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Radon in a Crawl Space: Where to Test and How It Is Fixed
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Where to put the test kit
- EPA: place the kit in the lowest lived-in level of the home, in a room used regularly but not the kitchen or bathroom, at least 20 inches above the floor.
- New Jersey: a crawl space is not a livable area. Measurements should not be made in kitchens, laundry rooms, closets, bathrooms or crawlspaces.
- North Dakota: if you have a crawl space, you should consider testing in the room above it.
Our test kit guide has the full steps. These sources do not say what a reading taken inside a crawl space would mean, so we do not interpret one.
How radon is reduced in a crawl space home
EPA says a home can have more than one foundation type, such as a basement under part of the home and a crawlspace under the rest. In that case a combination of techniques may be needed to get below 4 pCi/L.
| Method (EPA) | What it is | Typical radon reduction (EPA) |
|---|---|---|
| Submembrane suction | High-density plastic sheet over the earth floor. A vent pipe and fan draw radon from under the sheet and vent it outdoors. EPA calls it the most effective way when properly applied. | 50 to 99 percent |
| Active crawlspace depressurization | A fan draws air directly from the crawlspace. EPA says it generally does not work as well, needs attention to combustion appliance backdrafting, and can raise energy costs. | Not listed in the table |
| Natural ventilation of the crawlspace | Opening or adding vents. EPA says it can lower radon by reducing the home's suction on the soil and diluting radon under the home. | 0 to 50 percent |
Source: EPA, A Consumer's Guide to Radon Reduction, December 2016.
EPA says active ventilation uses a fan to blow air through the crawlspace. In colder climates, water pipes, sewer lines and appliances in the crawlspace may need insulating against the cold, and ventilation could raise energy costs.
Who should do the work
EPA recommends a qualified radon mitigation contractor. See how to find a certified contractor. Check local codes, and use licensed pros for any electrical work. After the system is in, test again.
Haven't tested the living level yet?
Testing is the only way to know your radon level. A mail-in kit is a low-cost way to start, and our guide shows how to place it so the result is reliable.
How to use a radon test kitBrowse radon test kitsCommon questions
Should I put a radon test in the crawl space?
Not usually. New Jersey says a crawl space is not a livable area and that measurements should not be made in crawlspaces. North Dakota says that if you have a crawl space, consider testing in the room above it. EPA says to place the kit in the lowest lived-in level of the home.
Can a home with a crawl space have radon?
Yes. EPA says any home may have a radon problem, including homes with or without basements.
What is the best radon fix for a crawl space?
EPA says submembrane suction, when properly applied, is the most effective way to reduce radon in crawlspace homes. A high-density plastic sheet covers the earth floor, and a vent pipe and fan draw the radon from under the sheet and vent it outdoors.
Will more crawl space vents fix it?
Sometimes, but not as well. EPA says crawlspace ventilation may lower indoor radon, and its table lists 0 to 50 percent for natural ventilation in a crawlspace, compared with 50 to 99 percent for submembrane suction. EPA says ventilation could raise energy costs and, in cold climates, pipes and appliances may need insulating.
Related guides
- U.S. EPA: Consumer’s Guide to Radon Reduction: How to Fix Your Home (EPA 402/K-10/005, December 2016)
- U.S. EPA: A Citizen’s Guide to Radon (EPA 402/K-12/002)
- North Dakota Department of Environmental Quality: Guidelines for Radon Testing in Residences
- New Jersey DEP Radon Program: Guidelines for Radon Testing in New Jersey
Free printable: Radon Test Day Checklist
EPA's testing steps in one page, plus what your result means. Download the one-page PDF now, or get it by email along with a short series of five helpful emails.