Radon is a natural product of uranium decay, and small amounts of uranium are nearly everywhere in the soil. The air on the inside of a home is almost always at a lower pressure than the air in the soil underneath your foundation, especially if you have an energy-efficient home. The negative pressure differential pulls radon gas from the soil into your home through any tiny opening that the gas can move through, such as cracks in your foundation. High levels of radon gas are a health risk—it increases your chances of developing lung cancer.
The only way you can know for sure that your home has radon gas is to test it. Radon test kits are inexpensive and will tell you whether or not the levels of radon gas in your home represent a health risk. If you do have radon gas in your home, you'll need to prevent more from entering. Depending on whether your home has a basement or a crawlspace, here are the radon mitigation techniques that can be used to prevent radon gas from entering your home.
If you don't have a basement or a crawlspace underneath your home, then your home is slab-on-grade. The most effective form of radon mitigation for these types of homes is sub slab suction.
Sub slab suction is a form of active mitigation wherein a radon mitigation contractor drills a hole into your home's foundation. A pipe is inserted into the hole and connected to an exhaust fan located either outside or in your attic. The exhaust fan draws air out of the pipe, which creates a negative pressure zone in the soil space underneath your home.
Similarly to how radon enters the interior of your home because of the negative pressure inside, the negative pressure zone underneath your home's foundation draws radon in the soil towards it. Radon gas is then sucked through the pipe and deposited harmlessly into the air outside of your home.
Depending on the soil underneath your home, multiple pipes may need to be installed and connected to the exhaust fan. Radon gas can travel through very rocky soil, but not solid rock. A radon mitigation contractor will perform smoke testing to determine how air moves through the soil underneath of your home, and then install pipes in as many locations as necessary to ensure that the majority of radon gas is sucked through them.
The exhaust fans used for active radon mitigation don't draw much energy—their energy usage is slightly higher than a lightbulb's. However, the motor in the fan will eventually burn out due to the fact that it's in continuous use. You'll generally need to replace your exhaust fan every five years.
Active sub slab mitigation can also be used for homes with basements, but there are some additional options you may consider as well. If your basement has a sump pump installed, the sump can be capped with a lid, and a suction pipe can be placed into the sump. Your radon mitigation contractor won't have to drill any holes in your basement if the sump can draw adequate amounts of radon out of the soil. The downside of this method is that the cap can make it difficult to see whether your sump pump is properly removing water from the sump.
If your basement has hollow block walls, the suction pipe used for active mitigation can be inserted into the walls instead of into the ground. This creates a negative pressure zone inside the wall cavity, which will draw radon gas towards it.
If your home has a crawlspace, then radon mitigation is extremely simple for you. There's no need to drill holes. Instead, a very durable plastic sheet is laid over the ground in your crawlspace, and then a suction pipe is laid underneath the sheet. This form of radon mitigation is called submembrane suction. Radon rising from the soil is trapped underneath the sheet and then drawn into the suction pipe, which expels the gas to the outside of your home.
Radon mitigation services are inexpensive and require extremely little maintenance. The only maintenance that's required is making sure the exhaust fan is always running. You'll need to replace it if it fails. If the inside of your home has high levels of radon gas, call a radon mitigation service and have them perform some tests to see how air flows throughout the soil—they'll recommend the best mitigation approach for your home.