Home Buyers: Know What to Ask For
Basic Radon-Resistant New Construction Techniques for Your Home
Based on a rash of recent poorly engineered prefab radon system experiences, I felt it necessary to rehash an old post. All of the techniques and materials described below are commonly used in home construction. While the techniques may vary for different house foundations and building site requirements, the five basic features that should included in new construction to prevent radon from entering the home are:
Plastic Sheeting or Vapor Barrier / Retarder: Place heavy duty plastic sheeting (6 mil. polyethylene) or a vapor retarder on top of the gravel to prevent the soil gases from entering the house. The sheeting also keeps the concrete from clogging the gravel layer when the slab is poured.
A Vent Pipe: Run a 3-inch or 4-inch solid PVC pipe, vertically from the gravel layer (stubbed up when the slab is poured) through the house’s conditioned space and roof to safely vent radon and other soil gases outside above the house. Whenever possible - 4" pipe is a better choice as it allows for up to double the volume of air to be removed out from under the slab as compared to 3".
For very large footprints, multiple vertical stacks are recommended. We did a project in a Greenwich estate that had 6 stacks. (Although serving a different purpose, this vent pipe is similar to the drain waste vent, DWV, installed by the plumber for the sanitary system.) This pipe should be labeled "Radon System."
Sealing and Caulking: Seal all openings, cracks, and crevices in the concrete foundation floor (including the slab perimeter; floor wall joint) and walls with polyurethane caulk to prevent radon and other soil gases from entering the home.
Junction Box: An electrical outlet should be provided near the pipe location in the attic. This is allows for easy fan connection in the event the system has to be activated to effectively reduce radon concentrations.
- inaccessible attic locations (pipe located where no one can fit),
- slab stubs located at opposite end of basement from ceiling stub (results in excessive pipe runs),
- multiple slab level layouts not being addressed.