Does Opening Windows Reduce Radon? Here's What Quebec Homeowners Need to Know

If you've recently learned about radon, one of the first questions you might ask is: Can I simply open my windows to lower radon levels?

The short answer is yes—but only temporarily.

While opening windows can improve ventilation and may reduce indoor radon concentrations for a short period, it is not a reliable or permanent solution. If your home has elevated radon levels, the only proven way to keep them low over the long term is through a professionally designed radon mitigation system.

Here's what homeowners in Montreal and across Quebec should know.

What Is Radon?

Radon is a naturally occurring radioactive gas that forms as uranium breaks down in soil and rock. It is invisible, odourless, and tasteless, making it impossible to detect without specialized testing.

As radon rises from the ground, it can enter homes through:

• Foundation cracks

• Construction joints

• Gaps around plumbing or utility lines

• Floor drains

• Sump pits

• Crawl spaces

Once inside, radon can accumulate to levels that pose a health risk, particularly in lower levels of the home.

According to Health Canada, radon is the leading cause of lung cancer among non-smokers and is responsible for more than 3,200 lung cancer deaths each year in Canada.

Does Opening Windows Help?

Opening windows increases the exchange of indoor and outdoor air, which can temporarily dilute radon concentrations inside your home. In addition make sure to open minimum two windows per floor to create a cross ventilation. Opening one window per floor may actually cause increase in radon levels, also turning your bathroom fan will increase radon.

However, this reduction is usually:

• Temporary

• Inconsistent

• Weather dependent

• Difficult to maintain year-round

As soon as the windows are closed, radon entering through the soil can begin accumulating again.

For this reason, simply opening windows should never be considered a substitute for radon mitigation if testing shows elevated levels.

Why Opening Windows Isn't a Permanent Solution

Radon Is Continuously Entering Your Home

Radon isn't generated inside your house—it comes from the soil beneath it.

Even while windows are open, new radon gas continues entering through the foundation.

Once the windows close, indoor levels can rise again within hours or days depending on:

• Soil conditions

• Air pressure

• Weather

• Home construction

• HVAC operation

Quebec Winters Make It Impractical

For homeowners in Montreal and throughout Quebec, keeping windows open for extended periods simply isn't realistic.

During winter months:

• Heating costs increase significantly.

• Cold outdoor air reduces comfort.

• Frozen pipes can become a concern.

• Energy efficiency suffers.

Ironically, winter is also when many homes experience higher radon levels because houses are sealed tightly to conserve heat.

What About Airing Out the Basement?

Some homeowners believe they can solve a radon problem by opening basement windows.

While this may lower readings temporarily during the ventilation period, it does not stop radon from entering the home.

Think of it like mopping up water while a pipe continues leaking—you may reduce what's visible for a short time, but the source of the problem remains.

Can Fans Help?

Portable fans, bathroom fans, or ceiling fans may move air around your home, but they are not designed to remove radon from its source.

In some situations, fans can even change the pressure inside the home in ways that increase radon entry from the soil.

Because every home is different, relying on fans alone is not recommended as a radon reduction strategy.

The Only Way to Know Your Radon Level Is to Test

Because radon cannot be seen or smelled, testing is the only way to determine whether your home has elevated levels.

Health Canada recommends long-term testing for at least 91 days, ideally during the heating season when homes are closed up and readings are most representative of typical exposure.

Even if your neighbour's home tested low, your own home could have very different radon levels. Two houses built side by side can produce significantly different results because of differences in soil conditions, foundation construction, ventilation, and air pressure.

What Happens If Your Results Are High?

If testing shows radon levels above Health Canada's guideline of 200 Bq/m³, (our recommendation is above 100 Bq/m3) the next step is to install a radon mitigation system.

The most common solution is active soil depressurization, which works by:

• Drawing radon gas from beneath the foundation

• Venting it safely through the foundation wall as low to the ground as possible

• Preventing the gas from entering your living space

Professionally installed systems can often reduce radon levels by 80% to 99%, providing long-term protection for your household.

Should You Leave Windows Closed During a Radon Test?

For long-term radon testing, homeowners should continue living normally.

There is no need to keep windows permanently closed, but avoid making unusual changes to your home's ventilation solely to influence the results. The goal is to measure the radon levels your family is actually exposed to during everyday living.

Following the testing instructions provided with your radon test kit will help ensure accurate and meaningful results.

Protect Your Home With Confidence

Opening a window may provide a brief reduction in indoor radon levels, but it does not address the source of the problem. If your home has elevated radon, the most effective solution is to identify the issue through proper testing and, if necessary, install a professionally designed mitigation system.

At Radon Montreal, we help homeowners across Montreal and surrounding communities understand their radon risk through reliable self testing and proven professional mitigation solutions. Whether you're purchasing a home, have never tested before, or recently received elevated results, our team is here to help you create a healthier indoor environment for your family.

Ready to find out if your home's radon level is safe? Contact Radon Montreal today to learn more about self radon testing and mitigation services.