With the mention of "radioactive dust" are you sure it's radon, as that should not produce dust, and not some other source of radiation in the attic? Like I don't kow what, a lot of old gas mantle filaments.
Any notion of whether it's β or ɣ radiation you're detecting?
Demolition is going to need careful monitoring to ensure you don't contaminate the entire site.
I have 3 geiger counters that do Gamma, Beta and X-Ray. They do not register anything beyond the background noise. My Alpha detector is the only one that picks up the spikes from the hepa filters and my attic.
Any notion of whether it's β or ɣ radiation you're detecting?
Demolition is going to need careful monitoring to ensure you don't contaminate the entire site.