R-4 per inch. A UL Listed 'non-toxic' product. Fluted for moisture migration. Technically, mass is not a resistor, rather it is a very slow conductor. Cementituous block consists of a great deal of thermal mass.
Thermal mass has the capacity to absorb and store heat or cool.
Lag - is the time it takes the temperature on one side of a wall to penetrate to the other side. Thermal Flywheel - is a feature unique to this masonry system. As the sun's rays hit the exterior wall the energy begins to move through the block. But as the day progresses the sun's rays move off the wall. The sun has heated and penetrated the wall but its energy does not reach the other side because of the extended thermal path and middle lineal wall.