removing H2O, not just Rn?

 We did a 3-month test which showed 204 Bequerel/cubic metre of radon in our basement. The threshold for leisurely mitigation is 200. Argh! 

And apparently, when selling a house, you must disclose any information you have about radon.

So we got a radon mitigation system installed. 

Carefree Properties professional installation

It depressurizes under the foundation slab, and blows the radon-laden air it collects out the side of the house. A possible side effect is sub-slab humidity will also get blown out, and stop rising through cracks into our basement.

'Way too early to tell, but this data from the crawlspace humidity sensor is encouraging:

The crawlspace humidity dropped slightly when the radon system started, but rose higher than the baseline earlier in the day after I turned off the crawlspace dehumidifier.  But it isn't still rising. 

The dehumidifer costs about $250 per year to run, and our experience is the equipment breaks every 2-3 years. The fan in the radon system uses less than a tenth as much power. It's showing just over 20 watts, or about $40 per year. If it can deal with the humidity, it'll pay for itself in less than five years. 

I went down to check on this afternoon, and the outlet pipe was glowing! Radioactivity, oh no!

But actually, just the afternoon sun shining on the side of the house.