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What I should know when buying a home that has a radon system installed?

When you are purchasing a house there are many components within the house that need to be understood. One system that home buyers may not be completely familiar with is a home’s radon removal system.

We will go forward with the assumption that the home has some level of radon mitigation already installed. Buying a home without a mitigation system, testing for radon in a real estate transaction, and the basics of what radon is are all good topics for another post. For now, let us just focus on the differences between passive and active radon removal systems.

Shared components.

In either a passive or active system most of the parts are the same. Both systems will have a 3” PVC (Poly Vinyl Chloride – Plastic) pipe. Depending on the home, the pipe will be set and sealed inside the home’s sump pump well (if there is one) or a hole will be cut into the basement slab and the pipe is then set below the slab. In homes that have a dirt floor crawl space, a membrane of plastic is added to encapsulate or seal the area. From there, the pipe is added below the membrane. The pipe is then routed to the exterior. In some homes, the pipe will exit the building through the rim joist and then be secured to the exterior cladding of the home. In other cases, the pipe will be routed through the interior wall or the garage space and then out through the roof. In either scenario, the pipe will extend a minimum of 12” above the roof line. Basically put, the pipe is acting like a straw. It is a pathway for the radon gasses below the foundation of the home to be routed above the roof.

Passive system.

What is described above is a passive system or a system that does not have a means of depressurizing the area below the slab of the home or below a crawl space membrane. As of 2009, any new construction home built in Minnesota is required to have a passive piping system installed.

Things to know:

· A passive system will lower the radon levels in a building, but without testing, we can’t definitively say that levels are reduced to a point that would be considered safe.

· If the home also has an HRV or ERV system (another topic for another day) installed, then that system will also help to lower radon levels.

· Knowing that most of the structure is in place, if there were the need to add a fan, the cost would be reasonable, and the installation process would be relatively simple.

· Recommendations: See if the previous owners had ever done a radon measurement test. If there is no recorded history, the new owners should do a short-term test. This is something the homeowners can do themselves, without the need to hire a professional. Once the radon levels are known, the homeowner should follow the EPA’s guidelines.

Radon Mitigation system

By definition, an active radon mitigation system will have a suction fan installed at some point on the pipe. The fan creates a negative pressure below the base of the home (slab, drain tile, or crawl space) and draws out the air, and expels it above the roof line.

Things to know:

· An active system will have a manometer or spirit vile installed to show pressure. This vile will have two columns of colored water. The two columns should be at different heights in the vile. This difference shows that there is pressure being created by the fan.

o If there is no separation in the columns of water then either the fan is off or there is a blockage in the pipe. Most often, the blockage will be the result of ice buildup during the winter.

· When the system was originally installed, the installation company was required to do a follow-up measurement test. If possible, a few items of information should be gained from the home’s current owners.

o Who installed the system and when?

o Is there a data/system tag visible on the pipe?

o What were the radon levels prior to installing the system?

o What was the level found when the follow-up test was done?

o Have there been subsequent measurement tests done after that?

§ If yes, when and what were the results?

o Since the installation of the system, have there been any major remodeling activities in the home?

· Recommendations: Moving forward, the EPA does recommend that the home be periodically retested to confirm that the system is operating to desired levels. An alternative strategy would be to purchase (roughly $250) a long-term radon monitor. An example of a monitor like this would be the Luft model from Sun Radon

Whether you have an active or passive system installed, consider these a bonus. Follow the recommendations listed above for your system type to fully relive their individual benefits.

As always, please don’t hesitate to reach out to me with questions.

Richard Katz


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