I'll suggest these tests to our neighboors, since they are the ones with the real toilet sweating problem!
And many thanks for having tempered my fears about the wall fan heater that will be close to our future toilet (http://www.stelpro.com/en/pdf/RWF_E.pdf). I really appreciate this.
We'll have to correct the rest of our home's heaters, and Geniescience is already helping a lot on this aspect.
Thanks to you all!