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.
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.
At a glance · 1 min read
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.
| Aspect | Windows open | Windows closed again |
|---|---|---|
| Radon level | Can drop as outdoor air dilutes indoor air | Most often returns to where it was within about 12 hours |
| Cost | Heated or cooled air is lost, and conditioning outside air costs much more | Back to normal |
| Practicality | Discomfort, energy cost and security concerns | None |
That is why natural ventilation is treated only as a temporary way to reduce radon, and is not counted as radon
In a picture · 1 min read
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
Crawlspace homes
Any type of home
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.
At a glance · 1 min read
| Method | How it works | Limits |
|---|---|---|
| Crawlspace vents | Opening or adding vents lowers radon by reducing the home's suction on the soil and diluting radon under the house | Pipes, sewer lines and appliances may need insulating in cold climates, and energy costs can rise |
| Crawlspace fan | A fan blows air through the crawlspace instead of relying on natural circulation | The same energy and freezing concerns |
| Heat recovery ventilator | Brings in outdoor air while using outgoing air to warm or cool it | Variable effect; works best ventilating only the basement; must run all the time; heating and cooling costs can rise |
| House pressurization | A fan pushes air into the lowest level to hold radon out | Can bring in moisture and raise energy use; only worth trying after the common techniques fall short |
In a home that is not above the
At a glance · 1 min read
Because open windows lower the reading for a while,
| When | Windows |
|---|---|
| At least 12 hours before a 2- to 4-day test | Closed |
| During the test | Closed, with doors used only for normal entry and exit |
| If they are opened anyway | The 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 · 1 min read
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.
Opening windows, doors and vents on the lower floors adds ventilation and can lower radon for as long as they stay open.
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.
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.
No. Natural ventilation is only a temporary approach. At or above the action level, the fix is a mitigation system, usually soil suction.
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.
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.
How a mitigation system brings a high level down, the fan that runs it, and what it costs.
What gets rid of radon, how reduction and abatement work, and what they cost.
Read the guideHow a radon mitigation fan works, where it goes, what it costs to run and replace.
Read the guideHow mitigation systems reduce indoor radon, when to mitigate instead of retest, what a project involves, common mistakes, and how to confirm a system actually worked.
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