The force is used to determine the density of the insulation, which, in turn, is used to determine {HEAD ~ the thermal resistance} or R value of {TAIL ~ the insulation} 
of
The force is used to determine the density of the insulation , which , in turn , is used to determine { HEAD ~ the thermal resistance } or R value of { TAIL ~ the insulation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL