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Does opening windows reduce radon?

By Radon411 Editorial TeamUpdated How we research

Short answer

Opening windows can lower radon for a while, because outdoor air dilutes the radon indoors, but it is only temporary: once the windows are closed, levels most often return to where they were within about 12 hours. It costs heated or cooled air and is not considered radon mitigation.

Next step: a certified professional designs and installs the fix. Find a mitigation professional

Opening windows, doors and vents on the lower floors adds ventilation and mixes outdoor air with indoor air. The drawbacks are lost heated or cooled air, much higher costs to condition the outside air, discomfort and security concerns, which is why it counts only as a temporary measure.

are required during a short-term radon test for the same reason: a test run with the windows open describes the open house, not the home as it is lived in most of the year.

What to do next: test with the house closed up; if the result is high, a soil suction system lowers radon around the clock without relying on open windows.

What opening windows does to radon

Opening windows, doors and vents on the lower floors increases ventilation. The extra outdoor air mixes with indoor air that contains radon, and that can lower the radon level for as long as the openings stay open. Some natural ventilation happens in every home; opening up simply adds more.

Windows open and closed
AspectWindows openWindows closed again
Radon levelCan drop as outdoor air dilutes indoor airMost often returns to where it was within about 12 hours
CostHeated or cooled air is lost, and conditioning outside air costs much moreBack to normal
PracticalityDiscomfort, energy cost and security concernsNone

That is why natural ventilation is treated only as a temporary way to reduce radon, and is not counted as radon .

How ventilation compares with a radon system

Some techniques keep radon from entering the home; others reduce it after it has entered. The ones that prevent entry work best, which is why soil suction, drawing radon from below the house and venting it above the roof, is the most common and usually the most reliable fix.

Typical radon reduction, EPA

Basement and slab-on-grade homes

  • Subslab suction (subslab depressurization)50 to 99 percentWorks best if air can move easily in material under slab.

Crawlspace homes

  • Submembrane depressurization in a crawlspace50 to 99 percentLess heat loss than natural ventilation in cold winter climates.
  • Natural ventilation in a crawlspace0 to 50 percentCosts variable.

Any type of home

  • House (basement) pressurization50 to 99 percentWorks best with tight basement isolated from outdoors and upper floors.
  • 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.
Typical radon reduction for suction and for ventilation methods. Methods described only in words, such as natural ventilation, get no bar.

Subslab suction typically lowers radon by 50 to 99 percent and keeps working around the clock. Natural ventilation's effect is variable and temporary, and crawlspace ventilation typically manages 0 to 50 percent. More on the permanent fixes is in how to reduce radon.

Ventilation methods that can help

Ventilation approaches to radon
MethodHow it worksLimits
Crawlspace ventsOpening or adding vents lowers radon by reducing the home's suction on the soil and diluting radon under the housePipes, sewer lines and appliances may need insulating in cold climates, and energy costs can rise
Crawlspace fanA fan blows air through the crawlspace instead of relying on natural circulationThe same energy and freezing concerns
Heat recovery ventilatorBrings in outdoor air while using outgoing air to warm or cool itVariable effect; works best ventilating only the basement; must run all the time; heating and cooling costs can rise
House pressurizationA fan pushes air into the lowest level to hold radon outCan bring in moisture and raise energy use; only worth trying after the common techniques fall short

In a home that is not above the , opening windows and running fans and vents to circulate air, together with sealing cracks, are reasonable ways to keep radon as low as possible. Test again after any change. For basement fans, see would an exhaust fan in a basement reduce radon.

Windows and radon tests

Because open windows lower the reading for a while, are run with the house closed: windows shut, doors closed except for normal coming and going, and no fans bringing in outside air. For a test of 2 to 4 days, the house is closed for at least 12 hours before it starts.

Windows before and during a short-term test
WhenWindows
At least 12 hours before a 2- to 4-day testClosed
During the testClosed, with doors used only for normal entry and exit
If they are opened anywayThe result may be invalid, and interfering with a test is illegal in some states

A test taken with the house open describes the open house, not the closed-up home you live in most of the year. See can a radon test be manipulated.

Questions about windows and radon

Can you reduce radon by opening windows?

Temporarily. Opening windows dilutes radon while they stay open, but once they are closed, levels most often return within about 12 hours. It is not a substitute for mitigation.

Does opening basement windows reduce radon?

Opening windows, doors and vents on the lower floors adds ventilation and can lower radon for as long as they stay open.

How long does radon take to come back after closing the windows?

Most often about 12 hours. The source never stops: air pressure inside a home is usually lower than in the soil around it, so the house keeps drawing radon in through foundation cracks and other openings.

Do crawlspace vents reduce radon?

They can. Opening or adding crawlspace vents may lower indoor radon by reducing the home's suction on the soil and diluting the radon beneath it, typically by 0 to 50 percent. A sealed plastic sheet with a pipe and fan does far more.

Is opening windows enough if my level is high?

No. Natural ventilation is only a temporary approach. At or above the action level, the fix is a mitigation system, usually soil suction.

Do window fans help?

Fans and vents that circulate air are among the steps for keeping radon low in a home below the action level, but natural ventilation is only temporary, and fans that bring in outside air must be off during a short-term test.

Can I open the windows during a radon test?

No. Keep windows closed during a short-term test, and for a 2- to 4-day test close them at least 12 hours before it starts. See how to test for radon.

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