a Passive Radon System?
A passive system can be installed during construction. It’s called a passive system because it doesn’t use a fan, but creates a venting pathway. A passive radon system relies on natural airflow and pressure differences to move radon gas out of the home. It can lower levels, but in some cases, it won’t be enough. If post-construction testing shows high radon levels, a simple fan installation can convert the system to “active.”
What’s an Active Radon System?
An active system adds a specialized radon fan onto an existing passive system (or a retrofit installation) to draw soil gases out more forcefully. If radon levels test above the EPA action level of 4 pCi/L after move-in for a home with a passive system, adding a fan is a quick, low-cost upgrade.
What’s the Cost Difference Between an Active and Passive System?
The cost difference between installing a retrofit active system and building a passive system into your build is significant. Installing features during construction might cost a few hundred dollars, while retrofits, if you forgo a passive system, can cost hundreds to thousands.
Aesthetic Benefits of Installing During Construction
Adding a passive system during construction isn’t just about safety and savings — it’s also the most attractive choice. Because the piping and components are installed before drywall and finishes go up, the system can be routed cleanly through walls and hidden from view.
Homeowners avoid the bulky look of retrofitted piping on exterior siding or visible runs through finished rooms. The result is a radon-safe home that looks polished.
Passive Systems: Is The Pipe Enough?
Unfortunately, not all passive systems are created equal, and many homeowners and builders are misled.
On paper, a passive system sounds simple: a vent pipe and a barrier under the slab. But in practice, the system's effectiveness depends entirely on how well it’s designed, positioned, and installed.
A good passive system must meet these requirements:
Have a properly sloped vent pipe so condensation drains correctly.
Be routed with adequate attic clearance to allow for a future fan installation.
Start with a well-installed sub-slab layer that actually allows soil gases to move.
Follow EPA radon-resistant new construction (RRNC) codes so the system can be easily activated if needed.
If even one of these details is missed, the system may not work at all, leaving the home unprotected and you at risk of high radon levels in your home.
What Are Other Radon-Resistant Construction Techniques?
There’s more to it than just PVC. Building radon resistance into a new home involves layering additional safeguards to prevent gas from entering or accumulating indoors.
A gas-permeable layer: Gravel or another base beneath the foundation allows soil gases to move without pressurizing the slab.
A vapor barrier: Plastic sheeting or other barriers above the base block in crawlspaces prevent radon from seeping upward.
Sealing: Cracks, joints, and openings around plumbing and wiring are sealed tightly.
A vent pipe: A PVC pipe, called a vent pipe or radon pipe, is run vertically from beneath the foundation through the roof to safely vent radon outdoors. This is your “passive system” that allows radon to be directed out of the air you breathe.
Electrical rough-in: An outlet near the vent pipe in the attic makes it easy to add a fan later if testing shows it’s needed.
When installed correctly, these elements form a strong, reliable first line of defense against radon.
Why You Don’t Want Just Anyone Installing Your Radon System
In many new builds, the problem is that the passive radon system gets handed off to a plumber or subcontractor who has no radon training. Pipes get run the wrong way, vapor barriers are left unsealed, and attic access is blocked. From the outside, it looks like a radon system is in place. In reality, it’s non-functional.
This creates two major risks:
False security: homeowners think they’re protected when they aren’t.
Costly retrofits: fixing a broken or non-compliant system after the fact often costs far more than doing it right during construction.
Involving a certified radon mitigation professional is non-negotiable. A specialist understands airflow dynamics, EPA standards, and the system's long-term performance.
More importantly, they know how to design a system that actually works, not just one that “checks a box” on the build sheet.
Build Your Custom Home With Radon Safety in Mind
If you’re building a custom home in Tennessee, don’t let radon be an afterthought.
Radon-resistant construction is affordable, discreet, and one of the best investments you can make for your family’s health and your home’s value.
The Radon Guys specialize in radon-resistant new construction and can work directly with your builder to ensure everything is done right the first time. Contact us today to make sure your new home is safe from the ground up.
