How to hire a radon mitigation contractor: credentials, bids and the contract

Your radon test came back at or above 4 picocuries per liter (pCi/L), EPA's action level, or between 2 and 4 pCi/L, where EPA says to consider fixing. The next step is hiring someone to install a radon reduction system. EPA recommends using a certified or qualified radon mitigation contractor, because, in its words, without the proper equipment or technical knowledge "you could actually increase your radon level or create other potential hazards."

This guide follows EPA's Consumer's Guide to Radon Reduction step by step: checking credentials, comparing estimates, and making sure the contract protects you.

Step 1: Start with your state radon office

Every state has a radon program or contact, listed by EPA and on each of our state radon pages. Call or check the website first. Your state office can tell you:

• whether your state licenses or certifies radon mitigation contractors (many do, and some require it by law);
• where to find the list of credentialed contractors in your area;
• whether there are local rules, such as permits, for installing a system;
• whether the state has data on typical radon levels in your county.

If your state licenses contractors, hire only a licensed one. It's usually the strongest protection you have.

Step 2: Check national credentials

In states that don't regulate radon services, EPA says to ask whether the contractor holds a professional proficiency or certification credential and follows industry consensus standards. EPA recognizes two national radon proficiency programs:

• the National Radon Proficiency Program (NRPP);
• the National Radon Safety Board (NRSB).

Both publish searchable lists of credentialed professionals. EPA notes that these programs usually give members a photo ID card showing their qualification. Ask to see it, and confirm the credential is current on the program's website. A mitigation credential is different from a measurement (testing) credential, so make sure the contractor holds the right one.

Also ask which installation standard they follow. EPA points to ASTM E2121, the standard practice for installing radon mitigation systems in existing low-rise homes.

Step 3: Get more than one estimate

EPA suggests getting estimates from more than one qualified contractor. Most homes can be fixed for about the same cost as other common home repairs, according to EPA, but the price depends on the home's size, foundation and the method needed. A contractor should look at the house before quoting. EPA's checklist asks:

• Did the contractor inspect your home's structure before giving an estimate?
• Did they review your radon test results and check whether proper testing procedures were followed?
• Does the proposal include diagnostic testing before the system is designed? (Often a "pressure field extension" test that checks how well suction spreads under the slab.)
• Does it include a warning device to tell you if the system stops working?
• Does it include testing after installation to make sure the system works?
• Is there a guarantee to reduce radon to 4 pCi/L or below, and for how long?
• Does the contractor show proof of state certification or a national credential, liability insurance, bonding, and the licenses required locally?

Comparing bids fairly

The cheapest bid isn't always the best value. EPA's guide points out that:

• a less expensive system may cost more to operate and maintain;
• a less expensive system may look worse, for example with the vent pipe running up the front of the house;
• a more expensive system may be best for your home;
• the quality of materials affects how long the system lasts.

Ask each contractor where the pipe will run, where the fan will sit, where the exhaust will discharge, how they'll seal the sump or major cracks, and how much the fan will add to your electric bill.

Step 4: Know what a good installation looks like

You don't need to design the system, but knowing EPA's basics helps you spot a bad proposal.

• Soil suction is the usual method. In homes with a basement or slab-on-grade foundation, EPA says radon is usually reduced by one of four types of soil suction: subslab, drain-tile, sump-hole or block-wall suction. Active subslab suction (subslab depressurization) is "the most common and usually the most reliable." Our guide to radon mitigation systems explains how it works.
• Crawlspaces get a membrane. EPA calls submembrane suction, a sealed plastic sheet over the crawlspace floor with a pipe and fan, the most effective approach for crawlspace homes.
• The exhaust must vent safely. EPA says soil suction exhaust pipes must vent above the surface of the roof and 10 feet or more above the ground, and at least 10 feet from windows, doors or other openings that could let radon back in, if the pipe doesn't vent at least 2 feet above them.
• The fan must not sit in or below living space. EPA says it should go in unconditioned space such as an attic or outside, and an outdoor fan must meet local codes for exterior use.
• The system must be labeled, so no one later disconnects or changes it by accident.
• Sealing helps but isn't enough alone. Sealing cracks and openings is part of most systems, but EPA doesn't recommend sealing alone as a fix.

If a proposal relies on an air purifier, a "radon-absorbing" paint or sealing alone, ask why, and get a second opinion.

Step 5: Get a written contract before work begins

EPA says to ask the contractor to prepare a contract before any work starts, read it before you sign, and make sure it matches the proposal. The contract should include:

• the total cost, including taxes and permit fees, and how much is due upfront (if any);
• what work will be done before and during installation, what the system consists of, and how it will operate;
• a statement that the contractor carries liability insurance and is bonded in case of injury or property damage during the job;
• a guarantee that the contractor is responsible for damage during the job and cleanup afterward;
• details of any guarantee to reduce radon below a negotiated level, such as 2 pCi/L, and the conditions attached;
• details of warranties on the fan and other hardware;
• a statement that the contractor will follow state and local building codes and get any required permits.

EPA also suggests considering optional additions that may cost more upfront but be worth it, such as an extended warranty, a service plan or improved appearance.

Step 6: Test after it's installed

EPA recommends a post-mitigation radon test within 30 days of installation, but no sooner than 24 hours after the system starts running with the fan on. Use a 2- to 7-day test, with windows and doors closed for 12 hours before and during the test except for normal entry and exit.

The contractor may run its own test, and that's fine. EPA also recommends an independent follow-up test, either by a separate tester or a kit you place yourself, to avoid any conflict of interest. Our guide to how to test your home for radon explains placement, and the radon level calculator puts your result in context.

Before the contractor leaves, EPA says to make sure they explain the system, show how it operates and how to maintain it, and give you written operating and maintenance instructions and copies of any warranties.

Red flags

• No state license where one is required, or no current national credential.
• A quote over the phone without seeing the house or the test results.
• Pressure to sign the same day, or a large cash deposit.
• No warning device, no post-installation test, or no written contract.
• An exhaust that discharges at ground level or next to a window.
• A contractor who sold you the test and is now selling the fix, with no option for an independent retest.

When you're buying or selling

Real estate deals often have short deadlines. The same steps apply, but plan ahead: get estimates early, and make sure the contract says who pays and who handles the post-mitigation test. Our guide to radon when buying or selling a home covers negotiating repairs.

After the job

Keep the contract, the warranty, the before-and-after test results and the maintenance instructions together. They matter when you sell. Then read our guide to living with a radon mitigation system for the manometer, the fan and retesting.