Replies

1. 
   Piffin | Dec 14, 2003 02:51pm | #1

   Couple of thoughts, one of which is too late for you but might helpsomeone else. The Certanteed Formadrain system is intended to make radon removal easier but you use it for forming the footings.

   The other is that JLC haad and article on this a few months ago. You could seaarch their site and buy the article.

   .

   Excellence is its own reward!

2. 
   calvin | Dec 14, 2003 06:10pm | #2

   Before foambd, vapor bar. and pouring here in NW OH. when we built, I put perf drain tile around the interior and ran it to daylight (hillside const.).  My thoughts were it would capture any interior water (seems to have been none) and give a place to passively rid the underslab of any radon.  Took a bit of time, very little money.   Be sure to make arrangement to actively remove it if necessary with electric for a fan.  Some ideas were to run an interior vent up from the slab and out the roof.  Might want to run that pipe now while the walls are open. 

   Remodeling Contractor just outside the Glass City.

   Quittin' Time

3. 
   dIrishInMe | Dec 14, 2003 08:23pm | #3

   I don't know a lot about this, but a builder I used to work for did this:

   Prior to basement slab placing, put a 3" PVC  tee under the vapor barrier in the gravel with a capped off 3" pipe that comes up through the slab.  The 2 horizontal legs of the tee are connected to nothing.   After framing, but before insulation/sheetrock, run the 3" pipe up through a plumbing wall, chase, etc, to the attic.  (schedule 20 for all this is fine - schedule 40 is a waste).  Place a wired electrical box near the termination of the pipe in the attic.  Blank cover on the box.   Then, if radon is identified as a problem later, an inline suction fan can be installed in the 3" pipe in the attic, and a vent stack can be run out through the roof. 

   The idea is to create a negative pressure under the slab to evacuate the radon gas.  It would probably be a good idea if after placing the Tee and stubbed off 3" pipe you sealed the Tu-Tuff around the 3" pipe.  Duct sealant or Poly const. adhesive will work for this.

   BTW - are you putting a perimeter drain tile around the inside perimeter of the foundation under the slab that is to exit to daylight?  Just curious.  

   Matt
4. 
   rebuilder | Dec 14, 2003 11:25pm | #4

   I'm in western NC and there's alot of radon hype around here. I see alot of after market fixes and see it in new construction as well. Dig a trench  in your gravel through your basement in an oval shape deep enough to bury perf. pipe. Cap one end and run the other out of the wall. Seal everything under vapor barrier with taped seams. A suction fan hooks to the open air end which in turns hooks to a vent stack usually running up the side of your house which ends up looking like $hit on a pink rag to me, but everyone else seems to think highly of the whole system! Good luck!

5. 
   DavidThomas | Dec 15, 2003 01:44am | #5

   One approach is negative pressure.  Another is "wash" out the radon with a little fresh air flow.  You still get a negative pressure, it is just a different design approach.

   Say the house is long on the E-W axis.  Put a 3-inch 90 in the NW corner and run 3" perf pipe due south.  (Pref pipe is under vapor barrier and 2" foam).  Cap it at the SW corner.  This is where fresh air will be introduced to the gravel bed.

   Put a 3-inch 90 in the SE corner and run 3" perf pipe due north.   Cap it at the NE corner.  This is where radon-containing air will be extracted. 

   Extract from the opposite corner as you allow fresh air in.  Sketch it out and flip it over - top for bottom or side to side - to fit your site.

   Flow through the gravel is balanced - think of a grid network of eletrical resistors.

   The reason I prefer to have a distinct air inlet is that then you get to choose the air source.  It could be basement air.  It could be cold outside air.  It could be hot air from the attic.  It could be stinky air from the bathroom.  With the foam, getting the gravel warmer or colder doesn't offer much.  But another design might RFH or RF Cool the basement by selecting hot or cold air to flow under the slab. 

   Also, by valving the inlet and watching the extraction vacuum, you could assess the leakiness of the gravel bed (through the foundation, slab, utility penetrations, etc.  Qualitatively, when the extraction vacuum transitions from one regime to another, the valve size equates to total leak area.

   Of course, the exhaust has to go outside and standard design constraints apply - above the roof peak by a few feet, ideally.  Or far enough away to avoid eddy effects.  Some folks would buy a bigger fan.  But the fan runs 24/365/50 years.  So like a chimney, put in a proper stack.   Then you can use a small, low-wattage, quiet fan.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska