How Hard Is It to Sell a House with High Radon Levels?

With the Environmental Protection Agency estimating that nearly 1 out of every 15 homes in the United States has elevated radon levels, you might be anxious about whether radon in your home will be an obstacle to selling your house.

Radon is a radioactive gas that is so prevalent, we’re exposed to it daily. It only becomes dangerous when it accumulates to certain levels, increasing the risk of lung cancer, says the National Cancer Institute (NCI) in Bethesda, Maryland. Scientists estimate that 15,000 to 22,000 lung cancer deaths nationwide each year are related to radon.

Fortunately, it’s not hard to sell a house with radon, provided that you alert potential buyers and mitigate the problem, say Brian Thomas, a top real estate agent in the Denver, Colorado area, with 16 years of experience. “For as much fear and uncertainty as radon causes, there’s an easy fix.”

Why is radon so common in American households?

Radon is an odorless, tasteless, invisible gas released from the normal decay of certain elements in rocks and soil: uranium, thorium, and radium. It typically diffuses into the air, but it can dissolve into groundwater, then disperse when the water is used.

“Every house either has radon, had radon, or will have radon,” said Thomas.

That’s no exaggeration. Radon moves through a home via cracks in floors or walls, construction joints, and gaps in foundations around pipes, pumps, and wires. Because it’s such a heavy gas, radon tends to collect in low-lying areas without adequate ventilation, such as basements and crawl spaces, although even homes without basements can have a radon issue.

However, you need to be concerned when the radon level in your home registers 4 pCi/L (picocuries per liter of air), experts say.

Although the American Cancer Society says that elevated radon levels have been found in every state, an EPA map of radon zones offers more detail, showing that predicted average indoor screening levels of 4pCi/L often turn up in northern states such as Maine, Idaho, Montana, North Dakota, and Iowa.

This level of indoor radon also appears on average through parts of Wyoming, Colorado, Nevada, Utah, Washington State, Minnesota, Wisconsin, and northeastern and central states such as Illinois, Ohio, and Pennsylvania, the map shows.

No part of the country is free from radon, with at least 2 pCi/L appearing on average in southern states such as Texas, Louisiana and Florida, as well as Alaska and Hawaii.

Testing for radon

 Two short-term tests of two to three days each, or a long-term test of 90 days are certified ways to measure the radon in your home.

The test needs to last for such a long time because interior radon levels can fluctuate based on the ground shifting and other factors. “One day it could be sky high, and the next day, nothing. I’ve seen that over and over again,” Thomas said.

To be valid, the test should be recent, e.g., within two years, especially if you’ve renovated or altered your home since a previous test. A radon test involves placing a test kit in the lowest lived-in level of a home at least 20 inches above the floor and away from exterior walls, high heat, and high humidity.

You can test for radon yourself by purchasing a DIY kit at a home improvement store for about $10 to $25. The National Radon Program Services at Kansas State University also offers discounted test kits for purchase online.

While this is a good starting point, the EPA recommends contacting your state radon office for assistance in finding a qualified tester if you’re putting your home on the market. Buyers frequently want an independent party to handle the test, not someone involved in the home sale.

A professional radon gas inspection, which includes a test, averages between $150 and $300, depending on your home’s size. If bundled into the cost of a standard home inspection, expect to pay $90 to $250 on top of the home inspection fee.

Disclosing radon during your home sale

 There is no uniform radon disclosure in the United States. At least 29 states—including Alaska, Delaware, Maine, Maryland, Michigan, New Hampshire, New York, and North Carolina—require disclosure of radon hazards upon the sale of property, according to the National Conference of State Legislatures (NCSL).

Some state laws, such as the Illinois Radon Awareness Act and the Illinois Real Property Disclosure Act, specify not only consumer awareness but licensing for radon testing and mitigation professionals. Check HomeLight’s guide to real estate disclosure laws nationwide to learn more about what your state requires.

In addition, at least nine states, including California, Illinois, Maryland, Minnesota, and Oregon, require all new homes to be built following radon-resistant new construction standards.

Although Colorado does not have a mandatory radon real estate disclosure, Thomas said his clients often have disclosed the results of radon tests, as well as how they’ve addressed the problem, such as by installing a radon mitigation system (more on that below).

“There are a few people that say that they won’t own a home that has radon issues,” he said.

“I would recommend to people that before they put their house on the market to have a home inspection done and have a radon test done. That way, you know what other buyers are going to be looking for, and you will give the buyer peace of mind.

“The more you can put the buyer at ease when they walk in the front door, the better.” 

Does radon reduce home value?

Radon can affect your home’s value, depending on the level present and what you’ve done to mitigate it. Checking for radon isn’t normally in an appraiser’s scope of work, so most appraisers never know if a “market significant” or “detrimental to health” amount of radon is present, said Mike Ford, a general certified real estate appraiser serving greater metropolitan Los Angeles since 1986.

However, an appraiser will look at whether a homeowner or an ASHI-certified home inspector has reported any radon and then check for other similarly affected housing that’s sold—not an easy task, Ford said.

Selling a house with high radon levels

If your home’s radon tests have shown 4 pCi/L or more, you have a couple of options during the sale process.

1. Install a radon mitigation system

The simplest way to reduce radon in a home is to install a mitigation system. According to the EPA’s Consumers Guide to Radon Reduction, the type of mitigation system you need depends on the foundation of your house. Costs will vary based on your home’s construction, design, and your local climate, but the national average cost for installation is $1,200.

For basement and slab-on grade foundations (meaning the concrete is poured at the ground level), the most popular and trusted type of radon mitigation system is active sub slab depressurization, according to the EPA. 

This method uses suction points that are drilled in the subslab (usually four to six inch holes that look like hollow pits). A fan installed in an unconditioned part of the home such as the attic or exterior draws up radon gas through PVC piping and releases it into the air.

Homes with crawl spaces might instead cover the earth floor with a high-density plastic sheet, and use a vent pipe and a fan to force the radon gas outside.

Newer construction may rely on passive mitigation, where pipes are installed in the foundation, creating a natural vacuum and directing the radon out of the house without use of a fan. However, the EPA says this isn’t always as effective and active systems are typically more desirable even for new homes with radon-resistant features.

(Note that some homes have multiple foundation types. In the Midwest, it’s common for a house to have a basement and crawlspace, meaning multiple types of radon mitigation may be required.)

Radon mitigation systems can take from three to five hours to install, and you can expect to see lower radon levels within 24 hours after installation.

The EPA also recommends radon-resistant techniques, such as sealing and caulking all below-grade openings in the foundation.

How to find a trustworthy radon mitigation company

When searching for a mitigation company, whether through referrals from your real estate agent or online directories of home improvement professionals, look for licensing through your state’s environmental health department, or those advertising accreditation through the National Environmental Laboratory Accreditation Program (NELAP).

One of the latter, Air Chek, Inc., founded in 1985, has sold more than 4 million radon test kits worldwide and is a member of the RadonAway referral network, which performs at least 100 to 150 mitigation jobs per year.

Radon mitigation professionals will certify their work, but Thomas said any warranty typically lasts only about two years, because of how the ground level shifts and radon levels change over time. (That’s why the EPA considers a recent radon test to be within the past two years.)

2. Offer buyers a credit

If you don’t have the time or the finances to cover radon mitigation, you can put buyers at ease by offering some type of credit so that they can remedy the problem. Thomas says he’s done this many times, both in terms of offering buyers a credit at closing costs to install a mitigation system, or in having buyers and seller split the cost.

Some mitigation companies “will go ahead and install [a mitigation system] and take the payment out of the proceeds of the sale,” he added. “People don’t have the money to do it up front.”

Whatever you choose, remember that having radon in your home doesn’t mean that it won’t sell. In fact, because radon levels almost always can be reduced, they shouldn’t prohibit a sale, notes the National Radon Program Service at Kansas State University: “As long as the issue is resolved in the real estate transaction, the radon level should not be a deterrent to buying any home.”