here are a few reasons why radon levels in Twin Cities homes are higher in winter than at other times of year. One of the main reasons is something known as the “stack effect“: when the air indoors is much warmer than the air outdoors, a vacuum is created in the lower levels of the home. This vacuum effect pulls soil gases like radon into homes at an increased rate.

Another reason that indoor radon levels rise in winter is because homes tend to be closed up with little ventilation. With windows opened and air conditioning running frequently during summer, radon gas is often vented from within homes. But in winter, with the heat running and the windows always closed, radon will quickly accumulate in a home. On top of this, snow and ice can block soil surfaces, forcing radon sideways into foundations instead of letting it escape into the atmosphere.