A custom home builder in Williamson County called Radon 1 last spring with a question. He had just sold a home that tested at 7.2 pCi/L during the buyer’s inspection. The buyer asked for mitigation as a condition of closing. The bill came in at $2,800, and the builder absorbed it to keep the deal alive. On his next project, he asked us about doing it differently from the start.
Radon-resistant new construction, or RRNC, is the answer to that question. Instead of treating radon as a post-occupancy problem, RRNC installs a passive radon system during framing. The cost runs $400 to $600 at construction. Activating it later, if testing shows it is needed, costs another few hundred dollars. Compare that to $2,000 to $4,000 for a full mitigation after the home is built. For builders in Tennessee and Kentucky, both EPA Zone 1 states, RRNC is becoming the standard rather than the exception.
Key Takeaways
RRNC Costs $400 to $600 at Framing: A passive system installed during construction is dramatically cheaper than post-occupancy mitigation, which runs $2,000 to $4,000.
Tennessee and Kentucky Are EPA Zone 1: Both states sit in the highest-risk radon category. Builders who plan for radon avoid surprise closing-table mitigation bills.
Passive Systems Can Be Activated Later: If post-construction testing shows elevated levels, adding a fan turns the passive system active for a few hundred dollars.
Buyer Confidence Goes Up: Marketing an RRNC home signals to buyers that the builder thought about indoor air quality from the start.
Radon 1 Works Directly With Builders: Our team coordinates with framers and HVAC subs so RRNC is built in cleanly, not bolted on.
Call (615) 257-9818 to discuss RRNC for your next project.
What RRNC Actually Includes
RRNC is a set of construction techniques that prepare a home to handle radon before it becomes a problem. The core components are simple. A layer of gas-permeable aggregate goes under the slab. On top of the aggregate sits a vapor barrier. From there, a vertical vent pipe runs from the sub-slab area through the home to the roof. Sealing details close common radon entry points like joints, openings around plumbing, and the sump pit.
Together, these elements create a path for radon to escape passively, driven by natural convection. In many homes, this passive flow alone keeps indoor radon below the EPA action level of 4.0 pCi/L. When passive flow is not enough, adding a fan to the vent pipe converts the system to active mitigation. The activation happens in hours rather than days, because the hard work was done at framing.
EPA published the RRNC standard, known as ASTM E1465, decades ago. Major homebuilders in radon-prone regions have used it for years. The technique is well documented and easy to specify in plans.
The Cost Comparison That Drives the Decision
For a typical 2,000 to 3,000 square foot home, RRNC adds $400 to $600 to the construction budget. That cost covers materials and the additional framing labor to install the pipe, aggregate, and barrier correctly. For a builder doing twenty homes a year, RRNC adds roughly $10,000 to annual material costs.
Now consider the alternative. If even one in five of those homes tests above 4.0 pCi/L after closing, the builder faces either a $2,000 to $4,000 mitigation bill per home or a difficult conversation with the buyer. Four mitigated homes at $3,000 each is $12,000, more than the entire RRNC line item for the year. And that math assumes the builder catches the issue before legal exposure starts mounting.
For higher-volume builders, the math gets dramatic quickly. RRNC is one of the few risk-reduction strategies in residential construction with a clearly positive expected value. The break-even is well below the average post-occupancy hit rate in Zone 1. For multifamily projects, the same logic applies even more strongly, which is why commercial radon work often includes RRNC specs from the start.
Why Tennessee and Kentucky Specifically
Both Tennessee and Kentucky fall into EPA Zone 1, which means predicted average indoor radon levels above 4.0 pCi/L. County-level data varies, but counties around Nashville, Knoxville, Chattanooga, and Bowling Green consistently produce homes with elevated readings. A builder in these markets who does not plan for radon is rolling dice on every closing.
Soil geology in the region contributes to the pattern. Karst limestone and certain shale formations release radon at higher rates than other geologies. The same conditions that produce caves and sinkholes also produce a steady supply of radon gas. RRNC works regardless of soil type, but the value of the technique is highest in geologies like these.
Some jurisdictions now require RRNC in new construction, particularly multifamily developments financed through programs like HUD. Builders who adopt the standard early stay ahead of the curve and reduce the odds of a costly retrofit later.
How Radon 1 Coordinates With Your Build
Our team has worked with builders across Tennessee on RRNC for years. We come in during the plan review stage to make sure the vent pipe routing, sub-slab prep, and roof penetration are designed correctly. We coordinate directly with framers, HVAC subs, and roofers so each trade knows what RRNC requires from them.
After the home is built, we offer post-construction radon testing to confirm passive performance. If levels come in above the EPA action level, we activate the system by adding a fan. The same crew handles both the passive install and the activation, so warranty coverage stays clean and the system is documented from day one.
For builders doing multiple projects, we offer pricing that reflects the volume relationship. Once your framers and HVAC subs have done RRNC two or three times, the install becomes faster and the cost predictable. That repeatability is part of why builders who try RRNC once usually adopt it as the default.
How This Connects to Your Sales Process
Homes built with RRNC give your sales team a real talking point. Buyers in Zone 1 increasingly ask about radon. When your spec sheet shows that the home is RRNC-equipped with documentation from a certified radon company, the conversation moves past concern and into confidence. For higher-end builds, RRNC also fits the indoor air quality narrative that pairs well with HVAC, ventilation, and humidity control features.
When the next deal asks about radon, your answer is no longer “we will see at inspection.” Your answer is that the home was built to handle it, the vent path is documented, and Radon 1 will test the home after closing if the buyer wants confirmation. That changes the closing dynamic.
Call (615) 257-9818 or visit our contact page to discuss RRNC pricing and scheduling for your upcoming projects.
Frequently Asked Questions
How much does RRNC add to my construction cost?
For most single-family homes between 2,000 and 3,000 square feet, the materials and labor for RRNC add $400 to $600 per home. The cost varies slightly with home size, slab configuration, and roof complexity. Builders who repeat RRNC across multiple projects often see the per-home cost drop as their framers become familiar with the install.
What if my passive system does not keep radon below 4.0 pCi/L?
Activation is fast and inexpensive. We add a fan to the vent pipe, which converts the passive system to active mitigation. The labor and materials for activation typically run a few hundred dollars, far less than installing a full mitigation system after the fact. The pipe, aggregate, and sealing work are already in place from RRNC.
Can RRNC be added to a home that is already framed?
Yes, but the cost increases. The most efficient time to install RRNC is before the slab is poured. Adding the pipe, aggregate, and vapor barrier after framing is possible but requires more cutting and patching. Builders who plan for RRNC at the design stage capture the full cost advantage.
Does Radon 1 work with builders outside of Nashville?
Yes. Our crews work across Tennessee, Kentucky, and parts of Alabama, Georgia, and North Carolina. Multifamily and tract-home projects fit our schedule well because the install repeats across units. Call (615) 257-9818 to discuss RRNC for your build area.