Radon mitigation: sub slab depressurization (SSD)

[Richard904]

Is this the proper forum to ask a radon mitigation question?

In the Northeast sub slab depressurization is common to reduce radon in the home. We are selling our house this year, the home radon testing was high, and therefore we have to consider mitigation. The real estate people say radon testing is a common question among the buyers.

Many vendors show the piping from the basement exiting to the outside of the house at the basement level, then the fan is down low, and the gas is blown up exiting above the roof of the house. The State of Massachusetts radon people say it is much better to have this all internal, go up through a closet or maybe the wall, then the fan is in the attic. They claim this avoids the freezing problem in the PVC piping and extends the life of the fan, and parenthetically looks better. Does anyone have any experience with the pros-and-cons of internal versus external piping and fan life?

[resercon]

http://www.epa.gov/radon/pubs/citguide.html#howdoes

This is an EPA site for Citizen Guide to Radon. My Radon license # is MET11803. I have been asked this question thousands of times. It is preferrable to have the fan inside the structure than outside it. But what usually dictates its placement is feasiblity.

If you read the EPA's publication, you will notice that radon usually enters the home through penetrations in the slab and foundation walls. The most common culprits are sump pits and french drains. If these exists in your home, they will have to be sealed prior to the installation of a SSD system. Sealed does not mean that it stops their function, it means it is sealed to prevent radon gas from entering the house.

If you sealed these areas, which is not that expensive to do, and any cracks and around penetrations around pipes, you might not need the Sub Slab Depressurization system. From the EPA site not only will you find out more about radon but it also gives you your State Radon Office, lists of licensed Measurers and Mitigators, a place for homeowner testing kits, the action threshold if there is one for real estate transactions and a lot more.

While it may appear that the first and best option for high radon readings in a home is SSD system, I believe it should be the last option.

[Richard904]

We have a typical split entry home, so downstairs on slab is a family room and the fourth bedroom and a half bath and a two car garage. We have good ceramic tile over every room except the family room which is carpeted. The quality of the slab is poor with some cracks in the garage, and I am sure some underneath the other rooms hidden by the tile and the carpet. There is no sump pump, but there is heating pipe going through the slab. Can this effectively be sealed enough to really reduce the radon count? Also we are on a hilltop with a lot of ledge.

[resercon]

Radon Mitigation primarily deals with sealing paths that allow radon gas to enter the house. Because it is a gas, it does not diffuse through materials. It would plate out and become harmless to you and your family. What this means is that there must be an entry point or points for the radon to enter.

If this was my house, I would seal the areas most likely to be the source. Such as the cracks in the garage slab, the area around heating and plumbing pipes that come through the slab into the house. Then I would spend $15. to $20. on a homeowner test kit and test the house again.

If the reading came back high, then I would call a radon mitigator. Mitigators have to be licensed and the standard is to measure before and after mitigation. And they are more familar with identifying sources of access for radon.

Most State radon agencies, not only give you a list of licensed mitigators but also the price ranges for mitigation in your area.

[Richard904]

We have a set of steel columns down the center of the house, and in the house itself those are concealed behind an interior wall. I suspect the conditions underneath that wall where the columns are supported. If there are voids or incomplete slab there, then in some way all that would have to be sealed. What do they do? Can they just inject grout?

[resercon]

If there is access to the columns, then they will seal it. It would be just as simple to seal the wall surrounding the columns. Meaning to say if the walls were air tight, the radon gas could not diffuse through the walls.