Going by specifications the steel fill fraction is 0.22% for P and 0.09% for Q, which are meant for Insulated exterior (structural/non-structural) wall. The num

Going by specifications the steel fill fraction is 0.22% for P and 0.09% for Q, which are meant for Insulated exterior (structural/non-structural) wall. The numbers work out, even for a moderately more conductive steel. I wonder if they fill the inside of tubes with rock wool.