We are in the process of buying a house, and it's an ideal house in nearly all respects, but the inspection found unacceptably high levels of radon in the basement. The only radon pump I've ever seen was electrically driven. We intend to ask the local radon mitigation folks about off-grid solutions, but wondered if anyone here had successfully mitigated radon without using grid electric, oil, or propane on an otherwise grid-linked property...all resources and ideas welcome.
Also, I'm wondering if the radon situation (once mitigated) would preclude building a root cellaring area in the basement. The floor is mostly poured concrete except for about a 5x8' area that is dirt, and I had intended to put the root cellar over the dirt. Thanks in advance for any insights.
My home has a simple PVC 4-6 in. diameter vent pipe about 25 feet high extending from below the basement slab in the gravel layer to a foot or two above roof line. The warm air in the pipe creates a convection flow upward since the pipe is kept warm within the envelope of the house. Make up air is drawn in through an horizontal pipe that begins on the opposite side of the basement from the vertical vent pipe. It is buried down below grade as it leaves the house and then exits to open air about 20 feet from the basement wall. (The grade slopes away from the house at this point.) I would guess that in the summer with A/C on in the house, the air flow in the system may reverse and flow down the vent pipe and out through the buried make-up air pipe. In either case, the radon is vented out of the house. You would need to include the root cellar area and slab it over also to make this passive system work.
This was approved by my local county inspectors in Montgomery County, MD. Of course a scheme like this depends on a reasonable amount of gravel below the basement slab, preferably covered with plastic sheeting before the slab is poured. If you have such a basement this could work quite well.
If you can't do this, consider a creating a constant low flow of fresh air through the basement and use a small solar panel and several batteries to power the vent fan which would exhaust the air..
I am an Architect and not a mechanical engineer, but have had some experiences with radon systems. In new construction we typically use a 15 mil vapor barrier over crushed stone with a grid of perforated pipe set in it, typically 4" in diameter. The pipe needs to extend above the roof as you stated. If we have reason to believe from testing that a site has radon issues we install the system, but then test the building again after the system is installed to confirm that the radon is still an issue. Sometimes the vapor barrier is enough to mitigate the issue. Then the fan does not need to be installed (the perfect off the grid system).
If there is an issue verified by retesting, then the fan is installed. The size of the fan need not be very large, it only needs to create negative pressure in the pipe system so that gasses that build up travel up the pipe and not into the building. I would think that a fan connected to a small solar panel would do the trick even if the it ran intermitantly with the sun, but that would need to be verified in your conditition
The more expense you go through sealing the floor the more likely you will not need to install the fan. Less expensive systems, lke a plastic track that is installed at the basement perimeter, where the slab meets the wall, rely more heavily on the movement of air.
Good luck solving the problem, hope this helps a bit.
Depending on the height of your basement, you might consider installig a grid of PVC piping embedded in gravel on the existing basement floor and then putting a plastic membrane and or insullation covered by a concrete "new" floor in which might also contain flexible pipling for hydrodronic heating; which would make the basement easier to heat and much more usable!
There was a great article in JLC (Journel of Light Construction) about someone that heated their entire home using a tankless water heater; you might be able to get a back issue by calling (802) 879-3335 or joining either their online membership http://is.gd/WclaaV or buying a DVD which would give you acces to all their back issues.
If your "new" house is going to have tight fitting vinyl windows and leak proof doors then both inside moisture and radon issues need to be addressed.
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