Renovation season in St. Louis brings a predictable mix of optimism and dust. Kitchens come out, basements get opened up, foundations get patched, and houses breathe differently than they did before. That last part matters more than most homeowners realize. When you change how a building breathes, you change how soil gases move, and that includes radon. Testing for radon before you start swinging hammers can save you money, help you plan the work more intelligently, and, most importantly, protect everyone who spends time in the home.
I have spent years working with homeowners, remodelers, and property managers across St. Louis, St. Charles, and the Metro East. I’ve crawled through the clays of Dogtown and the sandy soils out near Wentzville. I’ve stood in half-framed basements where the new egress window cut through a surprise vein of damp, crumbly soil that smelled like the earth after a storm. The homes varied, but one pattern stayed constant: renovations can push radon levels up or down in unpredictable ways. If you want fewer surprises and healthier air, test before you renovate, and plan for a radon mitigation system if you need one.
What radon really is, and why St. Louis homes are at risk
Radon is a colorless, odorless gas that forms when uranium in soil and rock breaks down. It seeps up through the ground and can enter your home through foundation cracks, sump pits, crawl spaces, and utility penetrations. Outdoors it dissipates quickly, but indoors it can concentrate. The health concern is well documented: long-term exposure to elevated radon significantly increases the risk of lung cancer. Smokers face an even higher risk, but non-smokers are not in the clear. The Environmental Protection Agency recommends taking action at or above 4.0 picocuries per liter (pCi/L), and plenty of professionals suggest considering mitigation even when results land in the 2.0 to 3.9 range, especially if young children or elderly family members live in the home.
St. Louis sits in a geological mix. Parts of the city and surrounding counties rest on limestone with fractures, pockets of fill from old construction, and varying soil compositions that change block by block. I have seen homes two doors apart test at 1.9 and 11.3 pCi/L during the same weather pattern. The assumption that your house will behave like your neighbor’s is risky. Weather shifts, water tables, and construction details all play a role. Basements built in the 1920s with fieldstone walls behave differently than 1990s walk-outs with drain tile and sump pumps. If you want certainty, you test.
Why testing before renovations matters more than testing after
Renovations can reshuffle pressure dynamics inside a home. That phrase sounds abstract, so let me translate it into what I’ve watched on job sites. You open walls, install a new HVAC return, cut a new drain for a bathroom, or tighten up air sealing for energy efficiency, and suddenly the house pulls on the soil like a slow, persistent vacuum. Radon moves along the path of least resistance. If you create a stronger pathway, you can increase entry rates without realizing it.
Here are a few real examples from local projects:
- A Tower Grove South bungalow started with a pre-renovation average of 2.7 pCi/L. After the basement slab was cut for new plumbing and the new mechanical system was commissioned, the post-renovation average rose to 6.1 pCi/L. The fix required a sub-slab depressurization radon system and a carefully sealed sump lid. If we had tested first and stubbed in for a radon system during the early rough-in phase, the cost and mess would have been lower. A newer home in O’Fallon measured at 3.4 pCi/L before adding a bedroom in the basement. The homeowner opted to add passive radon rough-ins during construction. After the finish work, the level nudged to 4.2 pCi/L. We activated the passive lines with a fan, and the home now tests at 0.9 pCi/L. Because the infrastructure was planned during renovations, the activation took a couple of hours and avoided surface piping. A Lafayette Square brick home with a limestone foundation tested at 5.8 pCi/L, but the owner wanted to lower levels before installing high-end wood floors. We mitigated first, then sealed slab cracks and joints during the flooring prep. The long-term monitor now hovers around 1.3 pCi/L, and we avoided ripping into finished floors to add piping later.
Testing before you start gives you three advantages. First, you learn your baseline. Second, you can integrate radon mitigation into the renovation plan, which often reduces labor and keeps the system discreet. Third, you avoid delays when a final inspection or a buyer’s test flags a high reading after you’ve already invested in finishes.
How radon levels shift during common renovation activities
Each renovation decision touches airflow or soil contact in some way. Here are the typical culprits:
Opening the slab. If you cut the basement floor to add a bathroom or adjust plumbing, you create direct pathways from the soil to the living space. Even with temporary patching, minor leaks persist until the slab is permanently sealed.
Tightening the envelope. Air sealing, spray foam, new windows, and weatherization reduce uncontrolled leaks to the outdoors. That is good for energy but can increase stack effect and depressurize the lowest level, which can draw more radon.
HVAC changes. New furnaces, added returns, or different duct arrangements can change pressure zones. I’ve seen basements go slightly negative relative to the soil after adding a large return, particularly Radon system Air Sense Environmental- Radon Mitigation & Testing in homes where supply and return balance was not carefully tuned.
Sump pumps and drain tile. An open sump pit acts like a chimney for soil gases. During remodeling, sump lids come off and on repeatedly. A sealed, gasketed lid with proper penetrations for discharge and power is a small upgrade with a large impact.
New additions and crawl spaces. Building an addition with a partial crawl space or slab on grade can change soil gas dispersion. If that area is connected to the main basement, pressure imbalances can pull radon from one zone to another.
These changes don’t guarantee higher radon, but the risk is real enough that responsible planning pays for itself.
The right way to test before renovations
Short-term test kits have a place, but context matters. The most reliable picture comes from a combination of approaches.
Start with a pre-renovation screening. If timing is tight, use a high-quality short-term test of 48 to 96 hours, following closed-house conditions. Place it in the lowest livable level, away from drafts, exterior walls, and direct heat. If you have a sump, don’t place the device directly beside it, but keep it within the general basement zone to reflect typical occupied air.
If your schedule allows, run a long-term test. A monitor that records for 30 to 90 days gives a truer average across weather swings. Radon levels can double during heavy rain or prolonged cold, so a longer test smooths out spikes.
Document the results before demolition. This gives you a baseline that you can compare against when the dust settles.
If your reading lands at or above 4.0 pCi/L, plan for mitigation. If it sits between 2.0 and 3.9, consider your risk tolerance, the scope of renovation, and whether you can rough-in a radon system for an easy activation later.
Planning mitigation into the scope, even if you might not need it
When you are remodeling, you have a rare opportunity. Walls are open, ceilings are exposed, and you can run pipe and wiring with minimal patchwork. Many St. Louis radon specialists will coordinate with your general contractor to create a clean path for a radon system that hides within chases or mechanical rooms. I frequently suggest a two-stage approach.
First, rough-in a passive radon system. That includes a sealed suction point under the slab, a vertical PVC riser through conditioned space up to the attic or rim joist, and a capped roof or exterior termination ready for a fan. Seal the sump lid and major slab cracks as part of the floor prep. This work is quick during renovation and minimal after.
Second, test again once the renovation is complete and the HVAC is balanced. If the final reading remains under your target, you leave the system passive. If it creeps higher, you add a radon-specific fan, a manometer, and an exterior disconnect. Activation usually takes half a day or less when the rough-in is already there.
The cost delta is significant. Running new PVC across finished rooms or along exterior siding after the fact can add expense and compromise aesthetics. Planning keeps both cost and appearance in check.
Choosing a radon mitigation contractor who understands renovations
Not every radon specialist is comfortable coordinating with renovators. The right pro will know how to navigate structural elements, manage penetrations carefully, and sequence work with other trades. When homeowners ask for recommendations for a radon mitigation contractor during a remodel, I tell them to look for three qualities: building-science literacy, clean job-site habits, and a willingness to collaborate on layout with the GC or designer.
The difference shows up in the details. I’ve seen neat, nearly invisible installs where the radon system tucks beside a plumbing stack and exits through a back gable. I’ve also seen poorly placed fans vibrate near bedrooms or discharge under soffits where windows draw air right back into the house. A thoughtful installer will discuss fan location, vibration isolation mounts, aesthetic choices for exterior pipe routing, and how to maintain access to shut-offs and clean-outs. If you search for “radon mitigation near me,” read the reviews with an eye for these nuances, not just star ratings.
What a typical radon mitigation system looks like in St. Louis homes
The most common solution here is sub-slab depressurization. Think of it as controlled suction under your concrete, so soil gases move toward a designed point instead of spreading randomly. Here’s what that usually involves:
A suction pit under the slab. The contractor cores a hole in the basement floor, excavates a small pit in the gravel or soil beneath, and inserts a PVC pipe. If your home has drain tile, tying into that network can reduce the number of suction points needed, but the connection must be done carefully to avoid water issues.
Sealing. Sump pit lids get sealed with gaskets, and slab cracks or joints receive a high-quality sealant. Perimeter sealing is not about making the foundation airtight; it is about maximizing the pressure difference between sub-slab and indoor air.
Vertical vent piping. The pipe runs from the suction point through the house and exits above the roofline or through an exterior wall to a vertical discharge that keeps exhaust above the eave line. Routing inside conditioned space improves performance and reduces condensation risk in winter.
A radon-specific fan. These fans are designed to run continuously for years with low energy use, usually similar to a small light bulb. In our climate, selecting a fan that handles colder months without icing is important.
Monitoring and labels. A simple U-tube manometer shows that the fan is creating suction. Some systems add digital monitors that alert if pressure drops. Labels matter for future owners and inspectors, as do electrical disconnects placed to code.
For homes with crawl spaces, a separate strategy uses a sealed membrane over the soil with a suction point beneath. Mixed foundations, common in older St. Louis neighborhoods, may need a hybrid approach.
Integrating mitigation into specific renovation scopes
Kitchens on the first floor rarely touch the foundation directly, but they may come with new duct runs or make-up air for high-powered range hoods. Those can lower pressure in the basement if not balanced. I recommend homeowners test before and after kitchen remodels in older homes, especially if simultaneous weatherization work tightens the envelope.
Basement finishes are the big one. If you are adding bedrooms or a family room downstairs, you will likely install new egress windows, rework drains, and add cooling returns. Each decision can shift radon behavior. The most efficient path is to test, create a suction pit and sealed sump lid during slab work, run the vent pipe within new walls, and save activation for later if needed. Many St. Louis city inspectors have grown familiar with seeing a neat, labeled radon stack alongside plumbing vent chases in finished basements.
Bathroom additions on lower levels nearly always cut the slab. I keep a simple rule of thumb: if the jackhammer is coming out, plan for at least a passive radon rough-in.
Additions with new foundations deserve soil gas planning from the start. Bedding gravel, perforated drain tile, and a simple stub-out for a radon system cost very little during foundation work and leave you ready either to remain passive or to add a fan after final testing.
Addressing common objections I hear from homeowners and contractors
“We never had a problem before.” That may be true, but your house is about to change. The baseline was for a different building configuration. Testing takes little time and removes guesswork.
“I’ll just use a short-term test after we finish.” Post-renovation testing is necessary, but waiting can create a headache. If results come back high, you’ll be routing pipe through your new space and opening fresh drywall. Planning early keeps your options open.
“Radon is only a problem in certain counties.” St. Louis City and County show a mix, not a uniform low or high map. I’ve seen elevated results everywhere from Kirkwood to Belleville to the Central West End. The only reliable answer is your test.
“Fans are noisy and ugly.” A well-placed fan is quiet. The right mount and exterior routing solve both noise and visual issues. Painted exterior piping blends easily, and interior runs can disappear in a utility chase.
“It’s an extra cost.” True, but it is usually modest compared to the renovation budget. The value shows up in lower health risk, smoother inspections, and a plus on a future listing where buyers ask about radon.
Weather, timing, and how to read your numbers
Radon is not static. Winter often yields higher readings because homes are closed up and stack effect is stronger. Heavy rain can trap soil gases and push them sideways into foundations. Windy days create fluctuating pressures that may lower or raise what your test sees.
Two practical tips help interpret results:
If your short-term test lands near a threshold during shoulder seasons, consider confirming with a long-term test or retesting during winter, when levels tend to be higher. This is especially relevant if your family spends significant time in the basement.
If you completed deep air sealing or changed HVAC in the middle of a test, redo the measurement once the new airflow patterns settle. I usually wait a week after commissioning a new system.
How real estate considerations intersect with remodeling and radon
Many homeowners renovate with an eye toward selling within a few years. Buyers have grown more savvy about radon. If your listing lands with a finished basement and no radon history, expect the buyer to test. A known, documented low level or an installed radon mitigation system can streamline negotiations and reduce last-minute concessions. A system installed by a reputable St. Louis radon company, with permits and visible pressure monitoring, signals care and diligence. It is a small but meaningful asset, especially in neighborhoods where basements are used as living space.
Working with St. Louis inspectors and local norms
Across municipalities, inspectors vary, but several themes repeat. They appreciate sealed sump lids, labeled piping, and proper electrical disconnects for fans. They look for discharge points above the roofline or sufficiently far from operable windows and soffit intakes. They prefer clean penetrations through fire-rated assemblies with proper fire stopping, just as they would for plumbing vents. When the mitigation is planned alongside the renovation permit, sign-offs go faster. If you search for “Radon mitigation St Louis” or “Stl radon,” you will find contractors who regularly coordinate these details and can align schedules with framing, rough plumbing, and electrical inspections.
Costs, maintenance, and what living with a radon system feels like
A typical active radon system in the St. Louis area often falls in a mid-range price bracket, influenced by factors like number of suction points, crawl spaces, and piping route complexity. Rough-ins during renovation reduce costs later. Operating costs are modest. Most fans consume around the power of a small bulb, and many run quietly for 7 to 10 years before needing replacement. Maintenance is minimal: glance at the U-tube manometer monthly to confirm suction, listen for unusual fan noise, and keep discharge clear of obstructions like ivy or nests.
If your home uses a heat recovery ventilator or energy recovery ventilator, a knowledgeable contractor will consider how that system interacts with radon mitigation. Usually, they coexist well. In rare cases, balancing may be adjusted to avoid counteracting the sub-slab depressurization.
A brief, practical pre-renovation radon checklist
- Test now, before demolition, using a quality device and proper placement. If results are 4.0 pCi/L or higher, plan mitigation as part of the scope; at 2.0 to 3.9, at least rough-in a passive system. Coordinate with your GC to run vent pipe through walls or chases while they are open. Seal the sump pit and obvious slab cracks during floor prep; insist on a gasketed, bolted lid. Retest after HVAC balancing and occupancy to confirm final performance.
A note on DIY vs. professional work
Homeowners sometimes ask about installing a radon system themselves. I’ve seen competent DIY jobs in simple layouts, but renovations introduce complexity. You already have electricians, plumbers, and inspectors in the mix. Small mistakes alter performance: an undersized suction pit, a poorly sealed sump cap, a fan installed in conditioned space that adds noise, or a discharge too close to an operable window. Given the long-term health stakes and the synergy with renovation sequencing, working with a qualified radon mitigation contractor is a better bet. If you want to do part of the work yourself, some pros will let you handle simple prep tasks while they handle the critical design and commissioning.
Pulling it together for St. Louis homes
The thread that connects all of this is simple. Renovations change your home’s pressure balance. Radon responds to those changes. Testing before you start and planning for mitigation protects your family and preserves your budget. It also respects the character of your house, whether that means tucking a neat radon riser behind a century-old plaster wall or routing a modern system cleanly through a new mechanical room. When you assemble your renovation team, add radon to the early conversations. Search for “radon mitigation near me” or ask your GC which St. Louis radon specialists they trust. Baselines first, smart rough-ins second, verification at the end. That rhythm keeps surprises off the punch list and healthy air in the rooms you just worked so hard to improve.
If you need a starting point, gather your current floor plans and any notes on foundation type, presence of a sump, and where you plan to open the slab. A short call with a local pro who understands St. Louis soils can turn those notes into a clean, efficient plan. The difference shows up not only in your final radon number, but also in how quiet, discreet, and durable your radon system becomes. In a city where basements are often real living space, that quiet success is exactly the outcome you want.
Air Sense Environmental – Radon Mitigation & Testing
Business Name: Air Sense Environmental – Radon Mitigation & TestingAddress: 5237 Old Alton Edwardsville Rd, Edwardsville, IL 62025, United States
Phone: (618) 556-4774
Website: https://www.airsenseenvironmental.com/
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https://www.airsenseenvironmental.com/Air Sense Environmental is a quality-driven indoor air quality specialist serving Edwardsville, IL and the surrounding Metro East region.
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Popular Questions About Air Sense Environmental – Radon Mitigation & Testing
What services does Air Sense Environmental provide?
Air Sense Environmental provides professional radon testing, radon mitigation system installation, indoor air quality solutions, and crawl space encapsulation services in Edwardsville, Illinois and surrounding areas.Why is radon testing important in Illinois homes?
Radon is an odorless and invisible radioactive gas that can accumulate indoors. Testing is the only way to determine radon levels and protect your household from long-term exposure risks.How long does a professional radon test take?
Professional radon testing typically runs for a minimum of 48 hours using continuous monitoring equipment to ensure accurate results.What is a radon mitigation system?
A radon mitigation system is a professionally installed ventilation system that reduces indoor radon levels by safely venting the gas outside the home.How do I contact Air Sense Environmental?
You can call (618) 556-4774, visit https://www.airsenseenvironmental.com/, or view directions at https://maps.app.goo.gl/XTPhHjJpogDFN9va8 to schedule service.Landmarks Near Edwardsville, IL
Southern Illinois University Edwardsville (SIUE)A major public university campus that serves as a cultural and educational hub for the Edwardsville community.
The Wildey Theatre
A historic downtown venue hosting concerts, films, and live entertainment throughout the year.
Watershed Nature Center
A scenic preserve offering walking trails, environmental education, and family-friendly outdoor experiences.
Edwardsville City Park
A popular local park featuring walking paths, sports facilities, and community events.
Madison County Transit Trails
An extensive regional trail system ideal for biking and walking across the Metro East area.
If you live near these Edwardsville landmarks and need professional radon testing or mitigation, contact Air Sense Environmental at (618) 556-4774 or visit https://www.airsenseenvironmental.com/.