Radon system

Most of a radon system is a white plastic pipe. Minnesota's mitigation page describes systems that use a fan to continuously pull air from the soil and vent it outdoors through a pipe that ends above the edge of the roof, and says the pipe can either run inside or outside the home. Its component list is the clearest inventory of the parts.

Exterior radon mitigation system or a pipe inside the house

Both are common, and Nebraska describes each. In one, the pipe rises from the suction point to the floor joists, runs horizontally to the outside, and the fan is installed on the outside of the house, just above the point where the pipe exits the side of the house; the exhaust must still end 10 feet above the ground and 2 feet above any windows or doors within 10 feet. In the other, the pipe runs into an attached garage, up through the garage ceiling, and the fan sits on the pipe in the attic above. An exterior fan must be hard-wired into an electric circuit; an attic fan can plug into an outlet within six feet of it.

EPA's Consumer's Guide explains why soil suction is the method EPA generally recommends: soil suction prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe, or pipes, to the air above the home where it is quickly diluted. The fan creates a negative pressure or vacuum beneath the slab, so soil gas moves toward the pipe instead of into the rooms. People search for this as a radon pump system or a radon vent system; EPA's name is soil suction, or subslab depressurization.

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Typical radon reduction, EPA

0%25%50%75%100%

Basement and slab-on-grade homes

• Subslab suction (subslab depressurization)50 to 99 percentWorks best if air can move easily in material under slab.
• Passive subslab suction30 to 70 percentMay be more effective in cold climates; not as effective as active subslab suction.
• Drain tile suction50 to 99 percentCan work with either partial or complete drain tile loops.
• Block-wall suction50 to 99 percentOnly in homes with hollow block-walls; requires sealing of major openings.
• Sump-hole suction50 to 99 percentWorks best if air moves easily to sump from under the slab.

Crawlspace homes

• Submembrane depressurization in a crawlspace50 to 99 percentLess heat loss than natural ventilation in cold winter climates.

Any type of home

• Natural ventilationVariable/TemporarySignificant heated or cooled air loss; operating costs depend on utility rates and amount of ventilation.
• Heat recovery ventilation (HRV)VariableLimited use; effectiveness limited by radon concentration or the amount of ventilation air available for dilution by the HRV.

Radon ventilation: why soil suction beats opening windows

Radon ventilation, meaning more outdoor air, can lower radon too, but EPA treats it as a stopgap. Its Consumer's Guide says that once windows, doors and vents are closed, radon concentrations most often return to previous values within about 12 hours, and that natural ventilation should normally be regarded as only a temporary radon reduction approach. EPA describes a heat recovery ventilator as a way to add ventilation that, if properly balanced and maintained, stays constant throughout the year, and says HRVs are more effective in reducing radon levels when used to ventilate only the basement.

Do central heating and cooling systems spread radon inside a home?

They can. EPA's Building Radon Out says air handlers and leaky return ducts can not only draw in radon, they can also distribute it throughout a home, and that ducts passing through a crawlspace or beneath a slab should be of seamless material or sealed tightly. EPA's Home Buyer's and Seller's Guide lists changes in the heating, ventilation, and air conditioning (HVAC) system among the changes that might affect radon levels, which is one reason to retest after HVAC work.

A radon system should leave you with a label, a set of instructions and a file. EPA's Consumer's Guide says radon reduction systems must be clearly labeled, to avoid accidental changes to the system that could disrupt its function, and asks the contractor to completely explain the system, demonstrate how it operates and explain how to maintain it, with written operating and maintenance instructions and copies of any warranties.

The U-tube manometer is the gauge most systems carry. Minnesota's safety sheet describes it: it uses colored fluid in a tube to visually indicate the radon system is working, a small tube connects to a hole in the radon pipe, and the suction from the fan pulls the fluid up. Pennsylvania's rule for reading it is simple: the fan is running if the levels of fluid on each side of the glass tube are uneven.

1. 1

   Find the start-up reading

   Minnesota says the reading taken at installation is written on a sticker next to the manometer. EPA's 1994 standards require the gauge to be marked with the range of pressure readings that existed when the system was first activated.

2. 2

   Look at the fluid

   Uneven sides mean the fan is pulling. Even sides mean the fan stopped working or another part of the system is not working properly, Minnesota says.

3. 3

   Compare with the sticker

   Minnesota treats fluid levels that are even or significantly different than when the system was installed as a sign the system may not be functioning properly.

4. 4

   Check monthly

   Minnesota says both fan monitors should be checked monthly, along with the power source of the active notification monitor.

5. 5

   Retest on schedule

   The gauge shows suction, not radon. Only a radon test shows the level in the house.

How much vacuum should a radon system have?

There is no single right number. The right reading is the one your system had when it was installed and tested, because each system is sized to its own house. That is why EPA's 1994 standards have the installer measure suctions or flows in system piping or ducting to assure that the system is operating as designed, and mark the gauge with that range. A reading that drifts well away from the mark, up or down, is a reason to call the installer.

EPA's Consumer's Guide compares a radon system to a furnace or chimney: radon reduction systems need occasional maintenance, and maintaining one takes little effort and keeps the system working properly and radon levels low. The schedule below brings together what EPA and the state programs ask of an owner.

How long does a radon mitigation system last?

The pipe and sealing are meant to stay: EPA's 1994 standards require every system to be designed and installed as a permanent, integral addition to the building. The fan is the part that wears. EPA says fans may last for five years or more, that manufacturer warranties tend not to exceed five years, and that fans may then need to be repaired or replaced. EPA's FAQ puts a replacement at around $200 - $350 including parts and labor.

The first test after installation is the proof the system works. EPA's Consumer's Guide says a post-mitigation radon test should be done within 30 days of system installation, but no sooner than 24 hours after your system is in operation with the fan on, and recommends a two- to seven-day measurement with windows and doors closed 12 hours before and during the test, except for normal entry and exit. It recommends an independent follow-up measurement too, since having an independent tester or conducting the measurement yourself will eliminate any potential conflict of interest.

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1. Day of installation

   The system goes in

   Keep the fan running at all times: it must run continuously for the system to work correctly.

2. No sooner than 24 hours

   Earliest post-mitigation test

   Test no sooner than 24 hours after your system is in operation with the fan on, if it has one.

3. Within 30 days

   Post-mitigation test done

   A two- to seven-day measurement is recommended, and EPA recommends an independent follow-up radon measurement as well as any test the contractor runs.

4. At least every two years

   Retest

   Retest your home at least every two years to be sure radon levels remain low.

Test conditions: Windows and doors must be closed 12 hours before and during the test, except for normal entry and exit. Not drawn to scale.

After a remodel. After you remodel, retest in the lowest lived-in area to make sure the construction did not reduce the effectiveness of the radon reduction system.

How long after radon mitigation can you retest?

After at least a day of the fan running, and within 30 days: that is EPA's Consumer's Guide window, and Minnesota's sheet sets the same one, a short-term radon test between 24 hours and 30 days after the system is installed. See how long after radon mitigation can you retest.

Read each result against EPA's guidance. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. If a system is already installed and the result is still high, Minnesota says additional work may need to be performed to further lower the radon levels. The interpreter reads a result for you.

A system that stops working stops reducing radon. EPA says that if your monitor shows the system is not working properly, call a contractor to have it checked. Before that, a few causes are simple to rule out.

Minnesota's safety sheet lists openings its installers sometimes cannot reach, such as openings to the soil under a basement bathtub or shower, large covered cracks, and a floor-wall gap that must stay open to drain groundwater into a waterproofing system. It says these could make the radon system less efficient, less effective, or more costly to operate, and that they should be noted in the system paperwork.

The suction only exists while the fan runs, so a system that is off is not reducing radon. EPA's Consumer's Guide also says HRVs used for radon control should run all the time. See can I turn off my radon system.

EPA's Consumer's Guide says systems that use fans are more effective in reducing radon levels; however, they will slightly increase your electric bill. It adds that most systems cause some loss of heated or air conditioned air. Minnesota's safety sheet gives the fan's share, at a price of $0.10 per kilowatt hour.

The larger cost can be the conditioned air. Minnesota's estimate does not include energy lost because heated or cooled air from the building is vented to the outside by the radon mitigation system through unsealed openings to the soil. Sealing cracks, EPA says, reduces the loss of conditioned air. The radon fan guide has the full table.

A working system is what lowers the risk. EPA's Consumer's Guide says the lower the radon level in your home, the lower your family's risk of lung cancer, and that some radon reduction systems can reduce radon levels in your home by up to 99 percent. The system has two safety checks of its own that owners should know about.

Remodeling can change how well a system works. EPA's Consumer's Guide says that if you plan major structural changes, such as converting an unfinished basement area into living space, ask your radon contractor whether these changes could void any warranties; if you plan a new foundation for an addition, ask what measures should be taken to ensure reduced radon levels throughout the home; and after you remodel, retest in the lowest lived-in area to make sure the construction did not reduce the effectiveness of the system.

1. 1

   Before the work

   Ask the radon contractor whether the plans affect the system or its warranty, and keep the pipe, labels and gauge accessible.

2. 2

   During the work

   Do not cut, move or cover the pipe or unplug the fan. EPA says labels are there to avoid accidental changes to the system.

3. 3

   New openings

   Minnesota lists new sumps, drain tiles, sewer lines and shower or tub retrofits among openings to soil that call for a retest.

4. 4

   After the work

   Retest in the lowest lived-in area, as EPA advises.

A radon system is part of the house when it changes hands. EPA's Consumer's Guide says that if you are selling a home that has a radon reduction system, inform potential buyers and supply them with information about your system's operation and maintenance. EPA's Home Buyer's and Seller's Guide tells buyers: if the home has a radon-reduction system, ask the seller for any information they have about the system.

• Ask for the installation date, the installer and the system label.
• Ask for the pre- and post-mitigation test results and any later retests.
• Ask for the operating and maintenance instructions and warranties, and whether any warranty transfers to you, as EPA's contract checklist suggests asking.
• Look at the manometer: uneven fluid means the fan is running.
• Test with the fan running, as EPA's checklist requires, in the lowest level you will use.

Does a radon mitigation system hurt resale?

EPA's guides say the opposite. The Citizen's Guide says that where radon problems have been fixed, home sales have not been blocked or frustrated, and that the added protection is sometimes a good selling point. More in buying a house with radon, selling a house with radon and does a radon mitigation system hurt resale.

• The fan runs all the time and is never switched off.
• The manometer shows uneven fluid, close to the reading written at installation.
• Both fan monitors are checked monthly, and the alarm has power.
• The system is labeled, and the breaker for the fan is labeled.
• The operating instructions, warranties and every test result are in one folder.
• A post-mitigation test was done within 30 days of installation.
• The home is retested at least every two years, and after any renovation.
• Any HRV filter is cleaned and changed on schedule, and the HRV runs all the time.
• Anyone working on the house knows not to cut, move or cover the pipe.