My two cents of knowledge, which is very limited and comes mostly from discussions and training by Doug. We have used whole house filtration a few times in special circumstances where other alternatives were not viable and the initial radon levels were just above the action level. Pre and post testing was performed using an ERPISU device with results showing that we did achieve a reduction in RDP's using whole house filtration.

One challenge comes when the current occupant sells the property and the new owner has a radon test performed, which of course will still show an elevated radon gas result. We have stressed to our client that subsequent radon testing will need to be also be done using an ERPISU monitor in order to determine that the whole house filtration system is still reducing RDP's.

I think that the biggest challenge comes in explaining the science to an owner and if any real estate agents are involved in a transaction. Agents are often very narrow minded and focused on the action level as being the end all for moving forward with a real estate deal. Trying to explain how whole house filtration works to reduce RDP's can be very difficult when so much focus is on radon in general.

Just a few thoughts on the topic from the field.

Polyurethane sealant does not work with DuraSkrim. While it will initially seem to bond, once everything cures, the barrier can peel right off. I found this out the hard way years ago and had to reseal an entire crawlspace. You have to use either Butyl sealant (gutter seal) from Radonaway or Acryl-r from PDS.