We regularly inspect homes with active radon mitigation systems. By active, we mean an installed radon fan is powered and removing air from beneath the home before it can become trapped inside. An installed system sometimes leads home buyers to opt out of radon testing.
I decided to write a blog post after two customers decided against testing for radon in air when they were purchasing their homes because a system was installed. They had a false sense of security. Both systems had blank installer stickers used to contact for service in the event of an issue. In the radon world, that's a red flag. Installers should be licensed AND experienced This is not a DIY project.
A properly installed system typically brings radon levels below 1.0 pCi/L, well below the EPA-recommended action level of 4.0 pCi/L. Just because the level of the home are below 4.0 pCi/L doesn't mean they can't decrease further.
Some systems we encounter are not installed by a professional and are not running optimally. Systems that should produce below 1.0 pCi/L are tested at 2.0 pCi/L or higher. While 2.0 pCi/L is below the action level, it can easily be lowered.
Radon risk is all about exposure. It's safe to assume your risk of skin cancer significantly increases when you sunburn four or more times per year. Are you content with two times? Shouldn't the goal be zero?
Radon Mitigation Systems 101:
Radon Fan: About the size of a basketball, the fan is located outside of the living space (exterior, garage, or attic). It gives off a slight hum and vibration (noticeable to the touch). It should be on a dedicated circuit to prevent inadvertent disabling.
Manometer: This is a tube full of ink that is mounted on the radon pipe inside the home (usually the basement). When the two sides are offset so the line looks like a "J", the fan is operating and pulling air out (or trying to). When the sides are not offset and it makes a "U", the fan is either not operating or the system is incorrectly installed. A "J" can be improved. More on that below...
Vent Pipe: A three inch vent pipe is made of PVC (no, gutters will not work as they are not airtight) and vents above the roof line and at least 10' from any opening. Pipes smaller than this are problematic because the radon fan itself has 3" openings. To push air out of a 2" tube from a 3" opening creates a "bottleneck" where pressure may force the radon gas to re-enter the home.
Common Active Radon Mitigation Installation Failures
Inoperable Fan: While obvious, its often overlooked. The buyer has a thousand pieces of information flying at them during a home showing and the agent only has a short time to help you view the home. An inoperable fan can easily be repaired, but only if you know about it. If the fan is not running, the system isn't working. If the fan was required in the first place, the home's radon levels are high.
Open Sump Pits: A hole for a sump pump is called a sump pit. It needs to be covered and sealed so it's airtight for the radon system to be optimal. Drains collect water from below your foundation and drain into your sump pit to be discharged. Those drains interact with where the radon removal system is operating. If the pit is not sealed, the fan is removing interior air via your sump pit and venting outside. Not only is it not running optimally, its wasting energy by venting conditioned air your already paid to heat or cool. Ever drink from a cracked straw? You're sucking in air instead of your drink (Radon is the drink...).
Cracks in Concrete: Some cracks are designed expansion joints and some are from drying and settling. Like any suction system, a radon system will choose the path of least resistance. If air is easier to feed the fan from a crack in your floor, it will take that air over the real issue of radon below your foundation. Sealing all cracks is simple and inexpensive with silicone caulking.
Fans Installed In A Basement: Each fan has an expected life of 10 years and therefore not permanently installed. Clamps are used to connect the fan to the pipe, not glue to make it airtight and permanent. Clamps can be installed poorly, inadvertently hit by the occupant, or faulty. A radon system works really hard to pull radon out but then could vent directly into the living space due to a faulty clamp. For this reason, the fan should always be installed in a non-living space (exterior, garage, or an attic).
Vents Not Terminating Away From Openings: Vents should be outside the home and vented at least 10' from any opening (window, door, etc), often above the roof line. If not vented properly, the radon can easily re-enter the home and actually increase exposure to certain areas of the home.
Stay safe out there,
Matt and Matt
Square One Home Inspections
207-560-3222