Issues With Sub Slab Ductwork
Sub slab ductwork refers to any ductwork that is laid in the ground and then comes up from the slab and into the room. This is a large source of radon because the ducts are not completely sealed and as the warm air moves through it pulls the radon up and spreads it throughout the home.
Usually we would mitigate a slab by putting a suction point in it, however because the ducts aren't sealed, our fan would pull a lot of air from the ductwork. This makes the system much less efficient and also reduces the energy efficiency of the home because we're exhausting the tempered air in the house.
Unfortunately the process for this mitigation can be costly. If there is a minimal amount of ductwork we can ignore it and instead install an ERV that forces fresh air into the home and exhausts the stale indoor air. This has been proven to adequately lower radon levels especially when combined with a mitigation system if there is a slab without the ductwork. This is what we did in a home in Huron, OH
The other option is to concrete over the existing sub slab ductwork and re-run ducts from other fresh air trunks in the house. This can be the most costly option, especially if the area is finished. This is necessary if the area being treated by the sub slab ducts is a very large portion of the home. For example we are using this method for a home in Akron, OH. However luckily the sub slab ductwork is only in one room and there is easy access to a large supply air trunk, without having to run more ductwork. Their levels are just above 4 pCi/L and we hope that by just abandoning the ductwork, we can effectively lower their levels without any further mitigation systems.
In conclusion, despite the complexity of this process we and others in the industry have proven these methods to be successful in radon mitigation efforts. And with this knowledge and experience, we are able to help more customers that might be turned away by other professionals.