Radon System Installation: What Homeowners in St. Louis Should Know

Anyone who has spent a winter in St. Louis understands the rhythm of a Midwestern house. The soil stays damp, the furnace runs, and windows stay shut for weeks. That is exactly when radon, a naturally occurring radioactive gas, tends to build up indoors. I have tested homes off Hampton, in Webster Groves, up in Florissant, and out to O’Fallon. The pattern repeats: two houses on the same block, built in the same year, can show very different radon levels. When it is your home and your family, averages do not matter. Your number does.

This is a practical guide, born from crawlspace dust and concrete dust, for anyone in the metro area weighing whether a radon mitigation system makes sense, what it should look like in a St. Louis house, and how to choose a radon mitigation contractor who knows the quirks of our local construction and soil.

What radon is doing under your house

Radon comes from uranium in the soil and rock beneath your foundation. It is odorless and invisible, which makes lab numbers and field meters your only honest look at it. In the Midwest, especially the Missouri River floodplain and glacial till areas, soil gas can move freely through subsoil and find its way through any path of least resistance. Think of the gap between a slab and a foundation wall, hairline cracks in basement floors, sump pits that are not capped, and utility penetrations. The house itself helps pull this gas inside. Warm air rises, which lowers pressure in the basement. The lower pressure acts like a straw in the soil, drawing in radon along with moisture and other soil gases.

Homes with basements are not the only ones at risk. Slab-on-grade ranch homes in South County, split-levels in St. Charles, even townhomes in Soulard have all produced elevated numbers during testing. Construction type influences the plan for mitigation, not the likelihood you need it.

When to test and how to read the result

If you have never tested, do it now, not someday. Short-term tests take 48 to 96 hours and are widely available. Long-term tests run 90 days or more and give a better sense of seasonal variation, but I rarely delay mitigation decisions when a short-term test comes back high during the heating season. The EPA action level is 4.0 pCi/L. In practice, many local buyers start negotiating at anything over 3.0 pCi/L, and I have seen transactions get uneasy at 2.7 pCi/L when the buyer’s family has a history of lung issues. If your number is over 4, you should plan to install a radon system. Between 2 and 4 calls for judgment. Consider how you use the basement, whether it will be a bedroom, and whether the number came during winter, when indoor levels are often highest.

There is a local wrinkle. St. Louis has older housing stock mixed with newer foundations. A 1920s stone basement with a thin slab might pull more soil gas than a well-sealed 1990s poured concrete foundation, but I have seen the reverse. Do not assume. Test.

How a radon mitigation system actually works

Most residential systems in our region are sub-slab depressurization. You create a controlled suction point under the slab, connect it to a sealed PVC pipe, attach an inline radon fan, and vent above the roofline. The fan runs continuously, drawing radon-laden air from beneath the home before it can enter the living space. Done right, it is unremarkable from the street and almost silent indoors.

Here is the key: the system does not “filter” the air under your home. It changes the pressure dynamics under the slab. The goal is a vacuum field under the entire foundation footprint so the house stops pulling radon inward. On ten installs, eight are straightforward. The other two demand finesse because the slab might be thick, the fill is tight, or there are separate foundation sections that do not communicate well.

St. Louis construction quirks that shape the design

This metro area sees a bit of everything: limestone ledge close to grade near the bluffs, compacted clay in the city, newer subdivisions with gravelly fill, and a mix of basements, slab additions, and garages set on different pours. Those details drive the design of your radon system.

I often find these patterns:

Many 1950s and 1960s basements poured without perimeter drain tile. That can mean poor sub-slab communication. We solve it by coring the suction pit closer to a known utility trench or by increasing the pit size and adding a secondary suction point. Sump pits in 1980s and 1990s homes are common and can be assets, but only if they are permanently sealed with a radon-rated lid and gaskets around discharge lines. An unsealed sump is a leak, not a suction point. Finished basements with luxury vinyl plank over foam underlayment are more airtight at the surface, which is good for indoor comfort, but you want to ensure your suction field is under the slab, not just under the flooring. Measuring pressure fields during and after installation becomes crucial. Tuck-under garages and room additions built on separate slabs often require either a pressure relief cut between slabs or a second suction point to avoid leaving one area untreated.

A St. Louis radon mitigation contractor who has drilled a few hundred pits around town will see these red flags in the first walkthrough. That experience, more than any brochure bullet points, determines whether you get a clean pass on post-mitigation testing.

What a clean, code-compliant installation looks like

Walk the outside of your house and picture the vent stack. The discharge needs to be at or above the eave line, away from operable windows and at least a few feet above grade where snow can drift. In St. Louis city and county jurisdictions, you also want that pipe to blend with downspouts or rear elevations when possible. White Schedule 40 PVC is standard. If it runs along a visible facade, paint it to match the siding after a few weeks of UV exposure so the paint bonds.

Indoors, look for neat glue joints, a proper firestop where the pipe penetrates floors, and a U-tube manometer mounted at eye level near the fan switch. The manometer does not show radon levels. It shows pressure difference, which tells you the fan is pulling air. If both sides of the red fluid are even, the fan is off. If they are offset, even by a small amount, the fan is on and the system is working as designed.

If a sump is present, the lid should be clear or opaque acrylic with a gasket, mechanical fasteners, and sealed penetrations for the pump cord and discharge. Sloppy foam or duct tape around a sump is a shortcut and will leak soil gas back into the house.

The fan location matters. I prefer mounting the fan outside the conditioned envelope, often in the garage attic or on the exterior just above the rim joist, then running the discharge up the sidewall to the roofline. Fans should not be installed in a living space or below grade. If it ever leaks, you want that to be outside.

The typical installation day, without the gloss

For most St. Louis homes, an install runs four to six hours. The contractor confirms the suction point, cores a 4 to 5 inch hole in the slab, and excavates a small pit, about the size of a five-gallon bucket. In dense clay, we enlarge the pit for better communication. The pipe is dry-fit first, then glued, strapped, and run to the fan. I prefer to drill a neat hole through the rim joist with an escutcheon plate rather than snake pipe through a joist bay that might hide plumbing or electrical.

Outside, the fan mounts to a bracket with vibration isolators. We add a clean condensate drip leg, slope exterior pipe slightly to shed rain, and strap it every 6 feet. If the run passes near a bedroom window, we check the clearance rule of thumb: keep the discharge at least 10 feet horizontally or 2 feet above the highest opening within 10 feet, whichever is greater. These are safety best practices, and they keep your Radon mitigation system from blowing straight back into the house.

Before we leave, we seal obvious slab cracks and the cold joint at the perimeter with polyurethane or epoxy. Think of sealing as the belt to the fan’s suspenders. It is not always required, but it helps the system maintain a lower sub-slab pressure with less fan power, which saves noise and electricity.

How quiet and how visible the system will be

Well-executed systems are surprisingly quiet. Standing next to an exterior-mounted fan, you will hear a soft whoosh, maybe 50 to 60 decibels up close, less than a conversation. Inside, you should not hear it in living areas. If you do, ask the installer to add a rubber isolation coupling or to adjust strapping. Vibration telegraphed through framing is avoidable with a couple of thoughtful tweaks.

As for appearance, many homeowners worry the stack will make the house look industrial. Integrated runs that follow a corner or a downspout line almost disappear after paint. On brick homes in the city, we sometimes route through the garage and up the rear elevation so the front facade remains clean. Creative routing must never trump safety or performance, but an experienced St. Louis radon installer usually has two or three tidy options to present.

The numbers that matter after the fan turns on

Post-mitigation testing is not optional. You want a short-term test 24 hours after the system has run continuously for at least a day, ideally 48 hours. Most of my clients see reductions to between 0.5 and 1.5 pCi/L. Occasionally, stubborn houses settle at 2 to 3 pCi/L. If you started at 15 and landed at 2.7, that is a strong reduction, but we look for more. A second suction point, improved sealing, or a higher-capacity fan often shaves off that last bit.

Over time, retest every two years, or sooner after foundation work, seismic activity, or if you replace flooring or sump components. St. Louis does not see dramatic earthquakes often, but even minor settling can open new pathways for soil gas. The fan itself typically lasts 5 to 10 years. Listen for bearing noise or check the manometer weekly. A sudden zero on the gauge usually means a tripped breaker, a failed fan, or a disconnected line.

Health, risk, and how mitigation fits into the bigger picture

Radon is the second leading cause of lung cancer in the United States after smoking. That statement is broad, but it is grounded in decades of epidemiology. Individual risk depends on exposure level and time. If you or someone in your home smokes, high radon multiplies the risk. That is one reason real estate agents in St. Louis have made radon testing nearly as routine as termite inspections during a sale. It is a straightforward fix compared to structural items, and buyers expect to see a clean test or a credit toward mitigation.

Some homeowners ask whether opening basement windows can solve the problem seasonally. Fresh air helps in the moment, but it is not a mitigation plan. Radon levels swing with weather and HVAC use. A dedicated Radon system delivers consistent, predictable reduction without relying on behavior that drifts over time.

Cost, warranties, and what signals value over a cheap bid

You will see a range. In the St. Louis area, a single-suction system for a typical basement often falls between 1,000 and 1,800 dollars. Multi-suction or complex routing can push it to 2,000 or more. A good bid includes the fan, all PVC and fittings, exterior strapping, a properly sealed sump lid if present, manometer, labeling, post-install short-term test, and a written performance guarantee that the post-mitigation number will be under the EPA level or the installer will make adjustments at no cost.

Warranties vary. Fans often carry a manufacturer warranty, commonly 5 years on higher-quality models. Ask who handles a warranty claim if the fan fails in year four. The better Radon mitigation contractor handles it for you rather than pointing to a phone number on the box.

I advise clients not to chase the lowest number. A clean pass on your St. Louis radon test and a system that looks like part of the house, not an afterthought, are worth a few hundred dollars more. Rework costs more than doing it right on day one.

Choosing the right contractor, and the red flags to avoid

When you search “Radon mitigation near me” or “Radon mitigation St Louis,” you will see national chains, one-truck shops, and general handymen offering to install a Radon system on the side. The last group is where I see most of the bad installs. State-level requirements evolve, but you want someone who installs radon systems weekly, not a few times a year.

Use this simple checklist when you talk to candidates:

Ask how they diagnose sub-slab communication before committing to a single suction point. Listen for terms like pressure field extension or smoke tests, not just “we’ll figure it out.” Request three photos of recent St. Louis radon projects in homes like yours, including a sump seal if you have one. Confirm they include post-mitigation testing and at least one free return visit if the first result is still high. Check whether they carry liability insurance, can pull permits if your municipality requires them, and will label the pipe and fan per industry standards. Make sure they will explain where the fan goes, how noise is handled, and what the pipe route will look like before drilling.

If a contractor hesitates on any of these, keep looking. Strong references and clear scope win the day.

Edge cases: crawlspaces, duplexes, and old stone basements

St. Louis has its share of partial crawlspaces, especially in older neighborhoods and in some South County ranches. If you have an exposed-earth crawl, mitigation includes sealing the crawl with a durable membrane and depressurizing under that liner. The plastic needs to be thick, seams overlapped and taped, and the perimeter mechanically fastened and sealed. Cutting corners here defeats the system.

Duplexes and two-family flats, common in the city, present a different challenge. Shared foundations can carry radon across units. Each unit often needs its own test, and the mitigation plan must respect property lines and shared spaces. Coordinating with both owners or landlord and tenant saves headaches.

For century homes with fieldstone walls and thin or patched slabs, we sometimes add perimeter sealing and larger suction pits to compensate for rough subgrade. You are not chasing a perfect seal in these homes. You are creating a strong and stable pressure field. It is doable, and I have turned 12 pCi/L basements in Tower Grove into 1.2 with a two-point system and some careful crack work.

Maintenance that actually matters

You do not need to service a radon system like an HVAC unit. The fan runs continuously, quietly consuming roughly the power of a light bulb. What you should do is straightforward. Glance at the U-tube weekly for the first month, then monthly after that. If you notice the offset shrinking toward zero, call your installer. After a heavy storm, look at exterior strapping and check the discharge for leaves or debris, though vertical runs rarely clog.

If the sump pump is replaced, reseal the lid and penetrations. When you finish a basement, tell your installer before drywall goes up. It is easier to plan pipe routes and add a service tee while the walls are open than to cut finished surfaces later.

Retest every couple of years. Kits are inexpensive, and a single low reading is only as good as the conditions the day you ran it. Think of periodic testing like checking smoke alarms. You hope for boredom, but the risk justifies the routine.

How mitigation affects a home sale in St. Louis

Buyers are savvy. Many write radon into the inspection contingency. If your home already has a documented system with a recent low test, you remove a negotiation chip from the table. That alone can repay the investment. Conversely, if a test during a contract shows 6.0 pCi/L and the buyer requests mitigation, choose the installer with an eye toward handoff. Provide the invoice, warranty, and the post-mitigation report to the buyer. It builds trust and smooths the close. Agents I work with tell me that clean documentation around St. Louis radon reduces last-minute anxiety more than almost any other inspection item.

When the first attempt does not drop the number enough

It happens. Tight clay under a slab, isolated footings, or even a buried beam pocket can interrupt sub-slab communication. If your post-test sits at 3.5 pCi/L, do not panic. The fix path is methodical. First, check system basics: manometer reading, fan operation, sealed sump, visible cracks. Second, measure pressure fields at drill points around the slab to see where suction is weak. Third, decide between a stronger fan or a second suction point. I prefer to add the second point when measurements show a dead zone. A bigger fan pulling on a poorly communicating slab will waste energy and still miss pockets.

In one Des Peres split-level, the initial system dropped a 10.8 to 3.2. By adding a second suction in the lower family room slab and sealing a hidden expansion joint we uncovered near the hearth, the number settled at 0.9. Data first, hole second. That approach saves guesses and drywall.

Energy use, indoor air, and side benefits

A common concern is whether a Radon system will pull conditioned air from the house and raise energy bills. A properly sealed system pulls from under the slab, not from the basement air. If you notice a strong draft in the basement after installation, it is a sign of leaks around the suction point or a leaky sump lid. Addressing those often lowers the fan’s workload and stabilizes indoor comfort.

There is a quiet bonus. Sub-slab depressurization often reduces other soil gases and moisture migration. Several clients have reported that their basement smells fresher and dehumidifiers run less frequently. I do not sell that as a promised outcome, but I do hear it often enough to mention.

When to call, and what to expect from a site visit

If your test reads high Radon mitigation st louis or you want a preemptive look before listing your home, a site visit should take 30 to 60 minutes. A solid Stl radon pro will ask about renovations, look for sump pits, check exterior routes for discharge, and measure the basement for pipe planning. They might drill a small pilot hole and test pressure if you authorize it. You should leave that meeting with a clear scope, a drawing or photo-marked plan, a firm price, and a timeline. Many companies can install within one to two weeks, faster during the busy spring real estate season if you ask.

Searching phrases like “St louis radon” or “Radon mitigation near me” will give you a start, but a neighbor’s recommendation is gold here. Houses on your block sit on similar soils and foundation types. A contractor who just finished your neighbor’s job has fresh local knowledge that transfers directly to your home.

The bottom line for St. Louis homeowners

Radon is a manageable risk. Testing is simple, and mitigation is a one-day project in most cases. The difference between a system that quietly protects your family for a decade and one that frustrates you with noise or marginal numbers lies in details: where the suction point goes, how the sump is sealed, how the fan is isolated, and whether post-mitigation testing guides any fine-tuning.

If you are shopping for a Radon mitigation system, look for clarity, experience, and local references. Expect a tidy install, a labeled pipe, a discrete fan location, and a written performance guarantee. If you already have a system, glance at the manometer, schedule a retest every couple of years, and keep an eye on sump work or foundation changes.

St. Louis homes keep their secrets. Radon does not have to be one of them. With a smart plan and a steady fan, the air under your slab stays where it belongs, and the air your family breathes stays safer.

Air Sense Environmental – Radon Mitigation & Testing

Business Name: Air Sense Environmental – Radon Mitigation & Testing
Address: 5237 Old Alton Edwardsville Rd, Edwardsville, IL 62025, United States
Phone: (618) 556-4774
Website: https://www.airsenseenvironmental.com/

Hours:
Monday: 9:00 AM – 5:00 PM
Tuesday: 9:00 AM – 5:00 PM
Wednesday: 9:00 AM – 5:00 PM
Thursday: 9:00 AM – 5:00 PM
Friday: 9:00 AM – 5:00 PM
Saturday: Closed
Sunday: Closed

Plus Code: RXMJ+98 Edwardsville, Illinois
Google Maps URL: https://maps.app.goo.gl/XTPhHjJpogDFN9va8

Google Maps Embed:

"@context": "https://schema.org", "@type": "HomeAndConstructionBusiness", "name": "Air Sense Environmental - Radon Mitigation & Testing", "url": "https://www.airsenseenvironmental.com/", "telephone": "+16185564774", "address": "@type": "PostalAddress", "streetAddress": "5237 Old Alton Edwardsville Rd", "addressLocality": "Edwardsville", "addressRegion": "IL", "postalCode": "62025", "addressCountry": "US" , "openingHoursSpecification": [ "@type": "OpeningHoursSpecification", "dayOfWeek": ["Monday"], "opens": "09:00", "closes": "17:00" , "@type": "OpeningHoursSpecification", "dayOfWeek": ["Tuesday"], "opens": "09:00", "closes": "17:00" , "@type": "OpeningHoursSpecification", "dayOfWeek": ["Wednesday"], "opens": "09:00", "closes": "17:00" , "@type": "OpeningHoursSpecification", "dayOfWeek": ["Thursday"], "opens": "09:00", "closes": "17:00" , "@type": "OpeningHoursSpecification", "dayOfWeek": ["Friday"], "opens": "09:00", "closes": "17:00" ], "geo": "@type": "GeoCoordinates", "latitude": "[Not listed – please confirm]", "longitude": "[Not listed – please confirm]" , "hasMap": "https://maps.app.goo.gl/XTPhHjJpogDFN9va8", "identifier": "[Not listed – please confirm]"

1) Semantic Triples

https://www.airsenseenvironmental.com/

Air Sense Environmental is a local indoor air quality specialist serving Edwardsville, IL and the surrounding Metro East region.

The team at Air Sense Environmental provides quality-driven radon testing, radon mitigation system installation, and crawl space encapsulation services tailored to protect residential indoor environments.

Homeowners throughout Edwardsville, IL rely on this highly rated local company for professional radon reduction systems designed to safely lower elevated radon levels.

To schedule radon testing or mitigation service, call (618) 556-4774 or visit https://www.airsenseenvironmental.com/ to speak with a quality-driven local specialist.

View the business location and directions on Google Maps: https://maps.app.goo.gl/XTPhHjJpogDFN9va8 and contact this professional radon mitigation provider for highly rated indoor air solutions.

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/.

Edit

Pub: 21 Feb 2026 20:09 UTC

Views: 2