Many homes in and around Prescott sit on crawl spaces instead of full basements or slabs. A crawl space is open to the soil below, and radon can move up from that soil into the living space above. If a test shows a high result, the fix for this foundation type is different from the one used in a basement home.
This page explains how crawl space radon systems work and why sealing is one piece of the job, not the whole job. This site connects callers with licensed and insured local radon professionals. Call (928) 582-8914 to be connected.
Why crawl spaces need their own approach
Radon is a radioactive gas that forms when uranium in soil, rock and water breaks down. You cannot see, smell or taste it. It can enter a home through cracks in floors and walls, gaps around pipes and wires, sump pits, crawl spaces and other openings in the foundation.
A crawl space has a large patch of bare ground and many small gaps where the house meets the soil. That makes it hard to stop radon by patching one spot. The usual approach treats the whole crawl space as one area to be managed.
Covering the floor with a sealed membrane
The first step in a typical crawl space system is covering the ground with a plastic membrane. The membrane acts as a barrier between the soil and the air in the crawl space. It is sealed so that soil gas has a harder time escaping into the space around it.
The membrane by itself is not the full answer. It creates a covered, enclosed area under it, and that area is what the next step uses.
Venting from beneath the membrane
The second step is called sub-membrane depressurization. A vent pipe is connected to the area under the membrane, and a fan draws the soil gas out. The pipe carries the gas outside and releases it above the roof line, away from windows and living areas.
This is the crawl space version of active soil depressurization, which is the most common radon reduction method. Instead of drawing from under a concrete slab, the system draws from under the plastic cover. The goal is to pull gas away from the home before it can drift upward.
Many systems include a simple pressure gauge that shows the fan is running. It is worth knowing where yours is and glancing at it from time to time.
Sealing openings as part of a system
Sealing gaps still has a role. Openings around pipes, wires and other penetrations in the foundation can be closed as part of the overall system. This makes the venting work better and limits the paths radon can take.
EPA does not recommend sealing cracks and openings as the only way to reduce radon. For that reason, sealing is not relied on alone. It works alongside the membrane and the vented fan, not in place of them.
Why this matters around Prescott
Prescott sits at about 5,400 feet in the Bradshaw Mountains. The Granite Dells granite just north of the city is about 1.4 billion years old and has an unusually high uranium content, according to the Arizona Geological Survey. The Survey notes that radon from this granite is a concern for people who build weather-tight homes on the rock.
That is worth thinking about for homes in newer subdivisions toward the Granite Dells, Prescott Lakes and the Willow Creek Road area. It also matters for older neighborhoods such as Miller Valley and Fort Whipple, and for homes along roads like Williamson Valley Road, Iron Springs Road and White Spar Road. Any home can have a radon problem, whether it is new or old.
Daily temperature swings here average nearly 30 degrees F, and winters bring light snow. In cooler months many people keep their homes closed up. A tightly closed home can hold radon in, which is one reason testing matters.
Test first, then retest
Testing is the only way to know a home's radon level. EPA recommends fixing a home at 4 pCi/L or higher and says to consider fixing it between 2 and 4 pCi/L. Our radon testing page covers how tests work and how to read a result.
After a system is installed, EPA recommends retesting to confirm it is working. It also recommends retesting about every two years and after major renovations. If you finish or change a crawl space later, check with a professional about the system.
Getting a quote and finding a professional
Cost depends on the foundation type, size and layout of the home. Professionals give a quote after looking at the crawl space, so there is no way to say in advance what a job will involve.
Arizona does not run a state radon certification program. EPA recommends hiring a nationally certified radon professional, such as one certified through the National Radon Proficiency Program or the National Radon Safety Board. This site connects callers with licensed and insured local professionals, and help is available in Prescott, Prescott Valley, Chino Valley, Dewey-Humboldt and across Yavapai County. Call (928) 582-8914 to talk through your crawl space.