My 50's era walkout home has radon problems because of broken heat ducts which are under the cement floor of the lower level, and which carry heat to the entire lower level. Video shows the ducts have split in several places, causing radon to be pulled from the soil into my house. Is there any way to fix the ducts without tearing open the cement floors? Is it possible to insert a sleeve into the ducts so that the sleeve would carry the heat without pulling radon into my house? Or must I seal the present ducts and have the furnace re-ducted through the ceiling of the lower level? I have been told normal radon mitigation methods are not going to work for this problem.